Add LRU cache support.

errors.go

@@ -106,117 +106,8 @@ func (e *ProxyError) WithMetadata(key string, value interface{}) *ProxyError {
 	return e
 }
 
-// Common error constructors
-
-// NewConnectionError creates a connection-related error
-func NewConnectionError(err error) *ProxyError {
-	code := ErrCodeConnectionRefused
-	if err != nil {
-		errStr := err.Error()
-		if contains(errStr, "reset") {
-			code = ErrCodeConnectionReset
-		}
-	}
-
-	return NewProxyError(code, "Failed to connect to backend", 502, true).
-		WithCause(err)
-}
-
-// NewTimeoutError creates a timeout error
-func NewTimeoutError(err error) *ProxyError {
-	return NewProxyError(ErrCodeTimeout, "Request timed out", 504, false).
-		WithCause(err)
-}
-
-// NewCircuitOpenError creates a circuit breaker open error
-func NewCircuitOpenError() *ProxyError {
-	return NewProxyError(ErrCodeCircuitOpen, "Service temporarily unavailable due to circuit breaker", 503, false).
-		WithDetails("The backend service is currently experiencing issues. Please try again later.")
-}
-
-// NewRateLimitError creates a rate limit error
-func NewRateLimitError(userID, role string) *ProxyError {
-	return NewProxyError(ErrCodeRateLimited, "Rate limit exceeded", 429, false).
-		WithDetails("You have exceeded the rate limit for your role").
-		WithMetadata("user_id", userID).
-		WithMetadata("role", role)
-}
-
-// NewBackendError creates a backend error from status code
-func NewBackendError(statusCode int, body string) *ProxyError {
-	code := ErrCodeBackendError
-	message := "Backend returned an error"
-	retryable := false
-
-	switch {
-	case statusCode == 429:
-		code = ErrCodeRateLimited
-		message = "Backend rate limit exceeded"
-		retryable = true
-	case statusCode == 503:
-		code = ErrCodeServiceUnavailable
-		message = "Backend service unavailable"
-		retryable = true
-	case statusCode == 502 || statusCode == 504:
-		code = ErrCodeBadGateway
-		message = "Bad gateway"
-		retryable = true
-	case statusCode >= 500:
-		code = ErrCodeBackendError
-		message = "Backend server error"
-		retryable = true
-	case statusCode == 404:
-		code = ErrCodeNotFound
-		message = "Resource not found"
-	case statusCode == 403:
-		code = ErrCodeForbidden
-		message = "Access forbidden"
-	case statusCode == 401:
-		code = ErrCodeUnauthorized
-		message = "Unauthorized"
-	case statusCode >= 400:
-		code = ErrCodeInvalidRequest
-		message = "Invalid request"
-	}
-
-	return NewProxyError(code, message, statusCode, retryable).
-		WithMetadata("backend_status", statusCode).
-		WithMetadata("backend_body", truncateString(body, 500))
-}
-
-// NewInvalidResponseError creates an invalid response error
-func NewInvalidResponseError(details string) *ProxyError {
-	return NewProxyError(ErrCodeInvalidResponse, "Backend returned invalid response", 502, false).
-		WithDetails(details)
-}
-
-// NewInternalError creates an internal error
-func NewInternalError(err error) *ProxyError {
-	return NewProxyError(ErrCodeInternalError, "Internal proxy error", 500, false).
-		WithCause(err)
-}
-
-// NewContextCanceledError creates a context canceled error
-func NewContextCanceledError() *ProxyError {
-	return NewProxyError(ErrCodeContextCanceled, "Request canceled", 499, false).
-		WithDetails("The request was canceled by the client")
-}
-
 // Helper functions
 
-func contains(s, substr string) bool {
-	return len(s) > 0 && len(substr) > 0 && len(s) >= len(substr) && (s == substr || len(s) > len(substr) && (s[:len(substr)] == substr || s[len(s)-len(substr):] == substr || containsMiddle(s, substr)))
-}
-
-func containsMiddle(s, substr string) bool {
-	for i := 0; i <= len(s)-len(substr); i++ {
-		if s[i:i+len(substr)] == substr {
-			return true
-		}
-	}
-	return false
-}
-
 func truncateString(s string, maxLen int) string {
 	if len(s) <= maxLen {
 		return s