package main

import (
	"fmt"
	"strconv"
	"time"

	"github.com/goccy/go-json"
	fiber "github.com/gofiber/fiber/v2"
	"github.com/gofiber/fiber/v2/middleware/cors"
	"github.com/google/uuid"

	graphql "github.com/lukaszraczylo/go-simple-graphql"
	libpack_cache "github.com/lukaszraczylo/graphql-monitoring-proxy/cache"
	libpack_config "github.com/lukaszraczylo/graphql-monitoring-proxy/config"
	libpack_logger "github.com/lukaszraczylo/graphql-monitoring-proxy/logging"
	libpack_monitoring "github.com/lukaszraczylo/graphql-monitoring-proxy/monitoring"
)

const (
	healthCheckQueryStr = `{ __typename }`
)

// HealthCheckResponse represents the response structure for health check endpoints
type HealthCheckResponse struct {
	Status       string                      `json:"status"`       // overall status: "healthy" or "unhealthy"
	Dependencies map[string]DependencyStatus `json:"dependencies"` // status of each dependency
	Timestamp    string                      `json:"timestamp"`    // when the health check was performed
}

// DependencyStatus represents the status of a dependency
type DependencyStatus struct {
	Error        *string `json:"error,omitempty"`
	Status       string  `json:"status"`
	ResponseTime int64   `json:"responseTime"`
}

// StartHTTPProxy initializes and starts the HTTP proxy server.
func StartHTTPProxy() error {
	cfg.Logger.Debug(&libpack_logger.LogMessage{
		Message: "Starting the HTTP proxy",
	})

	serverConfig := fiber.Config{
		DisableStartupMessage: true,
		AppName:               fmt.Sprintf("GraphQL Monitoring Proxy - %s v%s", libpack_config.PKG_NAME, libpack_config.PKG_VERSION),
		IdleTimeout:           time.Duration(cfg.Client.ClientTimeout) * time.Second,
		ReadTimeout:           time.Duration(cfg.Client.ClientTimeout) * time.Second,
		WriteTimeout:          time.Duration(cfg.Client.ClientTimeout) * time.Second,
		JSONEncoder:           json.Marshal,
		JSONDecoder:           json.Unmarshal,
	}

	server := fiber.New(serverConfig)

	server.Use(cors.New(cors.Config{
		AllowOrigins: "*",
	}))

	server.Use(AddRequestUUID)

	server.Get("/healthz", healthCheck)
	server.Get("/livez", healthCheck)
	server.Get("/health", healthCheck)

	// Register admin dashboard routes if enabled
	if cfg.AdminDashboard.Enable {
		adminDash := NewAdminDashboard(cfg.Logger)
		adminDash.RegisterRoutes(server)
	}

	// WebSocket support - must be registered before catch-all routes
	if cfg.WebSocket.Enable {
		server.Get("/v1/graphql", func(c *fiber.Ctx) error {
			if IsWebSocketRequest(c) {
				wsp := GetWebSocketProxy()
				if wsp != nil {
					return wsp.HandleWebSocket(c)
				}
			}
			return proxyTheRequestToDefault(c)
		})
	}

	server.Post("/*", processGraphQLRequest)
	server.Get("/*", proxyTheRequestToDefault)

	cfg.Logger.Info(&libpack_logger.LogMessage{
		Message: "GraphQL proxy starting",
		Pairs:   map[string]interface{}{"port": cfg.Server.PortGraphQL},
	})

	if err := server.Listen(fmt.Sprintf(":%d", cfg.Server.PortGraphQL)); err != nil {
		return fmt.Errorf("failed to start HTTP proxy server on port %d: %w",
			cfg.Server.PortGraphQL, err)
	}

	return nil
}

// proxyTheRequestToDefault proxies the request to the default GraphQL endpoint.
func proxyTheRequestToDefault(c *fiber.Ctx) error {
	return proxyTheRequest(c, cfg.Server.HostGraphQL)
}

// AddRequestUUID adds a unique request UUID to the context.
func AddRequestUUID(c *fiber.Ctx) error {
	c.Locals("request_uuid", uuid.NewString())
	return c.Next()
}

// checkAllowedURLs checks if the requested URL is allowed.
func checkAllowedURLs(c *fiber.Ctx) bool {
	if len(allowedUrls) == 0 {
		return true
	}
	path := c.OriginalURL()
	_, ok := allowedUrls[path]
	return ok
}

// healthCheck performs a comprehensive health check on the GraphQL server and its dependencies.
func healthCheck(c *fiber.Ctx) error {
	// Prepare the response structure
	response := HealthCheckResponse{
		Status:       "healthy",
		Dependencies: make(map[string]DependencyStatus),
		Timestamp:    time.Now().UTC().Format(time.RFC3339),
	}

	// Configure checks from query parameters
	checkGraphQL := true
	checkRedis := cfg.Cache.CacheRedisEnable

	// Parse query parameters to enable/disable specific checks
	if c.Query("check_graphql") == "false" {
		checkGraphQL = false
	}
	if c.Query("check_redis") == "false" {
		checkRedis = false
	}

	// Check GraphQL backend service
	if checkGraphQL {
		startTime := time.Now()
		graphqlStatus := DependencyStatus{
			Status: "up",
		}

		// Try to connect to main GraphQL endpoint
		endpoint := cfg.Server.HostGraphQL
		if len(cfg.Server.HealthcheckGraphQL) > 0 {
			endpoint = cfg.Server.HealthcheckGraphQL
		}

		// Create a new GraphQL client for the health check
		tempClient := graphql.NewConnection()
		tempClient.SetEndpoint(endpoint)
		_, err := tempClient.Query(healthCheckQueryStr, nil, nil)

		graphqlStatus.ResponseTime = time.Since(startTime).Milliseconds()

		if err != nil {
			errorMsg := err.Error()
			graphqlStatus.Status = "down"
			graphqlStatus.Error = &errorMsg
			response.Status = "unhealthy"

			cfg.Logger.Error(&libpack_logger.LogMessage{
				Message: "Health check: Can't reach the GraphQL server",
				Pairs: map[string]interface{}{
					"endpoint":         endpoint,
					"error":            errorMsg,
					"response_time_ms": graphqlStatus.ResponseTime,
				},
			})
			cfg.Monitoring.Increment(libpack_monitoring.MetricsFailed, nil)
		}

		response.Dependencies["graphql"] = graphqlStatus
	}

	// Check Redis connectivity if enabled
	if checkRedis && cfg.Cache.CacheRedisEnable {
		startTime := time.Now()
		redisStatus := DependencyStatus{
			Status: "up",
		}

		// Implement proper Redis connectivity test
		redisAccessible := false
		var redisError error

		if libpack_cache.IsCacheInitialized() {
			// Try a simple Redis operation to test connectivity
			testKey := "health_check_test"
			testValue := []byte("test")

			// Try to set and get a test value
			libpack_cache.CacheStore(testKey, testValue)
			retrievedValue := libpack_cache.CacheLookup(testKey)

			if retrievedValue != nil && string(retrievedValue) == "test" {
				redisAccessible = true
				// Clean up test key
				libpack_cache.CacheDelete(testKey)
			} else {
				redisError = fmt.Errorf("redis test operation failed")
			}
		} else {
			redisError = fmt.Errorf("cache not initialized")
		}

		redisStatus.ResponseTime = time.Since(startTime).Milliseconds()

		if !redisAccessible {
			errorMsg := "Failed to connect to Redis"
			if redisError != nil {
				errorMsg = redisError.Error()
			}
			redisStatus.Status = "down"
			redisStatus.Error = &errorMsg
			response.Status = "unhealthy"

			cfg.Logger.Error(&libpack_logger.LogMessage{
				Message: "Health check: Can't connect to Redis",
				Pairs: map[string]interface{}{
					"server":           cfg.Cache.CacheRedisURL,
					"error":            errorMsg,
					"response_time_ms": redisStatus.ResponseTime,
				},
			})
		}

		response.Dependencies["redis"] = redisStatus
	}

	// Determine appropriate HTTP status code
	httpStatus := fiber.StatusOK
	if response.Status == "unhealthy" {
		httpStatus = fiber.StatusServiceUnavailable
	}

	cfg.Logger.Debug(&libpack_logger.LogMessage{
		Message: "Health check completed",
		Pairs: map[string]interface{}{
			"status":       response.Status,
			"dependencies": response.Dependencies,
		},
	})

	// Return JSON response
	return c.Status(httpStatus).JSON(response)
}

// processGraphQLRequest handles the incoming GraphQL requests.
func processGraphQLRequest(c *fiber.Ctx) error {
	startTime := time.Now()

	// Extract user information and check permissions
	extractedUserID, extractedRoleName := extractUserInfo(c)

	// Check if user is banned
	if checkIfUserIsBanned(c, extractedUserID) {
		return c.Status(fiber.StatusForbidden).SendString("User is banned")
	}

	// Apply rate limiting if enabled
	if cfg.Client.RoleRateLimit && !rateLimitedRequest(extractedUserID, extractedRoleName) {
		return c.Status(fiber.StatusTooManyRequests).SendString("Rate limit exceeded, try again later")
	}

	// Parse the GraphQL query
	parsedResult := parseGraphQLQuery(c)
	if parsedResult.shouldBlock {
		return c.Status(fiber.StatusForbidden).SendString("Request blocked")
	}

	// Handle non-GraphQL requests
	if parsedResult.shouldIgnore {
		return proxyTheRequest(c, parsedResult.activeEndpoint)
	}

	// Handle caching
	wasCached, err := handleCaching(c, parsedResult, extractedUserID)
	if err != nil {
		return err
	}

	// Log and monitor the request
	logAndMonitorRequest(c, extractedUserID, parsedResult.operationType, parsedResult.operationName, wasCached, time.Since(startTime), startTime)

	return nil
}

// extractUserInfo extracts user ID and role from request headers
func extractUserInfo(c *fiber.Ctx) (string, string) {
	extractedUserID := "-"
	extractedRoleName := "-"

	// Extract from JWT if available
	if authorization := c.Get("Authorization"); authorization != "" &&
		(len(cfg.Client.JWTUserClaimPath) > 0 || len(cfg.Client.JWTRoleClaimPath) > 0) {
		extractedUserID, extractedRoleName = extractClaimsFromJWTHeader(authorization)
	}

	// Override role from header if configured
	if cfg.Client.RoleFromHeader != "" {
		if role := c.Get(cfg.Client.RoleFromHeader); role != "" {
			extractedRoleName = role
		}
	}

	return extractedUserID, extractedRoleName
}

// handleCaching manages the caching logic for GraphQL requests
func handleCaching(c *fiber.Ctx, parsedResult *parseGraphQLQueryResult, userID string) (bool, error) {
	// Calculate query hash for cache key
	calculatedQueryHash := libpack_cache.CalculateHash(c)

	// Set cache time from header or default
	if parsedResult.cacheTime == 0 {
		if cacheQuery := c.Get("X-Cache-Graphql-Query"); cacheQuery != "" {
			parsedResult.cacheTime, _ = strconv.Atoi(cacheQuery)
		} else {
			parsedResult.cacheTime = cfg.Cache.CacheTTL
		}
	}

	// Handle cache refresh directive
	if parsedResult.cacheRefresh {
		libpack_cache.CacheDelete(calculatedQueryHash)
	}

	// Check if caching is enabled
	cacheEnabled := parsedResult.cacheRequest || cfg.Cache.CacheEnable || cfg.Cache.CacheRedisEnable
	if !cacheEnabled {
		// No caching, just proxy the request
		if err := proxyTheRequest(c, parsedResult.activeEndpoint); err != nil {
			cfg.Monitoring.Increment(libpack_monitoring.MetricsFailed, nil)
			return false, c.Status(fiber.StatusInternalServerError).SendString("Can't proxy the request - try again later")
		}
		return false, nil
	}

	// Try to get from cache
	if cachedResponse := libpack_cache.CacheLookup(calculatedQueryHash); cachedResponse != nil {
		cfg.Monitoring.Increment(libpack_monitoring.MetricsCacheHit, nil)
		c.Set("X-Cache-Hit", "true")
		c.Set("Content-Type", "application/json")
		return true, c.Send(cachedResponse)
	}

	// Cache miss, proxy and cache
	cfg.Monitoring.Increment(libpack_monitoring.MetricsCacheMiss, nil)
	if err := proxyAndCacheTheRequest(c, calculatedQueryHash, parsedResult.cacheTime, parsedResult.activeEndpoint); err != nil {
		return false, err
	}

	return false, nil
}

// proxyAndCacheTheRequest proxies and caches the request if needed.
func proxyAndCacheTheRequest(c *fiber.Ctx, queryCacheHash string, cacheTime int, currentEndpoint string) error {
	if err := proxyTheRequest(c, currentEndpoint); err != nil {
		cfg.Logger.Error(&libpack_logger.LogMessage{
			Message: "Can't proxy the request",
			Pairs:   map[string]interface{}{"error": err.Error()},
		})
		cfg.Monitoring.Increment(libpack_monitoring.MetricsFailed, nil)
		return c.Status(fiber.StatusInternalServerError).SendString("Can't proxy the request - try again later")
	}

	libpack_cache.CacheStoreWithTTL(queryCacheHash, c.Response().Body(), time.Duration(cacheTime)*time.Second)
	cfg.Monitoring.Increment(libpack_monitoring.MetricsQueriesCached, nil)
	return c.Send(c.Response().Body())
}

// logAndMonitorRequest logs and monitors the request processing.
func logAndMonitorRequest(c *fiber.Ctx, userID, opType, opName string, wasCached bool, duration time.Duration, startTime time.Time) {
	labels := map[string]string{
		"op_type": opType,
		"op_name": opName,
		"cached":  strconv.FormatBool(wasCached),
		"user_id": userID,
	}

	if cfg.Server.AccessLog {
		cfg.Logger.Info(&libpack_logger.LogMessage{
			Message: "Request processed",
			Pairs: map[string]interface{}{
				"ip":           c.IP(),
				"fwd-ip":       c.Get("X-Forwarded-For"),
				"user_id":      userID,
				"op_type":      opType,
				"op_name":      opName,
				"time":         duration,
				"cache":        wasCached,
				"request_uuid": c.Locals("request_uuid"),
			},
		})
	}

	cfg.Monitoring.Increment(libpack_monitoring.MetricsSucceeded, nil)
	cfg.Monitoring.Increment(libpack_monitoring.MetricsExecutedQuery, labels)

	if !wasCached {
		cfg.Monitoring.UpdateDuration(libpack_monitoring.MetricsTimedQuery, labels, startTime)
		cfg.Monitoring.Update(libpack_monitoring.MetricsTimedQuery, labels, float64(duration.Milliseconds()))
	}
}