Splitting code into multiple files with reasonable testing coverage.

```
ok      github.com/lukaszraczylo/traefikoidc    117.017s        coverage: 72.6% of statements
ok      github.com/lukaszraczylo/traefikoidc/auth       0.505s  coverage: 87.1% of statements
ok      github.com/lukaszraczylo/traefikoidc/circuit_breaker    0.283s  coverage: 99.0% of statements
        github.com/lukaszraczylo/traefikoidc/config             coverage: 0.0% of statements
ok      github.com/lukaszraczylo/traefikoidc/handlers   0.349s  coverage: 98.2% of statements
ok      github.com/lukaszraczylo/traefikoidc/internal/providers (cached)        coverage: 94.3% of statements
ok      github.com/lukaszraczylo/traefikoidc/middleware 0.808s  coverage: 78.0% of statements
ok      github.com/lukaszraczylo/traefikoidc/recovery   0.653s  coverage: 100.0% of statements
ok      github.com/lukaszraczylo/traefikoidc/session/chunking   (cached)        coverage: 87.8% of statements
ok      github.com/lukaszraczylo/traefikoidc/session/core       (cached)        coverage: 85.6% of statements
ok      github.com/lukaszraczylo/traefikoidc/session/crypto     (cached)        coverage: 81.8% of statements
ok      github.com/lukaszraczylo/traefikoidc/session/storage    (cached)        coverage: 93.5% of statements
ok      github.com/lukaszraczylo/traefikoidc/session/validators (cached)        coverage: 98.8% of statements
````

auth/auth_handler.go

@@ -0,0 +1,360 @@
+// Package auth provides authentication-related functionality for the OIDC middleware.
+package auth
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/google/uuid"
+)
+
+// AuthHandler provides core authentication functionality for OIDC flows
+type AuthHandler struct {
+	logger         Logger
+	enablePKCE     bool
+	isGoogleProv   func() bool
+	isAzureProv    func() bool
+	clientID       string
+	authURL        string
+	issuerURL      string
+	scopes         []string
+	overrideScopes bool
+}
+
+// Logger interface for dependency injection
+type Logger interface {
+	Debugf(format string, args ...interface{})
+	Errorf(format string, args ...interface{})
+}
+
+// NewAuthHandler creates a new AuthHandler instance
+func NewAuthHandler(logger Logger, enablePKCE bool, isGoogleProv, isAzureProv func() bool,
+	clientID, authURL, issuerURL string, scopes []string, overrideScopes bool) *AuthHandler {
+	return &AuthHandler{
+		logger:         logger,
+		enablePKCE:     enablePKCE,
+		isGoogleProv:   isGoogleProv,
+		isAzureProv:    isAzureProv,
+		clientID:       clientID,
+		authURL:        authURL,
+		issuerURL:      issuerURL,
+		scopes:         scopes,
+		overrideScopes: overrideScopes,
+	}
+}
+
+// InitiateAuthentication initiates the OIDC authentication flow.
+// It generates CSRF tokens, nonce, PKCE parameters (if enabled), clears the session,
+// stores authentication state, and redirects the user to the OIDC provider.
+func (h *AuthHandler) InitiateAuthentication(rw http.ResponseWriter, req *http.Request,
+	session SessionData, redirectURL string,
+	generateNonce, generateCodeVerifier, deriveCodeChallenge func() (string, error)) {
+
+	h.logger.Debugf("Initiating new OIDC authentication flow for request: %s", req.URL.RequestURI())
+
+	const maxRedirects = 5
+	redirectCount := session.GetRedirectCount()
+	if redirectCount >= maxRedirects {
+		h.logger.Errorf("Maximum redirect limit (%d) exceeded, possible redirect loop detected", maxRedirects)
+		session.ResetRedirectCount()
+		http.Error(rw, "Authentication failed: Too many redirects", http.StatusLoopDetected)
+		return
+	}
+
+	session.IncrementRedirectCount()
+
+	csrfToken := uuid.NewString()
+	nonce, err := generateNonce()
+	if err != nil {
+		h.logger.Errorf("Failed to generate nonce: %v", err)
+		http.Error(rw, "Failed to generate nonce", http.StatusInternalServerError)
+		return
+	}
+
+	// Generate PKCE code verifier and challenge if PKCE is enabled
+	var codeVerifier, codeChallenge string
+	if h.enablePKCE {
+		codeVerifier, err = generateCodeVerifier()
+		if err != nil {
+			h.logger.Errorf("Failed to generate code verifier: %v", err)
+			http.Error(rw, "Failed to generate code verifier", http.StatusInternalServerError)
+			return
+		}
+		codeChallenge, err = deriveCodeChallenge()
+		if err != nil {
+			h.logger.Errorf("Failed to generate code challenge: %v", err)
+			http.Error(rw, "Failed to generate code challenge", http.StatusInternalServerError)
+			return
+		}
+		h.logger.Debugf("PKCE enabled, generated code challenge")
+	}
+
+	session.SetAuthenticated(false)
+	session.SetEmail("")
+	session.SetAccessToken("")
+	session.SetRefreshToken("")
+	session.SetIDToken("")
+	session.SetNonce("")
+	session.SetCodeVerifier("")
+
+	session.SetCSRF(csrfToken)
+	session.SetNonce(nonce)
+	if h.enablePKCE {
+		session.SetCodeVerifier(codeVerifier)
+	}
+	session.SetIncomingPath(req.URL.RequestURI())
+	h.logger.Debugf("Storing incoming path: %s", req.URL.RequestURI())
+
+	session.MarkDirty()
+
+	if err := session.Save(req, rw); err != nil {
+		h.logger.Errorf("Failed to save session before redirecting to provider: %v", err)
+		http.Error(rw, "Failed to save session", http.StatusInternalServerError)
+		return
+	}
+
+	h.logger.Debugf("Session saved before redirect. CSRF: %s, Nonce: %s",
+		csrfToken, nonce)
+
+	authURL := h.BuildAuthURL(redirectURL, csrfToken, nonce, codeChallenge)
+	h.logger.Debugf("Redirecting user to OIDC provider: %s", authURL)
+
+	http.Redirect(rw, req, authURL, http.StatusFound)
+}
+
+// BuildAuthURL constructs the OIDC provider authorization URL.
+// It builds the URL with all necessary parameters including client_id, scopes,
+// PKCE parameters, and provider-specific parameters for Google and Azure.
+func (h *AuthHandler) BuildAuthURL(redirectURL, state, nonce, codeChallenge string) string {
+	params := url.Values{}
+	params.Set("client_id", h.clientID)
+	params.Set("response_type", "code")
+	params.Set("redirect_uri", redirectURL)
+	params.Set("state", state)
+	params.Set("nonce", nonce)
+
+	if h.enablePKCE && codeChallenge != "" {
+		params.Set("code_challenge", codeChallenge)
+		params.Set("code_challenge_method", "S256")
+	}
+
+	scopes := make([]string, len(h.scopes))
+	copy(scopes, h.scopes)
+
+	if h.isGoogleProv() {
+		params.Set("access_type", "offline")
+		h.logger.Debugf("Google OIDC provider detected, added access_type=offline for refresh tokens")
+
+		params.Set("prompt", "consent")
+		h.logger.Debugf("Google OIDC provider detected, added prompt=consent to ensure refresh tokens")
+	} else if h.isAzureProv() {
+		params.Set("response_mode", "query")
+		h.logger.Debugf("Azure AD provider detected, added response_mode=query")
+
+		hasOfflineAccess := false
+
+		for _, scope := range scopes {
+			if scope == "offline_access" {
+				hasOfflineAccess = true
+				break
+			}
+		}
+
+		if !h.overrideScopes || (h.overrideScopes && len(h.scopes) == 0) {
+			if !hasOfflineAccess {
+				scopes = append(scopes, "offline_access")
+				h.logger.Debugf("Azure AD provider: Added offline_access scope (overrideScopes: %t, user scopes count: %d)", h.overrideScopes, len(h.scopes))
+			}
+		} else {
+			h.logger.Debugf("Azure AD provider: User is overriding scopes (count: %d), offline_access not automatically added.", len(h.scopes))
+		}
+	} else {
+		if !h.overrideScopes || (h.overrideScopes && len(h.scopes) == 0) {
+			hasOfflineAccess := false
+			for _, scope := range scopes {
+				if scope == "offline_access" {
+					hasOfflineAccess = true
+					break
+				}
+			}
+			if !hasOfflineAccess {
+				scopes = append(scopes, "offline_access")
+				h.logger.Debugf("Standard provider: Added offline_access scope (overrideScopes: %t, user scopes count: %d)", h.overrideScopes, len(h.scopes))
+			}
+		} else {
+			h.logger.Debugf("Standard provider: User is overriding scopes (count: %d), offline_access not automatically added.", len(h.scopes))
+		}
+	}
+
+	if len(scopes) > 0 {
+		finalScopeString := strings.Join(scopes, " ")
+		params.Set("scope", finalScopeString)
+		h.logger.Debugf("AuthHandler.BuildAuthURL: Final scope string being sent to OIDC provider: %s", finalScopeString)
+	}
+
+	return h.buildURLWithParams(h.authURL, params)
+}
+
+// buildURLWithParams constructs a URL by combining a base URL with query parameters.
+// It handles both relative and absolute URLs, validates URL security,
+// and properly encodes query parameters.
+func (h *AuthHandler) buildURLWithParams(baseURL string, params url.Values) string {
+	if baseURL != "" {
+		if strings.HasPrefix(baseURL, "http://") || strings.HasPrefix(baseURL, "https://") {
+			if err := h.validateURL(baseURL); err != nil {
+				h.logger.Errorf("URL validation failed for %s: %v", baseURL, err)
+				return ""
+			}
+		}
+	}
+
+	if !strings.HasPrefix(baseURL, "http://") && !strings.HasPrefix(baseURL, "https://") {
+		issuerURLParsed, err := url.Parse(h.issuerURL)
+		if err != nil {
+			h.logger.Errorf("Could not parse issuerURL: %s. Error: %v", h.issuerURL, err)
+			return ""
+		}
+
+		baseURLParsed, err := url.Parse(baseURL)
+		if err != nil {
+			h.logger.Errorf("Could not parse baseURL: %s. Error: %v", baseURL, err)
+			return ""
+		}
+
+		resolvedURL := issuerURLParsed.ResolveReference(baseURLParsed)
+
+		if err := h.validateURL(resolvedURL.String()); err != nil {
+			h.logger.Errorf("Resolved URL validation failed for %s: %v", resolvedURL.String(), err)
+			return ""
+		}
+
+		resolvedURL.RawQuery = params.Encode()
+		return resolvedURL.String()
+	}
+
+	u, err := url.Parse(baseURL)
+	if err != nil {
+		h.logger.Errorf("Could not parse absolute baseURL: %s. Error: %v", baseURL, err)
+		return ""
+	}
+
+	if err := h.validateParsedURL(u); err != nil {
+		h.logger.Errorf("Parsed URL validation failed for %s: %v", baseURL, err)
+		return ""
+	}
+
+	u.RawQuery = params.Encode()
+	return u.String()
+}
+
+// validateURL performs security validation on URLs to prevent SSRF attacks.
+// It checks for allowed schemes, validates hosts, and prevents access to private networks.
+func (h *AuthHandler) validateURL(urlStr string) error {
+	if urlStr == "" {
+		return fmt.Errorf("empty URL")
+	}
+
+	u, err := url.Parse(urlStr)
+	if err != nil {
+		return fmt.Errorf("invalid URL format: %w", err)
+	}
+
+	return h.validateParsedURL(u)
+}
+
+// validateParsedURL validates a parsed URL structure for security.
+// It checks schemes, hosts, and paths to prevent malicious URLs.
+func (h *AuthHandler) validateParsedURL(u *url.URL) error {
+	allowedSchemes := map[string]bool{
+		"https": true,
+		"http":  true,
+	}
+
+	if !allowedSchemes[u.Scheme] {
+		return fmt.Errorf("disallowed URL scheme: %s", u.Scheme)
+	}
+
+	if u.Scheme == "http" {
+		h.logger.Debugf("Warning: Using HTTP scheme for URL: %s", u.String())
+	}
+
+	if u.Host == "" {
+		return fmt.Errorf("missing host in URL")
+	}
+
+	if err := h.validateHost(u.Host); err != nil {
+		return fmt.Errorf("invalid host: %w", err)
+	}
+
+	if strings.Contains(u.Path, "..") {
+		return fmt.Errorf("path traversal detected in URL path")
+	}
+
+	return nil
+}
+
+// validateHost validates a hostname for security and reachability.
+// It prevents access to private networks and localhost addresses.
+func (h *AuthHandler) validateHost(host string) error {
+	if host == "" {
+		return fmt.Errorf("empty host")
+	}
+
+	// Strip port if present
+	if strings.Contains(host, ":") {
+		var err error
+		host, _, err = net.SplitHostPort(host)
+		if err != nil {
+			return fmt.Errorf("invalid host:port format: %w", err)
+		}
+	}
+
+	// Check for localhost variations
+	localhostVariations := []string{
+		"localhost", "127.0.0.1", "::1", "0.0.0.0",
+	}
+	for _, localhost := range localhostVariations {
+		if strings.EqualFold(host, localhost) {
+			return fmt.Errorf("localhost access not allowed: %s", host)
+		}
+	}
+
+	// Try to parse as IP address
+	if ip := net.ParseIP(host); ip != nil {
+		if ip.IsLoopback() {
+			return fmt.Errorf("loopback IP not allowed: %s", host)
+		}
+		if ip.IsPrivate() {
+			return fmt.Errorf("private IP not allowed: %s", host)
+		}
+		if ip.IsLinkLocalUnicast() {
+			return fmt.Errorf("link-local IP not allowed: %s", host)
+		}
+		if ip.IsMulticast() {
+			return fmt.Errorf("multicast IP not allowed: %s", host)
+		}
+	}
+
+	return nil
+}
+
+// SessionData interface for dependency injection
+type SessionData interface {
+	GetRedirectCount() int
+	ResetRedirectCount()
+	IncrementRedirectCount()
+	SetAuthenticated(bool)
+	SetEmail(string)
+	SetAccessToken(string)
+	SetRefreshToken(string)
+	SetIDToken(string)
+	SetNonce(string)
+	SetCodeVerifier(string)
+	SetCSRF(string)
+	SetIncomingPath(string)
+	MarkDirty()
+	Save(req *http.Request, rw http.ResponseWriter) error
+}

auth/auth_handler_test.go

@@ -0,0 +1,923 @@
+package auth
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"sync"
+	"testing"
+)
+
+// Mock logger for testing
+type mockLogger struct {
+	debugLogs []string
+	errorLogs []string
+	mu        sync.RWMutex
+}
+
+func (m *mockLogger) Debugf(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.debugLogs = append(m.debugLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockLogger) Errorf(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.errorLogs = append(m.errorLogs, fmt.Sprintf(format, args...))
+}
+
+//lint:ignore U1000 May be needed for future debug log verification tests
+func (m *mockLogger) getDebugLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.debugLogs))
+	copy(result, m.debugLogs)
+	return result
+}
+
+func (m *mockLogger) getErrorLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.errorLogs))
+	copy(result, m.errorLogs)
+	return result
+}
+
+//lint:ignore U1000 May be needed for future test isolation
+func (m *mockLogger) reset() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.debugLogs = nil
+	m.errorLogs = nil
+}
+
+// Mock session for testing
+type mockSession struct {
+	data          map[string]interface{}
+	redirectCount int
+	saveError     error
+	mu            sync.RWMutex
+	dirty         bool
+	authenticated bool
+	email         string
+	accessToken   string
+	refreshToken  string
+	idToken       string
+	nonce         string
+	codeVerifier  string
+	csrf          string
+	incomingPath  string
+}
+
+func newMockSession() *mockSession {
+	return &mockSession{
+		data: make(map[string]interface{}),
+	}
+}
+
+func (m *mockSession) GetRedirectCount() int {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.redirectCount
+}
+
+func (m *mockSession) ResetRedirectCount() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.redirectCount = 0
+}
+
+func (m *mockSession) IncrementRedirectCount() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.redirectCount++
+}
+
+func (m *mockSession) SetAuthenticated(auth bool) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.authenticated = auth
+}
+
+func (m *mockSession) SetEmail(email string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.email = email
+}
+
+func (m *mockSession) SetAccessToken(token string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.accessToken = token
+}
+
+func (m *mockSession) SetRefreshToken(token string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.refreshToken = token
+}
+
+func (m *mockSession) SetIDToken(token string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.idToken = token
+}
+
+func (m *mockSession) SetNonce(nonce string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.nonce = nonce
+}
+
+func (m *mockSession) SetCodeVerifier(verifier string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.codeVerifier = verifier
+}
+
+func (m *mockSession) SetCSRF(csrf string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.csrf = csrf
+}
+
+func (m *mockSession) SetIncomingPath(path string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.incomingPath = path
+}
+
+func (m *mockSession) MarkDirty() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.dirty = true
+}
+
+func (m *mockSession) Save(req *http.Request, rw http.ResponseWriter) error {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.saveError
+}
+
+func (m *mockSession) setSaveError(err error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.saveError = err
+}
+
+// Test helper functions
+func createTestAuthHandler(logger Logger, enablePKCE bool, isGoogle, isAzure func() bool) *AuthHandler {
+	return NewAuthHandler(
+		logger,
+		enablePKCE,
+		isGoogle,
+		isAzure,
+		"test-client-id",
+		"https://provider.example.com/auth",
+		"https://provider.example.com",
+		[]string{"openid", "email", "profile"},
+		false,
+	)
+}
+
+func TestNewAuthHandler(t *testing.T) {
+	tests := []struct {
+		name           string
+		logger         Logger
+		enablePKCE     bool
+		clientID       string
+		authURL        string
+		issuerURL      string
+		scopes         []string
+		overrideScopes bool
+	}{
+		{
+			name:           "creates handler with basic config",
+			logger:         &mockLogger{},
+			enablePKCE:     true,
+			clientID:       "test-client",
+			authURL:        "https://example.com/auth",
+			issuerURL:      "https://example.com",
+			scopes:         []string{"openid", "email"},
+			overrideScopes: false,
+		},
+		{
+			name:           "creates handler with PKCE disabled",
+			logger:         &mockLogger{},
+			enablePKCE:     false,
+			clientID:       "test-client",
+			authURL:        "https://example.com/auth",
+			issuerURL:      "https://example.com",
+			scopes:         []string{"openid"},
+			overrideScopes: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			isGoogle := func() bool { return false }
+			isAzure := func() bool { return false }
+
+			handler := NewAuthHandler(
+				tt.logger,
+				tt.enablePKCE,
+				isGoogle,
+				isAzure,
+				tt.clientID,
+				tt.authURL,
+				tt.issuerURL,
+				tt.scopes,
+				tt.overrideScopes,
+			)
+
+			if handler == nil {
+				t.Fatal("NewAuthHandler returned nil")
+			}
+
+			if handler.clientID != tt.clientID {
+				t.Errorf("Expected clientID %s, got %s", tt.clientID, handler.clientID)
+			}
+
+			if handler.enablePKCE != tt.enablePKCE {
+				t.Errorf("Expected enablePKCE %v, got %v", tt.enablePKCE, handler.enablePKCE)
+			}
+
+			if handler.authURL != tt.authURL {
+				t.Errorf("Expected authURL %s, got %s", tt.authURL, handler.authURL)
+			}
+
+			if handler.issuerURL != tt.issuerURL {
+				t.Errorf("Expected issuerURL %s, got %s", tt.issuerURL, handler.issuerURL)
+			}
+
+			if handler.overrideScopes != tt.overrideScopes {
+				t.Errorf("Expected overrideScopes %v, got %v", tt.overrideScopes, handler.overrideScopes)
+			}
+		})
+	}
+}
+
+func TestInitiateAuthentication(t *testing.T) {
+	tests := []struct {
+		name                      string
+		enablePKCE                bool
+		initialRedirectCount      int
+		generateNonceError        error
+		generateCodeVerifierError error
+		deriveCodeChallengeError  error
+		sessionSaveError          error
+		expectedStatusCode        int
+		expectRedirect            bool
+	}{
+		{
+			name:               "successful authentication without PKCE",
+			enablePKCE:         false,
+			expectedStatusCode: http.StatusFound,
+			expectRedirect:     true,
+		},
+		{
+			name:               "successful authentication with PKCE",
+			enablePKCE:         true,
+			expectedStatusCode: http.StatusFound,
+			expectRedirect:     true,
+		},
+		{
+			name:               "fails when nonce generation fails",
+			enablePKCE:         false,
+			generateNonceError: fmt.Errorf("nonce generation failed"),
+			expectedStatusCode: http.StatusInternalServerError,
+			expectRedirect:     false,
+		},
+		{
+			name:                      "fails when code verifier generation fails",
+			enablePKCE:                true,
+			generateCodeVerifierError: fmt.Errorf("code verifier generation failed"),
+			expectedStatusCode:        http.StatusInternalServerError,
+			expectRedirect:            false,
+		},
+		{
+			name:                     "fails when code challenge derivation fails",
+			enablePKCE:               true,
+			deriveCodeChallengeError: fmt.Errorf("code challenge derivation failed"),
+			expectedStatusCode:       http.StatusInternalServerError,
+			expectRedirect:           false,
+		},
+		{
+			name:               "fails when session save fails",
+			enablePKCE:         false,
+			sessionSaveError:   fmt.Errorf("session save failed"),
+			expectedStatusCode: http.StatusInternalServerError,
+			expectRedirect:     false,
+		},
+		{
+			name:                 "fails when redirect count exceeds limit",
+			enablePKCE:           false,
+			initialRedirectCount: 5,
+			expectedStatusCode:   http.StatusLoopDetected,
+			expectRedirect:       false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			logger := &mockLogger{}
+			session := newMockSession()
+			session.redirectCount = tt.initialRedirectCount
+			if tt.sessionSaveError != nil {
+				session.setSaveError(tt.sessionSaveError)
+			}
+
+			handler := createTestAuthHandler(logger, tt.enablePKCE, func() bool { return false }, func() bool { return false })
+
+			req := httptest.NewRequest("GET", "/test", nil)
+			rw := httptest.NewRecorder()
+
+			generateNonce := func() (string, error) {
+				if tt.generateNonceError != nil {
+					return "", tt.generateNonceError
+				}
+				return "test-nonce", nil
+			}
+
+			generateCodeVerifier := func() (string, error) {
+				if tt.generateCodeVerifierError != nil {
+					return "", tt.generateCodeVerifierError
+				}
+				return "test-code-verifier", nil
+			}
+
+			deriveCodeChallenge := func() (string, error) {
+				if tt.deriveCodeChallengeError != nil {
+					return "", tt.deriveCodeChallengeError
+				}
+				return "test-code-challenge", nil
+			}
+
+			handler.InitiateAuthentication(
+				rw, req, session,
+				"https://example.com/callback",
+				generateNonce,
+				generateCodeVerifier,
+				deriveCodeChallenge,
+			)
+
+			if rw.Code != tt.expectedStatusCode {
+				t.Errorf("Expected status code %d, got %d", tt.expectedStatusCode, rw.Code)
+			}
+
+			if tt.expectRedirect {
+				location := rw.Header().Get("Location")
+				if location == "" {
+					t.Error("Expected redirect location header, got empty")
+				}
+				if !strings.Contains(location, "https://provider.example.com/auth") {
+					t.Errorf("Expected redirect to auth URL, got %s", location)
+				}
+			}
+
+			// Verify error logs for failure cases
+			if tt.expectedStatusCode != http.StatusFound {
+				errorLogs := logger.getErrorLogs()
+				if len(errorLogs) == 0 {
+					t.Error("Expected error logs for failure case, got none")
+				}
+			}
+		})
+	}
+}
+
+func TestBuildAuthURL(t *testing.T) {
+	tests := []struct {
+		name           string
+		enablePKCE     bool
+		isGoogle       bool
+		isAzure        bool
+		scopes         []string
+		overrideScopes bool
+		codeChallenge  string
+		expectedParams map[string]string
+		expectContains []string
+	}{
+		{
+			name:          "builds URL without PKCE for standard provider",
+			enablePKCE:    false,
+			isGoogle:      false,
+			isAzure:       false,
+			scopes:        []string{"openid", "email"},
+			codeChallenge: "",
+			expectedParams: map[string]string{
+				"client_id":     "test-client-id",
+				"response_type": "code",
+				"state":         "test-state",
+				"nonce":         "test-nonce",
+				"scope":         "openid email offline_access",
+			},
+		},
+		{
+			name:          "builds URL with PKCE for standard provider",
+			enablePKCE:    true,
+			isGoogle:      false,
+			isAzure:       false,
+			scopes:        []string{"openid", "email"},
+			codeChallenge: "test-challenge",
+			expectedParams: map[string]string{
+				"client_id":             "test-client-id",
+				"response_type":         "code",
+				"state":                 "test-state",
+				"nonce":                 "test-nonce",
+				"code_challenge":        "test-challenge",
+				"code_challenge_method": "S256",
+				"scope":                 "openid email offline_access",
+			},
+		},
+		{
+			name:       "builds URL for Google provider",
+			enablePKCE: false,
+			isGoogle:   true,
+			isAzure:    false,
+			scopes:     []string{"openid", "email"},
+			expectedParams: map[string]string{
+				"client_id":     "test-client-id",
+				"response_type": "code",
+				"state":         "test-state",
+				"nonce":         "test-nonce",
+				"access_type":   "offline",
+				"prompt":        "consent",
+				"scope":         "openid email",
+			},
+		},
+		{
+			name:       "builds URL for Azure provider",
+			enablePKCE: false,
+			isGoogle:   false,
+			isAzure:    true,
+			scopes:     []string{"openid", "email"},
+			expectedParams: map[string]string{
+				"client_id":     "test-client-id",
+				"response_type": "code",
+				"state":         "test-state",
+				"nonce":         "test-nonce",
+				"response_mode": "query",
+				"scope":         "openid email offline_access",
+			},
+		},
+		{
+			name:           "handles scope override for Azure",
+			enablePKCE:     false,
+			isGoogle:       false,
+			isAzure:        true,
+			scopes:         []string{"custom-scope"},
+			overrideScopes: true,
+			expectedParams: map[string]string{
+				"client_id":     "test-client-id",
+				"response_type": "code",
+				"state":         "test-state",
+				"nonce":         "test-nonce",
+				"response_mode": "query",
+				"scope":         "custom-scope",
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			logger := &mockLogger{}
+			isGoogleFunc := func() bool { return tt.isGoogle }
+			isAzureFunc := func() bool { return tt.isAzure }
+
+			handler := NewAuthHandler(
+				logger,
+				tt.enablePKCE,
+				isGoogleFunc,
+				isAzureFunc,
+				"test-client-id",
+				"https://provider.example.com/auth",
+				"https://provider.example.com",
+				tt.scopes,
+				tt.overrideScopes,
+			)
+
+			authURL := handler.BuildAuthURL(
+				"https://example.com/callback",
+				"test-state",
+				"test-nonce",
+				tt.codeChallenge,
+			)
+
+			if authURL == "" {
+				t.Fatal("BuildAuthURL returned empty string")
+			}
+
+			parsedURL, err := url.Parse(authURL)
+			if err != nil {
+				t.Fatalf("Failed to parse auth URL: %v", err)
+			}
+
+			// Check base URL
+			expectedBase := "https://provider.example.com/auth"
+			actualBase := fmt.Sprintf("%s://%s%s", parsedURL.Scheme, parsedURL.Host, parsedURL.Path)
+			if actualBase != expectedBase {
+				t.Errorf("Expected base URL %s, got %s", expectedBase, actualBase)
+			}
+
+			// Check required parameters
+			query := parsedURL.Query()
+			for param, expectedValue := range tt.expectedParams {
+				actualValue := query.Get(param)
+				if actualValue != expectedValue {
+					t.Errorf("Expected %s=%s, got %s=%s", param, expectedValue, param, actualValue)
+				}
+			}
+
+			// Check that contains expected strings
+			for _, contains := range tt.expectContains {
+				if !strings.Contains(authURL, contains) {
+					t.Errorf("Expected URL to contain %s, got %s", contains, authURL)
+				}
+			}
+		})
+	}
+}
+
+func TestValidateURL(t *testing.T) {
+	logger := &mockLogger{}
+	handler := createTestAuthHandler(logger, false, func() bool { return false }, func() bool { return false })
+
+	tests := []struct {
+		name        string
+		url         string
+		expectError bool
+		errorMsg    string
+	}{
+		{
+			name:        "valid HTTPS URL",
+			url:         "https://example.com/path",
+			expectError: false,
+		},
+		{
+			name:        "valid HTTP URL",
+			url:         "http://example.com/path",
+			expectError: false,
+		},
+		{
+			name:        "empty URL",
+			url:         "",
+			expectError: true,
+			errorMsg:    "empty URL",
+		},
+		{
+			name:        "invalid scheme",
+			url:         "ftp://example.com/path",
+			expectError: true,
+			errorMsg:    "disallowed URL scheme",
+		},
+		{
+			name:        "missing host",
+			url:         "https:///path",
+			expectError: true,
+			errorMsg:    "missing host in URL",
+		},
+		{
+			name:        "localhost not allowed",
+			url:         "https://localhost/path",
+			expectError: true,
+			errorMsg:    "localhost access not allowed",
+		},
+		{
+			name:        "127.0.0.1 not allowed",
+			url:         "https://127.0.0.1/path",
+			expectError: true,
+			errorMsg:    "localhost access not allowed",
+		},
+		{
+			name:        "private IP not allowed",
+			url:         "https://192.168.1.1/path",
+			expectError: true,
+			errorMsg:    "private IP not allowed",
+		},
+		{
+			name:        "path traversal not allowed",
+			url:         "https://example.com/../path",
+			expectError: true,
+			errorMsg:    "path traversal detected",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := handler.validateURL(tt.url)
+
+			if tt.expectError {
+				if err == nil {
+					t.Errorf("Expected error for URL %s, got nil", tt.url)
+				} else if tt.errorMsg != "" && !strings.Contains(err.Error(), tt.errorMsg) {
+					t.Errorf("Expected error to contain %s, got %s", tt.errorMsg, err.Error())
+				}
+			} else {
+				if err != nil {
+					t.Errorf("Expected no error for URL %s, got %v", tt.url, err)
+				}
+			}
+		})
+	}
+}
+
+func TestValidateHost(t *testing.T) {
+	logger := &mockLogger{}
+	handler := createTestAuthHandler(logger, false, func() bool { return false }, func() bool { return false })
+
+	tests := []struct {
+		name        string
+		host        string
+		expectError bool
+		errorMsg    string
+	}{
+		{
+			name:        "valid domain",
+			host:        "example.com",
+			expectError: false,
+		},
+		{
+			name:        "valid domain with port",
+			host:        "example.com:443",
+			expectError: false,
+		},
+		{
+			name:        "empty host",
+			host:        "",
+			expectError: true,
+			errorMsg:    "empty host",
+		},
+		{
+			name:        "localhost",
+			host:        "localhost",
+			expectError: true,
+			errorMsg:    "localhost access not allowed",
+		},
+		{
+			name:        "localhost with port",
+			host:        "localhost:8080",
+			expectError: true,
+			errorMsg:    "localhost access not allowed",
+		},
+		{
+			name:        "127.0.0.1",
+			host:        "127.0.0.1",
+			expectError: true,
+			errorMsg:    "localhost access not allowed",
+		},
+		{
+			name:        "::1 (IPv6 localhost)",
+			host:        "::1",
+			expectError: true,
+			errorMsg:    "invalid host:port format",
+		},
+		{
+			name:        "private IP 192.168.1.1",
+			host:        "192.168.1.1",
+			expectError: true,
+			errorMsg:    "private IP not allowed",
+		},
+		{
+			name:        "private IP 10.0.0.1",
+			host:        "10.0.0.1",
+			expectError: true,
+			errorMsg:    "private IP not allowed",
+		},
+		{
+			name:        "invalid host:port format",
+			host:        "example.com:99999", // Use invalid port number instead
+			expectError: false,               // This actually doesn't error in Go's net.SplitHostPort
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := handler.validateHost(tt.host)
+
+			if tt.expectError {
+				if err == nil {
+					t.Errorf("Expected error for host %s, got nil", tt.host)
+				} else if tt.errorMsg != "" && !strings.Contains(err.Error(), tt.errorMsg) {
+					t.Errorf("Expected error to contain %s, got %s", tt.errorMsg, err.Error())
+				}
+			} else {
+				if err != nil {
+					t.Errorf("Expected no error for host %s, got %v", tt.host, err)
+				}
+			}
+		})
+	}
+}
+
+func TestBuildURLWithParams(t *testing.T) {
+	logger := &mockLogger{}
+	handler := NewAuthHandler(
+		logger,
+		false,
+		func() bool { return false },
+		func() bool { return false },
+		"test-client-id",
+		"https://provider.example.com/auth",
+		"https://provider.example.com",
+		[]string{"openid"},
+		false,
+	)
+
+	tests := []struct {
+		name        string
+		baseURL     string
+		params      url.Values
+		expected    string
+		expectError bool
+	}{
+		{
+			name:     "absolute HTTPS URL with params",
+			baseURL:  "https://example.com/auth",
+			params:   url.Values{"param1": []string{"value1"}, "param2": []string{"value2"}},
+			expected: "https://example.com/auth?param1=value1&param2=value2",
+		},
+		{
+			name:     "relative URL resolved against issuer",
+			baseURL:  "/auth/endpoint",
+			params:   url.Values{"client_id": []string{"test"}},
+			expected: "https://provider.example.com/auth/endpoint?client_id=test",
+		},
+		{
+			name:        "invalid absolute URL",
+			baseURL:     "https://localhost/auth",
+			params:      url.Values{},
+			expectError: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := handler.buildURLWithParams(tt.baseURL, tt.params)
+
+			if tt.expectError {
+				if result != "" {
+					t.Errorf("Expected empty result for invalid URL, got %s", result)
+				}
+			} else {
+				if result == "" {
+					t.Error("Expected non-empty result, got empty string")
+				}
+
+				// Parse and compare the result
+				resultURL, err := url.Parse(result)
+				if err != nil {
+					t.Fatalf("Failed to parse result URL: %v", err)
+				}
+
+				expectedURL, err := url.Parse(tt.expected)
+				if err != nil {
+					t.Fatalf("Failed to parse expected URL: %v", err)
+				}
+
+				if resultURL.Scheme != expectedURL.Scheme {
+					t.Errorf("Expected scheme %s, got %s", expectedURL.Scheme, resultURL.Scheme)
+				}
+				if resultURL.Host != expectedURL.Host {
+					t.Errorf("Expected host %s, got %s", expectedURL.Host, resultURL.Host)
+				}
+				if resultURL.Path != expectedURL.Path {
+					t.Errorf("Expected path %s, got %s", expectedURL.Path, resultURL.Path)
+				}
+
+				// Check query parameters
+				resultQuery := resultURL.Query()
+				expectedQuery := expectedURL.Query()
+				for key, expectedValues := range expectedQuery {
+					resultValues := resultQuery[key]
+					if len(resultValues) != len(expectedValues) {
+						t.Errorf("Expected %d values for %s, got %d", len(expectedValues), key, len(resultValues))
+					}
+					for i, expectedValue := range expectedValues {
+						if i >= len(resultValues) || resultValues[i] != expectedValue {
+							t.Errorf("Expected %s=%s, got %s=%s", key, expectedValue, key, resultValues[i])
+						}
+					}
+				}
+			}
+		})
+	}
+}
+
+func TestConcurrentAccess(t *testing.T) {
+	logger := &mockLogger{}
+	handler := createTestAuthHandler(logger, true, func() bool { return false }, func() bool { return false })
+
+	const numGoroutines = 10
+	const numRequests = 5
+
+	var wg sync.WaitGroup
+	errors := make(chan error, numGoroutines*numRequests)
+
+	for i := 0; i < numGoroutines; i++ {
+		wg.Add(1)
+		go func(id int) {
+			defer wg.Done()
+			for j := 0; j < numRequests; j++ {
+				session := newMockSession()
+				req := httptest.NewRequest("GET", fmt.Sprintf("/test-%d-%d", id, j), nil)
+				rw := httptest.NewRecorder()
+
+				generateNonce := func() (string, error) {
+					return fmt.Sprintf("nonce-%d-%d", id, j), nil
+				}
+				generateCodeVerifier := func() (string, error) {
+					return fmt.Sprintf("verifier-%d-%d", id, j), nil
+				}
+				deriveCodeChallenge := func() (string, error) {
+					return fmt.Sprintf("challenge-%d-%d", id, j), nil
+				}
+
+				handler.InitiateAuthentication(
+					rw, req, session,
+					"https://example.com/callback",
+					generateNonce,
+					generateCodeVerifier,
+					deriveCodeChallenge,
+				)
+
+				if rw.Code != http.StatusFound {
+					errors <- fmt.Errorf("goroutine %d request %d: expected status %d, got %d",
+						id, j, http.StatusFound, rw.Code)
+				}
+			}
+		}(i)
+	}
+
+	wg.Wait()
+	close(errors)
+
+	var errorCount int
+	for err := range errors {
+		t.Error(err)
+		errorCount++
+	}
+
+	if errorCount > 0 {
+		t.Errorf("Found %d errors in concurrent access test", errorCount)
+	}
+}
+
+// Benchmark tests
+func BenchmarkInitiateAuthentication(b *testing.B) {
+	logger := &mockLogger{}
+	handler := createTestAuthHandler(logger, true, func() bool { return false }, func() bool { return false })
+
+	generateNonce := func() (string, error) { return "test-nonce", nil }
+	generateCodeVerifier := func() (string, error) { return "test-verifier", nil }
+	deriveCodeChallenge := func() (string, error) { return "test-challenge", nil }
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		session := newMockSession()
+		req := httptest.NewRequest("GET", "/test", nil)
+		rw := httptest.NewRecorder()
+
+		handler.InitiateAuthentication(
+			rw, req, session,
+			"https://example.com/callback",
+			generateNonce,
+			generateCodeVerifier,
+			deriveCodeChallenge,
+		)
+	}
+}
+
+func BenchmarkBuildAuthURL(b *testing.B) {
+	logger := &mockLogger{}
+	handler := createTestAuthHandler(logger, true, func() bool { return false }, func() bool { return false })
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		handler.BuildAuthURL(
+			"https://example.com/callback",
+			"test-state",
+			"test-nonce",
+			"test-challenge",
+		)
+	}
+}
+
+func BenchmarkValidateURL(b *testing.B) {
+	logger := &mockLogger{}
+	handler := createTestAuthHandler(logger, false, func() bool { return false }, func() bool { return false })
+
+	testURLs := []string{
+		"https://example.com/auth",
+		"https://provider.example.com/oauth/authorize",
+		"https://login.microsoftonline.com/tenant/oauth2/v2.0/authorize",
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		handler.validateURL(testURLs[i%len(testURLs)])
+	}
+}

cache_manager.go

@@ -0,0 +1,151 @@
+// Package traefikoidc provides OIDC authentication middleware for Traefik.
+package traefikoidc
+
+import (
+	"sync"
+	"time"
+)
+
+const (
+	defaultBlacklistDuration = 24 * time.Hour
+	defaultMaxBlacklistSize  = 10000
+)
+
+var (
+	globalCacheManager *CacheManager
+	cacheManagerOnce   sync.Once
+	cacheManagerMutex  sync.RWMutex
+)
+
+// CacheManager manages all caching components for the OIDC middleware.
+// It provides thread-safe access to token blacklist, token cache, metadata cache,
+// and JWK cache. This centralizes cache management to ensure efficient memory
+// usage and consistent cache behavior across the application.
+type CacheManager struct {
+	tokenBlacklist CacheInterface
+	tokenCache     *TokenCache
+	metadataCache  *MetadataCache
+	jwkCache       JWKCacheInterface
+	mu             sync.RWMutex
+}
+
+// GetGlobalCacheManager returns a singleton instance of CacheManager.
+// It initializes all cache components on first call and reuses the same instance
+// for subsequent calls. This ensures consistent cache state and efficient memory
+// usage across the entire application lifecycle.
+// Parameters:
+//   - wg: WaitGroup for coordinating cache cleanup during shutdown.
+//
+// Returns:
+//   - The global CacheManager instance.
+func GetGlobalCacheManager(wg *sync.WaitGroup) *CacheManager {
+	cacheManagerOnce.Do(func() {
+		globalCacheManager = &CacheManager{
+			tokenBlacklist: func() CacheInterface {
+				config := DefaultUnifiedCacheConfig()
+				config.MaxSize = defaultMaxBlacklistSize
+				c := NewUnifiedCache(config)
+				return NewCacheAdapter(c)
+			}(),
+			tokenCache:    NewTokenCache(),
+			metadataCache: NewMetadataCache(wg),
+			jwkCache:      &JWKCache{},
+		}
+	})
+	return globalCacheManager
+}
+
+// GetSharedTokenBlacklist returns the shared token blacklist cache.
+// This cache stores revoked or expired tokens to prevent replay attacks.
+// Access is protected by read lock to ensure thread safety.
+// Returns:
+//   - The shared token blacklist CacheInterface instance.
+func (cm *CacheManager) GetSharedTokenBlacklist() CacheInterface {
+	cm.mu.RLock()
+	defer cm.mu.RUnlock()
+	return cm.tokenBlacklist
+}
+
+// GetSharedTokenCache returns the shared token cache for verified tokens.
+// This cache stores claims from successfully verified tokens to avoid
+// repeated verification of the same tokens.
+// Access is protected by read lock to ensure thread safety.
+// Returns:
+//   - The shared TokenCache instance.
+func (cm *CacheManager) GetSharedTokenCache() *TokenCache {
+	cm.mu.RLock()
+	defer cm.mu.RUnlock()
+	return cm.tokenCache
+}
+
+// GetSharedMetadataCache returns the shared metadata cache.
+// This cache stores OIDC provider metadata (endpoints, keys) to avoid
+// repeated requests to the provider's .well-known configuration endpoint.
+// Access is protected by read lock to ensure thread safety.
+// Returns:
+//   - The shared MetadataCache instance.
+func (cm *CacheManager) GetSharedMetadataCache() *MetadataCache {
+	cm.mu.RLock()
+	defer cm.mu.RUnlock()
+	return cm.metadataCache
+}
+
+// GetSharedJWKCache returns the shared JWK (JSON Web Key) cache.
+// This cache stores public keys from the provider's JWKS endpoint
+// for token signature verification.
+// Access is protected by read lock to ensure thread safety.
+// Returns:
+//   - The shared JWKCacheInterface instance.
+func (cm *CacheManager) GetSharedJWKCache() JWKCacheInterface {
+	cm.mu.RLock()
+	defer cm.mu.RUnlock()
+	return cm.jwkCache
+}
+
+// Close gracefully shuts down all cache components and releases resources.
+// It closes all individual caches and cleans up their associated goroutines.
+// This method should be called when the middleware is shutting down.
+// Safe to call multiple times.
+// Returns:
+//   - An error if any cache fails to close properly, nil otherwise.
+func (cm *CacheManager) Close() error {
+	cm.mu.Lock()
+	defer cm.mu.Unlock()
+
+	if cm.tokenBlacklist != nil {
+		cm.tokenBlacklist.Close()
+		cm.tokenBlacklist = nil
+	}
+	if cm.tokenCache != nil {
+		cm.tokenCache.Close()
+		cm.tokenCache = nil
+	}
+	if cm.metadataCache != nil {
+		cm.metadataCache.Close()
+		cm.metadataCache = nil
+	}
+	if cm.jwkCache != nil {
+		cm.jwkCache.Close()
+		cm.jwkCache = nil
+	}
+
+	return nil
+}
+
+// CleanupGlobalCacheManager cleans up the global cache manager instance.
+// It closes all cache components but does NOT reset the singleton for re-initialization
+// to avoid race conditions with sync.Once. It's safe to call multiple times.
+// Returns:
+//   - An error if cache cleanup fails, nil otherwise.
+func CleanupGlobalCacheManager() error {
+	cacheManagerMutex.Lock()
+	defer cacheManagerMutex.Unlock()
+
+	if globalCacheManager != nil {
+		err := globalCacheManager.Close()
+		// Don't reset globalCacheManager to nil or cacheManagerOnce to avoid race conditions
+		// The cache manager remains closed and the Close() method handles multiple calls
+		return err
+	}
+	return nil
+}

circuit_breaker/circuit_breaker.go

@@ -0,0 +1,319 @@
+// Package circuit_breaker provides circuit breaker implementation for resilience
+package circuit_breaker
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// CircuitBreakerState represents the current state of a circuit breaker.
+// The circuit breaker pattern prevents cascading failures by monitoring
+// error rates and temporarily blocking requests to failing services.
+type CircuitBreakerState int
+
+// Circuit breaker states following the standard pattern:
+// Closed: Normal operation, requests flow through
+// Open: Circuit is tripped, requests are blocked
+// HalfOpen: Testing state, limited requests allowed to test recovery
+const (
+	// CircuitBreakerClosed allows all requests through (normal operation)
+	CircuitBreakerClosed CircuitBreakerState = iota
+	// CircuitBreakerOpen blocks all requests (service is failing)
+	CircuitBreakerOpen
+	// CircuitBreakerHalfOpen allows limited requests to test service recovery
+	CircuitBreakerHalfOpen
+)
+
+// String returns a string representation of the circuit breaker state
+func (s CircuitBreakerState) String() string {
+	switch s {
+	case CircuitBreakerClosed:
+		return "closed"
+	case CircuitBreakerOpen:
+		return "open"
+	case CircuitBreakerHalfOpen:
+		return "half-open"
+	default:
+		return "unknown"
+	}
+}
+
+// Logger interface for dependency injection
+type Logger interface {
+	Infof(format string, args ...interface{})
+	Errorf(format string, args ...interface{})
+	Debugf(format string, args ...interface{})
+}
+
+// BaseRecoveryMechanism interface for common functionality
+type BaseRecoveryMechanism interface {
+	RecordRequest()
+	RecordSuccess()
+	RecordFailure()
+	GetBaseMetrics() map[string]interface{}
+	LogInfo(format string, args ...interface{})
+	LogError(format string, args ...interface{})
+	LogDebug(format string, args ...interface{})
+}
+
+// CircuitBreaker implements the circuit breaker pattern for external service calls.
+// It monitors failure rates and automatically opens the circuit when failures
+// exceed the threshold, preventing further requests until the service recovers.
+type CircuitBreaker struct {
+	// baseRecovery provides common functionality
+	baseRecovery BaseRecoveryMechanism
+	// maxFailures is the threshold for opening the circuit
+	maxFailures int
+	// timeout is how long to wait before allowing requests in half-open state
+	timeout time.Duration
+	// resetTimeout is how long to wait before transitioning from open to half-open
+	resetTimeout time.Duration
+	// state tracks the current circuit breaker state
+	state CircuitBreakerState
+	// failures counts consecutive failures
+	failures int64
+	// lastFailureTime records when the last failure occurred
+	lastFailureTime time.Time
+	// mutex protects shared state
+	mutex sync.RWMutex
+	// logger for debugging and monitoring
+	logger Logger
+}
+
+// CircuitBreakerConfig holds configuration parameters for circuit breakers.
+// These settings control when the circuit opens and how it recovers.
+type CircuitBreakerConfig struct {
+	// MaxFailures is the number of failures before opening the circuit
+	MaxFailures int `json:"max_failures"`
+	// Timeout is how long to wait before trying to recover (open -> half-open)
+	Timeout time.Duration `json:"timeout"`
+	// ResetTimeout is how long to wait before fully closing the circuit
+	ResetTimeout time.Duration `json:"reset_timeout"`
+}
+
+// DefaultCircuitBreakerConfig returns sensible default configuration for circuit breakers.
+// Configured for typical web service scenarios with moderate tolerance for failures.
+func DefaultCircuitBreakerConfig() CircuitBreakerConfig {
+	return CircuitBreakerConfig{
+		MaxFailures:  2,
+		Timeout:      60 * time.Second,
+		ResetTimeout: 30 * time.Second,
+	}
+}
+
+// NewCircuitBreaker creates a new circuit breaker with the specified configuration.
+// The circuit breaker starts in the closed state, allowing all requests through.
+func NewCircuitBreaker(config CircuitBreakerConfig, logger Logger, baseRecovery BaseRecoveryMechanism) *CircuitBreaker {
+	return &CircuitBreaker{
+		baseRecovery: baseRecovery,
+		maxFailures:  config.MaxFailures,
+		timeout:      config.Timeout,
+		resetTimeout: config.ResetTimeout,
+		state:        CircuitBreakerClosed,
+		logger:       logger,
+	}
+}
+
+// ExecuteWithContext executes a function through the circuit breaker with context.
+// It checks if requests are allowed, executes the function, and updates the circuit state
+// based on the result. Implements the ErrorRecoveryMechanism interface.
+func (cb *CircuitBreaker) ExecuteWithContext(ctx context.Context, fn func() error) error {
+	if cb.baseRecovery != nil {
+		cb.baseRecovery.RecordRequest()
+	}
+
+	if !cb.allowRequest() {
+		return fmt.Errorf("circuit breaker is open")
+	}
+
+	err := fn()
+	if err != nil {
+		cb.recordFailure()
+		if cb.baseRecovery != nil {
+			cb.baseRecovery.RecordFailure()
+		}
+		return err
+	}
+
+	cb.recordSuccess()
+	if cb.baseRecovery != nil {
+		cb.baseRecovery.RecordSuccess()
+	}
+	return nil
+}
+
+// Execute executes a function through the circuit breaker without context.
+// This is provided for backward compatibility with existing code.
+func (cb *CircuitBreaker) Execute(fn func() error) error {
+	return cb.ExecuteWithContext(context.Background(), fn)
+}
+
+// allowRequest determines whether to allow a request based on the circuit state.
+// Handles state transitions from open to half-open based on timeout.
+func (cb *CircuitBreaker) allowRequest() bool {
+	cb.mutex.Lock()
+	defer cb.mutex.Unlock()
+
+	now := time.Now()
+
+	switch cb.state {
+	case CircuitBreakerClosed:
+		return true
+
+	case CircuitBreakerOpen:
+		if now.Sub(cb.lastFailureTime) > cb.timeout {
+			cb.state = CircuitBreakerHalfOpen
+			if cb.logger != nil {
+				cb.logger.Infof("Circuit breaker transitioning to half-open state")
+			}
+			return true
+		}
+		return false
+
+	case CircuitBreakerHalfOpen:
+		return true
+
+	default:
+		return false
+	}
+}
+
+// recordFailure records a failure and potentially opens the circuit.
+// Updates failure count and triggers state transitions when thresholds are exceeded.
+func (cb *CircuitBreaker) recordFailure() {
+	cb.mutex.Lock()
+	defer cb.mutex.Unlock()
+
+	cb.failures++
+	cb.lastFailureTime = time.Now()
+
+	switch cb.state {
+	case CircuitBreakerClosed:
+		if cb.failures >= int64(cb.maxFailures) {
+			cb.state = CircuitBreakerOpen
+			if cb.baseRecovery != nil {
+				cb.baseRecovery.LogError("Circuit breaker opened after %d failures", cb.failures)
+			}
+		}
+
+	case CircuitBreakerHalfOpen:
+		cb.state = CircuitBreakerOpen
+		if cb.baseRecovery != nil {
+			cb.baseRecovery.LogError("Circuit breaker returned to open state after failure in half-open")
+		}
+	}
+}
+
+// recordSuccess records a successful request and potentially closes the circuit.
+// Resets failure count and transitions from half-open to closed state on success.
+func (cb *CircuitBreaker) recordSuccess() {
+	cb.mutex.Lock()
+	defer cb.mutex.Unlock()
+
+	switch cb.state {
+	case CircuitBreakerHalfOpen:
+		cb.failures = 0
+		cb.state = CircuitBreakerClosed
+		if cb.baseRecovery != nil {
+			cb.baseRecovery.LogInfo("Circuit breaker closed after successful request in half-open state")
+		}
+
+	case CircuitBreakerClosed:
+		cb.failures = 0
+	}
+}
+
+// GetState returns the current state of the circuit breaker.
+// Thread-safe method for monitoring circuit breaker status.
+func (cb *CircuitBreaker) GetState() CircuitBreakerState {
+	cb.mutex.RLock()
+	defer cb.mutex.RUnlock()
+	return cb.state
+}
+
+// Reset resets the circuit breaker to its initial closed state.
+// Clears failure count and state, effectively recovering from any open state.
+func (cb *CircuitBreaker) Reset() {
+	cb.mutex.Lock()
+	defer cb.mutex.Unlock()
+
+	cb.state = CircuitBreakerClosed
+	atomic.StoreInt64(&cb.failures, 0)
+	if cb.baseRecovery != nil {
+		cb.baseRecovery.LogInfo("Circuit breaker has been reset")
+	}
+}
+
+// IsAvailable returns whether the circuit breaker is currently allowing requests.
+// This provides a quick way to check if the service is available.
+func (cb *CircuitBreaker) IsAvailable() bool {
+	return cb.allowRequest()
+}
+
+// GetMetrics returns comprehensive metrics about the circuit breaker.
+// Includes state information, failure counts, configuration, and base metrics.
+func (cb *CircuitBreaker) GetMetrics() map[string]interface{} {
+	cb.mutex.RLock()
+	state := cb.state
+	failures := cb.failures
+	lastFailureTime := cb.lastFailureTime
+	cb.mutex.RUnlock()
+
+	var metrics map[string]interface{}
+	if cb.baseRecovery != nil {
+		metrics = cb.baseRecovery.GetBaseMetrics()
+	} else {
+		metrics = make(map[string]interface{})
+	}
+
+	metrics["state"] = state.String()
+	metrics["current_failures"] = failures
+	metrics["max_failures"] = cb.maxFailures
+	metrics["timeout"] = cb.timeout.String()
+	metrics["reset_timeout"] = cb.resetTimeout.String()
+
+	if !lastFailureTime.IsZero() {
+		metrics["last_failure_time"] = lastFailureTime
+		metrics["time_since_last_failure"] = time.Since(lastFailureTime).String()
+	}
+
+	return metrics
+}
+
+// GetFailureCount returns the current failure count
+func (cb *CircuitBreaker) GetFailureCount() int64 {
+	cb.mutex.RLock()
+	defer cb.mutex.RUnlock()
+	return cb.failures
+}
+
+// GetLastFailureTime returns the time of the last failure
+func (cb *CircuitBreaker) GetLastFailureTime() time.Time {
+	cb.mutex.RLock()
+	defer cb.mutex.RUnlock()
+	return cb.lastFailureTime
+}
+
+// IsOpen returns true if the circuit breaker is in open state
+func (cb *CircuitBreaker) IsOpen() bool {
+	cb.mutex.RLock()
+	defer cb.mutex.RUnlock()
+	return cb.state == CircuitBreakerOpen
+}
+
+// IsClosed returns true if the circuit breaker is in closed state
+func (cb *CircuitBreaker) IsClosed() bool {
+	cb.mutex.RLock()
+	defer cb.mutex.RUnlock()
+	return cb.state == CircuitBreakerClosed
+}
+
+// IsHalfOpen returns true if the circuit breaker is in half-open state
+func (cb *CircuitBreaker) IsHalfOpen() bool {
+	cb.mutex.RLock()
+	defer cb.mutex.RUnlock()
+	return cb.state == CircuitBreakerHalfOpen
+}

circuit_breaker/circuit_breaker_test.go

@@ -0,0 +1,981 @@
+package circuit_breaker
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+// Mock implementations for testing
+type mockLogger struct {
+	infoLogs  []string
+	errorLogs []string
+	debugLogs []string
+	mu        sync.RWMutex
+}
+
+func (m *mockLogger) Infof(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.infoLogs = append(m.infoLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockLogger) Errorf(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.errorLogs = append(m.errorLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockLogger) Debugf(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.debugLogs = append(m.debugLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockLogger) getInfoLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.infoLogs))
+	copy(result, m.infoLogs)
+	return result
+}
+
+//lint:ignore U1000 May be needed for future error log verification tests
+func (m *mockLogger) getErrorLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.errorLogs))
+	copy(result, m.errorLogs)
+	return result
+}
+
+//lint:ignore U1000 May be needed for future test isolation
+func (m *mockLogger) reset() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.infoLogs = nil
+	m.errorLogs = nil
+	m.debugLogs = nil
+}
+
+type mockBaseRecoveryMechanism struct {
+	requestCount int64
+	successCount int64
+	failureCount int64
+	infoLogs     []string
+	errorLogs    []string
+	debugLogs    []string
+	baseMetrics  map[string]interface{}
+	mu           sync.RWMutex
+}
+
+func newMockBaseRecovery() *mockBaseRecoveryMechanism {
+	return &mockBaseRecoveryMechanism{
+		baseMetrics: make(map[string]interface{}),
+	}
+}
+
+func (m *mockBaseRecoveryMechanism) RecordRequest() {
+	atomic.AddInt64(&m.requestCount, 1)
+}
+
+func (m *mockBaseRecoveryMechanism) RecordSuccess() {
+	atomic.AddInt64(&m.successCount, 1)
+}
+
+func (m *mockBaseRecoveryMechanism) RecordFailure() {
+	atomic.AddInt64(&m.failureCount, 1)
+}
+
+func (m *mockBaseRecoveryMechanism) GetBaseMetrics() map[string]interface{} {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	result := make(map[string]interface{})
+	for k, v := range m.baseMetrics {
+		result[k] = v
+	}
+	result["total_requests"] = atomic.LoadInt64(&m.requestCount)
+	result["total_successes"] = atomic.LoadInt64(&m.successCount)
+	result["total_failures"] = atomic.LoadInt64(&m.failureCount)
+	return result
+}
+
+func (m *mockBaseRecoveryMechanism) LogInfo(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.infoLogs = append(m.infoLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockBaseRecoveryMechanism) LogError(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.errorLogs = append(m.errorLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockBaseRecoveryMechanism) LogDebug(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.debugLogs = append(m.debugLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockBaseRecoveryMechanism) getRequestCount() int64 {
+	return atomic.LoadInt64(&m.requestCount)
+}
+
+func (m *mockBaseRecoveryMechanism) getSuccessCount() int64 {
+	return atomic.LoadInt64(&m.successCount)
+}
+
+func (m *mockBaseRecoveryMechanism) getFailureCount() int64 {
+	return atomic.LoadInt64(&m.failureCount)
+}
+
+func (m *mockBaseRecoveryMechanism) getInfoLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.infoLogs))
+	copy(result, m.infoLogs)
+	return result
+}
+
+func (m *mockBaseRecoveryMechanism) getErrorLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.errorLogs))
+	copy(result, m.errorLogs)
+	return result
+}
+
+func TestCircuitBreakerState_String(t *testing.T) {
+	tests := []struct {
+		state    CircuitBreakerState
+		expected string
+	}{
+		{CircuitBreakerClosed, "closed"},
+		{CircuitBreakerOpen, "open"},
+		{CircuitBreakerHalfOpen, "half-open"},
+		{CircuitBreakerState(999), "unknown"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.expected, func(t *testing.T) {
+			result := tt.state.String()
+			if result != tt.expected {
+				t.Errorf("Expected %s, got %s", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestDefaultCircuitBreakerConfig(t *testing.T) {
+	config := DefaultCircuitBreakerConfig()
+
+	if config.MaxFailures != 2 {
+		t.Errorf("Expected MaxFailures to be 2, got %d", config.MaxFailures)
+	}
+
+	if config.Timeout != 60*time.Second {
+		t.Errorf("Expected Timeout to be 60s, got %v", config.Timeout)
+	}
+
+	if config.ResetTimeout != 30*time.Second {
+		t.Errorf("Expected ResetTimeout to be 30s, got %v", config.ResetTimeout)
+	}
+}
+
+func TestNewCircuitBreaker(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  3,
+		Timeout:      30 * time.Second,
+		ResetTimeout: 15 * time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	if cb == nil {
+		t.Fatal("NewCircuitBreaker returned nil")
+	}
+
+	if cb.maxFailures != 3 {
+		t.Errorf("Expected maxFailures to be 3, got %d", cb.maxFailures)
+	}
+
+	if cb.timeout != 30*time.Second {
+		t.Errorf("Expected timeout to be 30s, got %v", cb.timeout)
+	}
+
+	if cb.resetTimeout != 15*time.Second {
+		t.Errorf("Expected resetTimeout to be 15s, got %v", cb.resetTimeout)
+	}
+
+	if cb.state != CircuitBreakerClosed {
+		t.Errorf("Expected initial state to be Closed, got %v", cb.state)
+	}
+
+	if cb.logger != logger {
+		t.Error("Expected logger to be set")
+	}
+
+	if cb.baseRecovery != baseRecovery {
+		t.Error("Expected baseRecovery to be set")
+	}
+}
+
+func TestCircuitBreaker_ExecuteWithContext_Success(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  2,
+		Timeout:      time.Second,
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	callCount := 0
+	testFunc := func() error {
+		callCount++
+		return nil
+	}
+
+	ctx := context.Background()
+	err := cb.ExecuteWithContext(ctx, testFunc)
+
+	if err != nil {
+		t.Errorf("Expected no error, got %v", err)
+	}
+
+	if callCount != 1 {
+		t.Errorf("Expected function to be called once, got %d", callCount)
+	}
+
+	if cb.GetState() != CircuitBreakerClosed {
+		t.Errorf("Expected state to remain Closed, got %v", cb.GetState())
+	}
+
+	if baseRecovery.getRequestCount() != 1 {
+		t.Errorf("Expected 1 request recorded, got %d", baseRecovery.getRequestCount())
+	}
+
+	if baseRecovery.getSuccessCount() != 1 {
+		t.Errorf("Expected 1 success recorded, got %d", baseRecovery.getSuccessCount())
+	}
+}
+
+func TestCircuitBreaker_ExecuteWithContext_Failure(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  2,
+		Timeout:      time.Second,
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	testError := fmt.Errorf("test error")
+	testFunc := func() error {
+		return testError
+	}
+
+	ctx := context.Background()
+	err := cb.ExecuteWithContext(ctx, testFunc)
+
+	if err != testError {
+		t.Errorf("Expected test error, got %v", err)
+	}
+
+	if cb.GetState() != CircuitBreakerClosed {
+		t.Errorf("Expected state to remain Closed after single failure, got %v", cb.GetState())
+	}
+
+	if baseRecovery.getRequestCount() != 1 {
+		t.Errorf("Expected 1 request recorded, got %d", baseRecovery.getRequestCount())
+	}
+
+	if baseRecovery.getFailureCount() != 1 {
+		t.Errorf("Expected 1 failure recorded, got %d", baseRecovery.getFailureCount())
+	}
+}
+
+func TestCircuitBreaker_Execute(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  1,
+		Timeout:      time.Second,
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	callCount := 0
+	testFunc := func() error {
+		callCount++
+		return nil
+	}
+
+	err := cb.Execute(testFunc)
+
+	if err != nil {
+		t.Errorf("Expected no error, got %v", err)
+	}
+
+	if callCount != 1 {
+		t.Errorf("Expected function to be called once, got %d", callCount)
+	}
+}
+
+func TestCircuitBreaker_OpenAfterMaxFailures(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  2,
+		Timeout:      time.Second,
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	testError := fmt.Errorf("test error")
+	testFunc := func() error {
+		return testError
+	}
+
+	ctx := context.Background()
+
+	// First failure
+	err := cb.ExecuteWithContext(ctx, testFunc)
+	if err != testError {
+		t.Errorf("Expected test error on first failure, got %v", err)
+	}
+	if cb.GetState() != CircuitBreakerClosed {
+		t.Errorf("Expected state to remain Closed after first failure, got %v", cb.GetState())
+	}
+
+	// Second failure - should open circuit
+	err = cb.ExecuteWithContext(ctx, testFunc)
+	if err != testError {
+		t.Errorf("Expected test error on second failure, got %v", err)
+	}
+	if cb.GetState() != CircuitBreakerOpen {
+		t.Errorf("Expected state to be Open after max failures, got %v", cb.GetState())
+	}
+
+	// Third attempt - should be blocked
+	callCount := 0
+	blockedFunc := func() error {
+		callCount++
+		return nil
+	}
+	err = cb.ExecuteWithContext(ctx, blockedFunc)
+	if err == nil {
+		t.Error("Expected error when circuit is open")
+	}
+	if callCount != 0 {
+		t.Errorf("Expected function not to be called when circuit is open, got %d calls", callCount)
+	}
+}
+
+func TestCircuitBreaker_HalfOpenTransition(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  1,
+		Timeout:      10 * time.Millisecond, // Very short for testing
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	// Trigger circuit opening
+	testError := fmt.Errorf("test error")
+	err := cb.ExecuteWithContext(context.Background(), func() error {
+		return testError
+	})
+	if err != testError {
+		t.Errorf("Expected test error, got %v", err)
+	}
+	if cb.GetState() != CircuitBreakerOpen {
+		t.Errorf("Expected state to be Open, got %v", cb.GetState())
+	}
+
+	// Wait for timeout
+	time.Sleep(15 * time.Millisecond)
+
+	// Next request should transition to half-open
+	callCount := 0
+	testFunc := func() error {
+		callCount++
+		return nil
+	}
+
+	err = cb.ExecuteWithContext(context.Background(), testFunc)
+	if err != nil {
+		t.Errorf("Expected no error in half-open state, got %v", err)
+	}
+	if callCount != 1 {
+		t.Errorf("Expected function to be called in half-open state, got %d calls", callCount)
+	}
+	if cb.GetState() != CircuitBreakerClosed {
+		t.Errorf("Expected state to be Closed after successful half-open request, got %v", cb.GetState())
+	}
+}
+
+func TestCircuitBreaker_HalfOpenFailureReturnsToOpen(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  1,
+		Timeout:      10 * time.Millisecond,
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	// Trigger circuit opening
+	testError := fmt.Errorf("test error")
+	_ = cb.ExecuteWithContext(context.Background(), func() error {
+		return testError
+	})
+	if cb.GetState() != CircuitBreakerOpen {
+		t.Errorf("Expected state to be Open, got %v", cb.GetState())
+	}
+
+	// Wait for timeout to allow half-open transition
+	time.Sleep(15 * time.Millisecond)
+
+	// First call should transition to half-open, but we'll force it by checking allowRequest
+	if !cb.allowRequest() {
+		t.Error("Expected allowRequest to return true after timeout")
+	}
+	if cb.GetState() != CircuitBreakerHalfOpen {
+		t.Errorf("Expected state to be HalfOpen, got %v", cb.GetState())
+	}
+
+	// Failure in half-open should return to open
+	err := cb.ExecuteWithContext(context.Background(), func() error {
+		return testError
+	})
+	if err != testError {
+		t.Errorf("Expected test error, got %v", err)
+	}
+	if cb.GetState() != CircuitBreakerOpen {
+		t.Errorf("Expected state to return to Open after half-open failure, got %v", cb.GetState())
+	}
+}
+
+func TestCircuitBreaker_Reset(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  1,
+		Timeout:      time.Second,
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	// Trigger circuit opening
+	testError := fmt.Errorf("test error")
+	_ = cb.ExecuteWithContext(context.Background(), func() error {
+		return testError
+	})
+	if cb.GetState() != CircuitBreakerOpen {
+		t.Errorf("Expected state to be Open, got %v", cb.GetState())
+	}
+
+	// Reset circuit
+	cb.Reset()
+
+	if cb.GetState() != CircuitBreakerClosed {
+		t.Errorf("Expected state to be Closed after reset, got %v", cb.GetState())
+	}
+
+	if cb.GetFailureCount() != 0 {
+		t.Errorf("Expected failure count to be 0 after reset, got %d", cb.GetFailureCount())
+	}
+
+	// Should allow requests again
+	callCount := 0
+	err := cb.ExecuteWithContext(context.Background(), func() error {
+		callCount++
+		return nil
+	})
+	if err != nil {
+		t.Errorf("Expected no error after reset, got %v", err)
+	}
+	if callCount != 1 {
+		t.Errorf("Expected function to be called after reset, got %d calls", callCount)
+	}
+}
+
+func TestCircuitBreaker_IsAvailable(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  1,
+		Timeout:      10 * time.Millisecond,
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	// Initially available
+	if !cb.IsAvailable() {
+		t.Error("Expected circuit breaker to be available initially")
+	}
+
+	// Trigger opening
+	testError := fmt.Errorf("test error")
+	cb.ExecuteWithContext(context.Background(), func() error {
+		return testError
+	})
+
+	// Should not be available when open
+	if cb.IsAvailable() {
+		t.Error("Expected circuit breaker to be unavailable when open")
+	}
+
+	// Wait for timeout
+	time.Sleep(15 * time.Millisecond)
+
+	// Should be available again after timeout (half-open)
+	if !cb.IsAvailable() {
+		t.Error("Expected circuit breaker to be available after timeout")
+	}
+}
+
+func TestCircuitBreaker_StateCheckers(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  1,
+		Timeout:      10 * time.Millisecond,
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	// Initially closed
+	if !cb.IsClosed() {
+		t.Error("Expected circuit breaker to be closed initially")
+	}
+	if cb.IsOpen() {
+		t.Error("Expected circuit breaker not to be open initially")
+	}
+	if cb.IsHalfOpen() {
+		t.Error("Expected circuit breaker not to be half-open initially")
+	}
+
+	// Trigger opening
+	testError := fmt.Errorf("test error")
+	cb.ExecuteWithContext(context.Background(), func() error {
+		return testError
+	})
+
+	// Should be open
+	if cb.IsClosed() {
+		t.Error("Expected circuit breaker not to be closed when open")
+	}
+	if !cb.IsOpen() {
+		t.Error("Expected circuit breaker to be open")
+	}
+	if cb.IsHalfOpen() {
+		t.Error("Expected circuit breaker not to be half-open when open")
+	}
+
+	// Wait for timeout and trigger half-open
+	time.Sleep(15 * time.Millisecond)
+	cb.allowRequest() // This will transition to half-open
+
+	// Should be half-open
+	if cb.IsClosed() {
+		t.Error("Expected circuit breaker not to be closed when half-open")
+	}
+	if cb.IsOpen() {
+		t.Error("Expected circuit breaker not to be open when half-open")
+	}
+	if !cb.IsHalfOpen() {
+		t.Error("Expected circuit breaker to be half-open")
+	}
+}
+
+func TestCircuitBreaker_GetMetrics(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  2,
+		Timeout:      30 * time.Second,
+		ResetTimeout: 15 * time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	baseRecovery.baseMetrics["custom_metric"] = "custom_value"
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	// Record some activity
+	testError := fmt.Errorf("test error")
+	cb.ExecuteWithContext(context.Background(), func() error {
+		return testError
+	})
+
+	metrics := cb.GetMetrics()
+
+	// Check circuit breaker specific metrics
+	if metrics["state"] != "closed" {
+		t.Errorf("Expected state to be 'closed', got %v", metrics["state"])
+	}
+
+	if metrics["current_failures"] != int64(1) {
+		t.Errorf("Expected current_failures to be 1, got %v", metrics["current_failures"])
+	}
+
+	if metrics["max_failures"] != 2 {
+		t.Errorf("Expected max_failures to be 2, got %v", metrics["max_failures"])
+	}
+
+	if metrics["timeout"] != "30s" {
+		t.Errorf("Expected timeout to be '30s', got %v", metrics["timeout"])
+	}
+
+	if metrics["reset_timeout"] != "15s" {
+		t.Errorf("Expected reset_timeout to be '15s', got %v", metrics["reset_timeout"])
+	}
+
+	// Check base metrics are included
+	if metrics["total_requests"] != int64(1) {
+		t.Errorf("Expected total_requests to be 1, got %v", metrics["total_requests"])
+	}
+
+	if metrics["custom_metric"] != "custom_value" {
+		t.Errorf("Expected custom_metric to be 'custom_value', got %v", metrics["custom_metric"])
+	}
+
+	// Check failure time metrics
+	if _, exists := metrics["last_failure_time"]; !exists {
+		t.Error("Expected last_failure_time to exist")
+	}
+
+	if _, exists := metrics["time_since_last_failure"]; !exists {
+		t.Error("Expected time_since_last_failure to exist")
+	}
+}
+
+func TestCircuitBreaker_GetMetrics_NoBaseRecovery(t *testing.T) {
+	config := DefaultCircuitBreakerConfig()
+	logger := &mockLogger{}
+	cb := NewCircuitBreaker(config, logger, nil)
+
+	metrics := cb.GetMetrics()
+
+	// Should still have circuit breaker metrics
+	if metrics["state"] != "closed" {
+		t.Errorf("Expected state to be 'closed', got %v", metrics["state"])
+	}
+
+	if metrics["max_failures"] != 2 {
+		t.Errorf("Expected max_failures to be 2, got %v", metrics["max_failures"])
+	}
+
+	// Should not have base metrics
+	if _, exists := metrics["total_requests"]; exists {
+		t.Error("Expected total_requests not to exist without base recovery")
+	}
+}
+
+func TestCircuitBreaker_GetLastFailureTime(t *testing.T) {
+	config := DefaultCircuitBreakerConfig()
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	// Initially should be zero
+	if !cb.GetLastFailureTime().IsZero() {
+		t.Error("Expected last failure time to be zero initially")
+	}
+
+	// Record a failure
+	before := time.Now()
+	testError := fmt.Errorf("test error")
+	cb.ExecuteWithContext(context.Background(), func() error {
+		return testError
+	})
+	after := time.Now()
+
+	lastFailure := cb.GetLastFailureTime()
+	if lastFailure.IsZero() {
+		t.Error("Expected last failure time to be set after failure")
+	}
+
+	if lastFailure.Before(before) || lastFailure.After(after) {
+		t.Errorf("Expected last failure time to be between %v and %v, got %v",
+			before, after, lastFailure)
+	}
+}
+
+func TestCircuitBreaker_ExecuteWithoutBaseRecovery(t *testing.T) {
+	config := DefaultCircuitBreakerConfig()
+	logger := &mockLogger{}
+	cb := NewCircuitBreaker(config, logger, nil)
+
+	callCount := 0
+	testFunc := func() error {
+		callCount++
+		return nil
+	}
+
+	err := cb.ExecuteWithContext(context.Background(), testFunc)
+
+	if err != nil {
+		t.Errorf("Expected no error, got %v", err)
+	}
+
+	if callCount != 1 {
+		t.Errorf("Expected function to be called once, got %d", callCount)
+	}
+
+	// Should work fine without base recovery
+	if cb.GetState() != CircuitBreakerClosed {
+		t.Errorf("Expected state to be Closed, got %v", cb.GetState())
+	}
+}
+
+func TestCircuitBreaker_ConcurrentAccess(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  10, // Higher threshold for concurrent test
+		Timeout:      100 * time.Millisecond,
+		ResetTimeout: 50 * time.Millisecond,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	const numGoroutines = 10
+	const numOperations = 50
+
+	var wg sync.WaitGroup
+	successCount := int64(0)
+	errorCount := int64(0)
+
+	for i := 0; i < numGoroutines; i++ {
+		wg.Add(1)
+		go func(id int) {
+			defer wg.Done()
+			for j := 0; j < numOperations; j++ {
+				err := cb.ExecuteWithContext(context.Background(), func() error {
+					// Simulate some failures
+					if j%10 == 9 { // Every 10th operation fails
+						return fmt.Errorf("simulated error")
+					}
+					return nil
+				})
+
+				if err != nil {
+					atomic.AddInt64(&errorCount, 1)
+				} else {
+					atomic.AddInt64(&successCount, 1)
+				}
+
+				// Intermittently check state and metrics
+				if j%5 == 0 {
+					cb.GetState()
+					cb.GetMetrics()
+					cb.IsAvailable()
+				}
+			}
+		}(i)
+	}
+
+	wg.Wait()
+
+	// Verify we got both successes and errors
+	finalSuccessCount := atomic.LoadInt64(&successCount)
+	finalErrorCount := atomic.LoadInt64(&errorCount)
+
+	if finalSuccessCount == 0 {
+		t.Error("Expected some successful operations")
+	}
+
+	if finalErrorCount == 0 {
+		t.Error("Expected some failed operations")
+	}
+
+	totalOperations := finalSuccessCount + finalErrorCount
+	expectedMax := int64(numGoroutines * numOperations)
+
+	if totalOperations > expectedMax {
+		t.Errorf("Expected at most %d operations, got %d", expectedMax, totalOperations)
+	}
+
+	t.Logf("Concurrent test completed: %d successes, %d errors, final state: %v",
+		finalSuccessCount, finalErrorCount, cb.GetState())
+}
+
+func TestCircuitBreaker_StateTransitionLogging(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  1,
+		Timeout:      10 * time.Millisecond,
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	// Trigger circuit opening
+	testError := fmt.Errorf("test error")
+	cb.ExecuteWithContext(context.Background(), func() error {
+		return testError
+	})
+
+	// Check that error was logged when circuit opened
+	errorLogs := baseRecovery.getErrorLogs()
+	if len(errorLogs) == 0 {
+		t.Error("Expected error log when circuit breaker opened")
+	} else {
+		if !contains(errorLogs, "Circuit breaker opened after") {
+			t.Errorf("Expected circuit opening log, got %v", errorLogs)
+		}
+	}
+
+	// Wait and trigger half-open
+	time.Sleep(15 * time.Millisecond)
+
+	// Successful request should close circuit and log
+	cb.ExecuteWithContext(context.Background(), func() error {
+		return nil
+	})
+
+	// Check that success was logged when circuit closed
+	infoLogs := baseRecovery.getInfoLogs()
+	if len(infoLogs) == 0 {
+		t.Error("Expected info log when circuit breaker closed")
+	} else {
+		if !contains(infoLogs, "Circuit breaker closed after successful request") {
+			t.Errorf("Expected circuit closing log, got %v", infoLogs)
+		}
+	}
+
+	// Reset should also be logged
+	cb.Reset()
+	infoLogs = baseRecovery.getInfoLogs()
+	if !contains(infoLogs, "Circuit breaker has been reset") {
+		t.Errorf("Expected reset log, got %v", infoLogs)
+	}
+}
+
+func TestCircuitBreaker_LoggerTransitionLogging(t *testing.T) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  1,
+		Timeout:      10 * time.Millisecond,
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	// Wait for timeout and check half-open transition logging
+	testError := fmt.Errorf("test error")
+	cb.ExecuteWithContext(context.Background(), func() error {
+		return testError
+	})
+
+	// Wait for timeout
+	time.Sleep(15 * time.Millisecond)
+
+	// Next allowRequest call should log transition to half-open
+	cb.allowRequest()
+
+	infoLogs := logger.getInfoLogs()
+	if len(infoLogs) == 0 {
+		t.Error("Expected info log for half-open transition")
+	} else {
+		if !contains(infoLogs, "Circuit breaker transitioning to half-open state") {
+			t.Errorf("Expected half-open transition log, got %v", infoLogs)
+		}
+	}
+}
+
+// Helper function to check if a slice contains a string with substring
+func contains(slice []string, substr string) bool {
+	for _, s := range slice {
+		if len(s) >= len(substr) && s[:len(substr)] == substr {
+			return true
+		}
+	}
+	return false
+}
+
+// Benchmark tests
+func BenchmarkCircuitBreaker_ExecuteWithContext_Success(b *testing.B) {
+	config := DefaultCircuitBreakerConfig()
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	testFunc := func() error {
+		return nil
+	}
+
+	ctx := context.Background()
+
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			cb.ExecuteWithContext(ctx, testFunc)
+		}
+	})
+}
+
+func BenchmarkCircuitBreaker_ExecuteWithContext_Failure(b *testing.B) {
+	config := CircuitBreakerConfig{
+		MaxFailures:  1000, // High threshold to avoid opening during benchmark
+		Timeout:      time.Second,
+		ResetTimeout: time.Second,
+	}
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	testError := fmt.Errorf("test error")
+	testFunc := func() error {
+		return testError
+	}
+
+	ctx := context.Background()
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		cb.ExecuteWithContext(ctx, testFunc)
+	}
+}
+
+func BenchmarkCircuitBreaker_GetState(b *testing.B) {
+	config := DefaultCircuitBreakerConfig()
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			cb.GetState()
+		}
+	})
+}
+
+func BenchmarkCircuitBreaker_GetMetrics(b *testing.B) {
+	config := DefaultCircuitBreakerConfig()
+	logger := &mockLogger{}
+	baseRecovery := newMockBaseRecovery()
+	cb := NewCircuitBreaker(config, logger, baseRecovery)
+
+	// Add some activity
+	for i := 0; i < 100; i++ {
+		if i%2 == 0 {
+			cb.ExecuteWithContext(context.Background(), func() error { return nil })
+		} else {
+			cb.ExecuteWithContext(context.Background(), func() error { return fmt.Errorf("error") })
+		}
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		cb.GetMetrics()
+	}
+}

config/settings.go

@@ -0,0 +1,209 @@
+// Package config provides configuration management for the OIDC middleware
+package config
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+)
+
+const (
+	minEncryptionKeyLength = 16
+	ConstSessionTimeout    = 86400
+)
+
+//lint:ignore U1000 May be referenced for default exclusion patterns
+var defaultExcludedURLs = map[string]struct{}{
+	"/favicon.ico":  {},
+	"/robots.txt":   {},
+	"/health":       {},
+	"/.well-known/": {},
+	"/metrics":      {},
+	"/ping":         {},
+	"/api/":         {},
+	"/static/":      {},
+	"/assets/":      {},
+	"/js/":          {},
+	"/css/":         {},
+	"/images/":      {},
+	"/fonts/":       {},
+}
+
+// Settings manages configuration and initialization for the OIDC middleware
+type Settings struct {
+	logger Logger
+}
+
+// Logger interface for dependency injection
+type Logger interface {
+	Debug(msg string)
+	Debugf(format string, args ...interface{})
+	Info(msg string)
+	Infof(format string, args ...interface{})
+	Error(msg string)
+	Errorf(format string, args ...interface{})
+}
+
+// Config represents the configuration for the OIDC middleware
+type Config struct {
+	ProviderURL               string         `json:"providerUrl"`
+	ClientID                  string         `json:"clientId"`
+	ClientSecret              string         `json:"clientSecret"`
+	CallbackURL               string         `json:"callbackUrl"`
+	LogoutURL                 string         `json:"logoutUrl"`
+	PostLogoutRedirectURI     string         `json:"postLogoutRedirectUri"`
+	SessionEncryptionKey      string         `json:"sessionEncryptionKey"`
+	ForceHTTPS                bool           `json:"forceHttps"`
+	LogLevel                  string         `json:"logLevel"`
+	Scopes                    []string       `json:"scopes"`
+	OverrideScopes            bool           `json:"overrideScopes"`
+	AllowedUsers              []string       `json:"allowedUsers"`
+	AllowedUserDomains        []string       `json:"allowedUserDomains"`
+	AllowedRolesAndGroups     []string       `json:"allowedRolesAndGroups"`
+	ExcludedURLs              []string       `json:"excludedUrls"`
+	EnablePKCE                bool           `json:"enablePkce"`
+	RateLimit                 int            `json:"rateLimit"`
+	RefreshGracePeriodSeconds int            `json:"refreshGracePeriodSeconds"`
+	Headers                   []HeaderConfig `json:"headers"`
+	HTTPClient                *http.Client   `json:"-"`
+	CookieDomain              string         `json:"cookieDomain"`
+}
+
+// HeaderConfig represents header template configuration
+type HeaderConfig struct {
+	Name  string `json:"name"`
+	Value string `json:"value"`
+}
+
+// NewSettings creates a new Settings instance
+func NewSettings(logger Logger) *Settings {
+	return &Settings{
+		logger: logger,
+	}
+}
+
+// CreateConfig creates a default configuration
+func CreateConfig() *Config {
+	return &Config{
+		LogLevel:                  "INFO",
+		ForceHTTPS:                true,
+		EnablePKCE:                true,
+		RateLimit:                 10,
+		RefreshGracePeriodSeconds: 60,
+	}
+}
+
+// InitializeTraefikOidc would initialize and configure a new TraefikOidc instance
+// This functionality has been moved to the main New function in main.go
+// This function is kept for compatibility but should not be used
+func (s *Settings) InitializeTraefikOidc(ctx context.Context, next http.Handler, config *Config, name string) (interface{}, error) {
+	return nil, fmt.Errorf("InitializeTraefikOidc is deprecated - use New function from main package instead")
+}
+
+//lint:ignore U1000 Kept for backward compatibility
+func (s *Settings) setupHeaderTemplates(t interface{}, config *Config, logger Logger) error {
+	logger.Debug("setupHeaderTemplates is deprecated")
+	return nil
+}
+
+//lint:ignore U1000 May be needed for future background service management
+func (s *Settings) startBackgroundServices(ctx context.Context, logger Logger) {
+	startReplayCacheCleanup(ctx, logger)
+
+	// Start memory monitoring for leak detection and performance insights
+	memoryMonitor := GetGlobalMemoryMonitor()
+	memoryMonitor.StartMonitoring(ctx, 60*time.Second) // Monitor every minute
+	logger.Debug("Started global memory monitoring")
+}
+
+// Utility functions
+
+//lint:ignore U1000 May be needed for future scope processing
+func deduplicateScopes(scopes []string) []string {
+	seen := make(map[string]bool)
+	result := []string{}
+	for _, scope := range scopes {
+		if !seen[scope] {
+			seen[scope] = true
+			result = append(result, scope)
+		}
+	}
+	return result
+}
+
+//lint:ignore U1000 May be needed for future scope merging operations
+func mergeScopes(defaultScopes, userScopes []string) []string {
+	result := make([]string, len(defaultScopes))
+	copy(result, defaultScopes)
+	return append(result, userScopes...)
+}
+
+//lint:ignore U1000 May be needed for future utility operations
+func createStringMap(items []string) map[string]struct{} {
+	result := make(map[string]struct{})
+	for _, item := range items {
+		result[item] = struct{}{}
+	}
+	return result
+}
+
+//lint:ignore U1000 May be needed for future case-insensitive operations
+func createCaseInsensitiveStringMap(items []string) map[string]struct{} {
+	result := make(map[string]struct{})
+	for _, item := range items {
+		result[strings.ToLower(item)] = struct{}{}
+	}
+	return result
+}
+
+//lint:ignore U1000 May be needed for future test environment detection
+func isTestMode() bool {
+	// This function should be implemented based on environment detection logic
+	return false
+}
+
+// External dependencies that need to be provided
+// TraefikOidc struct is defined in types.go
+
+// These functions need to be provided by external packages
+func NewLogger(level string) Logger                                          { return nil }
+func CreateDefaultHTTPClient() *http.Client                                  { return nil }
+func CreateTokenHTTPClient() *http.Client                                    { return nil }
+func GetGlobalCacheManager(*sync.WaitGroup) CacheManager                     { return nil }
+func NewSessionManager(string, bool, string, Logger) (SessionManager, error) { return nil, nil }
+func NewErrorRecoveryManager(Logger) ErrorRecoveryManager                    { return nil }
+
+//lint:ignore U1000 May be needed for future token claim extraction
+func extractClaims(string) (map[string]interface{}, error) { return nil, nil }
+
+//lint:ignore U1000 May be needed for future replay attack prevention
+func startReplayCacheCleanup(context.Context, Logger) {}
+func GetGlobalMemoryMonitor() MemoryMonitor           { return nil }
+
+// Interfaces for external dependencies
+type CacheManager interface {
+	GetSharedTokenBlacklist() CacheInterface
+	GetSharedTokenCache() *TokenCache
+	GetSharedMetadataCache() *MetadataCache
+	GetSharedJWKCache() JWKCacheInterface
+	Close() error
+}
+type SessionManager interface{}
+type ErrorRecoveryManager interface{}
+type MemoryMonitor interface {
+	StartMonitoring(ctx context.Context, interval time.Duration)
+}
+type CacheInterface interface {
+	Set(key string, value interface{}, ttl time.Duration)
+	Get(key string) (interface{}, bool)
+	Delete(key string)
+	SetMaxSize(size int)
+	Cleanup()
+	Close()
+}
+type TokenCache struct{}
+type MetadataCache struct{}
+type JWKCacheInterface interface{}

handlers/oauth_handler.go

@@ -0,0 +1,276 @@
+// Package handlers provides HTTP request handlers for the OIDC middleware.
+package handlers
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+// OAuthHandler handles OAuth callback requests
+type OAuthHandler struct {
+	logger                Logger
+	sessionManager        SessionManager
+	tokenExchanger        TokenExchanger
+	tokenVerifier         TokenVerifier
+	extractClaimsFunc     func(tokenString string) (map[string]interface{}, error)
+	isAllowedDomainFunc   func(email string) bool
+	redirURLPath          string
+	sendErrorResponseFunc func(rw http.ResponseWriter, req *http.Request, message string, code int)
+}
+
+// Logger interface for dependency injection
+type Logger interface {
+	Debugf(format string, args ...interface{})
+	Errorf(format string, args ...interface{})
+	Error(msg string)
+}
+
+// SessionManager interface for session operations
+type SessionManager interface {
+	GetSession(req *http.Request) (SessionData, error)
+}
+
+// SessionData interface for session data operations
+type SessionData interface {
+	GetCSRF() string
+	GetNonce() string
+	GetCodeVerifier() string
+	GetIncomingPath() string
+	GetAuthenticated() bool
+	SetAuthenticated(bool) error
+	SetEmail(string)
+	SetIDToken(string)
+	SetAccessToken(string)
+	SetRefreshToken(string)
+	SetCSRF(string)
+	SetNonce(string)
+	SetCodeVerifier(string)
+	SetIncomingPath(string)
+	ResetRedirectCount()
+	Save(req *http.Request, rw http.ResponseWriter) error
+	returnToPoolSafely()
+}
+
+// TokenExchanger interface for token operations
+type TokenExchanger interface {
+	ExchangeCodeForToken(ctx context.Context, grantType string, codeOrToken string, redirectURL string, codeVerifier string) (*TokenResponse, error)
+}
+
+// TokenVerifier interface for token verification
+type TokenVerifier interface {
+	VerifyToken(token string) error
+}
+
+// TokenResponse represents the response from token exchange
+type TokenResponse struct {
+	IDToken      string
+	AccessToken  string
+	RefreshToken string
+}
+
+// NewOAuthHandler creates a new OAuth handler
+func NewOAuthHandler(logger Logger, sessionManager SessionManager, tokenExchanger TokenExchanger,
+	tokenVerifier TokenVerifier, extractClaimsFunc func(string) (map[string]interface{}, error),
+	isAllowedDomainFunc func(string) bool, redirURLPath string,
+	sendErrorResponseFunc func(http.ResponseWriter, *http.Request, string, int)) *OAuthHandler {
+
+	return &OAuthHandler{
+		logger:                logger,
+		sessionManager:        sessionManager,
+		tokenExchanger:        tokenExchanger,
+		tokenVerifier:         tokenVerifier,
+		extractClaimsFunc:     extractClaimsFunc,
+		isAllowedDomainFunc:   isAllowedDomainFunc,
+		redirURLPath:          redirURLPath,
+		sendErrorResponseFunc: sendErrorResponseFunc,
+	}
+}
+
+// HandleCallback handles OAuth callback requests
+func (h *OAuthHandler) HandleCallback(rw http.ResponseWriter, req *http.Request, redirectURL string) {
+	session, err := h.sessionManager.GetSession(req)
+	if err != nil {
+		h.logger.Errorf("Session error during callback: %v", err)
+		h.sendErrorResponseFunc(rw, req, "Session error during callback", http.StatusInternalServerError)
+		return
+	}
+	defer session.returnToPoolSafely()
+
+	h.logger.Debugf("Handling callback, URL: %s", req.URL.String())
+
+	if req.URL.Query().Get("error") != "" {
+		errorDescription := req.URL.Query().Get("error_description")
+		if errorDescription == "" {
+			errorDescription = req.URL.Query().Get("error")
+		}
+		h.logger.Errorf("Authentication error from provider during callback: %s - %s", req.URL.Query().Get("error"), errorDescription)
+		h.sendErrorResponseFunc(rw, req, fmt.Sprintf("Authentication error from provider: %s", errorDescription), http.StatusBadRequest)
+		return
+	}
+
+	state := req.URL.Query().Get("state")
+	if state == "" {
+		h.logger.Error("No state in callback")
+		h.sendErrorResponseFunc(rw, req, "State parameter missing in callback", http.StatusBadRequest)
+		return
+	}
+
+	csrfToken := session.GetCSRF()
+	if csrfToken == "" {
+		h.logger.Errorf("CSRF token missing in session during callback. Authenticated: %v, Request URL: %s",
+			session.GetAuthenticated(), req.URL.String())
+
+		cookie, err := req.Cookie("_oidc_raczylo_m")
+		if err != nil {
+			h.logger.Errorf("Main session cookie not found in request: %v", err)
+		} else {
+			h.logger.Errorf("Main session cookie exists but CSRF token is empty. Cookie value length: %d", len(cookie.Value))
+		}
+
+		h.sendErrorResponseFunc(rw, req, "CSRF token missing in session", http.StatusBadRequest)
+		return
+	}
+
+	if state != csrfToken {
+		h.logger.Error("State parameter does not match CSRF token in session during callback")
+		h.sendErrorResponseFunc(rw, req, "Invalid state parameter (CSRF mismatch)", http.StatusBadRequest)
+		return
+	}
+
+	code := req.URL.Query().Get("code")
+	if code == "" {
+		h.logger.Error("No code in callback")
+		h.sendErrorResponseFunc(rw, req, "No authorization code received in callback", http.StatusBadRequest)
+		return
+	}
+
+	codeVerifier := session.GetCodeVerifier()
+
+	tokenResponse, err := h.tokenExchanger.ExchangeCodeForToken(req.Context(), "authorization_code", code, redirectURL, codeVerifier)
+	if err != nil {
+		h.logger.Errorf("Failed to exchange code for token during callback: %v", err)
+		h.sendErrorResponseFunc(rw, req, "Authentication failed: Could not exchange code for token", http.StatusInternalServerError)
+		return
+	}
+
+	if err = h.tokenVerifier.VerifyToken(tokenResponse.IDToken); err != nil {
+		h.logger.Errorf("Failed to verify id_token during callback: %v", err)
+		h.sendErrorResponseFunc(rw, req, "Authentication failed: Could not verify ID token", http.StatusInternalServerError)
+		return
+	}
+
+	claims, err := h.extractClaimsFunc(tokenResponse.IDToken)
+	if err != nil {
+		h.logger.Errorf("Failed to extract claims during callback: %v", err)
+		h.sendErrorResponseFunc(rw, req, "Authentication failed: Could not extract claims from token", http.StatusInternalServerError)
+		return
+	}
+
+	nonceClaim, ok := claims["nonce"].(string)
+	if !ok || nonceClaim == "" {
+		h.logger.Error("Nonce claim missing in id_token during callback")
+		h.sendErrorResponseFunc(rw, req, "Authentication failed: Nonce missing in token", http.StatusInternalServerError)
+		return
+	}
+
+	sessionNonce := session.GetNonce()
+	if sessionNonce == "" {
+		h.logger.Error("Nonce not found in session during callback")
+		h.sendErrorResponseFunc(rw, req, "Authentication failed: Nonce missing in session", http.StatusInternalServerError)
+		return
+	}
+
+	if nonceClaim != sessionNonce {
+		h.logger.Error("Nonce claim does not match session nonce during callback")
+		h.sendErrorResponseFunc(rw, req, "Authentication failed: Nonce mismatch", http.StatusInternalServerError)
+		return
+	}
+
+	email, _ := claims["email"].(string)
+	if email == "" {
+		h.logger.Errorf("Email claim missing or empty in token during callback")
+		h.sendErrorResponseFunc(rw, req, "Authentication failed: Email missing in token", http.StatusInternalServerError)
+		return
+	}
+	if !h.isAllowedDomainFunc(email) {
+		h.logger.Errorf("Disallowed email domain during callback: %s", email)
+		h.sendErrorResponseFunc(rw, req, "Authentication failed: Email domain not allowed", http.StatusForbidden)
+		return
+	}
+
+	if err := session.SetAuthenticated(true); err != nil {
+		h.logger.Errorf("Failed to set authenticated state and regenerate session ID: %v", err)
+		h.sendErrorResponseFunc(rw, req, "Failed to update session", http.StatusInternalServerError)
+		return
+	}
+	session.SetEmail(email)
+	session.SetIDToken(tokenResponse.IDToken)
+	session.SetAccessToken(tokenResponse.AccessToken)
+	session.SetRefreshToken(tokenResponse.RefreshToken)
+
+	session.SetCSRF("")
+	session.SetNonce("")
+	session.SetCodeVerifier("")
+
+	session.ResetRedirectCount()
+
+	redirectPath := "/"
+	if incomingPath := session.GetIncomingPath(); incomingPath != "" && incomingPath != h.redirURLPath {
+		redirectPath = incomingPath
+	}
+	session.SetIncomingPath("")
+
+	if err := session.Save(req, rw); err != nil {
+		h.logger.Errorf("Failed to save session after callback: %v", err)
+		h.sendErrorResponseFunc(rw, req, "Failed to save session after callback", http.StatusInternalServerError)
+		return
+	}
+
+	h.logger.Debugf("Callback successful, redirecting to %s", redirectPath)
+	http.Redirect(rw, req, redirectPath, http.StatusFound)
+}
+
+// URLHelper provides utility methods for URL operations
+type URLHelper struct {
+	logger Logger
+}
+
+// NewURLHelper creates a new URL helper
+func NewURLHelper(logger Logger) *URLHelper {
+	return &URLHelper{logger: logger}
+}
+
+// DetermineExcludedURL checks if a URL path should bypass OIDC authentication.
+// It compares the request path against configured excluded URL prefixes.
+func (h *URLHelper) DetermineExcludedURL(currentRequest string, excludedURLs map[string]struct{}) bool {
+	for excludedURL := range excludedURLs {
+		if strings.HasPrefix(currentRequest, excludedURL) {
+			h.logger.Debugf("URL is excluded - got %s / excluded hit: %s", currentRequest, excludedURL)
+			return true
+		}
+	}
+	return false
+}
+
+// DetermineScheme determines the URL scheme for building redirect URLs.
+// It checks X-Forwarded-Proto header first, then TLS presence.
+func (h *URLHelper) DetermineScheme(req *http.Request) string {
+	if scheme := req.Header.Get("X-Forwarded-Proto"); scheme != "" {
+		return scheme
+	}
+	if req.TLS != nil {
+		return "https"
+	}
+	return "http"
+}
+
+// DetermineHost determines the host for building redirect URLs.
+// It checks X-Forwarded-Host header first, then falls back to req.Host.
+func (h *URLHelper) DetermineHost(req *http.Request) string {
+	if host := req.Header.Get("X-Forwarded-Host"); host != "" {
+		return host
+	}
+	return req.Host
+}

handlers/oauth_handler_test.go

@@ -0,0 +1,983 @@
+package handlers
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+)
+
+// Mock implementations for testing
+type mockLogger struct {
+	debugLogs []string
+	errorLogs []string
+	mu        sync.RWMutex
+}
+
+func (m *mockLogger) Debugf(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.debugLogs = append(m.debugLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockLogger) Errorf(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.errorLogs = append(m.errorLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockLogger) Error(msg string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.errorLogs = append(m.errorLogs, msg)
+}
+
+//lint:ignore U1000 May be needed for future debug log verification tests
+func (m *mockLogger) getDebugLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.debugLogs))
+	copy(result, m.debugLogs)
+	return result
+}
+
+//lint:ignore U1000 May be needed for future error log verification tests
+func (m *mockLogger) getErrorLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.errorLogs))
+	copy(result, m.errorLogs)
+	return result
+}
+
+//lint:ignore U1000 May be needed for future test isolation
+func (m *mockLogger) reset() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.debugLogs = nil
+	m.errorLogs = nil
+}
+
+type mockSessionManager struct {
+	sessionData  *mockSessionData
+	sessionError error
+	mu           sync.RWMutex
+}
+
+func (m *mockSessionManager) GetSession(req *http.Request) (SessionData, error) {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	if m.sessionError != nil {
+		return nil, m.sessionError
+	}
+	return m.sessionData, nil
+}
+
+func (m *mockSessionManager) setSessionError(err error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.sessionError = err
+}
+
+type mockSessionData struct {
+	csrf          string
+	nonce         string
+	codeVerifier  string
+	incomingPath  string
+	authenticated bool
+	email         string
+	idToken       string
+	accessToken   string
+	refreshToken  string
+	saveError     error
+	setAuthError  error
+	mu            sync.RWMutex
+	returned      bool
+}
+
+func newMockSessionData() *mockSessionData {
+	return &mockSessionData{
+		csrf:          "test-csrf-token",
+		nonce:         "test-nonce",
+		codeVerifier:  "test-code-verifier",
+		incomingPath:  "/original/path",
+		authenticated: false,
+	}
+}
+
+func (m *mockSessionData) GetCSRF() string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.csrf
+}
+
+func (m *mockSessionData) GetNonce() string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.nonce
+}
+
+func (m *mockSessionData) GetCodeVerifier() string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.codeVerifier
+}
+
+func (m *mockSessionData) GetIncomingPath() string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.incomingPath
+}
+
+func (m *mockSessionData) GetAuthenticated() bool {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.authenticated
+}
+
+func (m *mockSessionData) SetAuthenticated(auth bool) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.setAuthError != nil {
+		return m.setAuthError
+	}
+	m.authenticated = auth
+	return nil
+}
+
+func (m *mockSessionData) SetEmail(email string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.email = email
+}
+
+func (m *mockSessionData) SetIDToken(token string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.idToken = token
+}
+
+func (m *mockSessionData) SetAccessToken(token string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.accessToken = token
+}
+
+func (m *mockSessionData) SetRefreshToken(token string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.refreshToken = token
+}
+
+func (m *mockSessionData) SetCSRF(csrf string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.csrf = csrf
+}
+
+func (m *mockSessionData) SetNonce(nonce string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.nonce = nonce
+}
+
+func (m *mockSessionData) SetCodeVerifier(verifier string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.codeVerifier = verifier
+}
+
+func (m *mockSessionData) SetIncomingPath(path string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.incomingPath = path
+}
+
+func (m *mockSessionData) ResetRedirectCount() {
+	// Mock implementation
+}
+
+func (m *mockSessionData) Save(req *http.Request, rw http.ResponseWriter) error {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.saveError
+}
+
+func (m *mockSessionData) returnToPoolSafely() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.returned = true
+}
+
+func (m *mockSessionData) setSaveError(err error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.saveError = err
+}
+
+func (m *mockSessionData) setSetAuthError(err error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.setAuthError = err
+}
+
+type mockTokenExchanger struct {
+	tokenResponse *TokenResponse
+	exchangeError error
+	mu            sync.RWMutex
+}
+
+func (m *mockTokenExchanger) ExchangeCodeForToken(ctx context.Context, grantType string, codeOrToken string, redirectURL string, codeVerifier string) (*TokenResponse, error) {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	if m.exchangeError != nil {
+		return nil, m.exchangeError
+	}
+	return m.tokenResponse, nil
+}
+
+//lint:ignore U1000 May be needed for future token exchange tests
+func (m *mockTokenExchanger) setTokenResponse(response *TokenResponse) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.tokenResponse = response
+}
+
+func (m *mockTokenExchanger) setExchangeError(err error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.exchangeError = err
+}
+
+type mockTokenVerifier struct {
+	verifyError error
+}
+
+func (m *mockTokenVerifier) VerifyToken(token string) error {
+	return m.verifyError
+}
+
+// Test helper functions
+func createTestOAuthHandler() *OAuthHandler {
+	logger := &mockLogger{}
+	sessionManager := &mockSessionManager{sessionData: newMockSessionData()}
+	tokenExchanger := &mockTokenExchanger{
+		tokenResponse: &TokenResponse{
+			IDToken:      "test.id.token",
+			AccessToken:  "test-access-token",
+			RefreshToken: "test-refresh-token",
+		},
+	}
+	tokenVerifier := &mockTokenVerifier{}
+
+	extractClaimsFunc := func(tokenString string) (map[string]interface{}, error) {
+		return map[string]interface{}{
+			"nonce": "test-nonce",
+			"email": "[email protected]",
+			"sub":   "test-user-id",
+		}, nil
+	}
+
+	isAllowedDomainFunc := func(email string) bool {
+		return strings.HasSuffix(email, "@example.com")
+	}
+
+	sendErrorResponseFunc := func(rw http.ResponseWriter, req *http.Request, message string, code int) {
+		http.Error(rw, message, code)
+	}
+
+	return NewOAuthHandler(logger, sessionManager, tokenExchanger, tokenVerifier,
+		extractClaimsFunc, isAllowedDomainFunc, "/auth/callback", sendErrorResponseFunc)
+}
+
+func TestNewOAuthHandler(t *testing.T) {
+	handler := createTestOAuthHandler()
+
+	if handler == nil {
+		t.Fatal("NewOAuthHandler returned nil")
+	}
+
+	if handler.logger == nil {
+		t.Error("Expected logger to be set")
+	}
+
+	if handler.sessionManager == nil {
+		t.Error("Expected sessionManager to be set")
+	}
+
+	if handler.tokenExchanger == nil {
+		t.Error("Expected tokenExchanger to be set")
+	}
+
+	if handler.redirURLPath != "/auth/callback" {
+		t.Errorf("Expected redirURLPath to be '/auth/callback', got %s", handler.redirURLPath)
+	}
+}
+
+func TestHandleCallback_Success(t *testing.T) {
+	handler := createTestOAuthHandler()
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusFound {
+		t.Errorf("Expected status %d, got %d", http.StatusFound, rw.Code)
+	}
+
+	location := rw.Header().Get("Location")
+	if location != "/original/path" {
+		t.Errorf("Expected redirect to '/original/path', got %s", location)
+	}
+
+	sessionData := handler.sessionManager.(*mockSessionManager).sessionData
+	if sessionData.email != "[email protected]" {
+		t.Errorf("Expected email to be set to '[email protected]', got %s", sessionData.email)
+	}
+
+	if !sessionData.authenticated {
+		t.Error("Expected session to be authenticated")
+	}
+}
+
+func TestHandleCallback_SessionError(t *testing.T) {
+	handler := createTestOAuthHandler()
+	sessionManager := handler.sessionManager.(*mockSessionManager)
+	sessionManager.setSessionError(fmt.Errorf("session error"))
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", http.StatusInternalServerError, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Session error during callback") {
+		t.Errorf("Expected session error message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_AuthError(t *testing.T) {
+	handler := createTestOAuthHandler()
+
+	req := httptest.NewRequest("GET", "/auth/callback?error=access_denied&error_description=User+denied+access", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusBadRequest {
+		t.Errorf("Expected status %d, got %d", http.StatusBadRequest, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "User denied access") {
+		t.Errorf("Expected error description in response, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_MissingState(t *testing.T) {
+	handler := createTestOAuthHandler()
+
+	req := httptest.NewRequest("GET", "/auth/callback?code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusBadRequest {
+		t.Errorf("Expected status %d, got %d", http.StatusBadRequest, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "State parameter missing") {
+		t.Errorf("Expected state missing message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_MissingCSRFToken(t *testing.T) {
+	handler := createTestOAuthHandler()
+	sessionData := handler.sessionManager.(*mockSessionManager).sessionData
+	sessionData.csrf = "" // Clear CSRF token
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusBadRequest {
+		t.Errorf("Expected status %d, got %d", http.StatusBadRequest, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "CSRF token missing in session") {
+		t.Errorf("Expected CSRF missing message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_CSRFMismatch(t *testing.T) {
+	handler := createTestOAuthHandler()
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=wrong-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusBadRequest {
+		t.Errorf("Expected status %d, got %d", http.StatusBadRequest, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "CSRF mismatch") {
+		t.Errorf("Expected CSRF mismatch message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_MissingCode(t *testing.T) {
+	handler := createTestOAuthHandler()
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusBadRequest {
+		t.Errorf("Expected status %d, got %d", http.StatusBadRequest, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "No authorization code received") {
+		t.Errorf("Expected missing code message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_TokenExchangeError(t *testing.T) {
+	handler := createTestOAuthHandler()
+	tokenExchanger := handler.tokenExchanger.(*mockTokenExchanger)
+	tokenExchanger.setExchangeError(fmt.Errorf("token exchange failed"))
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", http.StatusInternalServerError, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Could not exchange code for token") {
+		t.Errorf("Expected token exchange error message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_TokenVerificationError(t *testing.T) {
+	handler := createTestOAuthHandler()
+	tokenVerifier := handler.tokenVerifier.(*mockTokenVerifier)
+	tokenVerifier.verifyError = fmt.Errorf("token verification failed")
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", http.StatusInternalServerError, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Could not verify ID token") {
+		t.Errorf("Expected token verification error message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_ClaimsExtractionError(t *testing.T) {
+	handler := createTestOAuthHandler()
+	handler.extractClaimsFunc = func(tokenString string) (map[string]interface{}, error) {
+		return nil, fmt.Errorf("claims extraction failed")
+	}
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", http.StatusInternalServerError, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Could not extract claims from token") {
+		t.Errorf("Expected claims extraction error message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_MissingNonceClaim(t *testing.T) {
+	handler := createTestOAuthHandler()
+	handler.extractClaimsFunc = func(tokenString string) (map[string]interface{}, error) {
+		return map[string]interface{}{
+			"email": "[email protected]",
+			"sub":   "test-user-id",
+		}, nil
+	}
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", http.StatusInternalServerError, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Nonce missing in token") {
+		t.Errorf("Expected nonce missing message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_MissingSessionNonce(t *testing.T) {
+	handler := createTestOAuthHandler()
+	sessionData := handler.sessionManager.(*mockSessionManager).sessionData
+	sessionData.nonce = "" // Clear session nonce
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", http.StatusInternalServerError, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Nonce missing in session") {
+		t.Errorf("Expected nonce missing in session message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_NonceMismatch(t *testing.T) {
+	handler := createTestOAuthHandler()
+	handler.extractClaimsFunc = func(tokenString string) (map[string]interface{}, error) {
+		return map[string]interface{}{
+			"nonce": "wrong-nonce",
+			"email": "[email protected]",
+			"sub":   "test-user-id",
+		}, nil
+	}
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", http.StatusInternalServerError, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Nonce mismatch") {
+		t.Errorf("Expected nonce mismatch message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_MissingEmail(t *testing.T) {
+	handler := createTestOAuthHandler()
+	handler.extractClaimsFunc = func(tokenString string) (map[string]interface{}, error) {
+		return map[string]interface{}{
+			"nonce": "test-nonce",
+			"sub":   "test-user-id",
+		}, nil
+	}
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", http.StatusInternalServerError, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Email missing in token") {
+		t.Errorf("Expected email missing message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_DisallowedEmailDomain(t *testing.T) {
+	handler := createTestOAuthHandler()
+	handler.extractClaimsFunc = func(tokenString string) (map[string]interface{}, error) {
+		return map[string]interface{}{
+			"nonce": "test-nonce",
+			"email": "[email protected]",
+			"sub":   "test-user-id",
+		}, nil
+	}
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusForbidden {
+		t.Errorf("Expected status %d, got %d", http.StatusForbidden, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Email domain not allowed") {
+		t.Errorf("Expected domain not allowed message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_SetAuthenticatedError(t *testing.T) {
+	handler := createTestOAuthHandler()
+	sessionData := handler.sessionManager.(*mockSessionManager).sessionData
+	sessionData.setSetAuthError(fmt.Errorf("failed to set authenticated"))
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", http.StatusInternalServerError, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Failed to update session") {
+		t.Errorf("Expected session update error message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_SessionSaveError(t *testing.T) {
+	handler := createTestOAuthHandler()
+	sessionData := handler.sessionManager.(*mockSessionManager).sessionData
+	sessionData.setSaveError(fmt.Errorf("failed to save session"))
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", http.StatusInternalServerError, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Failed to save session after callback") {
+		t.Errorf("Expected session save error message, got %s", responseBody)
+	}
+}
+
+func TestHandleCallback_DefaultRedirect(t *testing.T) {
+	handler := createTestOAuthHandler()
+	sessionData := handler.sessionManager.(*mockSessionManager).sessionData
+	sessionData.incomingPath = "" // No incoming path
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusFound {
+		t.Errorf("Expected status %d, got %d", http.StatusFound, rw.Code)
+	}
+
+	location := rw.Header().Get("Location")
+	if location != "/" {
+		t.Errorf("Expected redirect to '/', got %s", location)
+	}
+}
+
+func TestHandleCallback_CallbackPathNotRedirected(t *testing.T) {
+	handler := createTestOAuthHandler()
+	sessionData := handler.sessionManager.(*mockSessionManager).sessionData
+	sessionData.incomingPath = "/auth/callback" // Incoming path is callback path
+
+	req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+	rw := httptest.NewRecorder()
+
+	handler.HandleCallback(rw, req, "https://example.com/callback")
+
+	if rw.Code != http.StatusFound {
+		t.Errorf("Expected status %d, got %d", http.StatusFound, rw.Code)
+	}
+
+	location := rw.Header().Get("Location")
+	if location != "/" {
+		t.Errorf("Expected redirect to '/' when incoming path is callback path, got %s", location)
+	}
+}
+
+func TestURLHelper_NewURLHelper(t *testing.T) {
+	logger := &mockLogger{}
+	helper := NewURLHelper(logger)
+
+	if helper == nil {
+		t.Fatal("NewURLHelper returned nil")
+	}
+
+	if helper.logger != logger {
+		t.Error("Expected logger to be set correctly")
+	}
+}
+
+func TestURLHelper_DetermineExcludedURL(t *testing.T) {
+	logger := &mockLogger{}
+	helper := NewURLHelper(logger)
+
+	tests := []struct {
+		name         string
+		currentReq   string
+		excludedURLs map[string]struct{}
+		expected     bool
+	}{
+		{
+			name:       "matches excluded URL",
+			currentReq: "/health/check",
+			excludedURLs: map[string]struct{}{
+				"/health": {},
+			},
+			expected: true,
+		},
+		{
+			name:       "does not match excluded URL",
+			currentReq: "/protected/resource",
+			excludedURLs: map[string]struct{}{
+				"/health": {},
+				"/api":    {},
+			},
+			expected: false,
+		},
+		{
+			name:         "empty excluded URLs",
+			currentReq:   "/any/path",
+			excludedURLs: map[string]struct{}{},
+			expected:     false,
+		},
+		{
+			name:       "exact match",
+			currentReq: "/health",
+			excludedURLs: map[string]struct{}{
+				"/health": {},
+			},
+			expected: true,
+		},
+		{
+			name:       "prefix match",
+			currentReq: "/api/v1/users",
+			excludedURLs: map[string]struct{}{
+				"/api": {},
+			},
+			expected: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := helper.DetermineExcludedURL(tt.currentReq, tt.excludedURLs)
+			if result != tt.expected {
+				t.Errorf("Expected %v, got %v", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestURLHelper_DetermineScheme(t *testing.T) {
+	logger := &mockLogger{}
+	helper := NewURLHelper(logger)
+
+	tests := []struct {
+		name     string
+		req      *http.Request
+		expected string
+	}{
+		{
+			name: "X-Forwarded-Proto header present",
+			req: func() *http.Request {
+				req := httptest.NewRequest("GET", "/test", nil)
+				req.Header.Set("X-Forwarded-Proto", "https")
+				return req
+			}(),
+			expected: "https",
+		},
+		{
+			name: "TLS present",
+			req: func() *http.Request {
+				req := httptest.NewRequest("GET", "/test", nil)
+				req.TLS = &tls.ConnectionState{}
+				return req
+			}(),
+			expected: "https",
+		},
+		{
+			name:     "no TLS or header",
+			req:      httptest.NewRequest("GET", "/test", nil),
+			expected: "http",
+		},
+		{
+			name: "X-Forwarded-Proto takes precedence over TLS",
+			req: func() *http.Request {
+				req := httptest.NewRequest("GET", "/test", nil)
+				req.Header.Set("X-Forwarded-Proto", "http")
+				req.TLS = &tls.ConnectionState{}
+				return req
+			}(),
+			expected: "http",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := helper.DetermineScheme(tt.req)
+			if result != tt.expected {
+				t.Errorf("Expected %s, got %s", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestURLHelper_DetermineHost(t *testing.T) {
+	logger := &mockLogger{}
+	helper := NewURLHelper(logger)
+
+	tests := []struct {
+		name     string
+		req      *http.Request
+		expected string
+	}{
+		{
+			name: "X-Forwarded-Host header present",
+			req: func() *http.Request {
+				req := httptest.NewRequest("GET", "http://example.com/test", nil)
+				req.Header.Set("X-Forwarded-Host", "proxy.example.com")
+				return req
+			}(),
+			expected: "proxy.example.com",
+		},
+		{
+			name:     "no X-Forwarded-Host header",
+			req:      httptest.NewRequest("GET", "http://example.com/test", nil),
+			expected: "example.com",
+		},
+		{
+			name: "X-Forwarded-Host with port",
+			req: func() *http.Request {
+				req := httptest.NewRequest("GET", "http://example.com:8080/test", nil)
+				req.Header.Set("X-Forwarded-Host", "proxy.example.com:443")
+				return req
+			}(),
+			expected: "proxy.example.com:443",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := helper.DetermineHost(tt.req)
+			if result != tt.expected {
+				t.Errorf("Expected %s, got %s", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestConcurrentCallbacks(t *testing.T) {
+	const numGoroutines = 10
+	var wg sync.WaitGroup
+	errors := make(chan error, numGoroutines)
+
+	for i := 0; i < numGoroutines; i++ {
+		wg.Add(1)
+		go func(id int) {
+			defer wg.Done()
+
+			// Create unique session data for each goroutine
+			sessionData := newMockSessionData()
+			sessionData.csrf = fmt.Sprintf("csrf-token-%d", id)
+			sessionData.nonce = fmt.Sprintf("nonce-%d", id)
+
+			sessionManager := &mockSessionManager{sessionData: sessionData}
+			localHandler := createTestOAuthHandler()
+			localHandler.sessionManager = sessionManager
+
+			// Update extract claims function to match the session nonce
+			localHandler.extractClaimsFunc = func(tokenString string) (map[string]interface{}, error) {
+				return map[string]interface{}{
+					"nonce": fmt.Sprintf("nonce-%d", id),
+					"email": fmt.Sprintf("test%[email protected]", id),
+					"sub":   fmt.Sprintf("test-user-%d", id),
+				}, nil
+			}
+
+			req := httptest.NewRequest("GET",
+				fmt.Sprintf("/auth/callback?state=csrf-token-%d&code=auth-code-%d", id, id), nil)
+			rw := httptest.NewRecorder()
+
+			localHandler.HandleCallback(rw, req, "https://example.com/callback")
+
+			if rw.Code != http.StatusFound {
+				errors <- fmt.Errorf("goroutine %d: expected status %d, got %d",
+					id, http.StatusFound, rw.Code)
+			}
+		}(i)
+	}
+
+	wg.Wait()
+	close(errors)
+
+	var errorCount int
+	for err := range errors {
+		t.Error(err)
+		errorCount++
+	}
+
+	if errorCount > 0 {
+		t.Errorf("Found %d errors in concurrent callback test", errorCount)
+	}
+}
+
+// Benchmark tests
+func BenchmarkHandleCallback_Success(b *testing.B) {
+	handler := createTestOAuthHandler()
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		req := httptest.NewRequest("GET", "/auth/callback?state=test-csrf-token&code=test-auth-code", nil)
+		rw := httptest.NewRecorder()
+		handler.HandleCallback(rw, req, "https://example.com/callback")
+	}
+}
+
+func BenchmarkURLHelper_DetermineExcludedURL(b *testing.B) {
+	logger := &mockLogger{}
+	helper := NewURLHelper(logger)
+	excludedURLs := map[string]struct{}{
+		"/health": {},
+		"/api":    {},
+		"/status": {},
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		helper.DetermineExcludedURL("/protected/resource", excludedURLs)
+	}
+}
+
+func BenchmarkURLHelper_DetermineScheme(b *testing.B) {
+	logger := &mockLogger{}
+	helper := NewURLHelper(logger)
+	req := httptest.NewRequest("GET", "/test", nil)
+	req.Header.Set("X-Forwarded-Proto", "https")
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		helper.DetermineScheme(req)
+	}
+}

main.go

@@ -31,251 +31,9 @@ func createDefaultHTTPClient() *http.Client {
 }
 
 const (
-	ConstSessionTimeout      = 86400
+	ConstSessionTimeout = 86400
-	defaultBlacklistDuration = 24 * time.Hour
-	defaultMaxBlacklistSize  = 10000
 )
 
-var (
-	globalCacheManager *CacheManager
-	cacheManagerOnce   sync.Once
-	cacheManagerMutex  sync.RWMutex
-)
-
-// CacheManager manages all caching components for the OIDC middleware.
-// It provides thread-safe access to token blacklist, token cache, metadata cache,
-// and JWK cache. This centralizes cache management to ensure efficient memory
-// usage and consistent cache behavior across the application.
-// CacheInterface defines the common cache operations
-type CacheInterface interface {
-	Set(key string, value interface{}, ttl time.Duration)
-	Get(key string) (interface{}, bool)
-	Delete(key string)
-	SetMaxSize(size int)
-	Cleanup()
-	Close()
-}
-
-type CacheManager struct {
-	tokenBlacklist CacheInterface
-	tokenCache     *TokenCache
-	metadataCache  *MetadataCache
-	jwkCache       JWKCacheInterface
-	mu             sync.RWMutex
-}
-
-// GetGlobalCacheManager returns a singleton instance of CacheManager.
-// It initializes all cache components on first call and reuses the same instance
-// for subsequent calls. This ensures consistent cache state and efficient memory
-// usage across the entire application lifecycle.
-// Parameters:
-//   - wg: WaitGroup for coordinating cache cleanup during shutdown.
-//
-// Returns:
-//   - The global CacheManager instance.
-func GetGlobalCacheManager(wg *sync.WaitGroup) *CacheManager {
-	cacheManagerOnce.Do(func() {
-		globalCacheManager = &CacheManager{
-			tokenBlacklist: func() CacheInterface {
-				config := DefaultUnifiedCacheConfig()
-				config.MaxSize = defaultMaxBlacklistSize
-				c := NewUnifiedCache(config)
-				return NewCacheAdapter(c)
-			}(),
-			tokenCache:    NewTokenCache(),
-			metadataCache: NewMetadataCache(wg),
-			jwkCache:      &JWKCache{},
-		}
-	})
-	return globalCacheManager
-}
-
-// GetSharedTokenBlacklist returns the shared token blacklist cache.
-// This cache stores revoked or expired tokens to prevent replay attacks.
-// Access is protected by read lock to ensure thread safety.
-// Returns:
-//   - The shared token blacklist CacheInterface instance.
-func (cm *CacheManager) GetSharedTokenBlacklist() CacheInterface {
-	cm.mu.RLock()
-	defer cm.mu.RUnlock()
-	return cm.tokenBlacklist
-}
-
-// GetSharedTokenCache returns the shared token cache for verified tokens.
-// This cache stores claims from successfully verified tokens to avoid
-// repeated verification of the same tokens.
-// Access is protected by read lock to ensure thread safety.
-// Returns:
-//   - The shared TokenCache instance.
-func (cm *CacheManager) GetSharedTokenCache() *TokenCache {
-	cm.mu.RLock()
-	defer cm.mu.RUnlock()
-	return cm.tokenCache
-}
-
-// GetSharedMetadataCache returns the shared metadata cache.
-// This cache stores OIDC provider metadata (endpoints, keys) to avoid
-// repeated requests to the provider's .well-known configuration endpoint.
-// Access is protected by read lock to ensure thread safety.
-// Returns:
-//   - The shared MetadataCache instance.
-func (cm *CacheManager) GetSharedMetadataCache() *MetadataCache {
-	cm.mu.RLock()
-	defer cm.mu.RUnlock()
-	return cm.metadataCache
-}
-
-// GetSharedJWKCache returns the shared JWK (JSON Web Key) cache.
-// This cache stores public keys from the provider's JWKS endpoint
-// for token signature verification.
-// Access is protected by read lock to ensure thread safety.
-// Returns:
-//   - The shared JWKCacheInterface instance.
-func (cm *CacheManager) GetSharedJWKCache() JWKCacheInterface {
-	cm.mu.RLock()
-	defer cm.mu.RUnlock()
-	return cm.jwkCache
-}
-
-// Close gracefully shuts down all cache components and releases resources.
-// It closes all individual caches and cleans up their associated goroutines.
-// This method should be called when the middleware is shutting down.
-// Safe to call multiple times.
-// Returns:
-//   - An error if any cache fails to close properly, nil otherwise.
-func (cm *CacheManager) Close() error {
-	cm.mu.Lock()
-	defer cm.mu.Unlock()
-
-	if cm.tokenBlacklist != nil {
-		cm.tokenBlacklist.Close()
-		cm.tokenBlacklist = nil
-	}
-	if cm.tokenCache != nil {
-		cm.tokenCache.Close()
-		cm.tokenCache = nil
-	}
-	if cm.metadataCache != nil {
-		cm.metadataCache.Close()
-		cm.metadataCache = nil
-	}
-	if cm.jwkCache != nil {
-		cm.jwkCache.Close()
-		cm.jwkCache = nil
-	}
-
-	return nil
-}
-
-// CleanupGlobalCacheManager cleans up the global cache manager instance.
-// It closes all cache components but does NOT reset the singleton for re-initialization
-// to avoid race conditions with sync.Once. It's safe to call multiple times.
-// Returns:
-//   - An error if cache cleanup fails, nil otherwise.
-func CleanupGlobalCacheManager() error {
-	cacheManagerMutex.Lock()
-	defer cacheManagerMutex.Unlock()
-
-	if globalCacheManager != nil {
-		err := globalCacheManager.Close()
-		// Don't reset globalCacheManager to nil or cacheManagerOnce to avoid race conditions
-		// The cache manager remains closed and the Close() method handles multiple calls
-		return err
-	}
-	return nil
-}
-
-// TokenVerifier interface defines token verification capabilities.
-// Implementations should validate token format, signature, and claims.
-type TokenVerifier interface {
-	VerifyToken(token string) error
-}
-
-// JWTVerifier interface defines JWT-specific verification capabilities.
-// Implementations should validate JWT structure, signature using JWKs, and standard claims.
-type JWTVerifier interface {
-	VerifyJWTSignatureAndClaims(jwt *JWT, token string) error
-}
-
-// TokenExchanger interface defines OAuth 2.0 and OpenID Connect token exchange capabilities.
-// Implementations should handle authorization code exchange, refresh tokens, and revocation
-// according to the OAuth 2.0 and OpenID Connect specifications.
-type TokenExchanger interface {
-	ExchangeCodeForToken(ctx context.Context, grantType string, codeOrToken string, redirectURL string, codeVerifier string) (*TokenResponse, error)
-	GetNewTokenWithRefreshToken(refreshToken string) (*TokenResponse, error)
-	RevokeTokenWithProvider(token, tokenType string) error
-}
-
-// TraefikOidc is the main middleware struct that implements OIDC authentication for Traefik.
-// It integrates with various OIDC providers, manages sessions, caches tokens, and handles
-// the complete authentication flow. It's designed to work seamlessly with Traefik's
-// plugin system and provides flexible configuration options.
-type TraefikOidc struct {
-	jwkCache                   JWKCacheInterface
-	jwtVerifier                JWTVerifier
-	ctx                        context.Context
-	tokenVerifier              TokenVerifier
-	next                       http.Handler
-	tokenExchanger             TokenExchanger
-	initComplete               chan struct{}
-	limiter                    *rate.Limiter
-	tokenBlacklist             CacheInterface
-	headerTemplates            map[string]*template.Template
-	sessionManager             *SessionManager
-	tokenCleanupStopChan       chan struct{}
-	excludedURLs               map[string]struct{}
-	extractClaimsFunc          func(tokenString string) (map[string]interface{}, error)
-	initiateAuthenticationFunc func(rw http.ResponseWriter, req *http.Request, session *SessionData, redirectURL string)
-	metadataCache              *MetadataCache
-	allowedRolesAndGroups      map[string]struct{}
-	allowedUsers               map[string]struct{}
-	allowedUserDomains         map[string]struct{}
-	tokenCache                 *TokenCache
-	httpClient                 *http.Client
-	tokenHTTPClient            *http.Client
-	logger                     *Logger
-	metadataRefreshStopChan    chan struct{}
-	cancelFunc                 context.CancelFunc
-	errorRecoveryManager       *ErrorRecoveryManager
-	goroutineWG                *sync.WaitGroup
-	clientSecret               string
-	clientID                   string
-	name                       string
-	redirURLPath               string
-	logoutURLPath              string
-	tokenURL                   string
-	authURL                    string
-	endSessionURL              string
-	postLogoutRedirectURI      string
-	scheme                     string
-	jwksURL                    string
-	issuerURL                  string
-	revocationURL              string
-	providerURL                string
-	scopes                     []string
-	refreshGracePeriod         time.Duration
-	shutdownOnce               sync.Once
-	firstRequestMutex          sync.Mutex
-	forceHTTPS                 bool
-	enablePKCE                 bool
-	overrideScopes             bool
-	suppressDiagnosticLogs     bool
-	firstRequestReceived       bool
-	metadataRefreshStarted     bool
-}
-
-// ProviderMetadata represents OIDC provider configuration data.
-// This data is typically retrieved from the provider's .well-known/openid-configuration endpoint
-// and contains essential URLs for authentication, token exchange, and key retrieval.
-type ProviderMetadata struct {
-	Issuer        string `json:"issuer"`
-	AuthURL       string `json:"authorization_endpoint"`
-	TokenURL      string `json:"token_endpoint"`
-	JWKSURL       string `json:"jwks_uri"`
-	RevokeURL     string `json:"revocation_endpoint"`
-	EndSessionURL string `json:"end_session_endpoint"`
-}
-
 // isTestMode detects if the code is running in a test environment.
 // It checks various indicators including environment variables, command-line arguments,
 // and runtime compiler information to determine test context.

middleware/auth_middleware.go

@@ -0,0 +1,464 @@
+// Package middleware provides authentication middleware for OIDC flows
+package middleware
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+)
+
+// AuthMiddleware handles the main OIDC authentication flow
+type AuthMiddleware struct {
+	logger                    Logger
+	next                      http.Handler
+	sessionManager            SessionManager
+	authHandler               AuthHandler
+	oauthHandler              OAuthHandler
+	urlHelper                 URLHelper
+	tokenVerifier             TokenVerifier
+	extractClaimsFunc         func(tokenString string) (map[string]interface{}, error)
+	extractGroupsAndRolesFunc func(tokenString string) ([]string, []string, error)
+	sendErrorResponseFunc     func(rw http.ResponseWriter, req *http.Request, message string, code int)
+	refreshTokenFunc          func(rw http.ResponseWriter, req *http.Request, session SessionData) bool
+	isUserAuthenticatedFunc   func(session SessionData) (bool, bool, bool)
+	isAllowedDomainFunc       func(email string) bool
+	isAjaxRequestFunc         func(req *http.Request) bool
+	isRefreshTokenExpiredFunc func(session SessionData) bool
+	processLogoutFunc         func(rw http.ResponseWriter, req *http.Request)
+	excludedURLs              map[string]struct{}
+	allowedRolesAndGroups     map[string]struct{}
+	redirURLPath              string
+	logoutURLPath             string
+	refreshGracePeriod        time.Duration
+	initComplete              chan struct{}
+	issuerURL                 string
+	firstRequestReceived      bool
+	metadataRefreshStarted    bool
+	firstRequestMutex         sync.Mutex
+	providerURL               string
+	goroutineWG               *sync.WaitGroup
+	startTokenCleanupFunc     func()
+	startMetadataRefreshFunc  func(string)
+}
+
+// Logger interface for dependency injection
+type Logger interface {
+	Debug(msg string)
+	Debugf(format string, args ...interface{})
+	Error(msg string)
+	Errorf(format string, args ...interface{})
+	Info(msg string)
+	Infof(format string, args ...interface{})
+}
+
+// SessionManager interface for session operations
+type SessionManager interface {
+	CleanupOldCookies(rw http.ResponseWriter, req *http.Request)
+	GetSession(req *http.Request) (SessionData, error)
+}
+
+// SessionData interface for session data operations
+type SessionData interface {
+	GetEmail() string
+	GetAccessToken() string
+	GetIDToken() string
+	GetRefreshToken() string
+	Clear(req *http.Request, rw http.ResponseWriter) error
+	ResetRedirectCount()
+	returnToPoolSafely()
+}
+
+// AuthHandler interface for authentication operations
+type AuthHandler interface {
+	InitiateAuthentication(rw http.ResponseWriter, req *http.Request, session SessionData, redirectURL string,
+		generateNonce, generateCodeVerifier, deriveCodeChallenge func() (string, error))
+}
+
+// OAuthHandler interface for OAuth callback operations
+type OAuthHandler interface {
+	HandleCallback(rw http.ResponseWriter, req *http.Request, redirectURL string)
+}
+
+// URLHelper interface for URL operations
+type URLHelper interface {
+	DetermineExcludedURL(currentRequest string, excludedURLs map[string]struct{}) bool
+	DetermineScheme(req *http.Request) string
+	DetermineHost(req *http.Request) string
+}
+
+// TokenVerifier interface for token verification
+type TokenVerifier interface {
+	VerifyToken(token string) error
+}
+
+// NewAuthMiddleware creates a new authentication middleware
+func NewAuthMiddleware(
+	logger Logger,
+	next http.Handler,
+	sessionManager SessionManager,
+	authHandler AuthHandler,
+	oauthHandler OAuthHandler,
+	urlHelper URLHelper,
+	tokenVerifier TokenVerifier,
+	extractClaimsFunc func(string) (map[string]interface{}, error),
+	extractGroupsAndRolesFunc func(string) ([]string, []string, error),
+	sendErrorResponseFunc func(http.ResponseWriter, *http.Request, string, int),
+	refreshTokenFunc func(http.ResponseWriter, *http.Request, SessionData) bool,
+	isUserAuthenticatedFunc func(SessionData) (bool, bool, bool),
+	isAllowedDomainFunc func(string) bool,
+	isAjaxRequestFunc func(*http.Request) bool,
+	isRefreshTokenExpiredFunc func(SessionData) bool,
+	processLogoutFunc func(http.ResponseWriter, *http.Request),
+	excludedURLs map[string]struct{},
+	allowedRolesAndGroups map[string]struct{},
+	redirURLPath, logoutURLPath string,
+	refreshGracePeriod time.Duration,
+	initComplete chan struct{},
+	issuerURL, providerURL string,
+	goroutineWG *sync.WaitGroup,
+	startTokenCleanupFunc func(),
+	startMetadataRefreshFunc func(string),
+) *AuthMiddleware {
+	return &AuthMiddleware{
+		logger:                    logger,
+		next:                      next,
+		sessionManager:            sessionManager,
+		authHandler:               authHandler,
+		oauthHandler:              oauthHandler,
+		urlHelper:                 urlHelper,
+		tokenVerifier:             tokenVerifier,
+		extractClaimsFunc:         extractClaimsFunc,
+		extractGroupsAndRolesFunc: extractGroupsAndRolesFunc,
+		sendErrorResponseFunc:     sendErrorResponseFunc,
+		refreshTokenFunc:          refreshTokenFunc,
+		isUserAuthenticatedFunc:   isUserAuthenticatedFunc,
+		isAllowedDomainFunc:       isAllowedDomainFunc,
+		isAjaxRequestFunc:         isAjaxRequestFunc,
+		isRefreshTokenExpiredFunc: isRefreshTokenExpiredFunc,
+		processLogoutFunc:         processLogoutFunc,
+		excludedURLs:              excludedURLs,
+		allowedRolesAndGroups:     allowedRolesAndGroups,
+		redirURLPath:              redirURLPath,
+		logoutURLPath:             logoutURLPath,
+		refreshGracePeriod:        refreshGracePeriod,
+		initComplete:              initComplete,
+		issuerURL:                 issuerURL,
+		providerURL:               providerURL,
+		goroutineWG:               goroutineWG,
+		startTokenCleanupFunc:     startTokenCleanupFunc,
+		startMetadataRefreshFunc:  startMetadataRefreshFunc,
+	}
+}
+
+// ServeHTTP implements the main OIDC authentication middleware
+func (m *AuthMiddleware) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	if !strings.HasPrefix(req.URL.Path, "/health") {
+		m.firstRequestMutex.Lock()
+		if !m.firstRequestReceived {
+			m.firstRequestReceived = true
+			m.logger.Debug("Starting background tasks on first request")
+			m.startTokenCleanupFunc()
+
+			if !m.metadataRefreshStarted && m.providerURL != "" {
+				m.metadataRefreshStarted = true
+				if m.goroutineWG != nil {
+					m.goroutineWG.Add(1)
+				}
+				go func() {
+					defer func() {
+						if m.goroutineWG != nil {
+							m.goroutineWG.Done()
+						}
+						// Recover from panics to prevent goroutine leaks
+						if r := recover(); r != nil {
+							m.logger.Errorf("Start metadata refresh goroutine panic recovered: %v", r)
+						}
+					}()
+					m.startMetadataRefreshFunc(m.providerURL)
+				}()
+			}
+		}
+		m.firstRequestMutex.Unlock()
+	}
+
+	select {
+	case <-m.initComplete:
+		if m.issuerURL == "" {
+			m.logger.Error("OIDC provider metadata initialization failed or incomplete")
+			m.sendErrorResponseFunc(rw, req, "OIDC provider metadata initialization failed - please check provider availability and configuration", http.StatusServiceUnavailable)
+			return
+		}
+	case <-req.Context().Done():
+		m.logger.Debug("Request cancelled while waiting for OIDC initialization")
+		m.sendErrorResponseFunc(rw, req, "Request cancelled", http.StatusRequestTimeout)
+		return
+	case <-time.After(30 * time.Second):
+		m.logger.Error("Timeout waiting for OIDC initialization")
+		m.sendErrorResponseFunc(rw, req, "Timeout waiting for OIDC provider initialization - please try again later", http.StatusServiceUnavailable)
+		return
+	}
+
+	if m.urlHelper.DetermineExcludedURL(req.URL.Path, m.excludedURLs) {
+		m.logger.Debugf("Request path %s excluded by configuration, bypassing OIDC", req.URL.Path)
+		m.next.ServeHTTP(rw, req)
+		return
+	}
+
+	acceptHeader := req.Header.Get("Accept")
+	if strings.Contains(acceptHeader, "text/event-stream") {
+		m.logger.Debugf("Request accepts text/event-stream (%s), bypassing OIDC", acceptHeader)
+		m.next.ServeHTTP(rw, req)
+		return
+	}
+
+	m.sessionManager.CleanupOldCookies(rw, req)
+
+	session, err := m.sessionManager.GetSession(req)
+	if err != nil {
+		m.logger.Errorf("Error getting session: %v. Initiating authentication.", err)
+		cleanReq := req.Clone(req.Context())
+		session, _ = m.sessionManager.GetSession(cleanReq)
+		if session != nil {
+			defer session.returnToPoolSafely()
+			if clearErr := session.Clear(cleanReq, rw); clearErr != nil {
+				m.logger.Errorf("Error clearing potentially corrupted session: %v", clearErr)
+			}
+		} else {
+			m.logger.Error("Critical session error: Failed to get even a new session.")
+			m.sendErrorResponseFunc(rw, req, "Critical session error", http.StatusInternalServerError)
+			return
+		}
+		scheme := m.urlHelper.DetermineScheme(req)
+		host := m.urlHelper.DetermineHost(req)
+		redirectURL := buildFullURL(scheme, host, m.redirURLPath)
+		m.authHandler.InitiateAuthentication(rw, req, session, redirectURL,
+			generateNonce, generateCodeVerifier, deriveCodeChallenge)
+		return
+	}
+
+	defer session.returnToPoolSafely()
+
+	scheme := m.urlHelper.DetermineScheme(req)
+	host := m.urlHelper.DetermineHost(req)
+	redirectURL := buildFullURL(scheme, host, m.redirURLPath)
+
+	if req.URL.Path == m.logoutURLPath {
+		m.processLogoutFunc(rw, req)
+		return
+	}
+	if req.URL.Path == m.redirURLPath {
+		m.oauthHandler.HandleCallback(rw, req, redirectURL)
+		return
+	}
+
+	authenticated, needsRefresh, expired := m.isUserAuthenticatedFunc(session)
+
+	if expired {
+		m.logger.Debug("Session token is definitively expired or invalid, initiating re-auth")
+		m.handleExpiredToken(rw, req, session, redirectURL)
+		return
+	}
+
+	email := session.GetEmail()
+	if authenticated && email != "" {
+		if !m.isAllowedDomainFunc(email) {
+			m.logger.Infof("User with email %s is not from an allowed domain", email)
+			errorMsg := fmt.Sprintf("Access denied: Your email domain is not allowed. To log out, visit: %s", m.logoutURLPath)
+			m.sendErrorResponseFunc(rw, req, errorMsg, http.StatusForbidden)
+			return
+		}
+	}
+
+	if authenticated && !needsRefresh {
+		m.logger.Debug("User authenticated and token valid, proceeding to process authorized request")
+		if accessToken := session.GetAccessToken(); accessToken != "" {
+			if strings.Count(accessToken, ".") == 2 {
+				if err := m.tokenVerifier.VerifyToken(accessToken); err != nil {
+					m.logger.Errorf("Access token validation failed: %v", err)
+					m.handleExpiredToken(rw, req, session, redirectURL)
+					return
+				}
+			} else {
+				m.logger.Debugf("Access token appears opaque, skipping JWT verification for it.")
+			}
+		}
+		m.processAuthorizedRequest(rw, req, session, redirectURL)
+		return
+	}
+
+	m.handleRefreshFlow(rw, req, session, redirectURL, needsRefresh, authenticated)
+}
+
+// handleExpiredToken handles expired tokens by initiating re-authentication
+func (m *AuthMiddleware) handleExpiredToken(rw http.ResponseWriter, req *http.Request, session SessionData, redirectURL string) {
+	session.ResetRedirectCount()
+	m.authHandler.InitiateAuthentication(rw, req, session, redirectURL,
+		generateNonce, generateCodeVerifier, deriveCodeChallenge)
+}
+
+// handleRefreshFlow handles token refresh flow or initiates authentication
+func (m *AuthMiddleware) handleRefreshFlow(rw http.ResponseWriter, req *http.Request, session SessionData, redirectURL string, needsRefresh, authenticated bool) {
+	refreshTokenPresent := session.GetRefreshToken() != ""
+	isAjaxRequest := m.isAjaxRequestFunc(req)
+	refreshTokenExpired := refreshTokenPresent && m.isRefreshTokenExpiredFunc(session)
+	shouldAttemptRefresh := needsRefresh && refreshTokenPresent && !refreshTokenExpired
+
+	// If AJAX request and refresh token expired, return 401 immediately
+	if isAjaxRequest && refreshTokenExpired {
+		m.logger.Debug("AJAX request with expired refresh token, returning 401")
+		m.sendErrorResponseFunc(rw, req, "Session expired", http.StatusUnauthorized)
+		return
+	}
+
+	if shouldAttemptRefresh {
+		m.handleTokenRefresh(rw, req, session, redirectURL, needsRefresh, authenticated, isAjaxRequest)
+		return
+	}
+
+	m.logger.Debugf("Initiating full OIDC authentication flow (authenticated=%v, needsRefresh=%v, refreshTokenPresent=%v)", authenticated, needsRefresh, refreshTokenPresent)
+
+	// If AJAX request without valid authentication, return 401
+	if isAjaxRequest {
+		m.logger.Debug("AJAX request requires authentication, sending 401 Unauthorized")
+		m.sendErrorResponseFunc(rw, req, "Authentication required", http.StatusUnauthorized)
+		return
+	}
+
+	// Reset redirect count when starting fresh authentication flow
+	session.ResetRedirectCount()
+	m.authHandler.InitiateAuthentication(rw, req, session, redirectURL,
+		generateNonce, generateCodeVerifier, deriveCodeChallenge)
+}
+
+// handleTokenRefresh handles the token refresh process
+func (m *AuthMiddleware) handleTokenRefresh(rw http.ResponseWriter, req *http.Request, session SessionData, redirectURL string, needsRefresh, authenticated, isAjaxRequest bool) {
+	if needsRefresh && authenticated {
+		m.logger.Debug("Session token needs proactive refresh, attempting refresh")
+	} else if needsRefresh && !authenticated {
+		m.logger.Debug("ID token invalid/expired, but refresh token found. Attempting refresh.")
+	}
+
+	refreshed := m.refreshTokenFunc(rw, req, session)
+	if refreshed {
+		email := session.GetEmail()
+		if email != "" && !m.isAllowedDomainFunc(email) {
+			m.logger.Infof("User with refreshed token email %s is not from an allowed domain", email)
+			errorMsg := fmt.Sprintf("Access denied: Your email domain is not allowed. To log out, visit: %s", m.logoutURLPath)
+			m.sendErrorResponseFunc(rw, req, errorMsg, http.StatusForbidden)
+			return
+		}
+
+		m.logger.Debug("Token refresh successful, proceeding to process authorized request")
+		m.processAuthorizedRequest(rw, req, session, redirectURL)
+		return
+	}
+
+	m.logger.Debug("Token refresh failed, requiring re-authentication")
+	if isAjaxRequest {
+		m.logger.Debug("AJAX request with failed token refresh, sending 401 Unauthorized")
+		m.sendErrorResponseFunc(rw, req, "Token refresh failed", http.StatusUnauthorized)
+	} else {
+		m.logger.Debug("Browser request with failed token refresh, initiating re-auth")
+		// Reset redirect count when starting fresh auth after failed refresh to prevent redirect loops
+		session.ResetRedirectCount()
+		m.authHandler.InitiateAuthentication(rw, req, session, redirectURL,
+			generateNonce, generateCodeVerifier, deriveCodeChallenge)
+	}
+}
+
+// processAuthorizedRequest processes requests for authenticated users
+func (m *AuthMiddleware) processAuthorizedRequest(rw http.ResponseWriter, req *http.Request, session SessionData, redirectURL string) {
+	email := session.GetEmail()
+	if email == "" {
+		m.logger.Info("No email found in session during final processing, initiating re-auth")
+		// Reset redirect count to prevent loops when session is invalid
+		session.ResetRedirectCount()
+		m.authHandler.InitiateAuthentication(rw, req, session, redirectURL,
+			generateNonce, generateCodeVerifier, deriveCodeChallenge)
+		return
+	}
+
+	tokenForClaims := session.GetIDToken()
+	if tokenForClaims == "" {
+		tokenForClaims = session.GetAccessToken()
+		if tokenForClaims == "" && len(m.allowedRolesAndGroups) > 0 {
+			m.logger.Error("No token available but roles/groups checks are required")
+			// Reset redirect count to prevent loops when token is missing
+			session.ResetRedirectCount()
+			m.authHandler.InitiateAuthentication(rw, req, session, redirectURL,
+				generateNonce, generateCodeVerifier, deriveCodeChallenge)
+			return
+		}
+	}
+
+	// Initialize empty slices
+	var groups, roles []string
+
+	if tokenForClaims != "" {
+		var err error
+		groups, roles, err = m.extractGroupsAndRolesFunc(tokenForClaims)
+		if err != nil && len(m.allowedRolesAndGroups) > 0 {
+			m.logger.Errorf("Failed to extract groups and roles: %v", err)
+			// Reset redirect count to prevent loops when claim extraction fails
+			session.ResetRedirectCount()
+			m.authHandler.InitiateAuthentication(rw, req, session, redirectURL,
+				generateNonce, generateCodeVerifier, deriveCodeChallenge)
+			return
+		} else if err == nil {
+			if len(groups) > 0 {
+				req.Header.Set("X-User-Groups", strings.Join(groups, ","))
+			}
+			if len(roles) > 0 {
+				req.Header.Set("X-User-Roles", strings.Join(roles, ","))
+			}
+		}
+	}
+
+	if len(m.allowedRolesAndGroups) > 0 {
+		allowed := false
+		for _, roleOrGroup := range append(groups, roles...) {
+			if _, ok := m.allowedRolesAndGroups[roleOrGroup]; ok {
+				allowed = true
+				break
+			}
+		}
+		if !allowed {
+			m.logger.Infof("User with email %s does not have any allowed roles or groups", email)
+			errorMsg := fmt.Sprintf("Access denied: You do not have any of the allowed roles or groups. To log out, visit: %s", m.logoutURLPath)
+			m.sendErrorResponseFunc(rw, req, errorMsg, http.StatusForbidden)
+			return
+		}
+	}
+
+	req.Header.Set("X-Forwarded-User", email)
+	req.Header.Set("X-Auth-Request-Redirect", req.URL.RequestURI())
+	req.Header.Set("X-Auth-Request-User", email)
+	if idToken := session.GetIDToken(); idToken != "" {
+		req.Header.Set("X-Auth-Request-Token", idToken)
+	}
+
+	m.next.ServeHTTP(rw, req)
+}
+
+// buildFullURL constructs a full URL from scheme, host, and path components
+func buildFullURL(scheme, host, path string) string {
+	return fmt.Sprintf("%s://%s%s", scheme, host, path)
+}
+
+// These functions need to be provided by the calling code or injected as dependencies
+func generateNonce() (string, error) {
+	// This function needs to be implemented or injected
+	return "", fmt.Errorf("generateNonce not implemented")
+}
+
+func generateCodeVerifier() (string, error) {
+	// This function needs to be implemented or injected
+	return "", fmt.Errorf("generateCodeVerifier not implemented")
+}
+
+func deriveCodeChallenge() (string, error) {
+	// This function needs to be implemented or injected
+	return "", fmt.Errorf("deriveCodeChallenge not implemented")
+}

middleware/auth_middleware_test.go

@@ -0,0 +1,980 @@
+package middleware
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+// Mock implementations for testing
+type mockLogger struct {
+	debugLogs []string
+	infoLogs  []string
+	errorLogs []string
+	mu        sync.RWMutex
+}
+
+func (m *mockLogger) Debug(msg string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.debugLogs = append(m.debugLogs, msg)
+}
+
+func (m *mockLogger) Debugf(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.debugLogs = append(m.debugLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockLogger) Error(msg string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.errorLogs = append(m.errorLogs, msg)
+}
+
+func (m *mockLogger) Errorf(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.errorLogs = append(m.errorLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockLogger) Info(msg string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.infoLogs = append(m.infoLogs, msg)
+}
+
+func (m *mockLogger) Infof(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.infoLogs = append(m.infoLogs, fmt.Sprintf(format, args...))
+}
+
+//lint:ignore U1000 May be needed for future debug log verification tests
+func (m *mockLogger) getDebugLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.debugLogs))
+	copy(result, m.debugLogs)
+	return result
+}
+
+//lint:ignore U1000 May be needed for future error log verification tests
+func (m *mockLogger) getErrorLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.errorLogs))
+	copy(result, m.errorLogs)
+	return result
+}
+
+//lint:ignore U1000 May be needed for future test isolation
+func (m *mockLogger) reset() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.debugLogs = nil
+	m.infoLogs = nil
+	m.errorLogs = nil
+}
+
+type mockSessionManager struct {
+	cleanupCalled bool
+	sessionData   *mockSessionData
+	sessionError  error
+	callCount     int // Track how many times GetSession is called
+	mu            sync.RWMutex
+}
+
+func (m *mockSessionManager) CleanupOldCookies(rw http.ResponseWriter, req *http.Request) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.cleanupCalled = true
+}
+
+func (m *mockSessionManager) GetSession(req *http.Request) (SessionData, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	m.callCount++
+
+	// First call returns error, second call (for clean request) returns valid session
+	if m.sessionError != nil && m.callCount == 1 {
+		return nil, m.sessionError
+	}
+
+	return m.sessionData, nil
+}
+
+func (m *mockSessionManager) setSessionError(err error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.sessionError = err
+	m.callCount = 0 // Reset call count when setting error
+}
+
+type mockSessionData struct {
+	email        string
+	accessToken  string
+	idToken      string
+	refreshToken string
+	clearError   error
+	mu           sync.RWMutex
+	returned     bool
+}
+
+func newMockSessionData() *mockSessionData {
+	return &mockSessionData{}
+}
+
+func (m *mockSessionData) GetEmail() string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.email
+}
+
+func (m *mockSessionData) GetAccessToken() string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.accessToken
+}
+
+func (m *mockSessionData) GetIDToken() string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.idToken
+}
+
+func (m *mockSessionData) GetRefreshToken() string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.refreshToken
+}
+
+func (m *mockSessionData) Clear(req *http.Request, rw http.ResponseWriter) error {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.clearError
+}
+
+func (m *mockSessionData) ResetRedirectCount() {
+	// Mock implementation
+}
+
+func (m *mockSessionData) returnToPoolSafely() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.returned = true
+}
+
+func (m *mockSessionData) setEmail(email string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.email = email
+}
+
+func (m *mockSessionData) setAccessToken(token string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.accessToken = token
+}
+
+func (m *mockSessionData) setIDToken(token string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.idToken = token
+}
+
+func (m *mockSessionData) setRefreshToken(token string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.refreshToken = token
+}
+
+//lint:ignore U1000 May be needed for future session clear testing
+func (m *mockSessionData) setClearError(err error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.clearError = err
+}
+
+type mockAuthHandler struct {
+	initiateCalled bool
+	mu             sync.RWMutex
+}
+
+func (m *mockAuthHandler) InitiateAuthentication(rw http.ResponseWriter, req *http.Request, session SessionData, redirectURL string,
+	generateNonce, generateCodeVerifier, deriveCodeChallenge func() (string, error)) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.initiateCalled = true
+	http.Redirect(rw, req, "https://provider.example.com/auth", http.StatusFound)
+}
+
+func (m *mockAuthHandler) wasInitiateCalled() bool {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.initiateCalled
+}
+
+//lint:ignore U1000 May be needed for future test isolation
+func (m *mockAuthHandler) reset() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.initiateCalled = false
+}
+
+type mockOAuthHandler struct {
+	handleCallbackCalled bool
+	mu                   sync.RWMutex
+}
+
+func (m *mockOAuthHandler) HandleCallback(rw http.ResponseWriter, req *http.Request, redirectURL string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.handleCallbackCalled = true
+	rw.WriteHeader(http.StatusOK)
+	rw.Write([]byte("callback handled"))
+}
+
+func (m *mockOAuthHandler) wasHandleCallbackCalled() bool {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.handleCallbackCalled
+}
+
+type mockURLHelper struct {
+	excludedResult bool
+	scheme         string
+	host           string
+}
+
+func (m *mockURLHelper) DetermineExcludedURL(currentRequest string, excludedURLs map[string]struct{}) bool {
+	return m.excludedResult
+}
+
+func (m *mockURLHelper) DetermineScheme(req *http.Request) string {
+	if m.scheme != "" {
+		return m.scheme
+	}
+	return "https"
+}
+
+func (m *mockURLHelper) DetermineHost(req *http.Request) string {
+	if m.host != "" {
+		return m.host
+	}
+	return "example.com"
+}
+
+type mockTokenVerifier struct {
+	verifyError error
+}
+
+func (m *mockTokenVerifier) VerifyToken(token string) error {
+	return m.verifyError
+}
+
+type mockHandler struct {
+	serveHTTPCalled bool
+	mu              sync.RWMutex
+}
+
+func (m *mockHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.serveHTTPCalled = true
+	rw.WriteHeader(http.StatusOK)
+	rw.Write([]byte("next handler called"))
+}
+
+func (m *mockHandler) wasServeHTTPCalled() bool {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.serveHTTPCalled
+}
+
+//lint:ignore U1000 May be needed for future test isolation
+func (m *mockHandler) reset() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.serveHTTPCalled = false
+}
+
+// Test helper functions
+func createTestMiddleware() *AuthMiddleware {
+	logger := &mockLogger{}
+	nextHandler := &mockHandler{}
+	sessionManager := &mockSessionManager{sessionData: newMockSessionData()}
+	authHandler := &mockAuthHandler{}
+	oauthHandler := &mockOAuthHandler{}
+	urlHelper := &mockURLHelper{}
+	tokenVerifier := &mockTokenVerifier{}
+
+	extractClaimsFunc := func(tokenString string) (map[string]interface{}, error) {
+		return map[string]interface{}{"sub": "test-user", "email": "[email protected]"}, nil
+	}
+
+	extractGroupsAndRolesFunc := func(tokenString string) ([]string, []string, error) {
+		return []string{"group1"}, []string{"role1"}, nil
+	}
+
+	sendErrorResponseFunc := func(rw http.ResponseWriter, req *http.Request, message string, code int) {
+		http.Error(rw, message, code)
+	}
+
+	refreshTokenFunc := func(rw http.ResponseWriter, req *http.Request, session SessionData) bool {
+		return true
+	}
+
+	isUserAuthenticatedFunc := func(session SessionData) (bool, bool, bool) {
+		return true, false, false // authenticated, needsRefresh, expired
+	}
+
+	isAllowedDomainFunc := func(email string) bool {
+		return true
+	}
+
+	isAjaxRequestFunc := func(req *http.Request) bool {
+		return strings.Contains(req.Header.Get("Accept"), "application/json") ||
+			strings.Contains(req.Header.Get("Content-Type"), "application/json")
+	}
+
+	isRefreshTokenExpiredFunc := func(session SessionData) bool {
+		return false
+	}
+
+	processLogoutFunc := func(rw http.ResponseWriter, req *http.Request) {
+		rw.WriteHeader(http.StatusOK)
+		rw.Write([]byte("logged out"))
+	}
+
+	excludedURLs := make(map[string]struct{})
+	allowedRolesAndGroups := make(map[string]struct{})
+	initComplete := make(chan struct{})
+	close(initComplete) // Initialize as complete
+	var goroutineWG sync.WaitGroup
+
+	startTokenCleanupFunc := func() {
+		// Mock implementation
+	}
+
+	startMetadataRefreshFunc := func(providerURL string) {
+		// Mock implementation
+	}
+
+	return NewAuthMiddleware(
+		logger,
+		nextHandler,
+		sessionManager,
+		authHandler,
+		oauthHandler,
+		urlHelper,
+		tokenVerifier,
+		extractClaimsFunc,
+		extractGroupsAndRolesFunc,
+		sendErrorResponseFunc,
+		refreshTokenFunc,
+		isUserAuthenticatedFunc,
+		isAllowedDomainFunc,
+		isAjaxRequestFunc,
+		isRefreshTokenExpiredFunc,
+		processLogoutFunc,
+		excludedURLs,
+		allowedRolesAndGroups,
+		"/auth/callback",
+		"/auth/logout",
+		30*time.Second,
+		initComplete,
+		"https://provider.example.com",
+		"https://provider.example.com",
+		&goroutineWG,
+		startTokenCleanupFunc,
+		startMetadataRefreshFunc,
+	)
+}
+
+func TestNewAuthMiddleware(t *testing.T) {
+	middleware := createTestMiddleware()
+
+	if middleware == nil {
+		t.Fatal("NewAuthMiddleware returned nil")
+	}
+
+	if middleware.logger == nil {
+		t.Error("Expected logger to be set")
+	}
+
+	if middleware.next == nil {
+		t.Error("Expected next handler to be set")
+	}
+
+	if middleware.redirURLPath != "/auth/callback" {
+		t.Errorf("Expected redirURLPath to be '/auth/callback', got %s", middleware.redirURLPath)
+	}
+
+	if middleware.logoutURLPath != "/auth/logout" {
+		t.Errorf("Expected logoutURLPath to be '/auth/logout', got %s", middleware.logoutURLPath)
+	}
+}
+
+func TestServeHTTP_ExcludedURL(t *testing.T) {
+	middleware := createTestMiddleware()
+	urlHelper := &mockURLHelper{excludedResult: true}
+	middleware.urlHelper = urlHelper
+
+	req := httptest.NewRequest("GET", "/excluded/path", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	nextHandler := middleware.next.(*mockHandler)
+	if !nextHandler.wasServeHTTPCalled() {
+		t.Error("Expected next handler to be called for excluded URL")
+	}
+
+	if rw.Code != http.StatusOK {
+		t.Errorf("Expected status 200, got %d", rw.Code)
+	}
+}
+
+func TestServeHTTP_EventStreamBypass(t *testing.T) {
+	middleware := createTestMiddleware()
+
+	req := httptest.NewRequest("GET", "/test", nil)
+	req.Header.Set("Accept", "text/event-stream")
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	nextHandler := middleware.next.(*mockHandler)
+	if !nextHandler.wasServeHTTPCalled() {
+		t.Error("Expected next handler to be called for event stream request")
+	}
+}
+
+func TestServeHTTP_InitializationTimeout(t *testing.T) {
+	t.Skip("Skipping timeout test to avoid long delays")
+	logger := &mockLogger{}
+	nextHandler := &mockHandler{}
+	sessionManager := &mockSessionManager{sessionData: newMockSessionData()}
+	authHandler := &mockAuthHandler{}
+	oauthHandler := &mockOAuthHandler{}
+	urlHelper := &mockURLHelper{}
+	tokenVerifier := &mockTokenVerifier{}
+
+	// Create initComplete channel but don't close it to simulate timeout
+	initComplete := make(chan struct{})
+	var goroutineWG sync.WaitGroup
+
+	middleware := NewAuthMiddleware(
+		logger,
+		nextHandler,
+		sessionManager,
+		authHandler,
+		oauthHandler,
+		urlHelper,
+		tokenVerifier,
+		func(string) (map[string]interface{}, error) { return nil, nil },
+		func(string) ([]string, []string, error) { return nil, nil, nil },
+		func(rw http.ResponseWriter, req *http.Request, message string, code int) {
+			http.Error(rw, message, code)
+		},
+		func(http.ResponseWriter, *http.Request, SessionData) bool { return false },
+		func(SessionData) (bool, bool, bool) { return false, false, false },
+		func(string) bool { return true },
+		func(*http.Request) bool { return false },
+		func(SessionData) bool { return false },
+		func(http.ResponseWriter, *http.Request) {},
+		make(map[string]struct{}),
+		make(map[string]struct{}),
+		"/auth/callback",
+		"/auth/logout",
+		10*time.Millisecond, // Very short timeout for testing
+		initComplete,
+		"",
+		"https://provider.example.com",
+		&goroutineWG,
+		func() {},
+		func(string) {},
+	)
+
+	req := httptest.NewRequest("GET", "/test", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	if rw.Code != http.StatusServiceUnavailable {
+		t.Errorf("Expected status %d, got %d", http.StatusServiceUnavailable, rw.Code)
+	}
+}
+
+func TestServeHTTP_SessionError(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.setSessionError(fmt.Errorf("session error"))
+
+	// Ensure we have valid session data for the second call
+	sessionManager.sessionData = newMockSessionData()
+
+	req := httptest.NewRequest("GET", "/test", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	authHandler := middleware.authHandler.(*mockAuthHandler)
+	if !authHandler.wasInitiateCalled() {
+		t.Error("Expected InitiateAuthentication to be called when session error occurs")
+	}
+}
+
+func TestServeHTTP_LogoutPath(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionData.setEmail("[email protected]")
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	req := httptest.NewRequest("GET", "/auth/logout", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	if rw.Code != http.StatusOK {
+		t.Errorf("Expected status 200 for logout, got %d", rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "logged out") {
+		t.Errorf("Expected logout response, got %s", responseBody)
+	}
+}
+
+func TestServeHTTP_CallbackPath(t *testing.T) {
+	middleware := createTestMiddleware()
+
+	req := httptest.NewRequest("GET", "/auth/callback?code=test", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	oauthHandler := middleware.oauthHandler.(*mockOAuthHandler)
+	if !oauthHandler.wasHandleCallbackCalled() {
+		t.Error("Expected HandleCallback to be called for callback path")
+	}
+}
+
+func TestServeHTTP_AuthenticatedUser(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionData.setEmail("[email protected]")
+	sessionData.setAccessToken("valid.jwt.token")
+	sessionData.setIDToken("id.jwt.token")
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	req := httptest.NewRequest("GET", "/protected", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	nextHandler := middleware.next.(*mockHandler)
+	if !nextHandler.wasServeHTTPCalled() {
+		t.Error("Expected next handler to be called for authenticated user")
+	}
+
+	// Check that user headers are set
+	if req.Header.Get("X-Forwarded-User") != "[email protected]" {
+		t.Errorf("Expected X-Forwarded-User header to be set to '[email protected]', got %s", req.Header.Get("X-Forwarded-User"))
+	}
+
+	if req.Header.Get("X-Auth-Request-User") != "[email protected]" {
+		t.Errorf("Expected X-Auth-Request-User header to be set to '[email protected]', got %s", req.Header.Get("X-Auth-Request-User"))
+	}
+}
+
+func TestServeHTTP_DomainNotAllowed(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionData.setEmail("[email protected]")
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	// Set isAllowedDomainFunc to return false
+	middleware.isAllowedDomainFunc = func(email string) bool {
+		return false
+	}
+
+	req := httptest.NewRequest("GET", "/protected", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	if rw.Code != http.StatusForbidden {
+		t.Errorf("Expected status %d for disallowed domain, got %d", http.StatusForbidden, rw.Code)
+	}
+
+	responseBody := rw.Body.String()
+	if !strings.Contains(responseBody, "Access denied") {
+		t.Errorf("Expected access denied message, got %s", responseBody)
+	}
+}
+
+func TestServeHTTP_TokenRefreshNeeded(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionData.setEmail("[email protected]")
+	sessionData.setRefreshToken("refresh-token")
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	// Set authenticated but needs refresh
+	middleware.isUserAuthenticatedFunc = func(session SessionData) (bool, bool, bool) {
+		return true, true, false // authenticated, needsRefresh, not expired
+	}
+
+	req := httptest.NewRequest("GET", "/protected", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	nextHandler := middleware.next.(*mockHandler)
+	if !nextHandler.wasServeHTTPCalled() {
+		t.Error("Expected next handler to be called after successful token refresh")
+	}
+}
+
+func TestServeHTTP_AjaxRequestWithoutAuth(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	// Set user as not authenticated
+	middleware.isUserAuthenticatedFunc = func(session SessionData) (bool, bool, bool) {
+		return false, false, false
+	}
+
+	req := httptest.NewRequest("GET", "/api/data", nil)
+	req.Header.Set("Accept", "application/json")
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	if rw.Code != http.StatusUnauthorized {
+		t.Errorf("Expected status %d for AJAX request without auth, got %d", http.StatusUnauthorized, rw.Code)
+	}
+}
+
+func TestServeHTTP_ExpiredToken(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionData.setEmail("[email protected]")
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	// Set token as expired
+	middleware.isUserAuthenticatedFunc = func(session SessionData) (bool, bool, bool) {
+		return false, false, true // not authenticated, no refresh needed, expired
+	}
+
+	req := httptest.NewRequest("GET", "/protected", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	authHandler := middleware.authHandler.(*mockAuthHandler)
+	if !authHandler.wasInitiateCalled() {
+		t.Error("Expected InitiateAuthentication to be called for expired token")
+	}
+}
+
+func TestServeHTTP_RoleBasedAccess(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionData.setEmail("[email protected]")
+	sessionData.setIDToken("id.jwt.token")
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	// Set required roles
+	middleware.allowedRolesAndGroups = map[string]struct{}{
+		"admin":  {},
+		"group1": {},
+	}
+
+	// User has group1 which is allowed
+	middleware.extractGroupsAndRolesFunc = func(tokenString string) ([]string, []string, error) {
+		return []string{"group1"}, []string{"user"}, nil
+	}
+
+	req := httptest.NewRequest("GET", "/admin", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	nextHandler := middleware.next.(*mockHandler)
+	if !nextHandler.wasServeHTTPCalled() {
+		t.Error("Expected next handler to be called for user with allowed role")
+	}
+
+	// Check that group headers are set
+	if req.Header.Get("X-User-Groups") != "group1" {
+		t.Errorf("Expected X-User-Groups header to be set to 'group1', got %s", req.Header.Get("X-User-Groups"))
+	}
+}
+
+func TestServeHTTP_RoleBasedAccessDenied(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionData.setEmail("[email protected]")
+	sessionData.setIDToken("id.jwt.token")
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	// Set required roles that user doesn't have
+	middleware.allowedRolesAndGroups = map[string]struct{}{
+		"admin": {},
+	}
+
+	// User doesn't have admin role
+	middleware.extractGroupsAndRolesFunc = func(tokenString string) ([]string, []string, error) {
+		return []string{"group1"}, []string{"user"}, nil
+	}
+
+	req := httptest.NewRequest("GET", "/admin", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	if rw.Code != http.StatusForbidden {
+		t.Errorf("Expected status %d for user without required role, got %d", http.StatusForbidden, rw.Code)
+	}
+}
+
+func TestHandleTokenRefresh_FailedRefresh(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionData.setEmail("[email protected]")
+	sessionData.setRefreshToken("refresh-token")
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	// Set refresh to fail
+	middleware.refreshTokenFunc = func(rw http.ResponseWriter, req *http.Request, session SessionData) bool {
+		return false
+	}
+
+	// Set authenticated but needs refresh
+	middleware.isUserAuthenticatedFunc = func(session SessionData) (bool, bool, bool) {
+		return true, true, false
+	}
+
+	req := httptest.NewRequest("GET", "/protected", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	authHandler := middleware.authHandler.(*mockAuthHandler)
+	if !authHandler.wasInitiateCalled() {
+		t.Error("Expected InitiateAuthentication to be called after failed token refresh")
+	}
+}
+
+func TestBuildFullURL(t *testing.T) {
+	tests := []struct {
+		scheme   string
+		host     string
+		path     string
+		expected string
+	}{
+		{"https", "example.com", "/callback", "https://example.com/callback"},
+		{"http", "localhost:8080", "/auth", "http://localhost:8080/auth"},
+		{"https", "api.example.com", "/oauth/callback", "https://api.example.com/oauth/callback"},
+	}
+
+	for _, tt := range tests {
+		t.Run(fmt.Sprintf("%s_%s_%s", tt.scheme, tt.host, tt.path), func(t *testing.T) {
+			result := buildFullURL(tt.scheme, tt.host, tt.path)
+			if result != tt.expected {
+				t.Errorf("Expected %s, got %s", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestConcurrentRequests(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionData.setEmail("[email protected]")
+	sessionData.setAccessToken("valid.jwt.token")
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	const numGoroutines = 10
+	const numRequests = 5
+
+	var wg sync.WaitGroup
+	errors := make(chan error, numGoroutines*numRequests)
+
+	for i := 0; i < numGoroutines; i++ {
+		wg.Add(1)
+		go func(id int) {
+			defer wg.Done()
+			for j := 0; j < numRequests; j++ {
+				req := httptest.NewRequest("GET", fmt.Sprintf("/test-%d-%d", id, j), nil)
+				rw := httptest.NewRecorder()
+
+				middleware.ServeHTTP(rw, req)
+
+				if rw.Code != http.StatusOK {
+					errors <- fmt.Errorf("goroutine %d request %d: expected status 200, got %d", id, j, rw.Code)
+				}
+			}
+		}(i)
+	}
+
+	wg.Wait()
+	close(errors)
+
+	var errorCount int
+	for err := range errors {
+		t.Error(err)
+		errorCount++
+	}
+
+	if errorCount > 0 {
+		t.Errorf("Found %d errors in concurrent request test", errorCount)
+	}
+}
+
+func TestServeHTTP_TokenVerificationFailure(t *testing.T) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionData.setEmail("[email protected]")
+	sessionData.setAccessToken("invalid.jwt.token")
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	// Set token verifier to return error
+	tokenVerifier := middleware.tokenVerifier.(*mockTokenVerifier)
+	tokenVerifier.verifyError = fmt.Errorf("token verification failed")
+
+	req := httptest.NewRequest("GET", "/protected", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	authHandler := middleware.authHandler.(*mockAuthHandler)
+	if !authHandler.wasInitiateCalled() {
+		t.Error("Expected InitiateAuthentication to be called after token verification failure")
+	}
+}
+
+func TestServeHTTP_HealthCheckBypass(t *testing.T) {
+	middleware := createTestMiddleware()
+
+	// Set up URL helper to return excluded result for health check
+	urlHelper := &mockURLHelper{excludedResult: true}
+	middleware.urlHelper = urlHelper
+
+	req := httptest.NewRequest("GET", "/health", nil)
+	rw := httptest.NewRecorder()
+
+	middleware.ServeHTTP(rw, req)
+
+	nextHandler := middleware.next.(*mockHandler)
+	if !nextHandler.wasServeHTTPCalled() {
+		t.Error("Expected next handler to be called for health check")
+	}
+}
+
+func TestServeHTTP_RequestCancellation(t *testing.T) {
+	logger := &mockLogger{}
+	nextHandler := &mockHandler{}
+	sessionManager := &mockSessionManager{sessionData: newMockSessionData()}
+
+	// Create initComplete channel but don't close it to simulate slow initialization
+	initComplete := make(chan struct{})
+	var goroutineWG sync.WaitGroup
+
+	middleware := NewAuthMiddleware(
+		logger,
+		nextHandler,
+		sessionManager,
+		&mockAuthHandler{},
+		&mockOAuthHandler{},
+		&mockURLHelper{},
+		&mockTokenVerifier{},
+		func(string) (map[string]interface{}, error) { return nil, nil },
+		func(string) ([]string, []string, error) { return nil, nil, nil },
+		func(rw http.ResponseWriter, req *http.Request, message string, code int) {
+			http.Error(rw, message, code)
+		},
+		func(http.ResponseWriter, *http.Request, SessionData) bool { return false },
+		func(SessionData) (bool, bool, bool) { return false, false, false },
+		func(string) bool { return true },
+		func(*http.Request) bool { return false },
+		func(SessionData) bool { return false },
+		func(http.ResponseWriter, *http.Request) {},
+		make(map[string]struct{}),
+		make(map[string]struct{}),
+		"/auth/callback",
+		"/auth/logout",
+		30*time.Second,
+		initComplete,
+		"https://provider.example.com",
+		"https://provider.example.com",
+		&goroutineWG,
+		func() {},
+		func(string) {},
+	)
+
+	// Create context that gets cancelled
+	ctx, cancel := context.WithCancel(context.Background())
+	req := httptest.NewRequest("GET", "/test", nil).WithContext(ctx)
+	rw := httptest.NewRecorder()
+
+	// Cancel context immediately
+	cancel()
+
+	middleware.ServeHTTP(rw, req)
+
+	if rw.Code != http.StatusRequestTimeout {
+		t.Errorf("Expected status %d for cancelled request, got %d", http.StatusRequestTimeout, rw.Code)
+	}
+}
+
+// Benchmark tests
+func BenchmarkServeHTTP_AuthenticatedUser(b *testing.B) {
+	middleware := createTestMiddleware()
+	sessionData := newMockSessionData()
+	sessionData.setEmail("[email protected]")
+	sessionData.setAccessToken("valid.jwt.token")
+	sessionManager := middleware.sessionManager.(*mockSessionManager)
+	sessionManager.sessionData = sessionData
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		req := httptest.NewRequest("GET", "/protected", nil)
+		rw := httptest.NewRecorder()
+		middleware.ServeHTTP(rw, req)
+	}
+}
+
+func BenchmarkServeHTTP_ExcludedURL(b *testing.B) {
+	middleware := createTestMiddleware()
+	urlHelper := &mockURLHelper{excludedResult: true}
+	middleware.urlHelper = urlHelper
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		req := httptest.NewRequest("GET", "/excluded", nil)
+		rw := httptest.NewRecorder()
+		middleware.ServeHTTP(rw, req)
+	}
+}

recovery/error_handler.go

@@ -0,0 +1,258 @@
+// Package recovery provides error recovery and resilience mechanisms
+package recovery
+
+import (
+	"context"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// ErrorRecoveryMechanism defines the interface for error recovery strategies.
+// It provides a common contract for implementing various resilience patterns
+// (circuit breaker, retry, graceful degradation) to handle transient failures
+// and protect downstream services from cascading failures.
+type ErrorRecoveryMechanism interface {
+	// ExecuteWithContext executes a function with error recovery mechanisms
+	ExecuteWithContext(ctx context.Context, fn func() error) error
+	// GetMetrics returns metrics about the recovery mechanism's performance
+	GetMetrics() map[string]interface{}
+	// Reset resets the mechanism to its initial state
+	Reset()
+	// IsAvailable returns whether the mechanism is available for requests
+	IsAvailable() bool
+}
+
+// Logger interface for dependency injection
+type Logger interface {
+	Infof(format string, args ...interface{})
+	Errorf(format string, args ...interface{})
+	Debugf(format string, args ...interface{})
+}
+
+// BaseRecoveryMechanism provides common functionality and metrics tracking
+// for all error recovery mechanisms. It handles request/failure/success counting,
+// timing information, and logging capabilities for derived recovery mechanisms.
+type BaseRecoveryMechanism struct {
+	// startTime tracks when the mechanism was created
+	startTime time.Time
+	// lastFailureTime records the most recent failure timestamp
+	lastFailureTime time.Time
+	// lastSuccessTime records the most recent success timestamp
+	lastSuccessTime time.Time
+	// logger for debugging and monitoring
+	logger Logger
+	// name identifies this recovery mechanism instance
+	name string
+	// totalRequests counts all requests processed
+	totalRequests int64
+	// totalFailures counts failed requests
+	totalFailures int64
+	// totalSuccesses counts successful requests
+	totalSuccesses int64
+	// mutex protects shared state access
+	mutex sync.RWMutex
+}
+
+// NewBaseRecoveryMechanism creates a new base recovery mechanism with the given name and logger.
+// This serves as the foundation for specific recovery mechanism implementations.
+func NewBaseRecoveryMechanism(name string, logger Logger) *BaseRecoveryMechanism {
+	if logger == nil {
+		logger = NewNoOpLogger()
+	}
+
+	return &BaseRecoveryMechanism{
+		name:      name,
+		logger:    logger,
+		startTime: time.Now(),
+	}
+}
+
+// RecordRequest increments the total request counter.
+// This method is thread-safe using atomic operations.
+func (b *BaseRecoveryMechanism) RecordRequest() {
+	atomic.AddInt64(&b.totalRequests, 1)
+}
+
+// RecordSuccess increments the success counter and updates the last success timestamp.
+// This method is thread-safe using atomic operations for counters
+// and mutex protection for timestamp updates.
+func (b *BaseRecoveryMechanism) RecordSuccess() {
+	atomic.AddInt64(&b.totalSuccesses, 1)
+
+	b.mutex.Lock()
+	defer b.mutex.Unlock()
+	b.lastSuccessTime = time.Now()
+}
+
+// RecordFailure increments the failure counter and updates the last failure timestamp.
+// This method is thread-safe using atomic operations for counters
+// and mutex protection for timestamp updates.
+func (b *BaseRecoveryMechanism) RecordFailure() {
+	atomic.AddInt64(&b.totalFailures, 1)
+
+	b.mutex.Lock()
+	defer b.mutex.Unlock()
+	b.lastFailureTime = time.Now()
+}
+
+// GetBaseMetrics returns basic metrics collected by the base recovery mechanism.
+// This includes request counts, success/failure rates, and timing information.
+func (b *BaseRecoveryMechanism) GetBaseMetrics() map[string]interface{} {
+	b.mutex.RLock()
+	defer b.mutex.RUnlock()
+
+	totalReqs := atomic.LoadInt64(&b.totalRequests)
+	totalSucc := atomic.LoadInt64(&b.totalSuccesses)
+	totalFail := atomic.LoadInt64(&b.totalFailures)
+
+	metrics := map[string]interface{}{
+		"name":            b.name,
+		"total_requests":  totalReqs,
+		"total_successes": totalSucc,
+		"total_failures":  totalFail,
+		"start_time":      b.startTime,
+	}
+
+	if totalReqs > 0 {
+		metrics["success_rate"] = float64(totalSucc) / float64(totalReqs)
+		metrics["failure_rate"] = float64(totalFail) / float64(totalReqs)
+	}
+
+	if !b.lastSuccessTime.IsZero() {
+		metrics["last_success_time"] = b.lastSuccessTime
+		metrics["time_since_last_success"] = time.Since(b.lastSuccessTime)
+	}
+
+	if !b.lastFailureTime.IsZero() {
+		metrics["last_failure_time"] = b.lastFailureTime
+		metrics["time_since_last_failure"] = time.Since(b.lastFailureTime)
+	}
+
+	metrics["uptime"] = time.Since(b.startTime)
+
+	return metrics
+}
+
+// LogInfo logs an info message if a logger is available
+func (b *BaseRecoveryMechanism) LogInfo(format string, args ...interface{}) {
+	if b.logger != nil {
+		b.logger.Infof(format, args...)
+	}
+}
+
+// LogError logs an error message if a logger is available
+func (b *BaseRecoveryMechanism) LogError(format string, args ...interface{}) {
+	if b.logger != nil {
+		b.logger.Errorf(format, args...)
+	}
+}
+
+// LogDebug logs a debug message if a logger is available
+func (b *BaseRecoveryMechanism) LogDebug(format string, args ...interface{}) {
+	if b.logger != nil {
+		b.logger.Debugf(format, args...)
+	}
+}
+
+// ErrorHandler provides centralized error handling and recovery coordination
+type ErrorHandler struct {
+	mechanisms []ErrorRecoveryMechanism
+	logger     Logger
+	mutex      sync.RWMutex
+}
+
+// NewErrorHandler creates a new error handler with the given mechanisms
+func NewErrorHandler(logger Logger, mechanisms ...ErrorRecoveryMechanism) *ErrorHandler {
+	return &ErrorHandler{
+		mechanisms: mechanisms,
+		logger:     logger,
+	}
+}
+
+// AddMechanism adds a recovery mechanism to the handler
+func (eh *ErrorHandler) AddMechanism(mechanism ErrorRecoveryMechanism) {
+	eh.mutex.Lock()
+	defer eh.mutex.Unlock()
+	eh.mechanisms = append(eh.mechanisms, mechanism)
+}
+
+// ExecuteWithRecovery executes a function with all configured recovery mechanisms
+func (eh *ErrorHandler) ExecuteWithRecovery(ctx context.Context, fn func() error) error {
+	eh.mutex.RLock()
+	mechanisms := make([]ErrorRecoveryMechanism, len(eh.mechanisms))
+	copy(mechanisms, eh.mechanisms)
+	eh.mutex.RUnlock()
+
+	// If no mechanisms are configured, execute directly
+	if len(mechanisms) == 0 {
+		return fn()
+	}
+
+	// Chain the mechanisms - each wraps the next
+	var wrappedFn func() error = fn
+	for i := len(mechanisms) - 1; i >= 0; i-- {
+		mechanism := mechanisms[i]
+		currentFn := wrappedFn
+		wrappedFn = func() error {
+			return mechanism.ExecuteWithContext(ctx, currentFn)
+		}
+	}
+
+	return wrappedFn()
+}
+
+// GetAllMetrics returns metrics from all configured mechanisms
+func (eh *ErrorHandler) GetAllMetrics() map[string]interface{} {
+	eh.mutex.RLock()
+	defer eh.mutex.RUnlock()
+
+	allMetrics := make(map[string]interface{})
+	for i, mechanism := range eh.mechanisms {
+		mechanismKey := "mechanism_" + string(rune(i))
+		allMetrics[mechanismKey] = mechanism.GetMetrics()
+	}
+
+	return allMetrics
+}
+
+// ResetAll resets all configured mechanisms
+func (eh *ErrorHandler) ResetAll() {
+	eh.mutex.RLock()
+	defer eh.mutex.RUnlock()
+
+	for _, mechanism := range eh.mechanisms {
+		mechanism.Reset()
+	}
+}
+
+// IsHealthy returns true if all mechanisms are available
+func (eh *ErrorHandler) IsHealthy() bool {
+	eh.mutex.RLock()
+	defer eh.mutex.RUnlock()
+
+	for _, mechanism := range eh.mechanisms {
+		if !mechanism.IsAvailable() {
+			return false
+		}
+	}
+
+	return true
+}
+
+// NoOpLogger provides a logger that does nothing
+type NoOpLogger struct{}
+
+// NewNoOpLogger creates a new no-op logger
+func NewNoOpLogger() *NoOpLogger {
+	return &NoOpLogger{}
+}
+
+// Infof does nothing
+func (l *NoOpLogger) Infof(format string, args ...interface{}) {}
+
+// Errorf does nothing
+func (l *NoOpLogger) Errorf(format string, args ...interface{}) {}
+
+// Debugf does nothing
+func (l *NoOpLogger) Debugf(format string, args ...interface{}) {}

recovery/error_handler_test.go

@@ -0,0 +1,827 @@
+package recovery
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"sync/atomic"
+	"testing"
+)
+
+// Mock implementations for testing
+type mockLogger struct {
+	infoLogs  []string
+	errorLogs []string
+	debugLogs []string
+	mu        sync.RWMutex
+}
+
+func (m *mockLogger) Infof(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.infoLogs = append(m.infoLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockLogger) Errorf(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.errorLogs = append(m.errorLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockLogger) Debugf(format string, args ...interface{}) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.debugLogs = append(m.debugLogs, fmt.Sprintf(format, args...))
+}
+
+func (m *mockLogger) getInfoLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.infoLogs))
+	copy(result, m.infoLogs)
+	return result
+}
+
+func (m *mockLogger) getErrorLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.errorLogs))
+	copy(result, m.errorLogs)
+	return result
+}
+
+func (m *mockLogger) getDebugLogs() []string {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	result := make([]string, len(m.debugLogs))
+	copy(result, m.debugLogs)
+	return result
+}
+
+//lint:ignore U1000 May be needed for future test isolation
+func (m *mockLogger) reset() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.infoLogs = nil
+	m.errorLogs = nil
+	m.debugLogs = nil
+}
+
+type mockRecoveryMechanism struct {
+	name             string
+	executeError     error
+	isAvailable      bool
+	resetCalled      bool
+	executeCallCount int64
+	metrics          map[string]interface{}
+	executeFunc      func(ctx context.Context, fn func() error) error
+	mu               sync.RWMutex
+}
+
+func newMockRecoveryMechanism(name string) *mockRecoveryMechanism {
+	return &mockRecoveryMechanism{
+		name:        name,
+		isAvailable: true,
+		metrics:     make(map[string]interface{}),
+	}
+}
+
+func (m *mockRecoveryMechanism) ExecuteWithContext(ctx context.Context, fn func() error) error {
+	if m.executeFunc != nil {
+		return m.executeFunc(ctx, fn)
+	}
+
+	atomic.AddInt64(&m.executeCallCount, 1)
+
+	m.mu.RLock()
+	err := m.executeError
+	m.mu.RUnlock()
+
+	if err != nil {
+		return err
+	}
+
+	return fn()
+}
+
+func (m *mockRecoveryMechanism) GetMetrics() map[string]interface{} {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	result := make(map[string]interface{})
+	for k, v := range m.metrics {
+		result[k] = v
+	}
+	result["name"] = m.name
+	result["execute_call_count"] = atomic.LoadInt64(&m.executeCallCount)
+	return result
+}
+
+func (m *mockRecoveryMechanism) Reset() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.resetCalled = true
+	atomic.StoreInt64(&m.executeCallCount, 0)
+}
+
+func (m *mockRecoveryMechanism) IsAvailable() bool {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.isAvailable
+}
+
+func (m *mockRecoveryMechanism) setExecuteError(err error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.executeError = err
+}
+
+func (m *mockRecoveryMechanism) setAvailable(available bool) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.isAvailable = available
+}
+
+func (m *mockRecoveryMechanism) wasResetCalled() bool {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.resetCalled
+}
+
+func (m *mockRecoveryMechanism) getExecuteCallCount() int64 {
+	return atomic.LoadInt64(&m.executeCallCount)
+}
+
+func TestNewBaseRecoveryMechanism(t *testing.T) {
+	tests := []struct {
+		name       string
+		loggerName string
+		logger     Logger
+	}{
+		{
+			name:       "with mock logger",
+			loggerName: "test-mechanism",
+			logger:     &mockLogger{},
+		},
+		{
+			name:       "with nil logger",
+			loggerName: "test-mechanism-nil",
+			logger:     nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			mechanism := NewBaseRecoveryMechanism(tt.loggerName, tt.logger)
+
+			if mechanism == nil {
+				t.Fatal("NewBaseRecoveryMechanism returned nil")
+			}
+
+			if mechanism.name != tt.loggerName {
+				t.Errorf("Expected name %s, got %s", tt.loggerName, mechanism.name)
+			}
+
+			if tt.logger == nil && mechanism.logger == nil {
+				t.Error("Expected NoOpLogger to be created when logger is nil")
+			}
+
+			if mechanism.startTime.IsZero() {
+				t.Error("Expected startTime to be set")
+			}
+		})
+	}
+}
+
+func TestBaseRecoveryMechanism_RecordMetrics(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism := NewBaseRecoveryMechanism("test", logger)
+
+	// Test initial state
+	if atomic.LoadInt64(&mechanism.totalRequests) != 0 {
+		t.Error("Expected initial totalRequests to be 0")
+	}
+	if atomic.LoadInt64(&mechanism.totalSuccesses) != 0 {
+		t.Error("Expected initial totalSuccesses to be 0")
+	}
+	if atomic.LoadInt64(&mechanism.totalFailures) != 0 {
+		t.Error("Expected initial totalFailures to be 0")
+	}
+
+	// Record some metrics
+	mechanism.RecordRequest()
+	mechanism.RecordSuccess()
+
+	if atomic.LoadInt64(&mechanism.totalRequests) != 1 {
+		t.Error("Expected totalRequests to be 1")
+	}
+	if atomic.LoadInt64(&mechanism.totalSuccesses) != 1 {
+		t.Error("Expected totalSuccesses to be 1")
+	}
+
+	mechanism.RecordRequest()
+	mechanism.RecordFailure()
+
+	if atomic.LoadInt64(&mechanism.totalRequests) != 2 {
+		t.Error("Expected totalRequests to be 2")
+	}
+	if atomic.LoadInt64(&mechanism.totalFailures) != 1 {
+		t.Error("Expected totalFailures to be 1")
+	}
+
+	// Check timestamps are set
+	if mechanism.lastSuccessTime.IsZero() {
+		t.Error("Expected lastSuccessTime to be set")
+	}
+	if mechanism.lastFailureTime.IsZero() {
+		t.Error("Expected lastFailureTime to be set")
+	}
+}
+
+func TestBaseRecoveryMechanism_GetBaseMetrics(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism := NewBaseRecoveryMechanism("test-metrics", logger)
+
+	// Record some activity
+	mechanism.RecordRequest()
+	mechanism.RecordRequest()
+	mechanism.RecordSuccess()
+	mechanism.RecordFailure()
+
+	metrics := mechanism.GetBaseMetrics()
+
+	expectedFields := []string{
+		"name", "total_requests", "total_successes", "total_failures",
+		"start_time", "success_rate", "failure_rate", "uptime",
+		"last_success_time", "time_since_last_success",
+		"last_failure_time", "time_since_last_failure",
+	}
+
+	for _, field := range expectedFields {
+		if _, exists := metrics[field]; !exists {
+			t.Errorf("Expected metric field %s to exist", field)
+		}
+	}
+
+	// Check specific values
+	if metrics["name"] != "test-metrics" {
+		t.Errorf("Expected name to be 'test-metrics', got %v", metrics["name"])
+	}
+
+	if metrics["total_requests"] != int64(2) {
+		t.Errorf("Expected total_requests to be 2, got %v", metrics["total_requests"])
+	}
+
+	if metrics["total_successes"] != int64(1) {
+		t.Errorf("Expected total_successes to be 1, got %v", metrics["total_successes"])
+	}
+
+	if metrics["total_failures"] != int64(1) {
+		t.Errorf("Expected total_failures to be 1, got %v", metrics["total_failures"])
+	}
+
+	if metrics["success_rate"] != float64(0.5) {
+		t.Errorf("Expected success_rate to be 0.5, got %v", metrics["success_rate"])
+	}
+
+	if metrics["failure_rate"] != float64(0.5) {
+		t.Errorf("Expected failure_rate to be 0.5, got %v", metrics["failure_rate"])
+	}
+}
+
+func TestBaseRecoveryMechanism_GetBaseMetrics_NoRequests(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism := NewBaseRecoveryMechanism("test-empty", logger)
+
+	metrics := mechanism.GetBaseMetrics()
+
+	// Should not have success_rate or failure_rate when no requests
+	if _, exists := metrics["success_rate"]; exists {
+		t.Error("Expected success_rate to not exist when no requests")
+	}
+	if _, exists := metrics["failure_rate"]; exists {
+		t.Error("Expected failure_rate to not exist when no requests")
+	}
+
+	// Should not have timestamp fields when no successes/failures
+	if _, exists := metrics["last_success_time"]; exists {
+		t.Error("Expected last_success_time to not exist when no successes")
+	}
+	if _, exists := metrics["last_failure_time"]; exists {
+		t.Error("Expected last_failure_time to not exist when no failures")
+	}
+}
+
+func TestBaseRecoveryMechanism_Logging(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism := NewBaseRecoveryMechanism("test-logging", logger)
+
+	mechanism.LogInfo("test info: %s", "value")
+	mechanism.LogError("test error: %d", 42)
+	mechanism.LogDebug("test debug: %v", true)
+
+	infoLogs := logger.getInfoLogs()
+	if len(infoLogs) != 1 || infoLogs[0] != "test info: value" {
+		t.Errorf("Expected info log 'test info: value', got %v", infoLogs)
+	}
+
+	errorLogs := logger.getErrorLogs()
+	if len(errorLogs) != 1 || errorLogs[0] != "test error: 42" {
+		t.Errorf("Expected error log 'test error: 42', got %v", errorLogs)
+	}
+
+	debugLogs := logger.getDebugLogs()
+	if len(debugLogs) != 1 || debugLogs[0] != "test debug: true" {
+		t.Errorf("Expected debug log 'test debug: true', got %v", debugLogs)
+	}
+}
+
+func TestBaseRecoveryMechanism_LoggingWithNilLogger(t *testing.T) {
+	mechanism := NewBaseRecoveryMechanism("test-nil-logger", nil)
+
+	// Should not panic when logger is nil (uses NoOpLogger)
+	mechanism.LogInfo("test info")
+	mechanism.LogError("test error")
+	mechanism.LogDebug("test debug")
+}
+
+func TestNewErrorHandler(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism1 := newMockRecoveryMechanism("mech1")
+	mechanism2 := newMockRecoveryMechanism("mech2")
+
+	handler := NewErrorHandler(logger, mechanism1, mechanism2)
+
+	if handler == nil {
+		t.Fatal("NewErrorHandler returned nil")
+	}
+
+	if handler.logger != logger {
+		t.Error("Expected logger to be set")
+	}
+
+	if len(handler.mechanisms) != 2 {
+		t.Errorf("Expected 2 mechanisms, got %d", len(handler.mechanisms))
+	}
+}
+
+func TestErrorHandler_AddMechanism(t *testing.T) {
+	logger := &mockLogger{}
+	handler := NewErrorHandler(logger)
+
+	if len(handler.mechanisms) != 0 {
+		t.Errorf("Expected 0 initial mechanisms, got %d", len(handler.mechanisms))
+	}
+
+	mechanism := newMockRecoveryMechanism("test")
+	handler.AddMechanism(mechanism)
+
+	if len(handler.mechanisms) != 1 {
+		t.Errorf("Expected 1 mechanism after adding, got %d", len(handler.mechanisms))
+	}
+}
+
+func TestErrorHandler_ExecuteWithRecovery_NoMechanisms(t *testing.T) {
+	logger := &mockLogger{}
+	handler := NewErrorHandler(logger)
+
+	callCount := 0
+	testFunc := func() error {
+		callCount++
+		return nil
+	}
+
+	ctx := context.Background()
+	err := handler.ExecuteWithRecovery(ctx, testFunc)
+
+	if err != nil {
+		t.Errorf("Expected no error, got %v", err)
+	}
+
+	if callCount != 1 {
+		t.Errorf("Expected function to be called once, got %d", callCount)
+	}
+}
+
+func TestErrorHandler_ExecuteWithRecovery_WithMechanisms(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism1 := newMockRecoveryMechanism("mech1")
+	mechanism2 := newMockRecoveryMechanism("mech2")
+	handler := NewErrorHandler(logger, mechanism1, mechanism2)
+
+	callCount := 0
+	testFunc := func() error {
+		callCount++
+		return nil
+	}
+
+	ctx := context.Background()
+	err := handler.ExecuteWithRecovery(ctx, testFunc)
+
+	if err != nil {
+		t.Errorf("Expected no error, got %v", err)
+	}
+
+	if callCount != 1 {
+		t.Errorf("Expected function to be called once, got %d", callCount)
+	}
+
+	// Both mechanisms should have been called
+	if mechanism1.getExecuteCallCount() != 1 {
+		t.Errorf("Expected mechanism1 to be called once, got %d", mechanism1.getExecuteCallCount())
+	}
+	if mechanism2.getExecuteCallCount() != 1 {
+		t.Errorf("Expected mechanism2 to be called once, got %d", mechanism2.getExecuteCallCount())
+	}
+}
+
+func TestErrorHandler_ExecuteWithRecovery_MechanismError(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism := newMockRecoveryMechanism("failing-mech")
+	mechanism.setExecuteError(fmt.Errorf("mechanism failed"))
+	handler := NewErrorHandler(logger, mechanism)
+
+	callCount := 0
+	testFunc := func() error {
+		callCount++
+		return nil
+	}
+
+	ctx := context.Background()
+	err := handler.ExecuteWithRecovery(ctx, testFunc)
+
+	if err == nil {
+		t.Error("Expected error from mechanism")
+	}
+
+	if err.Error() != "mechanism failed" {
+		t.Errorf("Expected 'mechanism failed', got %v", err)
+	}
+
+	// Function should not be called if mechanism fails
+	if callCount != 0 {
+		t.Errorf("Expected function not to be called, got %d calls", callCount)
+	}
+}
+
+func TestErrorHandler_ExecuteWithRecovery_FunctionError(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism := newMockRecoveryMechanism("mech")
+	handler := NewErrorHandler(logger, mechanism)
+
+	testFunc := func() error {
+		return fmt.Errorf("function failed")
+	}
+
+	ctx := context.Background()
+	err := handler.ExecuteWithRecovery(ctx, testFunc)
+
+	if err == nil {
+		t.Error("Expected error from function")
+	}
+
+	if err.Error() != "function failed" {
+		t.Errorf("Expected 'function failed', got %v", err)
+	}
+}
+
+func TestErrorHandler_GetAllMetrics(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism1 := newMockRecoveryMechanism("mech1")
+	mechanism2 := newMockRecoveryMechanism("mech2")
+	handler := NewErrorHandler(logger, mechanism1, mechanism2)
+
+	// Add some custom metrics
+	mechanism1.metrics["custom1"] = "value1"
+	mechanism2.metrics["custom2"] = "value2"
+
+	metrics := handler.GetAllMetrics()
+
+	if len(metrics) != 2 {
+		t.Errorf("Expected 2 mechanism metrics, got %d", len(metrics))
+	}
+
+	mechanism0Key := "mechanism_" + string(rune(0))
+	mechanism0Metrics, exists := metrics[mechanism0Key]
+	if !exists {
+		t.Errorf("Expected %s metrics to exist", mechanism0Key)
+	} else {
+		mechanismMap, ok := mechanism0Metrics.(map[string]interface{})
+		if !ok {
+			t.Error("Expected mechanism metrics to be a map")
+		} else {
+			if mechanismMap["name"] != "mech1" {
+				t.Errorf("Expected name 'mech1', got %v", mechanismMap["name"])
+			}
+			if mechanismMap["custom1"] != "value1" {
+				t.Errorf("Expected custom1 'value1', got %v", mechanismMap["custom1"])
+			}
+		}
+	}
+
+	mechanism1Key := "mechanism_" + string(rune(1))
+	mechanism1Metrics, exists := metrics[mechanism1Key]
+	if !exists {
+		t.Errorf("Expected %s metrics to exist", mechanism1Key)
+	} else {
+		mechanismMap, ok := mechanism1Metrics.(map[string]interface{})
+		if !ok {
+			t.Error("Expected mechanism metrics to be a map")
+		} else {
+			if mechanismMap["name"] != "mech2" {
+				t.Errorf("Expected name 'mech2', got %v", mechanismMap["name"])
+			}
+			if mechanismMap["custom2"] != "value2" {
+				t.Errorf("Expected custom2 'value2', got %v", mechanismMap["custom2"])
+			}
+		}
+	}
+}
+
+func TestErrorHandler_ResetAll(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism1 := newMockRecoveryMechanism("mech1")
+	mechanism2 := newMockRecoveryMechanism("mech2")
+	handler := NewErrorHandler(logger, mechanism1, mechanism2)
+
+	handler.ResetAll()
+
+	if !mechanism1.wasResetCalled() {
+		t.Error("Expected mechanism1 to be reset")
+	}
+	if !mechanism2.wasResetCalled() {
+		t.Error("Expected mechanism2 to be reset")
+	}
+}
+
+func TestErrorHandler_IsHealthy(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism1 := newMockRecoveryMechanism("mech1")
+	mechanism2 := newMockRecoveryMechanism("mech2")
+	handler := NewErrorHandler(logger, mechanism1, mechanism2)
+
+	// Initially both are available
+	if !handler.IsHealthy() {
+		t.Error("Expected handler to be healthy when all mechanisms are available")
+	}
+
+	// Make one mechanism unavailable
+	mechanism1.setAvailable(false)
+	if handler.IsHealthy() {
+		t.Error("Expected handler to be unhealthy when one mechanism is unavailable")
+	}
+
+	// Make both unavailable
+	mechanism2.setAvailable(false)
+	if handler.IsHealthy() {
+		t.Error("Expected handler to be unhealthy when all mechanisms are unavailable")
+	}
+
+	// Make both available again
+	mechanism1.setAvailable(true)
+	mechanism2.setAvailable(true)
+	if !handler.IsHealthy() {
+		t.Error("Expected handler to be healthy when all mechanisms are available again")
+	}
+}
+
+func TestErrorHandler_IsHealthy_NoMechanisms(t *testing.T) {
+	logger := &mockLogger{}
+	handler := NewErrorHandler(logger)
+
+	// Should be healthy with no mechanisms
+	if !handler.IsHealthy() {
+		t.Error("Expected handler to be healthy with no mechanisms")
+	}
+}
+
+func TestNoOpLogger(t *testing.T) {
+	logger := NewNoOpLogger()
+
+	if logger == nil {
+		t.Fatal("NewNoOpLogger returned nil")
+	}
+
+	// Should not panic
+	logger.Infof("test info: %s", "value")
+	logger.Errorf("test error: %d", 42)
+	logger.Debugf("test debug: %v", true)
+}
+
+func TestConcurrentAccess(t *testing.T) {
+	logger := &mockLogger{}
+	baseMechanism := NewBaseRecoveryMechanism("concurrent-test", logger)
+
+	const numGoroutines = 10
+	const numOperations = 100
+
+	var wg sync.WaitGroup
+	errors := make(chan error, numGoroutines)
+
+	// Test concurrent metric recording
+	for i := 0; i < numGoroutines; i++ {
+		wg.Add(1)
+		go func(id int) {
+			defer wg.Done()
+			for j := 0; j < numOperations; j++ {
+				baseMechanism.RecordRequest()
+				if j%2 == 0 {
+					baseMechanism.RecordSuccess()
+				} else {
+					baseMechanism.RecordFailure()
+				}
+
+				// Intermittently get metrics to test concurrent reads
+				if j%10 == 0 {
+					baseMechanism.GetBaseMetrics()
+				}
+			}
+		}(i)
+	}
+
+	wg.Wait()
+	close(errors)
+
+	var errorCount int
+	for err := range errors {
+		t.Error(err)
+		errorCount++
+	}
+
+	if errorCount > 0 {
+		t.Errorf("Found %d errors in concurrent access test", errorCount)
+	}
+
+	// Verify final counts
+	expectedRequests := int64(numGoroutines * numOperations)
+	expectedSuccesses := int64(numGoroutines * numOperations / 2)
+	expectedFailures := int64(numGoroutines * numOperations / 2)
+
+	if atomic.LoadInt64(&baseMechanism.totalRequests) != expectedRequests {
+		t.Errorf("Expected %d total requests, got %d", expectedRequests,
+			atomic.LoadInt64(&baseMechanism.totalRequests))
+	}
+
+	if atomic.LoadInt64(&baseMechanism.totalSuccesses) != expectedSuccesses {
+		t.Errorf("Expected %d total successes, got %d", expectedSuccesses,
+			atomic.LoadInt64(&baseMechanism.totalSuccesses))
+	}
+
+	if atomic.LoadInt64(&baseMechanism.totalFailures) != expectedFailures {
+		t.Errorf("Expected %d total failures, got %d", expectedFailures,
+			atomic.LoadInt64(&baseMechanism.totalFailures))
+	}
+}
+
+func TestErrorHandler_ConcurrentAccess(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism1 := newMockRecoveryMechanism("concurrent-mech1")
+	mechanism2 := newMockRecoveryMechanism("concurrent-mech2")
+	handler := NewErrorHandler(logger, mechanism1, mechanism2)
+
+	const numGoroutines = 5
+	const numExecutions = 20
+
+	var wg sync.WaitGroup
+	successCount := int64(0)
+
+	for i := 0; i < numGoroutines; i++ {
+		wg.Add(1)
+		go func(id int) {
+			defer wg.Done()
+			for j := 0; j < numExecutions; j++ {
+				err := handler.ExecuteWithRecovery(context.Background(), func() error {
+					atomic.AddInt64(&successCount, 1)
+					return nil
+				})
+				if err != nil {
+					t.Errorf("Unexpected error in goroutine %d: %v", id, err)
+				}
+
+				// Add some mechanisms concurrently
+				if j == 0 {
+					newMech := newMockRecoveryMechanism(fmt.Sprintf("dynamic-mech-%d", id))
+					handler.AddMechanism(newMech)
+				}
+
+				// Get metrics concurrently
+				if j%5 == 0 {
+					handler.GetAllMetrics()
+				}
+			}
+		}(i)
+	}
+
+	wg.Wait()
+
+	expectedSuccesses := int64(numGoroutines * numExecutions)
+	if atomic.LoadInt64(&successCount) != expectedSuccesses {
+		t.Errorf("Expected %d successes, got %d", expectedSuccesses,
+			atomic.LoadInt64(&successCount))
+	}
+
+	// Should have original 2 mechanisms plus 5 added dynamically
+	if len(handler.mechanisms) != 7 {
+		t.Errorf("Expected 7 mechanisms after concurrent additions, got %d",
+			len(handler.mechanisms))
+	}
+}
+
+func TestErrorHandler_ContextCancellation(t *testing.T) {
+	logger := &mockLogger{}
+	mechanism := newMockRecoveryMechanism("context-test")
+	handler := NewErrorHandler(logger, mechanism)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel() // Cancel immediately
+
+	executedCount := 0
+	testFunc := func() error {
+		executedCount++
+		return nil
+	}
+
+	// The mechanism implementation should handle context cancellation
+	// For our mock, we'll make it check context cancellation
+	mechanism.executeFunc = func(ctx context.Context, fn func() error) error {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+			atomic.AddInt64(&mechanism.executeCallCount, 1)
+			return fn()
+		}
+	}
+
+	err := handler.ExecuteWithRecovery(ctx, testFunc)
+
+	if err != context.Canceled {
+		t.Errorf("Expected context.Canceled, got %v", err)
+	}
+
+	if executedCount != 0 {
+		t.Errorf("Expected function not to execute when context is cancelled, got %d executions", executedCount)
+	}
+}
+
+// Benchmark tests
+func BenchmarkBaseRecoveryMechanism_RecordRequest(b *testing.B) {
+	logger := &mockLogger{}
+	mechanism := NewBaseRecoveryMechanism("benchmark", logger)
+
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			mechanism.RecordRequest()
+		}
+	})
+}
+
+func BenchmarkBaseRecoveryMechanism_RecordSuccess(b *testing.B) {
+	logger := &mockLogger{}
+	mechanism := NewBaseRecoveryMechanism("benchmark", logger)
+
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			mechanism.RecordSuccess()
+		}
+	})
+}
+
+func BenchmarkBaseRecoveryMechanism_GetBaseMetrics(b *testing.B) {
+	logger := &mockLogger{}
+	mechanism := NewBaseRecoveryMechanism("benchmark", logger)
+
+	// Add some data
+	for i := 0; i < 100; i++ {
+		mechanism.RecordRequest()
+		if i%2 == 0 {
+			mechanism.RecordSuccess()
+		} else {
+			mechanism.RecordFailure()
+		}
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		mechanism.GetBaseMetrics()
+	}
+}
+
+func BenchmarkErrorHandler_ExecuteWithRecovery(b *testing.B) {
+	logger := &mockLogger{}
+	mechanism := newMockRecoveryMechanism("benchmark")
+	handler := NewErrorHandler(logger, mechanism)
+
+	testFunc := func() error {
+		return nil
+	}
+
+	ctx := context.Background()
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		handler.ExecuteWithRecovery(ctx, testFunc)
+	}
+}

session/chunking/chunk_manager.go

@@ -0,0 +1,406 @@
+// Package chunking provides session chunking functionality for large tokens
+package chunking
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/gorilla/sessions"
+)
+
+const (
+	maxCookieSize = 1200
+)
+
+// TokenConfig defines validation and storage parameters for different token types.
+// It specifies size limits, format requirements, and security constraints to ensure
+// tokens can be safely stored in browser cookies while maintaining security.
+type TokenConfig struct {
+	Type              string
+	MinLength         int
+	MaxLength         int
+	MaxChunks         int
+	MaxChunkSize      int
+	AllowOpaqueTokens bool
+	RequireJWTFormat  bool
+}
+
+// Predefined configurations for each token type
+var (
+	AccessTokenConfig = TokenConfig{
+		Type:              "access",
+		MinLength:         5,
+		MaxLength:         100 * 1024,
+		MaxChunks:         25,
+		MaxChunkSize:      maxCookieSize,
+		AllowOpaqueTokens: true,
+		RequireJWTFormat:  false,
+	}
+
+	RefreshTokenConfig = TokenConfig{
+		Type:              "refresh",
+		MinLength:         5,
+		MaxLength:         50 * 1024,
+		MaxChunks:         15,
+		MaxChunkSize:      maxCookieSize,
+		AllowOpaqueTokens: true,
+		RequireJWTFormat:  false,
+	}
+
+	IDTokenConfig = TokenConfig{
+		Type:              "id",
+		MinLength:         5,
+		MaxLength:         75 * 1024,
+		MaxChunks:         20,
+		MaxChunkSize:      maxCookieSize,
+		AllowOpaqueTokens: false,
+		RequireJWTFormat:  true,
+	}
+)
+
+// TokenRetrievalResult represents the outcome of a token retrieval operation.
+// It contains either the successfully retrieved token or an error describing
+// what went wrong during retrieval.
+type TokenRetrievalResult struct {
+	Error error
+	Token string
+}
+
+// SessionEntry represents a session with expiration tracking
+type SessionEntry struct {
+	Session   *sessions.Session
+	ExpiresAt time.Time
+	LastUsed  time.Time
+}
+
+// Logger interface for dependency injection
+type Logger interface {
+	Debug(msg string)
+	Debugf(format string, args ...interface{})
+	Error(msg string)
+	Errorf(format string, args ...interface{})
+}
+
+// ChunkManager handles the complex logic of storing and retrieving large tokens
+// across multiple HTTP cookies. It provides comprehensive validation, security checks,
+// and error handling to ensure data integrity and prevent security vulnerabilities
+// throughout the process.
+type ChunkManager struct {
+	logger Logger
+	mutex  *sync.RWMutex
+	// sessionMap provides bounded session storage to prevent memory leaks
+	sessionMap  map[string]*SessionEntry
+	maxSessions int
+	sessionTTL  time.Duration
+	lastCleanup time.Time
+}
+
+// NewChunkManager creates a new ChunkManager instance with proper initialization.
+// It sets up logging and synchronization primitives for safe concurrent access.
+func NewChunkManager(logger Logger) *ChunkManager {
+	if logger == nil {
+		logger = NewNoOpLogger()
+	}
+
+	return &ChunkManager{
+		logger:      logger,
+		mutex:       &sync.RWMutex{},
+		sessionMap:  make(map[string]*SessionEntry),
+		maxSessions: 1000, // Reasonable limit to prevent memory leaks
+		sessionTTL:  24 * time.Hour,
+		lastCleanup: time.Now(),
+	}
+}
+
+// GetToken retrieves a token from either a single cookie or multiple chunk cookies.
+// It handles both compressed and uncompressed tokens and performs comprehensive
+// validation throughout the retrieval process.
+func (cm *ChunkManager) GetToken(
+	mainSession *sessions.Session,
+	chunks map[int]*sessions.Session,
+	config TokenConfig,
+	compressor TokenCompressor,
+) TokenRetrievalResult {
+
+	// Try to get token from main session first
+	if mainSession != nil {
+		if tokenValue, ok := mainSession.Values[config.Type+"_token"].(string); ok && tokenValue != "" {
+			cm.logger.Debugf("Found %s token in main session", config.Type)
+
+			// Check if token is compressed
+			decompressed := compressor.DecompressToken(tokenValue)
+			if decompressed != tokenValue {
+				cm.logger.Debugf("Decompressed %s token", config.Type)
+				return cm.processSingleToken(decompressed, true, config)
+			}
+
+			return cm.processSingleToken(tokenValue, false, config)
+		}
+	}
+
+	// If not in main session, try chunks
+	if len(chunks) == 0 {
+		return TokenRetrievalResult{
+			Error: nil,
+			Token: "",
+		}
+	}
+
+	cm.logger.Debugf("Found %d chunks for %s token, processing", len(chunks), config.Type)
+	return cm.processChunkedToken(chunks, config, compressor)
+}
+
+// processSingleToken validates and processes a single token
+func (cm *ChunkManager) processSingleToken(token string, compressed bool, config TokenConfig) TokenRetrievalResult {
+	if compressed {
+		cm.logger.Debugf("Processing compressed %s token (length: %d)", config.Type, len(token))
+	} else {
+		cm.logger.Debugf("Processing single %s token (length: %d)", config.Type, len(token))
+	}
+
+	return cm.validateToken(token, config)
+}
+
+// validateToken performs comprehensive validation on a token
+func (cm *ChunkManager) validateToken(token string, config TokenConfig) TokenRetrievalResult {
+	if token == "" {
+		return TokenRetrievalResult{Error: nil, Token: ""}
+	}
+
+	validator := NewTokenValidator()
+
+	// Basic validation
+	if err := validator.ValidateTokenSize(token, config); err != nil {
+		cm.logger.Errorf("Token size validation failed for %s: %v", config.Type, err)
+		return TokenRetrievalResult{Error: err, Token: ""}
+	}
+
+	// Format validation
+	if config.RequireJWTFormat {
+		if err := validator.ValidateJWTFormat(token, config.Type); err != nil {
+			cm.logger.Errorf("JWT format validation failed for %s: %v", config.Type, err)
+			return TokenRetrievalResult{Error: err, Token: ""}
+		}
+	} else if !config.AllowOpaqueTokens {
+		if err := validator.ValidateJWTFormat(token, config.Type); err != nil {
+			cm.logger.Errorf("Token format validation failed for %s: %v", config.Type, err)
+			return TokenRetrievalResult{Error: err, Token: ""}
+		}
+	}
+
+	// Content validation
+	if err := validator.ValidateTokenContent(token, config); err != nil {
+		cm.logger.Errorf("Token content validation failed for %s: %v", config.Type, err)
+		return TokenRetrievalResult{Error: err, Token: ""}
+	}
+
+	cm.logger.Debugf("Successfully validated %s token", config.Type)
+	return TokenRetrievalResult{Error: nil, Token: token}
+}
+
+// processChunkedToken reconstructs a token from multiple chunks
+func (cm *ChunkManager) processChunkedToken(chunks map[int]*sessions.Session, config TokenConfig, compressor TokenCompressor) TokenRetrievalResult {
+	if len(chunks) > config.MaxChunks {
+		return TokenRetrievalResult{
+			Error: &ChunkError{
+				Type:    config.Type,
+				Reason:  "too many chunks",
+				Details: "chunk count exceeds maximum allowed",
+			},
+			Token: "",
+		}
+	}
+
+	// Reconstruct token from chunks
+	reconstructedToken, err := cm.reconstructTokenFromChunks(chunks, config)
+	if err != nil {
+		cm.logger.Errorf("Failed to reconstruct %s token from chunks: %v", config.Type, err)
+		return TokenRetrievalResult{Error: err, Token: ""}
+	}
+
+	// Try decompression
+	decompressedToken := compressor.DecompressToken(reconstructedToken)
+	if decompressedToken != reconstructedToken {
+		cm.logger.Debugf("Decompressed reconstructed %s token", config.Type)
+		return cm.validateToken(decompressedToken, config)
+	}
+
+	return cm.validateToken(reconstructedToken, config)
+}
+
+// reconstructTokenFromChunks reconstructs a token from ordered chunks
+func (cm *ChunkManager) reconstructTokenFromChunks(chunks map[int]*sessions.Session, config TokenConfig) (string, error) {
+	if len(chunks) == 0 {
+		return "", &ChunkError{
+			Type:    config.Type,
+			Reason:  "no chunks found",
+			Details: "no chunk sessions available for reconstruction",
+		}
+	}
+
+	// Find the maximum chunk index to determine total chunks
+	maxIndex := -1
+	for index := range chunks {
+		if index > maxIndex {
+			maxIndex = index
+		}
+	}
+
+	if maxIndex < 0 {
+		return "", &ChunkError{
+			Type:    config.Type,
+			Reason:  "invalid chunk indices",
+			Details: "no valid chunk indices found",
+		}
+	}
+
+	// Reconstruct token by concatenating chunks in order
+	var tokenBuilder strings.Builder
+	for i := 0; i <= maxIndex; i++ {
+		chunk, exists := chunks[i]
+		if !exists || chunk == nil {
+			return "", &ChunkError{
+				Type:    config.Type,
+				Reason:  "missing chunk",
+				Details: fmt.Sprintf("chunk %d is missing", i),
+			}
+		}
+
+		chunkValue, ok := chunk.Values["value"].(string)
+		if !ok || chunkValue == "" {
+			return "", &ChunkError{
+				Type:    config.Type,
+				Reason:  "empty chunk",
+				Details: fmt.Sprintf("chunk %d has no value", i),
+			}
+		}
+
+		tokenBuilder.WriteString(chunkValue)
+	}
+
+	reconstructed := tokenBuilder.String()
+	if reconstructed == "" {
+		return "", &ChunkError{
+			Type:    config.Type,
+			Reason:  "empty reconstructed token",
+			Details: "all chunks were present but resulted in empty token",
+		}
+	}
+
+	cm.logger.Debugf("Successfully reconstructed %s token from %d chunks (length: %d)",
+		config.Type, len(chunks), len(reconstructed))
+
+	return reconstructed, nil
+}
+
+// CleanupExpiredSessions removes expired sessions from the session map
+func (cm *ChunkManager) CleanupExpiredSessions() {
+	cm.mutex.Lock()
+	defer cm.mutex.Unlock()
+
+	now := time.Now()
+
+	// Only cleanup if enough time has passed
+	if now.Sub(cm.lastCleanup) < time.Hour {
+		return
+	}
+
+	cm.lastCleanup = now
+	cleaned := 0
+
+	for key, entry := range cm.sessionMap {
+		if now.After(entry.ExpiresAt) || now.Sub(entry.LastUsed) > cm.sessionTTL {
+			delete(cm.sessionMap, key)
+			cleaned++
+		}
+	}
+
+	if cleaned > 0 {
+		cm.logger.Debugf("Cleaned up %d expired sessions", cleaned)
+	}
+}
+
+// StoreSession stores a session in the session map with expiration tracking
+func (cm *ChunkManager) StoreSession(key string, session *sessions.Session) {
+	cm.mutex.Lock()
+	defer cm.mutex.Unlock()
+
+	// Enforce maximum session limit
+	if len(cm.sessionMap) >= cm.maxSessions {
+		// Remove oldest entry
+		var oldestKey string
+		var oldestTime time.Time = time.Now()
+
+		for k, entry := range cm.sessionMap {
+			if entry.LastUsed.Before(oldestTime) {
+				oldestTime = entry.LastUsed
+				oldestKey = k
+			}
+		}
+
+		if oldestKey != "" {
+			delete(cm.sessionMap, oldestKey)
+		}
+	}
+
+	cm.sessionMap[key] = &SessionEntry{
+		Session:   session,
+		ExpiresAt: time.Now().Add(cm.sessionTTL),
+		LastUsed:  time.Now(),
+	}
+}
+
+// GetSession retrieves a session from the session map
+func (cm *ChunkManager) GetSession(key string) *sessions.Session {
+	cm.mutex.Lock()
+	defer cm.mutex.Unlock()
+
+	entry, exists := cm.sessionMap[key]
+	if !exists {
+		return nil
+	}
+
+	// Update last used time
+	entry.LastUsed = time.Now()
+	return entry.Session
+}
+
+// TokenCompressor interface for token compression operations
+type TokenCompressor interface {
+	CompressToken(token string) string
+	DecompressToken(compressed string) string
+}
+
+// ChunkError represents errors that occur during chunk operations
+type ChunkError struct {
+	Type    string
+	Reason  string
+	Details string
+}
+
+// Error implements the error interface
+func (ce *ChunkError) Error() string {
+	return fmt.Sprintf("%s chunk error: %s - %s", ce.Type, ce.Reason, ce.Details)
+}
+
+// NoOpLogger provides a no-op logger implementation
+type NoOpLogger struct{}
+
+// NewNoOpLogger creates a new no-op logger
+func NewNoOpLogger() *NoOpLogger {
+	return &NoOpLogger{}
+}
+
+// Debug does nothing
+func (l *NoOpLogger) Debug(msg string) {}
+
+// Debugf does nothing
+func (l *NoOpLogger) Debugf(format string, args ...interface{}) {}
+
+// Error does nothing
+func (l *NoOpLogger) Error(msg string) {}
+
+// Errorf does nothing
+func (l *NoOpLogger) Errorf(format string, args ...interface{}) {}

session/chunking/chunk_serializer.go

@@ -0,0 +1,279 @@
+// Package chunking provides chunk serialization functionality
+package chunking
+
+import (
+	"encoding/base64"
+	"fmt"
+	"strings"
+)
+
+// ChunkSerializer handles serialization and deserialization of token chunks
+type ChunkSerializer struct {
+	logger Logger
+}
+
+// NewChunkSerializer creates a new chunk serializer
+func NewChunkSerializer(logger Logger) *ChunkSerializer {
+	return &ChunkSerializer{
+		logger: logger,
+	}
+}
+
+// SerializeTokenToChunks splits a token into chunks suitable for cookie storage
+func (cs *ChunkSerializer) SerializeTokenToChunks(token string, config TokenConfig) ([]ChunkData, error) {
+	if token == "" {
+		return nil, fmt.Errorf("cannot serialize empty token")
+	}
+
+	if len(token) < config.MinLength {
+		return nil, fmt.Errorf("token too short: %d < %d", len(token), config.MinLength)
+	}
+
+	if len(token) > config.MaxLength {
+		return nil, fmt.Errorf("token too long: %d > %d", len(token), config.MaxLength)
+	}
+
+	// Calculate optimal chunk size
+	chunkSize := config.MaxChunkSize
+	if chunkSize <= 0 {
+		chunkSize = maxCookieSize
+	}
+
+	// Estimate number of chunks needed
+	estimatedChunks := (len(token) + chunkSize - 1) / chunkSize
+	if estimatedChunks > config.MaxChunks {
+		return nil, fmt.Errorf("token requires too many chunks: %d > %d", estimatedChunks, config.MaxChunks)
+	}
+
+	// Split token into chunks
+	chunks := make([]ChunkData, 0, estimatedChunks)
+	remaining := token
+
+	chunkIndex := 0
+	for len(remaining) > 0 {
+		if chunkIndex >= config.MaxChunks {
+			return nil, fmt.Errorf("exceeded maximum chunk count during serialization")
+		}
+
+		// Determine chunk size for this iteration
+		currentChunkSize := chunkSize
+		if len(remaining) < currentChunkSize {
+			currentChunkSize = len(remaining)
+		}
+
+		// Extract chunk
+		chunkContent := remaining[:currentChunkSize]
+		remaining = remaining[currentChunkSize:]
+
+		// Create chunk data
+		chunkData := ChunkData{
+			Index:    chunkIndex,
+			Content:  chunkContent,
+			Total:    estimatedChunks, // Will be updated after all chunks are created
+			Checksum: cs.calculateChecksum(chunkContent),
+		}
+
+		chunks = append(chunks, chunkData)
+		chunkIndex++
+	}
+
+	// Update total count in all chunks
+	actualChunks := len(chunks)
+	for i := range chunks {
+		chunks[i].Total = actualChunks
+	}
+
+	cs.logger.Debugf("Serialized %s token into %d chunks", config.Type, len(chunks))
+	return chunks, nil
+}
+
+// DeserializeTokenFromChunks reconstructs a token from chunk data
+func (cs *ChunkSerializer) DeserializeTokenFromChunks(chunks []ChunkData, config TokenConfig) (string, error) {
+	if len(chunks) == 0 {
+		return "", fmt.Errorf("no chunks provided for deserialization")
+	}
+
+	if len(chunks) > config.MaxChunks {
+		return "", fmt.Errorf("too many chunks: %d > %d", len(chunks), config.MaxChunks)
+	}
+
+	// Validate chunk consistency
+	expectedTotal := chunks[0].Total
+	for i, chunk := range chunks {
+		if chunk.Total != expectedTotal {
+			return "", fmt.Errorf("chunk %d has inconsistent total count: %d != %d", i, chunk.Total, expectedTotal)
+		}
+	}
+
+	if len(chunks) != expectedTotal {
+		return "", fmt.Errorf("chunk count mismatch: got %d, expected %d", len(chunks), expectedTotal)
+	}
+
+	// Sort chunks by index
+	orderedChunks := make([]ChunkData, expectedTotal)
+	for _, chunk := range chunks {
+		if chunk.Index < 0 || chunk.Index >= expectedTotal {
+			return "", fmt.Errorf("invalid chunk index: %d (total: %d)", chunk.Index, expectedTotal)
+		}
+
+		if orderedChunks[chunk.Index].Content != "" {
+			return "", fmt.Errorf("duplicate chunk index: %d", chunk.Index)
+		}
+
+		orderedChunks[chunk.Index] = chunk
+	}
+
+	// Verify all chunks are present
+	for i, chunk := range orderedChunks {
+		if chunk.Content == "" {
+			return "", fmt.Errorf("missing chunk at index: %d", i)
+		}
+
+		// Verify checksum
+		expectedChecksum := cs.calculateChecksum(chunk.Content)
+		if chunk.Checksum != expectedChecksum {
+			return "", fmt.Errorf("chunk %d checksum mismatch", i)
+		}
+	}
+
+	// Reconstruct token
+	var tokenBuilder strings.Builder
+	tokenBuilder.Grow(len(chunks) * config.MaxChunkSize) // Pre-allocate capacity
+
+	for _, chunk := range orderedChunks {
+		tokenBuilder.WriteString(chunk.Content)
+	}
+
+	reconstructedToken := tokenBuilder.String()
+
+	// Final validation
+	if len(reconstructedToken) < config.MinLength {
+		return "", fmt.Errorf("reconstructed token too short: %d < %d", len(reconstructedToken), config.MinLength)
+	}
+
+	if len(reconstructedToken) > config.MaxLength {
+		return "", fmt.Errorf("reconstructed token too long: %d > %d", len(reconstructedToken), config.MaxLength)
+	}
+
+	cs.logger.Debugf("Deserialized %s token from %d chunks (length: %d)", config.Type, len(chunks), len(reconstructedToken))
+	return reconstructedToken, nil
+}
+
+// EncodeChunk encodes chunk data for cookie storage
+func (cs *ChunkSerializer) EncodeChunk(chunk ChunkData) (string, error) {
+	// Create a simple format: index:total:checksum:content
+	encoded := fmt.Sprintf("%d:%d:%s:%s", chunk.Index, chunk.Total, chunk.Checksum, chunk.Content)
+
+	// Base64 encode the entire chunk for safe cookie storage
+	return base64.StdEncoding.EncodeToString([]byte(encoded)), nil
+}
+
+// DecodeChunk decodes chunk data from cookie storage
+func (cs *ChunkSerializer) DecodeChunk(encoded string) (ChunkData, error) {
+	// Base64 decode
+	decoded, err := base64.StdEncoding.DecodeString(encoded)
+	if err != nil {
+		return ChunkData{}, fmt.Errorf("failed to base64 decode chunk: %w", err)
+	}
+
+	// Parse the format: index:total:checksum:content
+	parts := strings.SplitN(string(decoded), ":", 4)
+	if len(parts) != 4 {
+		return ChunkData{}, fmt.Errorf("invalid chunk format: expected 4 parts, got %d", len(parts))
+	}
+
+	var index, total int
+	if _, err := fmt.Sscanf(parts[0], "%d", &index); err != nil {
+		return ChunkData{}, fmt.Errorf("invalid chunk index: %w", err)
+	}
+
+	if _, err := fmt.Sscanf(parts[1], "%d", &total); err != nil {
+		return ChunkData{}, fmt.Errorf("invalid chunk total: %w", err)
+	}
+
+	checksum := parts[2]
+	content := parts[3]
+
+	return ChunkData{
+		Index:    index,
+		Total:    total,
+		Content:  content,
+		Checksum: checksum,
+	}, nil
+}
+
+// ValidateChunkIntegrity validates the integrity of chunk data
+func (cs *ChunkSerializer) ValidateChunkIntegrity(chunk ChunkData) error {
+	if chunk.Index < 0 {
+		return fmt.Errorf("negative chunk index: %d", chunk.Index)
+	}
+
+	if chunk.Total <= 0 {
+		return fmt.Errorf("invalid total chunks: %d", chunk.Total)
+	}
+
+	if chunk.Index >= chunk.Total {
+		return fmt.Errorf("chunk index %d exceeds total %d", chunk.Index, chunk.Total)
+	}
+
+	if chunk.Content == "" {
+		return fmt.Errorf("empty chunk content at index %d", chunk.Index)
+	}
+
+	if chunk.Checksum == "" {
+		return fmt.Errorf("empty chunk checksum at index %d", chunk.Index)
+	}
+
+	// Verify checksum
+	expectedChecksum := cs.calculateChecksum(chunk.Content)
+	if chunk.Checksum != expectedChecksum {
+		return fmt.Errorf("chunk %d checksum mismatch: expected %s, got %s",
+			chunk.Index, expectedChecksum, chunk.Checksum)
+	}
+
+	return nil
+}
+
+// calculateChecksum calculates a simple checksum for chunk content
+func (cs *ChunkSerializer) calculateChecksum(content string) string {
+	// Simple checksum using length and first/last characters
+	if len(content) == 0 {
+		return "empty"
+	}
+
+	checksum := fmt.Sprintf("len%d", len(content))
+	if len(content) >= 1 {
+		checksum += fmt.Sprintf("_first%d", int(content[0]))
+	}
+	if len(content) >= 2 {
+		checksum += fmt.Sprintf("_last%d", int(content[len(content)-1]))
+	}
+
+	return checksum
+}
+
+// ChunkData represents a single chunk of token data
+type ChunkData struct {
+	Index    int    // Position of this chunk in the sequence
+	Total    int    // Total number of chunks for this token
+	Content  string // The actual chunk content
+	Checksum string // Simple checksum for integrity verification
+}
+
+// EstimateChunkCount estimates how many chunks a token will need
+func (cs *ChunkSerializer) EstimateChunkCount(tokenLength int, chunkSize int) int {
+	if chunkSize <= 0 {
+		chunkSize = maxCookieSize
+	}
+
+	return (tokenLength + chunkSize - 1) / chunkSize
+}
+
+// MaxTokenSizeForChunks calculates the maximum token size that can fit in the given number of chunks
+func (cs *ChunkSerializer) MaxTokenSizeForChunks(maxChunks int, chunkSize int) int {
+	if chunkSize <= 0 {
+		chunkSize = maxCookieSize
+	}
+
+	return maxChunks * chunkSize
+}

session/chunking/chunk_validator.go

@@ -0,0 +1,429 @@
+// Package chunking provides chunk validation functionality
+package chunking
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"strings"
+	"unicode"
+)
+
+// TokenValidator provides comprehensive validation for tokens and chunks
+type TokenValidator struct{}
+
+// NewTokenValidator creates a new token validator
+func NewTokenValidator() *TokenValidator {
+	return &TokenValidator{}
+}
+
+// ValidateTokenSize validates that a token is within size limits
+func (tv *TokenValidator) ValidateTokenSize(token string, config TokenConfig) error {
+	if len(token) == 0 {
+		return nil // Empty token is allowed
+	}
+
+	if len(token) < config.MinLength {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "token too short",
+			Details: fmt.Sprintf("length %d < minimum %d", len(token), config.MinLength),
+		}
+	}
+
+	if len(token) > config.MaxLength {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "token too long",
+			Details: fmt.Sprintf("length %d > maximum %d", len(token), config.MaxLength),
+		}
+	}
+
+	return nil
+}
+
+// ValidateJWTFormat validates that a token has proper JWT format
+func (tv *TokenValidator) ValidateJWTFormat(token string, tokenType string) error {
+	if token == "" {
+		return nil // Empty token is not an error
+	}
+
+	// JWT tokens must have exactly 3 parts separated by dots
+	parts := strings.Split(token, ".")
+	if len(parts) != 3 {
+		return &ValidationError{
+			Type:    tokenType,
+			Reason:  "invalid JWT format",
+			Details: fmt.Sprintf("expected 3 parts, got %d", len(parts)),
+		}
+	}
+
+	// Each part must be non-empty
+	for i, part := range parts {
+		if part == "" {
+			return &ValidationError{
+				Type:    tokenType,
+				Reason:  "empty JWT part",
+				Details: fmt.Sprintf("part %d is empty", i+1),
+			}
+		}
+	}
+
+	// Validate each part is valid base64
+	for i, part := range parts {
+		if err := tv.validateBase64JWT(part); err != nil {
+			return &ValidationError{
+				Type:    tokenType,
+				Reason:  "invalid base64 in JWT part",
+				Details: fmt.Sprintf("part %d: %v", i+1, err),
+			}
+		}
+	}
+
+	return nil
+}
+
+// ValidateTokenContent performs comprehensive content validation
+func (tv *TokenValidator) ValidateTokenContent(token string, config TokenConfig) error {
+	if token == "" {
+		return nil
+	}
+
+	// Validate character set
+	if err := tv.validateCharacterSet(token, config); err != nil {
+		return err
+	}
+
+	// Validate token structure based on type
+	if config.RequireJWTFormat {
+		return tv.validateJWTContent(token, config)
+	} else if config.AllowOpaqueTokens {
+		return tv.validateOpaqueTokenContent(token, config)
+	} else {
+		// Try JWT first, then fall back to opaque validation
+		if err := tv.validateJWTContent(token, config); err != nil {
+			return tv.validateOpaqueTokenContent(token, config)
+		}
+		return nil
+	}
+}
+
+// validateCharacterSet validates the character set of a token
+func (tv *TokenValidator) validateCharacterSet(token string, config TokenConfig) error {
+	for i, r := range token {
+		if !tv.isValidTokenCharacter(r) {
+			return &ValidationError{
+				Type:    config.Type,
+				Reason:  "invalid character",
+				Details: fmt.Sprintf("invalid character at position %d: %c (0x%X)", i, r, r),
+			}
+		}
+	}
+	return nil
+}
+
+// isValidTokenCharacter checks if a character is valid in a token
+func (tv *TokenValidator) isValidTokenCharacter(r rune) bool {
+	// Allow alphanumeric characters
+	if unicode.IsLetter(r) || unicode.IsNumber(r) {
+		return true
+	}
+
+	// Allow common token characters
+	validChars := ".-_~:/?#[]@!$&'()*+,;="
+	return strings.ContainsRune(validChars, r)
+}
+
+// validateJWTContent validates the content of a JWT token
+func (tv *TokenValidator) validateJWTContent(token string, config TokenConfig) error {
+	parts := strings.Split(token, ".")
+	if len(parts) != 3 {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "invalid JWT structure",
+			Details: "JWT must have exactly 3 parts",
+		}
+	}
+
+	// Validate header
+	if err := tv.validateJWTHeader(parts[0], config); err != nil {
+		return err
+	}
+
+	// Validate payload
+	if err := tv.validateJWTPayload(parts[1], config); err != nil {
+		return err
+	}
+
+	// Validate signature
+	if err := tv.validateJWTSignature(parts[2], config); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// validateJWTHeader validates a JWT header
+func (tv *TokenValidator) validateJWTHeader(header string, config TokenConfig) error {
+	decoded, err := tv.base64URLDecode(header)
+	if err != nil {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "invalid header encoding",
+			Details: err.Error(),
+		}
+	}
+
+	var headerData map[string]interface{}
+	if err := json.Unmarshal(decoded, &headerData); err != nil {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "invalid header JSON",
+			Details: err.Error(),
+		}
+	}
+
+	// Check required fields
+	if _, ok := headerData["alg"]; !ok {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "missing algorithm",
+			Details: "JWT header must contain 'alg' field",
+		}
+	}
+
+	if _, ok := headerData["typ"]; !ok {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "missing type",
+			Details: "JWT header must contain 'typ' field",
+		}
+	}
+
+	return nil
+}
+
+// validateJWTPayload validates a JWT payload
+func (tv *TokenValidator) validateJWTPayload(payload string, config TokenConfig) error {
+	decoded, err := tv.base64URLDecode(payload)
+	if err != nil {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "invalid payload encoding",
+			Details: err.Error(),
+		}
+	}
+
+	var payloadData map[string]interface{}
+	if err := json.Unmarshal(decoded, &payloadData); err != nil {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "invalid payload JSON",
+			Details: err.Error(),
+		}
+	}
+
+	// For ID tokens, check required claims
+	if config.Type == "id" {
+		requiredClaims := []string{"iss", "sub", "aud", "exp", "iat"}
+		for _, claim := range requiredClaims {
+			if _, ok := payloadData[claim]; !ok {
+				return &ValidationError{
+					Type:    config.Type,
+					Reason:  "missing required claim",
+					Details: fmt.Sprintf("ID token must contain '%s' claim", claim),
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
+// validateJWTSignature validates a JWT signature part
+func (tv *TokenValidator) validateJWTSignature(signature string, config TokenConfig) error {
+	if signature == "" {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "empty signature",
+			Details: "JWT signature cannot be empty",
+		}
+	}
+
+	// Just validate it's valid base64URL
+	_, err := tv.base64URLDecode(signature)
+	if err != nil {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "invalid signature encoding",
+			Details: err.Error(),
+		}
+	}
+
+	return nil
+}
+
+// validateOpaqueTokenContent validates opaque token content
+func (tv *TokenValidator) validateOpaqueTokenContent(token string, config TokenConfig) error {
+	if token == "" {
+		return nil
+	}
+
+	// Basic sanity checks for opaque tokens
+	if len(token) < 8 {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "token too short for opaque token",
+			Details: "opaque tokens should be at least 8 characters",
+		}
+	}
+
+	// Check for reasonable entropy
+	if tv.hasLowEntropy(token) {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "low entropy",
+			Details: "token appears to have low entropy",
+		}
+	}
+
+	return nil
+}
+
+// hasLowEntropy checks if a token has suspiciously low entropy
+func (tv *TokenValidator) hasLowEntropy(token string) bool {
+	if len(token) < 8 {
+		return true
+	}
+
+	// Count unique characters
+	uniqueChars := make(map[rune]bool)
+	for _, r := range token {
+		uniqueChars[r] = true
+	}
+
+	// If less than 50% of characters are unique, consider it low entropy
+	entropyRatio := float64(len(uniqueChars)) / float64(len(token))
+	return entropyRatio < 0.5
+}
+
+// validateBase64JWT validates base64URL encoding
+func (tv *TokenValidator) validateBase64JWT(data string) error {
+	_, err := tv.base64URLDecode(data)
+	return err
+}
+
+// base64URLDecode decodes base64URL encoded data
+func (tv *TokenValidator) base64URLDecode(data string) ([]byte, error) {
+	// Add padding if needed
+	switch len(data) % 4 {
+	case 2:
+		data += "=="
+	case 3:
+		data += "="
+	}
+
+	// Replace URL-safe characters
+	data = strings.ReplaceAll(data, "-", "+")
+	data = strings.ReplaceAll(data, "_", "/")
+
+	return base64.StdEncoding.DecodeString(data)
+}
+
+// ValidateChunkStructure validates the structure of chunk data
+func (tv *TokenValidator) ValidateChunkStructure(chunks []ChunkData, config TokenConfig) error {
+	if len(chunks) == 0 {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "no chunks provided",
+			Details: "chunk list is empty",
+		}
+	}
+
+	if len(chunks) > config.MaxChunks {
+		return &ValidationError{
+			Type:    config.Type,
+			Reason:  "too many chunks",
+			Details: fmt.Sprintf("got %d chunks, maximum is %d", len(chunks), config.MaxChunks),
+		}
+	}
+
+	// Validate each chunk
+	expectedTotal := chunks[0].Total
+	seenIndices := make(map[int]bool)
+
+	for i, chunk := range chunks {
+		// Check for duplicate indices
+		if seenIndices[chunk.Index] {
+			return &ValidationError{
+				Type:    config.Type,
+				Reason:  "duplicate chunk index",
+				Details: fmt.Sprintf("chunk index %d appears multiple times", chunk.Index),
+			}
+		}
+		seenIndices[chunk.Index] = true
+
+		// Validate individual chunk
+		if err := tv.validateChunkData(chunk, expectedTotal, config); err != nil {
+			return &ValidationError{
+				Type:    config.Type,
+				Reason:  "invalid chunk data",
+				Details: fmt.Sprintf("chunk %d: %v", i, err),
+			}
+		}
+	}
+
+	// Check for missing indices
+	for i := 0; i < expectedTotal; i++ {
+		if !seenIndices[i] {
+			return &ValidationError{
+				Type:    config.Type,
+				Reason:  "missing chunk index",
+				Details: fmt.Sprintf("chunk with index %d is missing", i),
+			}
+		}
+	}
+
+	return nil
+}
+
+// validateChunkData validates individual chunk data
+func (tv *TokenValidator) validateChunkData(chunk ChunkData, expectedTotal int, config TokenConfig) error {
+	if chunk.Index < 0 {
+		return fmt.Errorf("negative index: %d", chunk.Index)
+	}
+
+	if chunk.Total != expectedTotal {
+		return fmt.Errorf("inconsistent total: got %d, expected %d", chunk.Total, expectedTotal)
+	}
+
+	if chunk.Index >= chunk.Total {
+		return fmt.Errorf("index %d exceeds total %d", chunk.Index, chunk.Total)
+	}
+
+	if chunk.Content == "" {
+		return fmt.Errorf("empty content")
+	}
+
+	if len(chunk.Content) > config.MaxChunkSize {
+		return fmt.Errorf("chunk too large: %d > %d", len(chunk.Content), config.MaxChunkSize)
+	}
+
+	if chunk.Checksum == "" {
+		return fmt.Errorf("empty checksum")
+	}
+
+	return nil
+}
+
+// ValidationError represents a validation error
+type ValidationError struct {
+	Type    string
+	Reason  string
+	Details string
+}
+
+// Error implements the error interface
+func (ve *ValidationError) Error() string {
+	return fmt.Sprintf("%s validation error: %s - %s", ve.Type, ve.Reason, ve.Details)
+}

session/core/session_manager.go

@@ -0,0 +1,336 @@
+// Package core provides core session management functionality for the OIDC middleware
+package core
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/gorilla/sessions"
+)
+
+const (
+	minEncryptionKeyLength = 32
+	absoluteSessionTimeout = 24 * time.Hour
+)
+
+// SessionManager handles session creation, management and cleanup
+type SessionManager struct {
+	sessionPool  sync.Pool
+	store        sessions.Store
+	logger       Logger
+	chunkManager ChunkManager
+	cookieDomain string
+	cleanupMutex sync.RWMutex
+	forceHTTPS   bool
+	cleanupDone  bool
+}
+
+// Logger interface for dependency injection
+type Logger interface {
+	Debug(msg string)
+	Debugf(format string, args ...interface{})
+	Error(msg string)
+	Errorf(format string, args ...interface{})
+}
+
+// ChunkManager interface for chunk operations
+type ChunkManager interface {
+	CleanupExpiredSessions()
+}
+
+// SessionData interface for session data operations
+type SessionData interface {
+	Reset()
+	SetManager(manager *SessionManager)
+	SetAuthenticated(bool) error
+	GetAuthenticated() bool
+	GetAccessToken() string
+	GetRefreshToken() string
+	GetIDToken() string
+	GetEmail() string
+	GetCSRF() string
+	GetNonce() string
+	GetCodeVerifier() string
+	GetIncomingPath() string
+	GetRedirectCount() int
+	IncrementRedirectCount()
+	ResetRedirectCount()
+	MarkDirty()
+	IsDirty() bool
+	Save(r *http.Request, w http.ResponseWriter) error
+	Clear(r *http.Request, w http.ResponseWriter) error
+	GetRefreshTokenIssuedAt() time.Time
+	returnToPoolSafely()
+}
+
+// NewSessionManager creates a new SessionManager instance with secure defaults.
+// It initializes the cookie store with encryption, sets up session pooling,
+// and configures chunk management for large tokens.
+func NewSessionManager(encryptionKey string, forceHTTPS bool, cookieDomain string, logger Logger, chunkManager ChunkManager) (*SessionManager, error) {
+	if len(encryptionKey) < minEncryptionKeyLength {
+		return nil, fmt.Errorf("encryption key must be at least %d bytes long", minEncryptionKeyLength)
+	}
+
+	sm := &SessionManager{
+		store:        sessions.NewCookieStore([]byte(encryptionKey)),
+		forceHTTPS:   forceHTTPS,
+		cookieDomain: cookieDomain,
+		logger:       logger,
+		chunkManager: chunkManager,
+	}
+
+	sm.sessionPool.New = func() interface{} {
+		return NewSessionData(sm, logger)
+	}
+
+	return sm, nil
+}
+
+// GetSession retrieves or creates a session for the request
+func (sm *SessionManager) GetSession(r *http.Request) (SessionData, error) {
+	sessionDataInterface := sm.sessionPool.Get()
+	sessionData, ok := sessionDataInterface.(SessionData)
+	if !ok || sessionData == nil {
+		sessionData = NewSessionData(sm, sm.logger)
+	}
+
+	// Initialize the session data
+	err := sm.initializeSession(sessionData, r)
+	if err != nil {
+		sm.sessionPool.Put(sessionData)
+		return nil, fmt.Errorf("failed to initialize session: %w", err)
+	}
+
+	return sessionData, nil
+}
+
+// initializeSession initializes session data from HTTP request
+func (sm *SessionManager) initializeSession(sessionData SessionData, r *http.Request) error {
+	// Reset session data to clean state
+	sessionData.Reset()
+	sessionData.SetManager(sm)
+
+	// Load session data from cookies
+	session, err := sm.store.Get(r, MainCookieName())
+	if err != nil {
+		sm.logger.Debugf("Error getting main session: %v", err)
+		return nil // Not a fatal error, will create new session
+	}
+
+	// Extract and set session values
+	if auth, ok := session.Values["authenticated"].(bool); ok {
+		sessionData.SetAuthenticated(auth)
+	}
+
+	return nil
+}
+
+// CleanupOldCookies removes old/expired cookies from the response
+func (sm *SessionManager) CleanupOldCookies(w http.ResponseWriter, r *http.Request) {
+	sm.cleanupMutex.Lock()
+	defer sm.cleanupMutex.Unlock()
+
+	if sm.cleanupDone {
+		return
+	}
+
+	sm.logger.Debug("Starting cleanup of old session cookies")
+
+	oldCookieNames := []string{
+		"_oidc_session_old_v1",
+		"_oidc_session_legacy",
+		"_oidc_auth_state_old",
+		"_legacy_oidc_token",
+		"_old_session_chunks",
+	}
+
+	for _, cookieName := range oldCookieNames {
+		if cookie, err := r.Cookie(cookieName); err == nil && cookie.Value != "" {
+			sm.logger.Debugf("Expiring old cookie: %s", cookieName)
+			expiredCookie := &http.Cookie{
+				Name:     cookieName,
+				Value:    "",
+				Path:     "/",
+				Domain:   sm.cookieDomain,
+				Expires:  time.Unix(0, 0),
+				MaxAge:   -1,
+				Secure:   sm.shouldUseSecureCookies(r),
+				HttpOnly: true,
+				SameSite: http.SameSiteLaxMode,
+			}
+			http.SetCookie(w, expiredCookie)
+		}
+	}
+
+	sm.cleanupDone = true
+}
+
+// PeriodicChunkCleanup performs comprehensive session maintenance and cleanup
+func (sm *SessionManager) PeriodicChunkCleanup() {
+	if sm == nil || sm.logger == nil {
+		return
+	}
+
+	sm.logger.Debug("Starting comprehensive session cleanup cycle")
+
+	cleanupStart := time.Now()
+	var orphanedChunks, expiredSessions, cleanupErrors int
+
+	if sm.store != nil {
+		if cookieStore, ok := sm.store.(*sessions.CookieStore); ok {
+			sm.logger.Debug("Running session store cleanup")
+			_ = cookieStore
+		}
+	}
+
+	// Cleanup expired sessions in chunk manager to prevent memory leaks
+	if sm.chunkManager != nil {
+		sm.chunkManager.CleanupExpiredSessions()
+	}
+
+	poolCleaned := 0
+	for i := 0; i < 10; i++ {
+		if poolSession := sm.sessionPool.Get(); poolSession != nil {
+			if sessionData, ok := poolSession.(SessionData); ok && sessionData != nil {
+				sessionData.Reset()
+				poolCleaned++
+			}
+			sm.sessionPool.Put(poolSession)
+		}
+	}
+
+	cleanupDuration := time.Since(cleanupStart)
+	sm.logger.Debugf("Session cleanup completed in %v: pool_cleaned=%d, orphaned_chunks=%d, expired_sessions=%d, errors=%d",
+		cleanupDuration, poolCleaned, orphanedChunks, expiredSessions, cleanupErrors)
+}
+
+// ValidateSessionHealth performs comprehensive validation of session integrity
+func (sm *SessionManager) ValidateSessionHealth(sessionData SessionData) error {
+	if sessionData == nil {
+		return fmt.Errorf("session data is nil")
+	}
+
+	// Check if user is authenticated
+	if !sessionData.GetAuthenticated() {
+		return nil // Not authenticated is not an error
+	}
+
+	// Validate token formats
+	if accessToken := sessionData.GetAccessToken(); accessToken != "" {
+		if err := sm.validateTokenFormat(accessToken, "access"); err != nil {
+			return fmt.Errorf("invalid access token format: %w", err)
+		}
+	}
+
+	if idToken := sessionData.GetIDToken(); idToken != "" {
+		if err := sm.validateTokenFormat(idToken, "id"); err != nil {
+			return fmt.Errorf("invalid ID token format: %w", err)
+		}
+	}
+
+	// Check for session tampering
+	if err := sm.detectSessionTampering(sessionData); err != nil {
+		return fmt.Errorf("session tampering detected: %w", err)
+	}
+
+	return nil
+}
+
+// validateTokenFormat validates the format of JWT tokens
+func (sm *SessionManager) validateTokenFormat(token, tokenType string) error {
+	if token == "" {
+		return nil
+	}
+
+	// JWT tokens should have exactly 3 parts separated by dots
+	parts := strings.Split(token, ".")
+	if len(parts) != 3 {
+		return fmt.Errorf("%s token is not a valid JWT format", tokenType)
+	}
+
+	// Each part should be non-empty
+	for i, part := range parts {
+		if part == "" {
+			return fmt.Errorf("%s token part %d is empty", tokenType, i+1)
+		}
+	}
+
+	return nil
+}
+
+// detectSessionTampering detects potential tampering in session data
+func (sm *SessionManager) detectSessionTampering(sessionData SessionData) error {
+	email := sessionData.GetEmail()
+	authenticated := sessionData.GetAuthenticated()
+
+	// If authenticated but no email, that's suspicious
+	if authenticated && email == "" {
+		return fmt.Errorf("authenticated session without email")
+	}
+
+	// If email exists but not authenticated, that's also suspicious
+	if !authenticated && email != "" {
+		sm.logger.Debugf("Warning: Email exists (%s) but session not authenticated", email)
+	}
+
+	return nil
+}
+
+// GetSessionMetrics returns metrics about session usage
+func (sm *SessionManager) GetSessionMetrics() map[string]interface{} {
+	metrics := make(map[string]interface{})
+
+	metrics["store_type"] = fmt.Sprintf("%T", sm.store)
+	metrics["cookie_domain"] = sm.cookieDomain
+	metrics["force_https"] = sm.forceHTTPS
+	metrics["cleanup_done"] = sm.cleanupDone
+
+	return metrics
+}
+
+// shouldUseSecureCookies determines if cookies should be secure based on request
+func (sm *SessionManager) shouldUseSecureCookies(r *http.Request) bool {
+	if sm.forceHTTPS {
+		return true
+	}
+
+	// Check if the request came over HTTPS
+	if r.TLS != nil {
+		return true
+	}
+
+	// Check X-Forwarded-Proto header
+	if proto := r.Header.Get("X-Forwarded-Proto"); proto == "https" {
+		return true
+	}
+
+	return false
+}
+
+// getSessionOptions returns session options for the given security context
+func (sm *SessionManager) getSessionOptions(isSecure bool) *sessions.Options {
+	return &sessions.Options{
+		Path:     "/",
+		Domain:   sm.cookieDomain,
+		MaxAge:   int(absoluteSessionTimeout.Seconds()),
+		Secure:   isSecure,
+		HttpOnly: true,
+		SameSite: http.SameSiteLaxMode,
+	}
+}
+
+// Cookie name functions
+func MainCookieName() string     { return "_oidc_raczylo_m" }
+func AccessTokenCookie() string  { return "_oidc_raczylo_a" }
+func RefreshTokenCookie() string { return "_oidc_raczylo_r" }
+func IDTokenCookie() string      { return "_oidc_raczylo_id" }
+
+// NewSessionData creates a new session data instance
+func NewSessionData(manager *SessionManager, logger Logger) SessionData {
+	// This function should be implemented to return a concrete SessionData implementation
+	// The actual implementation depends on the SessionData struct definition
+	return nil
+}

session/crypto/session_crypto.go

@@ -0,0 +1,264 @@
+// Package crypto provides cryptographic operations for session management
+package crypto
+
+import (
+	"bytes"
+	"compress/gzip"
+	"crypto/rand"
+	"encoding/base64"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"strings"
+)
+
+// MemoryPools interface for memory management
+type MemoryPools interface {
+	GetCompressionBuffer() *bytes.Buffer
+	PutCompressionBuffer(*bytes.Buffer)
+	GetHTTPResponseBuffer() []byte
+	PutHTTPResponseBuffer([]byte)
+}
+
+// SessionCrypto provides cryptographic operations for session data
+type SessionCrypto struct {
+	memoryPools MemoryPools
+}
+
+// NewSessionCrypto creates a new session crypto instance
+func NewSessionCrypto(memoryPools MemoryPools) *SessionCrypto {
+	return &SessionCrypto{
+		memoryPools: memoryPools,
+	}
+}
+
+// GenerateSecureRandomString creates a cryptographically secure random string.
+// It generates random bytes using crypto/rand and encodes them as hexadecimal.
+// This is used for session IDs and other security-sensitive random values.
+func (sc *SessionCrypto) GenerateSecureRandomString(length int) (string, error) {
+	bytes := make([]byte, length)
+	if _, err := rand.Read(bytes); err != nil {
+		return "", fmt.Errorf("failed to generate random bytes: %w", err)
+	}
+	return hex.EncodeToString(bytes), nil
+}
+
+// CompressToken compresses a JWT token using gzip compression if beneficial.
+// It validates the token format, attempts compression, and verifies the compressed
+// data can be decompressed correctly. Only compresses if it reduces size.
+func (sc *SessionCrypto) CompressToken(token string) string {
+	if token == "" {
+		return token
+	}
+
+	// Validate JWT format (should have exactly 2 dots)
+	dotCount := strings.Count(token, ".")
+	if dotCount != 2 {
+		return token
+	}
+
+	// Don't try to compress extremely large tokens
+	if len(token) > 50*1024 {
+		return token
+	}
+
+	b := sc.memoryPools.GetCompressionBuffer()
+	defer sc.memoryPools.PutCompressionBuffer(b)
+
+	gz := gzip.NewWriter(b)
+
+	written, err := gz.Write([]byte(token))
+	if err != nil || written != len(token) {
+		return token
+	}
+
+	if err := gz.Close(); err != nil {
+		return token
+	}
+
+	compressedBytes := b.Bytes()
+	if len(compressedBytes) == 0 {
+		return token
+	}
+
+	compressed := base64.StdEncoding.EncodeToString(compressedBytes)
+
+	// Only use compression if it actually reduces size
+	if len(compressed) >= len(token) {
+		return token
+	}
+
+	// Verify compression integrity by attempting decompression
+	decompressed := sc.decompressTokenInternal(compressed)
+	if decompressed != token {
+		return token
+	}
+
+	// Final validation of decompressed token
+	if strings.Count(decompressed, ".") != 2 {
+		return token
+	}
+
+	return compressed
+}
+
+// DecompressToken decompresses a previously compressed token string.
+// It decodes the base64 data, validates gzip headers, and decompresses safely
+// with size limits to prevent compression bombs.
+func (sc *SessionCrypto) DecompressToken(compressed string) string {
+	return sc.decompressTokenInternal(compressed)
+}
+
+// decompressTokenInternal is the internal decompression function.
+// Separated internal function for integrity verification during compression.
+// It performs the actual decompression logic with proper resource management.
+func (sc *SessionCrypto) decompressTokenInternal(compressed string) string {
+	if compressed == "" {
+		return compressed
+	}
+
+	// Prevent decompression of extremely large inputs
+	if len(compressed) > 100*1024 {
+		return compressed
+	}
+
+	data, err := base64.StdEncoding.DecodeString(compressed)
+	if err != nil {
+		return compressed
+	}
+
+	if len(data) == 0 {
+		return compressed
+	}
+
+	// Validate gzip header
+	if len(data) < 2 || data[0] != 0x1f || data[1] != 0x8b {
+		return compressed
+	}
+
+	readerBuf := sc.memoryPools.GetHTTPResponseBuffer()
+	defer sc.memoryPools.PutHTTPResponseBuffer(readerBuf)
+
+	gz, err := gzip.NewReader(bytes.NewReader(data))
+	if err != nil {
+		return compressed
+	}
+
+	defer func() {
+		if closeErr := gz.Close(); closeErr != nil {
+			_ = closeErr
+		}
+	}()
+
+	// Limit decompressed size to prevent compression bombs
+	limitedReader := io.LimitReader(gz, 500*1024)
+
+	// Optimize for large buffer reuse
+	if cap(readerBuf) >= 512*1024 {
+		readerBuf = readerBuf[:cap(readerBuf)]
+		n, err := limitedReader.Read(readerBuf)
+		if err != nil && err != io.EOF {
+			return compressed
+		}
+		decompressed := readerBuf[:n]
+		return string(decompressed)
+	}
+
+	decompressed, err := io.ReadAll(limitedReader)
+	if err != nil {
+		return compressed
+	}
+
+	if len(decompressed) == 0 {
+		return compressed
+	}
+
+	decompressedStr := string(decompressed)
+
+	// Validate the decompressed token is a valid JWT
+	if decompressedStr != "" && strings.Count(decompressedStr, ".") != 2 {
+		return compressed
+	}
+
+	return decompressedStr
+}
+
+// ValidateTokenFormat validates that a token has the correct JWT format
+func (sc *SessionCrypto) ValidateTokenFormat(token string) bool {
+	if token == "" {
+		return false
+	}
+
+	// JWT tokens should have exactly 3 parts separated by dots
+	parts := strings.Split(token, ".")
+	if len(parts) != 3 {
+		return false
+	}
+
+	// Each part should be non-empty
+	for _, part := range parts {
+		if part == "" {
+			return false
+		}
+	}
+
+	return true
+}
+
+// IsTokenCompressed checks if a token appears to be compressed
+func (sc *SessionCrypto) IsTokenCompressed(token string) bool {
+	if token == "" {
+		return false
+	}
+
+	// JWT tokens have exactly 2 dots, compressed tokens don't
+	if strings.Count(token, ".") == 2 {
+		return false
+	}
+
+	// Try to decode as base64
+	data, err := base64.StdEncoding.DecodeString(token)
+	if err != nil {
+		return false
+	}
+
+	// Check for gzip header
+	if len(data) >= 2 && data[0] == 0x1f && data[1] == 0x8b {
+		return true
+	}
+
+	return false
+}
+
+// SecureWipeBytes securely wipes sensitive data from memory
+func (sc *SessionCrypto) SecureWipeBytes(data []byte) {
+	for i := range data {
+		data[i] = 0
+	}
+}
+
+// SecureWipeString securely wipes sensitive string data
+func (sc *SessionCrypto) SecureWipeString(s *string) {
+	if s != nil {
+		*s = ""
+	}
+}
+
+// Utility functions that don't require instance state
+
+// Min returns the minimum of two integers
+func Min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+// GenerateSecureRandomString creates a cryptographically secure random string without dependencies
+func GenerateSecureRandomString(length int) (string, error) {
+	bytes := make([]byte, length)
+	if _, err := rand.Read(bytes); err != nil {
+		return "", fmt.Errorf("failed to generate random bytes: %w", err)
+	}
+	return hex.EncodeToString(bytes), nil
+}

session/crypto/session_crypto_test.go

@@ -0,0 +1,900 @@
+package crypto
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/base64"
+	"strings"
+	"testing"
+)
+
+// Mock memory pools for testing
+type MockMemoryPools struct{}
+
+func (mp *MockMemoryPools) GetCompressionBuffer() *bytes.Buffer {
+	return &bytes.Buffer{}
+}
+
+func (mp *MockMemoryPools) PutCompressionBuffer(*bytes.Buffer) {
+	// Mock implementation - nothing to do
+}
+
+func (mp *MockMemoryPools) GetHTTPResponseBuffer() []byte {
+	return make([]byte, 32768) // 32KB buffer
+}
+
+func (mp *MockMemoryPools) PutHTTPResponseBuffer([]byte) {
+	// Mock implementation - nothing to do
+}
+
+// TestGenerateSecureRandomString tests secure random string generation
+func TestGenerateSecureRandomString(t *testing.T) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	tests := []struct {
+		name        string
+		length      int
+		expectError bool
+		description string
+	}{
+		{
+			name:        "Valid length",
+			length:      16,
+			expectError: false,
+			description: "Should generate random string of correct length",
+		},
+		{
+			name:        "Minimum length",
+			length:      1,
+			expectError: false,
+			description: "Should handle minimum length",
+		},
+		{
+			name:        "Zero length",
+			length:      0,
+			expectError: false,
+			description: "Should handle zero length",
+		},
+		{
+			name:        "Large length",
+			length:      1024,
+			expectError: false,
+			description: "Should handle large length",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := sc.GenerateSecureRandomString(tt.length)
+
+			if tt.expectError {
+				if err == nil {
+					t.Errorf("Expected error for %s, got nil", tt.description)
+				}
+				return
+			}
+
+			if err != nil {
+				t.Errorf("Unexpected error for %s: %v", tt.description, err)
+				return
+			}
+
+			// Check length (hex encoding doubles the length)
+			expectedLen := tt.length * 2
+			if len(result) != expectedLen {
+				t.Errorf("Expected length %d, got %d for %s", expectedLen, len(result), tt.description)
+			}
+
+			// Check that result is hex
+			for _, char := range result {
+				if !((char >= '0' && char <= '9') || (char >= 'a' && char <= 'f')) {
+					t.Errorf("Result contains non-hex character: %c", char)
+					break
+				}
+			}
+		})
+	}
+}
+
+// TestGenerateSecureRandomStringUniqueness tests that generated strings are unique
+func TestGenerateSecureRandomStringUniqueness(t *testing.T) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	// Generate multiple strings and check uniqueness
+	generated := make(map[string]bool)
+	for i := 0; i < 100; i++ {
+		result, err := sc.GenerateSecureRandomString(16)
+		if err != nil {
+			t.Fatalf("Failed to generate random string: %v", err)
+		}
+
+		if generated[result] {
+			t.Errorf("Generated duplicate string: %s", result)
+		}
+		generated[result] = true
+	}
+}
+
+// TestTokenCompressionIntegrity tests token compression and decompression
+func TestTokenCompressionIntegrity(t *testing.T) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	tests := []struct {
+		name        string
+		token       string
+		expectValid bool
+		description string
+	}{
+		{
+			name:        "Valid JWT small",
+			token:       "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c",
+			expectValid: true,
+			description: "Should compress and decompress small JWT correctly",
+		},
+		{
+			name:        "Valid JWT large",
+			token:       createLargeJWT(2000),
+			expectValid: true,
+			description: "Should compress and decompress large JWT correctly",
+		},
+		{
+			name:        "Invalid token - no dots",
+			token:       "invalidtoken",
+			expectValid: false,
+			description: "Should not compress token without dots",
+		},
+		{
+			name:        "Invalid token - wrong number of dots",
+			token:       "header.payload",
+			expectValid: false,
+			description: "Should not compress token with wrong number of dots",
+		},
+		{
+			name:        "Empty token",
+			token:       "",
+			expectValid: false,
+			description: "Should handle empty token",
+		},
+		{
+			name:        "Oversized token",
+			token:       createOversizedToken(),
+			expectValid: false,
+			description: "Should reject oversized tokens",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			compressed := sc.CompressToken(tt.token)
+
+			if !tt.expectValid {
+				// For invalid tokens, compression should return original
+				if compressed != tt.token {
+					t.Errorf("Expected compression to return original for invalid token, got different result")
+				}
+				return
+			}
+
+			// For valid tokens, test round-trip integrity
+			decompressed := sc.DecompressToken(compressed)
+			if decompressed != tt.token {
+				t.Errorf("Token integrity lost: original length=%d, compressed length=%d, decompressed length=%d",
+					len(tt.token), len(compressed), len(decompressed))
+			}
+
+			// Test that decompression is idempotent
+			decompressed2 := sc.DecompressToken(decompressed)
+			if decompressed2 != tt.token {
+				t.Errorf("Decompression not idempotent: %d != %d", len(decompressed2), len(tt.token))
+			}
+		})
+	}
+}
+
+// TestTokenCompressionCorruptionDetection tests corruption detection
+func TestTokenCompressionCorruptionDetection(t *testing.T) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	corruptionTests := []struct {
+		name           string
+		corruptedInput string
+		expectOriginal bool
+		description    string
+	}{
+		{
+			name:           "Corrupted base64",
+			corruptedInput: "invalid-base64!",
+			expectOriginal: true,
+			description:    "Should return original for corrupted base64",
+		},
+		{
+			name:           "Truncated compressed data",
+			corruptedInput: "H4sI", // Truncated gzip header
+			expectOriginal: true,
+			description:    "Should return original for truncated data",
+		},
+		{
+			name:           "Invalid gzip data",
+			corruptedInput: base64.StdEncoding.EncodeToString([]byte("not gzip data")),
+			expectOriginal: true,
+			description:    "Should return original for invalid gzip data",
+		},
+		{
+			name:           "Empty compressed data",
+			corruptedInput: "",
+			expectOriginal: true,
+			description:    "Should handle empty compressed data",
+		},
+	}
+
+	for _, tt := range corruptionTests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := sc.DecompressToken(tt.corruptedInput)
+			if tt.expectOriginal && result != tt.corruptedInput {
+				t.Errorf("Expected decompression to return original corrupted input, got: %q", result)
+			}
+		})
+	}
+
+	// Test that valid compression still works
+	t.Run("Valid compression verification", func(t *testing.T) {
+		validJWT := "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"
+		compressed := sc.CompressToken(validJWT)
+		decompressed := sc.DecompressToken(compressed)
+		if decompressed != validJWT {
+			t.Errorf("Valid compression/decompression failed: %q != %q", decompressed, validJWT)
+		}
+	})
+}
+
+// TestCompressionEfficiency tests that compression only occurs when beneficial
+func TestCompressionEfficiency(t *testing.T) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	tests := []struct {
+		name           string
+		token          string
+		shouldCompress bool
+		description    string
+	}{
+		{
+			name:           "Small JWT",
+			token:          "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c",
+			shouldCompress: false, // Small tokens might not benefit from compression
+			description:    "Small tokens should not be compressed if no benefit",
+		},
+		{
+			name:           "Large repetitive JWT",
+			token:          createLargeRepetitiveJWT(2000),
+			shouldCompress: true, // Repetitive data should compress well
+			description:    "Large repetitive tokens should be compressed",
+		},
+		{
+			name:           "Incompressible token",
+			token:          createIncompressibleJWT(1000),
+			shouldCompress: false, // Random data won't compress well
+			description:    "Incompressible tokens should not be compressed",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			compressed := sc.CompressToken(tt.token)
+			wasCompressed := compressed != tt.token
+
+			if tt.shouldCompress && !wasCompressed {
+				t.Errorf("Expected token to be compressed but it wasn't")
+			} else if !tt.shouldCompress && wasCompressed {
+				// This is okay - compression might still occur if beneficial
+				t.Logf("Token was compressed even though not expected (this is acceptable)")
+			}
+
+			// Verify decompression still works regardless
+			decompressed := sc.DecompressToken(compressed)
+			if decompressed != tt.token {
+				t.Errorf("Decompression failed for %s", tt.description)
+			}
+		})
+	}
+}
+
+// TestCompressionSizeLimits tests compression size limits
+func TestCompressionSizeLimits(t *testing.T) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	t.Run("Oversized token rejection", func(t *testing.T) {
+		oversizedToken := createOversizedToken()
+		compressed := sc.CompressToken(oversizedToken)
+
+		// Oversized tokens should not be compressed
+		if compressed != oversizedToken {
+			t.Error("Oversized token should not be compressed")
+		}
+	})
+
+	t.Run("Oversized compressed data rejection", func(t *testing.T) {
+		oversizedCompressed := strings.Repeat("a", 150*1024) // >100KB
+		decompressed := sc.DecompressToken(oversizedCompressed)
+
+		// Should return original when input is too large
+		if decompressed != oversizedCompressed {
+			t.Error("Oversized compressed data should be returned as-is")
+		}
+	})
+}
+
+// Helper functions for creating test tokens
+
+func createLargeJWT(size int) string {
+	header := "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9"
+	signature := "SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"
+
+	// Create payload that will result in desired total size
+	payloadSize := size - len(header) - len(signature) - 2 // -2 for dots
+	if payloadSize < 10 {
+		payloadSize = 10
+	}
+
+	payload := base64.StdEncoding.EncodeToString([]byte(strings.Repeat("x", payloadSize*3/4)))
+
+	return header + "." + payload + "." + signature
+}
+
+func createLargeRepetitiveJWT(size int) string {
+	header := "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9"
+	signature := "SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"
+
+	// Create repetitive payload that compresses well
+	payloadSize := size - len(header) - len(signature) - 2
+	if payloadSize < 10 {
+		payloadSize = 10
+	}
+
+	repetitiveData := strings.Repeat("repetitive_data_", payloadSize/16)
+	payload := base64.StdEncoding.EncodeToString([]byte(repetitiveData))
+
+	return header + "." + payload + "." + signature
+}
+
+func createIncompressibleJWT(size int) string {
+	header := "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9"
+	signature := "SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"
+
+	// Create random payload that won't compress well
+	payloadSize := size - len(header) - len(signature) - 2
+	if payloadSize < 10 {
+		payloadSize = 10
+	}
+
+	randomBytes := make([]byte, payloadSize*3/4)
+	rand.Read(randomBytes)
+	payload := base64.StdEncoding.EncodeToString(randomBytes)
+
+	return header + "." + payload + "." + signature
+}
+
+func createOversizedToken() string {
+	// Create a token larger than 50KB (the limit in CompressToken)
+	size := 55 * 1024 // 55KB
+	header := "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9"
+	signature := "SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"
+
+	payloadSize := size - len(header) - len(signature) - 2
+	payload := base64.StdEncoding.EncodeToString([]byte(strings.Repeat("x", payloadSize*3/4)))
+
+	return header + "." + payload + "." + signature
+}
+
+// BenchmarkCompression benchmarks compression operations
+func BenchmarkCompression(b *testing.B) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	b.Run("CompressLargeJWT", func(b *testing.B) {
+		largeToken := createLargeJWT(5000)
+		b.ResetTimer()
+
+		for i := 0; i < b.N; i++ {
+			_ = sc.CompressToken(largeToken)
+		}
+	})
+
+	b.Run("DecompressLargeJWT", func(b *testing.B) {
+		largeToken := createLargeJWT(5000)
+		compressed := sc.CompressToken(largeToken)
+		b.ResetTimer()
+
+		for i := 0; i < b.N; i++ {
+			_ = sc.DecompressToken(compressed)
+		}
+	})
+
+	b.Run("RoundTripCompression", func(b *testing.B) {
+		largeToken := createLargeJWT(5000)
+		b.ResetTimer()
+
+		for i := 0; i < b.N; i++ {
+			compressed := sc.CompressToken(largeToken)
+			_ = sc.DecompressToken(compressed)
+		}
+	})
+}
+
+// TestValidateTokenFormat tests JWT token format validation
+func TestValidateTokenFormat(t *testing.T) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	tests := []struct {
+		name     string
+		token    string
+		expected bool
+	}{
+		{
+			name:     "Valid JWT token",
+			token:    "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c",
+			expected: true,
+		},
+		{
+			name:     "Valid JWT with different content",
+			token:    "header.payload.signature",
+			expected: true,
+		},
+		{
+			name:     "Empty token",
+			token:    "",
+			expected: false,
+		},
+		{
+			name:     "Token with no dots",
+			token:    "nodots",
+			expected: false,
+		},
+		{
+			name:     "Token with one dot",
+			token:    "header.payload",
+			expected: false,
+		},
+		{
+			name:     "Token with four dots",
+			token:    "header.payload.signature.extra",
+			expected: false,
+		},
+		{
+			name:     "Token with empty header",
+			token:    ".payload.signature",
+			expected: false,
+		},
+		{
+			name:     "Token with empty payload",
+			token:    "header..signature",
+			expected: false,
+		},
+		{
+			name:     "Token with empty signature",
+			token:    "header.payload.",
+			expected: false,
+		},
+		{
+			name:     "Token with all empty parts",
+			token:    "..",
+			expected: false,
+		},
+		{
+			name:     "Opaque token",
+			token:    "opaque_token_without_dots",
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := sc.ValidateTokenFormat(tt.token)
+			if result != tt.expected {
+				t.Errorf("ValidateTokenFormat(%q) = %v, expected %v", tt.token, result, tt.expected)
+			}
+		})
+	}
+}
+
+// TestIsTokenCompressed tests token compression detection
+func TestIsTokenCompressed(t *testing.T) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	tests := []struct {
+		name     string
+		token    string
+		expected bool
+	}{
+		{
+			name:     "Empty token",
+			token:    "",
+			expected: false,
+		},
+		{
+			name:     "Valid JWT token (uncompressed)",
+			token:    "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c",
+			expected: false,
+		},
+		{
+			name:     "Invalid base64",
+			token:    "invalid!base64",
+			expected: false,
+		},
+		{
+			name:     "Valid base64 but not gzip",
+			token:    base64.StdEncoding.EncodeToString([]byte("not gzip data")),
+			expected: false,
+		},
+		{
+			name:     "Valid gzip header",
+			token:    base64.StdEncoding.EncodeToString([]byte{0x1f, 0x8b, 0x08, 0x00}), // gzip magic bytes
+			expected: true,
+		},
+		{
+			name:     "Partial gzip header",
+			token:    base64.StdEncoding.EncodeToString([]byte{0x1f}), // only first byte
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := sc.IsTokenCompressed(tt.token)
+			if result != tt.expected {
+				t.Errorf("IsTokenCompressed(%q) = %v, expected %v", tt.token, result, tt.expected)
+			}
+		})
+	}
+
+	// Test with actual compressed token
+	t.Run("Real compressed token", func(t *testing.T) {
+		originalToken := createLargeJWT(2000)
+		compressedToken := sc.CompressToken(originalToken)
+
+		// If compression occurred (token changed), it should be detected as compressed
+		if compressedToken != originalToken {
+			if !sc.IsTokenCompressed(compressedToken) {
+				t.Error("Failed to detect actual compressed token")
+			}
+		}
+
+		// Original token should not be detected as compressed
+		if sc.IsTokenCompressed(originalToken) {
+			t.Error("Original JWT detected as compressed")
+		}
+	})
+}
+
+// TestSecureWipeBytes tests secure byte wiping
+func TestSecureWipeBytes(t *testing.T) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	tests := []struct {
+		name string
+		data []byte
+	}{
+		{
+			name: "Normal byte slice",
+			data: []byte("sensitive data"),
+		},
+		{
+			name: "Empty slice",
+			data: []byte{},
+		},
+		{
+			name: "Single byte",
+			data: []byte{0xFF},
+		},
+		{
+			name: "Large data",
+			data: bytes.Repeat([]byte("secret"), 1000),
+		},
+		{
+			name: "Nil slice",
+			data: nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Create a copy to verify original content
+			original := make([]byte, len(tt.data))
+			copy(original, tt.data)
+
+			// Wipe the data
+			sc.SecureWipeBytes(tt.data)
+
+			// Verify all bytes are zero (except for nil slice)
+			if tt.data != nil {
+				for i, b := range tt.data {
+					if b != 0 {
+						t.Errorf("Byte at index %d not wiped: got %d, expected 0", i, b)
+					}
+				}
+			}
+
+			// Verify we had actual data to wipe (except for empty/nil cases)
+			if len(original) > 0 {
+				hasNonZero := false
+				for _, b := range original {
+					if b != 0 {
+						hasNonZero = true
+						break
+					}
+				}
+				if !hasNonZero {
+					t.Log("Test data was already all zeros")
+				}
+			}
+		})
+	}
+}
+
+// TestSecureWipeString tests secure string wiping
+func TestSecureWipeString(t *testing.T) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	tests := []struct {
+		name   string
+		input  *string
+		expect string
+	}{
+		{
+			name:   "Normal string",
+			input:  func() *string { s := "sensitive data"; return &s }(),
+			expect: "",
+		},
+		{
+			name:   "Empty string",
+			input:  func() *string { s := ""; return &s }(),
+			expect: "",
+		},
+		{
+			name:   "Long string",
+			input:  func() *string { s := strings.Repeat("secret", 1000); return &s }(),
+			expect: "",
+		},
+		{
+			name:   "Nil string pointer",
+			input:  nil,
+			expect: "", // This test verifies no panic occurs
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Store original value for verification
+			var original string
+			if tt.input != nil {
+				original = *tt.input
+			}
+
+			// Wipe the string
+			sc.SecureWipeString(tt.input)
+
+			// Verify result
+			if tt.input != nil {
+				if *tt.input != tt.expect {
+					t.Errorf("String not wiped properly: got %q, expected %q", *tt.input, tt.expect)
+				}
+			}
+
+			// Verify we had actual data to wipe (except for nil case)
+			if tt.input != nil && original != "" {
+				t.Logf("Successfully wiped string of length %d", len(original))
+			}
+		})
+	}
+}
+
+// TestMin tests the minimum utility function
+func TestMin(t *testing.T) {
+	tests := []struct {
+		name     string
+		a, b     int
+		expected int
+	}{
+		{
+			name:     "a smaller than b",
+			a:        5,
+			b:        10,
+			expected: 5,
+		},
+		{
+			name:     "b smaller than a",
+			a:        15,
+			b:        7,
+			expected: 7,
+		},
+		{
+			name:     "equal values",
+			a:        42,
+			b:        42,
+			expected: 42,
+		},
+		{
+			name:     "negative values",
+			a:        -10,
+			b:        -5,
+			expected: -10,
+		},
+		{
+			name:     "zero values",
+			a:        0,
+			b:        0,
+			expected: 0,
+		},
+		{
+			name:     "mixed positive and negative",
+			a:        -3,
+			b:        2,
+			expected: -3,
+		},
+		{
+			name:     "large numbers",
+			a:        1000000,
+			b:        999999,
+			expected: 999999,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := Min(tt.a, tt.b)
+			if result != tt.expected {
+				t.Errorf("Min(%d, %d) = %d, expected %d", tt.a, tt.b, result, tt.expected)
+			}
+		})
+	}
+}
+
+// TestGenerateSecureRandomStringStandalone tests the standalone random string function
+func TestGenerateSecureRandomStringStandalone(t *testing.T) {
+	tests := []struct {
+		name        string
+		length      int
+		expectError bool
+	}{
+		{
+			name:        "Valid length",
+			length:      16,
+			expectError: false,
+		},
+		{
+			name:        "Zero length",
+			length:      0,
+			expectError: false,
+		},
+		{
+			name:        "Large length",
+			length:      1024,
+			expectError: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := GenerateSecureRandomString(tt.length)
+
+			if tt.expectError {
+				if err == nil {
+					t.Error("Expected error but got none")
+				}
+				return
+			}
+
+			if err != nil {
+				t.Errorf("Unexpected error: %v", err)
+				return
+			}
+
+			// Check length (hex encoding doubles the length)
+			expectedLen := tt.length * 2
+			if len(result) != expectedLen {
+				t.Errorf("Expected length %d, got %d", expectedLen, len(result))
+			}
+
+			// Check that result is hex
+			for _, char := range result {
+				if !((char >= '0' && char <= '9') || (char >= 'a' && char <= 'f')) {
+					t.Errorf("Result contains non-hex character: %c", char)
+					break
+				}
+			}
+		})
+	}
+
+	// Test uniqueness
+	t.Run("Uniqueness test", func(t *testing.T) {
+		generated := make(map[string]bool)
+		for i := 0; i < 100; i++ {
+			result, err := GenerateSecureRandomString(16)
+			if err != nil {
+				t.Fatalf("Failed to generate random string: %v", err)
+			}
+
+			if generated[result] {
+				t.Errorf("Generated duplicate string: %s", result)
+			}
+			generated[result] = true
+		}
+	})
+}
+
+// TestCompressionEdgeCases tests edge cases for compression
+func TestCompressionEdgeCases(t *testing.T) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	t.Run("Token with exact size limit", func(t *testing.T) {
+		// Create token at exactly 50KB
+		token := createTokenWithExactSize(50 * 1024)
+		compressed := sc.CompressToken(token)
+
+		// Should still attempt compression at the limit
+		decompressed := sc.DecompressToken(compressed)
+		if decompressed != token {
+			t.Error("Failed to handle token at size limit")
+		}
+	})
+
+	t.Run("Compressed token with exact decompression limit", func(t *testing.T) {
+		// Create data that decompresses to exactly 100KB
+		largeData := strings.Repeat("a", 100*1024)
+		encoded := base64.StdEncoding.EncodeToString([]byte(largeData))
+
+		result := sc.DecompressToken(encoded)
+		// Should return original since it's not valid gzip
+		if result != encoded {
+			t.Error("Failed to handle large non-gzip data")
+		}
+	})
+}
+
+// Helper function to create token with exact size
+func createTokenWithExactSize(targetSize int) string {
+	header := "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9"
+	signature := "SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"
+
+	// Calculate needed payload size
+	dotsSize := 2 // two dots
+	otherSize := len(header) + len(signature) + dotsSize
+	payloadSize := targetSize - otherSize
+
+	if payloadSize <= 0 {
+		payloadSize = 10 // minimum payload
+	}
+
+	// Create payload of exact size
+	payload := strings.Repeat("x", payloadSize)
+
+	return header + "." + payload + "." + signature
+}
+
+// BenchmarkRandomGeneration benchmarks random string generation
+func BenchmarkRandomGeneration(b *testing.B) {
+	memoryPools := &MockMemoryPools{}
+	sc := NewSessionCrypto(memoryPools)
+
+	b.Run("Generate16Bytes", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_, _ = sc.GenerateSecureRandomString(16)
+		}
+	})
+
+	b.Run("Generate32Bytes", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_, _ = sc.GenerateSecureRandomString(32)
+		}
+	})
+}

session/storage/session_store.go

@@ -0,0 +1,320 @@
+// Package storage provides session storage operations for the OIDC middleware
+package storage
+
+import (
+	"fmt"
+	"net/http"
+	"sync"
+
+	"github.com/gorilla/sessions"
+)
+
+// SessionData represents a user's authentication session with comprehensive token management.
+// It handles main session data and supports large tokens that need to be
+// split across multiple cookies due to browser size limitations.
+type SessionData struct {
+	manager            SessionManager
+	request            *http.Request
+	mainSession        *sessions.Session
+	accessSession      *sessions.Session
+	refreshSession     *sessions.Session
+	idTokenSession     *sessions.Session
+	accessTokenChunks  map[int]*sessions.Session
+	refreshTokenChunks map[int]*sessions.Session
+	idTokenChunks      map[int]*sessions.Session
+	refreshMutex       sync.Mutex
+	sessionMutex       sync.RWMutex
+	dirty              bool
+	inUse              bool
+}
+
+// SessionManager interface for session management operations
+type SessionManager interface {
+	GetSessionOptions(isSecure bool) *sessions.Options
+	EnhanceSessionSecurity(options *sessions.Options, r *http.Request) *sessions.Options
+	GetLogger() Logger
+}
+
+// Logger interface for dependency injection
+type Logger interface {
+	Error(msg string)
+	Errorf(format string, args ...interface{})
+}
+
+// NewSessionData creates a new session data instance
+func NewSessionData(manager SessionManager) *SessionData {
+	return &SessionData{
+		manager:            manager,
+		accessTokenChunks:  make(map[int]*sessions.Session),
+		refreshTokenChunks: make(map[int]*sessions.Session),
+		idTokenChunks:      make(map[int]*sessions.Session),
+		refreshMutex:       sync.Mutex{},
+		sessionMutex:       sync.RWMutex{},
+		dirty:              false,
+		inUse:              false,
+	}
+}
+
+// IsDirty returns true if the session data has been modified since it was last loaded or saved.
+// This is used to optimize session saves by only writing when necessary.
+func (sd *SessionData) IsDirty() bool {
+	return sd.dirty
+}
+
+// MarkDirty marks the session as having pending changes that need to be saved.
+// This is used when session data hasn't changed in content but should still
+// trigger a session save (e.g., to ensure the cookie is re-issued).
+func (sd *SessionData) MarkDirty() {
+	sd.dirty = true
+}
+
+// Save persists all session data including main session and token chunks.
+// It applies security options, saves all session components, and handles
+// errors gracefully by continuing to save other components even if one fails.
+func (sd *SessionData) Save(r *http.Request, w http.ResponseWriter) error {
+	isSecure := r.Header.Get("X-Forwarded-Proto") == "https" || r.TLS != nil
+	if forceHTTPS := sd.manager.GetLogger(); forceHTTPS != nil {
+		// Add force HTTPS check if needed
+	}
+
+	options := sd.manager.GetSessionOptions(isSecure)
+	options = sd.manager.EnhanceSessionSecurity(options, r)
+
+	if sd.mainSession != nil {
+		sd.mainSession.Options = options
+	}
+	if sd.accessSession != nil {
+		sd.accessSession.Options = options
+	}
+	if sd.refreshSession != nil {
+		sd.refreshSession.Options = options
+	}
+	if sd.idTokenSession != nil {
+		sd.idTokenSession.Options = options
+	}
+
+	var firstErr error
+	saveOrLogError := func(s *sessions.Session, name string) {
+		if s == nil {
+			logger := sd.manager.GetLogger()
+			if logger != nil {
+				logger.Errorf("Attempted to save nil session: %s", name)
+			}
+			if firstErr == nil {
+				firstErr = fmt.Errorf("attempted to save nil session: %s", name)
+			}
+			return
+		}
+		if err := s.Save(r, w); err != nil {
+			errMsg := fmt.Errorf("failed to save %s session: %w", name, err)
+			logger := sd.manager.GetLogger()
+			if logger != nil {
+				logger.Error(errMsg.Error())
+			}
+			if firstErr == nil {
+				firstErr = errMsg
+			}
+		}
+	}
+
+	saveOrLogError(sd.mainSession, "main")
+	saveOrLogError(sd.accessSession, "access token")
+	saveOrLogError(sd.refreshSession, "refresh token")
+	saveOrLogError(sd.idTokenSession, "ID token")
+
+	for i, sessionChunk := range sd.accessTokenChunks {
+		if sessionChunk != nil {
+			sessionChunk.Options = options
+			saveOrLogError(sessionChunk, fmt.Sprintf("access token chunk %d", i))
+		}
+	}
+
+	for i, sessionChunk := range sd.refreshTokenChunks {
+		if sessionChunk != nil {
+			sessionChunk.Options = options
+			saveOrLogError(sessionChunk, fmt.Sprintf("refresh token chunk %d", i))
+		}
+	}
+
+	for i, sessionChunk := range sd.idTokenChunks {
+		if sessionChunk != nil {
+			sessionChunk.Options = options
+			saveOrLogError(sessionChunk, fmt.Sprintf("ID token chunk %d", i))
+		}
+	}
+
+	if firstErr == nil {
+		sd.dirty = false
+	}
+	return firstErr
+}
+
+// Clear completely clears all session data and safely returns the session to the pool.
+// It removes all authentication data, expires cookies, and handles panic recovery.
+func (sd *SessionData) Clear(r *http.Request, w http.ResponseWriter) error {
+	defer func() {
+		sd.returnToPoolSafely()
+	}()
+
+	sd.sessionMutex.Lock()
+	defer sd.sessionMutex.Unlock()
+
+	sd.clearAllSessionData(r, true)
+
+	// This is primarily for testing - in production w will often be nil
+	var err error
+	if w != nil {
+		if r != nil && r.Header.Get("X-Test-Error") == "true" {
+			if sd.mainSession != nil {
+				sd.mainSession.Values["error_trigger"] = func() {}
+			}
+		}
+
+		err = sd.Save(r, w)
+	}
+
+	sd.request = nil
+	return err
+}
+
+// clearAllSessionData clears all session data including main session and token chunks.
+// It removes all session values and optionally expires all associated cookies.
+func (sd *SessionData) clearAllSessionData(r *http.Request, expire bool) {
+	clearSessionValues(sd.mainSession, expire)
+	clearSessionValues(sd.accessSession, expire)
+	clearSessionValues(sd.refreshSession, expire)
+	clearSessionValues(sd.idTokenSession, expire)
+
+	if expire && r != nil {
+		sd.clearTokenChunks(r, sd.accessTokenChunks)
+		sd.clearTokenChunks(r, sd.refreshTokenChunks)
+		sd.clearTokenChunks(r, sd.idTokenChunks)
+	} else {
+		for k := range sd.accessTokenChunks {
+			delete(sd.accessTokenChunks, k)
+		}
+		for k := range sd.refreshTokenChunks {
+			delete(sd.refreshTokenChunks, k)
+		}
+		for k := range sd.idTokenChunks {
+			delete(sd.idTokenChunks, k)
+		}
+	}
+
+	if expire {
+		sd.dirty = true
+	}
+}
+
+// clearSessionValues removes all values from a session and optionally expires it.
+// This is used during session cleanup and logout operations.
+func clearSessionValues(session *sessions.Session, expire bool) {
+	if session == nil {
+		return
+	}
+
+	for k := range session.Values {
+		delete(session.Values, k)
+	}
+
+	if expire {
+		session.Options.MaxAge = -1
+	}
+}
+
+// clearTokenChunks clears token chunks from the session
+func (sd *SessionData) clearTokenChunks(r *http.Request, chunks map[int]*sessions.Session) {
+	for i, chunk := range chunks {
+		if chunk != nil {
+			clearSessionValues(chunk, true)
+		}
+		delete(chunks, i)
+	}
+}
+
+// returnToPoolSafely safely returns the session to the object pool
+func (sd *SessionData) returnToPoolSafely() {
+	defer func() {
+		if r := recover(); r != nil {
+			logger := sd.manager.GetLogger()
+			if logger != nil {
+				logger.Errorf("Panic during session pool return: %v", r)
+			}
+		}
+	}()
+
+	sd.sessionMutex.Lock()
+	defer sd.sessionMutex.Unlock()
+
+	if sd.inUse {
+		sd.inUse = false
+		sd.Reset()
+		// Pool return should be handled by calling code
+	}
+}
+
+// Reset resets the session data to a clean state
+func (sd *SessionData) Reset() {
+	sd.mainSession = nil
+	sd.accessSession = nil
+	sd.refreshSession = nil
+	sd.idTokenSession = nil
+
+	// Clear maps without recreating them
+	for k := range sd.accessTokenChunks {
+		delete(sd.accessTokenChunks, k)
+	}
+	for k := range sd.refreshTokenChunks {
+		delete(sd.refreshTokenChunks, k)
+	}
+	for k := range sd.idTokenChunks {
+		delete(sd.idTokenChunks, k)
+	}
+
+	sd.dirty = false
+	sd.inUse = false
+	sd.request = nil
+}
+
+// SetSessions sets the session objects
+func (sd *SessionData) SetSessions(main, access, refresh, idToken *sessions.Session) {
+	sd.mainSession = main
+	sd.accessSession = access
+	sd.refreshSession = refresh
+	sd.idTokenSession = idToken
+}
+
+// GetMainSession returns the main session
+func (sd *SessionData) GetMainSession() *sessions.Session {
+	return sd.mainSession
+}
+
+// GetAccessSession returns the access token session
+func (sd *SessionData) GetAccessSession() *sessions.Session {
+	return sd.accessSession
+}
+
+// GetRefreshSession returns the refresh token session
+func (sd *SessionData) GetRefreshSession() *sessions.Session {
+	return sd.refreshSession
+}
+
+// GetIDTokenSession returns the ID token session
+func (sd *SessionData) GetIDTokenSession() *sessions.Session {
+	return sd.idTokenSession
+}
+
+// GetTokenChunks returns the token chunk maps
+func (sd *SessionData) GetTokenChunks() (map[int]*sessions.Session, map[int]*sessions.Session, map[int]*sessions.Session) {
+	return sd.accessTokenChunks, sd.refreshTokenChunks, sd.idTokenChunks
+}
+
+// SetInUse marks the session as in use
+func (sd *SessionData) SetInUse(inUse bool) {
+	sd.inUse = inUse
+}
+
+// IsInUse returns whether the session is in use
+func (sd *SessionData) IsInUse() bool {
+	return sd.inUse
+}

session/validators/session_validator.go

@@ -0,0 +1,300 @@
+// Package validators provides validation functionality for session data
+package validators
+
+import (
+	"strings"
+	"time"
+)
+
+const (
+	maxBrowserCookieSize = 3500
+	maxCookieSize        = 1200
+)
+
+// SessionValidator provides validation operations for session data
+type SessionValidator struct{}
+
+// NewSessionValidator creates a new session validator
+func NewSessionValidator() *SessionValidator {
+	return &SessionValidator{}
+}
+
+// ValidateChunkSize checks if a chunk will fit within browser cookie limits.
+// It estimates the encoded size including cookie overhead and headers
+// to ensure the chunk won't exceed browser-imposed cookie size limits.
+func (sv *SessionValidator) ValidateChunkSize(chunkData string) bool {
+	estimatedEncodedSize := len(chunkData) + (len(chunkData)*50)/100
+	return estimatedEncodedSize <= maxBrowserCookieSize
+}
+
+// IsCorruptionMarker detects if data contains known corruption indicators.
+// It checks for specific corruption markers and invalid characters
+// that indicate the data has been tampered with or corrupted.
+func (sv *SessionValidator) IsCorruptionMarker(data string) bool {
+	if data == "" {
+		return false
+	}
+
+	corruptionMarkers := []string{
+		"__CORRUPTION_MARKER_TEST__",
+		"__INVALID_BASE64_DATA__",
+		"__CORRUPTED_CHUNK_DATA__",
+		"!@#$%^&*()",
+		"<<<CORRUPTED>>>",
+	}
+
+	for _, marker := range corruptionMarkers {
+		if data == marker {
+			return true
+		}
+	}
+
+	if len(data) > 10 {
+		invalidChars := "!@#$%^&*(){}[]|\\:;\"'<>?,`~"
+		for _, char := range invalidChars {
+			if strings.ContainsRune(data, char) {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+// ValidateTokenFormat validates that a token has the correct JWT format
+func (sv *SessionValidator) ValidateTokenFormat(token, tokenType string) error {
+	if token == "" {
+		return nil // Empty token is not an error
+	}
+
+	// JWT tokens should have exactly 3 parts separated by dots
+	parts := strings.Split(token, ".")
+	if len(parts) != 3 {
+		return &ValidationError{
+			Type:    tokenType,
+			Reason:  "invalid JWT format",
+			Details: "token must have exactly 3 parts separated by dots",
+		}
+	}
+
+	// Each part should be non-empty
+	for i, part := range parts {
+		if part == "" {
+			return &ValidationError{
+				Type:    tokenType,
+				Reason:  "empty token part",
+				Details: strings.Join([]string{"token part", string(rune(i + 1)), "is empty"}, " "),
+			}
+		}
+	}
+
+	return nil
+}
+
+// ValidateSessionIntegrity performs comprehensive validation of session data integrity
+func (sv *SessionValidator) ValidateSessionIntegrity(sessionData SessionData) error {
+	if sessionData == nil {
+		return &ValidationError{
+			Type:    "session",
+			Reason:  "nil session data",
+			Details: "session data cannot be nil",
+		}
+	}
+
+	// Check authentication state consistency
+	authenticated := sessionData.GetAuthenticated()
+	email := sessionData.GetEmail()
+
+	if authenticated && email == "" {
+		return &ValidationError{
+			Type:    "session",
+			Reason:  "authentication inconsistency",
+			Details: "session is authenticated but has no email",
+		}
+	}
+
+	// Validate token formats if present
+	if accessToken := sessionData.GetAccessToken(); accessToken != "" {
+		if err := sv.ValidateTokenFormat(accessToken, "access"); err != nil {
+			return err
+		}
+	}
+
+	if idToken := sessionData.GetIDToken(); idToken != "" {
+		if err := sv.ValidateTokenFormat(idToken, "id"); err != nil {
+			return err
+		}
+	}
+
+	if refreshToken := sessionData.GetRefreshToken(); refreshToken != "" {
+		// Refresh tokens don't have to be JWTs, so we do basic validation
+		if len(refreshToken) == 0 {
+			return &ValidationError{
+				Type:    "refresh",
+				Reason:  "empty refresh token",
+				Details: "refresh token cannot be empty if set",
+			}
+		}
+	}
+
+	return nil
+}
+
+// ValidateSessionTiming validates session timing and expiration
+func (sv *SessionValidator) ValidateSessionTiming(sessionData SessionData, maxAge time.Duration) error {
+	if sessionData == nil {
+		return &ValidationError{
+			Type:    "session",
+			Reason:  "nil session data",
+			Details: "session data cannot be nil",
+		}
+	}
+
+	// Check refresh token timing
+	refreshTokenIssuedAt := sessionData.GetRefreshTokenIssuedAt()
+	if !refreshTokenIssuedAt.IsZero() {
+		age := time.Since(refreshTokenIssuedAt)
+		if age > maxAge {
+			return &ValidationError{
+				Type:    "timing",
+				Reason:  "refresh token expired",
+				Details: strings.Join([]string{"refresh token age", age.String(), "exceeds max age", maxAge.String()}, " "),
+			}
+		}
+	}
+
+	return nil
+}
+
+// ValidateEmailDomain validates that an email belongs to an allowed domain
+func (sv *SessionValidator) ValidateEmailDomain(email string, allowedDomains map[string]struct{}) error {
+	if email == "" {
+		return &ValidationError{
+			Type:    "email",
+			Reason:  "empty email",
+			Details: "email cannot be empty",
+		}
+	}
+
+	if len(allowedDomains) == 0 {
+		return nil // No domain restrictions
+	}
+
+	parts := strings.Split(email, "@")
+	if len(parts) != 2 {
+		return &ValidationError{
+			Type:    "email",
+			Reason:  "invalid email format",
+			Details: "email must contain exactly one @ symbol",
+		}
+	}
+
+	domain := parts[1]
+	if _, allowed := allowedDomains[domain]; !allowed {
+		return &ValidationError{
+			Type:    "email",
+			Reason:  "domain not allowed",
+			Details: strings.Join([]string{"domain", domain, "is not in allowed domains list"}, " "),
+		}
+	}
+
+	return nil
+}
+
+// SplitIntoChunks splits a string into chunks that fit within cookie size limits
+func (sv *SessionValidator) SplitIntoChunks(s string, chunkSize int) []string {
+	effectiveChunkSize := min(chunkSize, maxCookieSize)
+
+	var chunks []string
+	for len(s) > 0 {
+		if len(s) > effectiveChunkSize {
+			chunks = append(chunks, s[:effectiveChunkSize])
+			s = s[effectiveChunkSize:]
+		} else {
+			chunks = append(chunks, s)
+			break
+		}
+	}
+	return chunks
+}
+
+// ValidateChunks validates all chunks in a chunk set
+func (sv *SessionValidator) ValidateChunks(chunks []string) error {
+	for i, chunk := range chunks {
+		if chunk == "" {
+			return &ValidationError{
+				Type:    "chunk",
+				Reason:  "empty chunk",
+				Details: strings.Join([]string{"chunk", string(rune(i)), "is empty"}, " "),
+			}
+		}
+
+		if !sv.ValidateChunkSize(chunk) {
+			return &ValidationError{
+				Type:    "chunk",
+				Reason:  "chunk too large",
+				Details: strings.Join([]string{"chunk", string(rune(i)), "exceeds size limit"}, " "),
+			}
+		}
+
+		if sv.IsCorruptionMarker(chunk) {
+			return &ValidationError{
+				Type:    "chunk",
+				Reason:  "corrupted chunk",
+				Details: strings.Join([]string{"chunk", string(rune(i)), "contains corruption markers"}, " "),
+			}
+		}
+	}
+
+	return nil
+}
+
+// ValidationError represents a validation error with context
+type ValidationError struct {
+	Type    string
+	Reason  string
+	Details string
+}
+
+// Error implements the error interface
+func (ve *ValidationError) Error() string {
+	return strings.Join([]string{ve.Type, "validation error:", ve.Reason, "-", ve.Details}, " ")
+}
+
+// SessionData interface for validation operations
+type SessionData interface {
+	GetAuthenticated() bool
+	GetEmail() string
+	GetAccessToken() string
+	GetIDToken() string
+	GetRefreshToken() string
+	GetRefreshTokenIssuedAt() time.Time
+}
+
+// Utility functions
+
+// min returns the minimum of two integers
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+// ValidateChunkSize is a package-level function for backward compatibility
+func ValidateChunkSize(chunkData string) bool {
+	sv := &SessionValidator{}
+	return sv.ValidateChunkSize(chunkData)
+}
+
+// IsCorruptionMarker is a package-level function for backward compatibility
+func IsCorruptionMarker(data string) bool {
+	sv := &SessionValidator{}
+	return sv.IsCorruptionMarker(data)
+}
+
+// SplitIntoChunks is a package-level function for backward compatibility
+func SplitIntoChunks(s string, chunkSize int) []string {
+	sv := &SessionValidator{}
+	return sv.SplitIntoChunks(s, chunkSize)
+}

types.go

@@ -0,0 +1,113 @@
+// Package traefikoidc provides OIDC authentication middleware for Traefik.
+package traefikoidc
+
+import (
+	"context"
+	"net/http"
+	"sync"
+	"text/template"
+	"time"
+
+	"golang.org/x/time/rate"
+)
+
+// CacheInterface defines the common cache operations
+type CacheInterface interface {
+	Set(key string, value interface{}, ttl time.Duration)
+	Get(key string) (interface{}, bool)
+	Delete(key string)
+	SetMaxSize(size int)
+	Cleanup()
+	Close()
+}
+
+// TokenVerifier interface defines token verification capabilities.
+// Implementations should validate token format, signature, and claims.
+type TokenVerifier interface {
+	VerifyToken(token string) error
+}
+
+// JWTVerifier interface defines JWT-specific verification capabilities.
+// Implementations should validate JWT structure, signature using JWKs, and standard claims.
+type JWTVerifier interface {
+	VerifyJWTSignatureAndClaims(jwt *JWT, token string) error
+}
+
+// TokenExchanger interface defines OAuth 2.0 and OpenID Connect token exchange capabilities.
+// Implementations should handle authorization code exchange, refresh tokens, and revocation
+// according to the OAuth 2.0 and OpenID Connect specifications.
+type TokenExchanger interface {
+	ExchangeCodeForToken(ctx context.Context, grantType string, codeOrToken string, redirectURL string, codeVerifier string) (*TokenResponse, error)
+	GetNewTokenWithRefreshToken(refreshToken string) (*TokenResponse, error)
+	RevokeTokenWithProvider(token, tokenType string) error
+}
+
+// ProviderMetadata represents OIDC provider configuration data.
+// This data is typically retrieved from the provider's .well-known/openid-configuration endpoint
+// and contains essential URLs for authentication, token exchange, and key retrieval.
+type ProviderMetadata struct {
+	Issuer        string `json:"issuer"`
+	AuthURL       string `json:"authorization_endpoint"`
+	TokenURL      string `json:"token_endpoint"`
+	JWKSURL       string `json:"jwks_uri"`
+	RevokeURL     string `json:"revocation_endpoint"`
+	EndSessionURL string `json:"end_session_endpoint"`
+}
+
+// TraefikOidc is the main middleware struct that implements OIDC authentication for Traefik.
+// It integrates with various OIDC providers, manages sessions, caches tokens, and handles
+// the complete authentication flow. It's designed to work seamlessly with Traefik's
+// plugin system and provides flexible configuration options.
+type TraefikOidc struct {
+	jwkCache                   JWKCacheInterface
+	jwtVerifier                JWTVerifier
+	ctx                        context.Context
+	tokenVerifier              TokenVerifier
+	next                       http.Handler
+	tokenExchanger             TokenExchanger
+	initComplete               chan struct{}
+	limiter                    *rate.Limiter
+	tokenBlacklist             CacheInterface
+	headerTemplates            map[string]*template.Template
+	sessionManager             *SessionManager
+	tokenCleanupStopChan       chan struct{}
+	excludedURLs               map[string]struct{}
+	extractClaimsFunc          func(tokenString string) (map[string]interface{}, error)
+	initiateAuthenticationFunc func(rw http.ResponseWriter, req *http.Request, session *SessionData, redirectURL string)
+	metadataCache              *MetadataCache
+	allowedRolesAndGroups      map[string]struct{}
+	allowedUsers               map[string]struct{}
+	allowedUserDomains         map[string]struct{}
+	tokenCache                 *TokenCache
+	httpClient                 *http.Client
+	tokenHTTPClient            *http.Client
+	logger                     *Logger
+	metadataRefreshStopChan    chan struct{}
+	cancelFunc                 context.CancelFunc
+	errorRecoveryManager       *ErrorRecoveryManager
+	goroutineWG                *sync.WaitGroup
+	clientSecret               string
+	clientID                   string
+	name                       string
+	redirURLPath               string
+	logoutURLPath              string
+	tokenURL                   string
+	authURL                    string
+	endSessionURL              string
+	postLogoutRedirectURI      string
+	scheme                     string
+	jwksURL                    string
+	issuerURL                  string
+	revocationURL              string
+	providerURL                string
+	scopes                     []string
+	refreshGracePeriod         time.Duration
+	shutdownOnce               sync.Once
+	firstRequestMutex          sync.Mutex
+	forceHTTPS                 bool
+	enablePKCE                 bool
+	overrideScopes             bool
+	suppressDiagnosticLogs     bool
+	firstRequestReceived       bool
+	metadataRefreshStarted     bool
+}