package middleware

import (
	"net/http"
	"strings"
	"sync"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v5"
	"github.com/google/uuid"
)

// UserClaims represents the JWT claims for a user
type UserClaims struct {
	UserID string `json:"user_id"`
	Email  string `json:"email"`
	Role   string `json:"role"`
	jwt.RegisteredClaims
}

// CORS returns a CORS middleware
func CORS() gin.HandlerFunc {
	return func(c *gin.Context) {
		origin := c.Request.Header.Get("Origin")

		// Allow localhost for development
		allowedOrigins := []string{
			"http://localhost:3000",
			"http://localhost:8000",
			"http://localhost:8080",
			"http://localhost:8083",
			"https://breakpilot.app",
		}

		allowed := false
		for _, o := range allowedOrigins {
			if origin == o {
				allowed = true
				break
			}
		}

		if allowed {
			c.Header("Access-Control-Allow-Origin", origin)
		}

		c.Header("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
		c.Header("Access-Control-Allow-Headers", "Origin, Content-Type, Authorization, X-Requested-With, X-Internal-API-Key")
		c.Header("Access-Control-Allow-Credentials", "true")
		c.Header("Access-Control-Max-Age", "86400")

		if c.Request.Method == "OPTIONS" {
			c.AbortWithStatus(http.StatusNoContent)
			return
		}

		c.Next()
	}
}

// RequestLogger logs each request
func RequestLogger() gin.HandlerFunc {
	return func(c *gin.Context) {
		start := time.Now()
		path := c.Request.URL.Path
		method := c.Request.Method

		c.Next()

		latency := time.Since(start)
		status := c.Writer.Status()

		// Log only in development or for errors
		if status >= 400 {
			gin.DefaultWriter.Write([]byte(
				method + " " + path + " " +
					string(rune(status)) + " " +
					latency.String() + "\n",
			))
		}
	}
}

// RateLimiter implements a simple in-memory rate limiter
func RateLimiter() gin.HandlerFunc {
	type client struct {
		count    int
		lastSeen time.Time
	}

	var (
		mu      sync.Mutex
		clients = make(map[string]*client)
	)

	// Clean up old entries periodically
	go func() {
		for {
			time.Sleep(time.Minute)
			mu.Lock()
			for ip, c := range clients {
				if time.Since(c.lastSeen) > time.Minute {
					delete(clients, ip)
				}
			}
			mu.Unlock()
		}
	}()

	return func(c *gin.Context) {
		ip := c.ClientIP()

		mu.Lock()
		defer mu.Unlock()

		if _, exists := clients[ip]; !exists {
			clients[ip] = &client{}
		}

		cli := clients[ip]

		// Reset count if more than a minute has passed
		if time.Since(cli.lastSeen) > time.Minute {
			cli.count = 0
		}

		cli.count++
		cli.lastSeen = time.Now()

		// Allow 100 requests per minute
		if cli.count > 100 {
			c.AbortWithStatusJSON(http.StatusTooManyRequests, gin.H{
				"error":   "rate_limit_exceeded",
				"message": "Too many requests. Please try again later.",
			})
			return
		}

		c.Next()
	}
}

// AuthMiddleware validates JWT tokens
func AuthMiddleware(jwtSecret string) gin.HandlerFunc {
	return func(c *gin.Context) {
		authHeader := c.GetHeader("Authorization")
		if authHeader == "" {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
				"error":   "missing_authorization",
				"message": "Authorization header is required",
			})
			return
		}

		// Extract token from "Bearer <token>"
		parts := strings.Split(authHeader, " ")
		if len(parts) != 2 || parts[0] != "Bearer" {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
				"error":   "invalid_authorization",
				"message": "Authorization header must be in format: Bearer <token>",
			})
			return
		}

		tokenString := parts[1]

		// Parse and validate token
		token, err := jwt.ParseWithClaims(tokenString, &UserClaims{}, func(token *jwt.Token) (interface{}, error) {
			return []byte(jwtSecret), nil
		})

		if err != nil {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
				"error":   "invalid_token",
				"message": "Invalid or expired token",
			})
			return
		}

		if claims, ok := token.Claims.(*UserClaims); ok && token.Valid {
			// Set user info in context
			c.Set("user_id", claims.UserID)
			c.Set("email", claims.Email)
			c.Set("role", claims.Role)
			c.Next()
		} else {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
				"error":   "invalid_claims",
				"message": "Invalid token claims",
			})
			return
		}
	}
}

// InternalAPIKeyMiddleware validates internal API key for service-to-service communication
func InternalAPIKeyMiddleware(apiKey string) gin.HandlerFunc {
	return func(c *gin.Context) {
		if apiKey == "" {
			c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{
				"error":   "config_error",
				"message": "Internal API key not configured",
			})
			return
		}

		providedKey := c.GetHeader("X-Internal-API-Key")
		if providedKey == "" {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
				"error":   "missing_api_key",
				"message": "X-Internal-API-Key header is required",
			})
			return
		}

		if providedKey != apiKey {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
				"error":   "invalid_api_key",
				"message": "Invalid API key",
			})
			return
		}

		c.Next()
	}
}

// AdminOnly ensures only admin users can access the route
func AdminOnly() gin.HandlerFunc {
	return func(c *gin.Context) {
		role, exists := c.Get("role")
		if !exists {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
				"error":   "unauthorized",
				"message": "User role not found",
			})
			return
		}

		roleStr, ok := role.(string)
		if !ok || (roleStr != "admin" && roleStr != "super_admin" && roleStr != "data_protection_officer") {
			c.AbortWithStatusJSON(http.StatusForbidden, gin.H{
				"error":   "forbidden",
				"message": "Admin access required",
			})
			return
		}

		c.Next()
	}
}

// GetUserID extracts the user ID from the context
func GetUserID(c *gin.Context) (uuid.UUID, error) {
	userIDStr, exists := c.Get("user_id")
	if !exists {
		return uuid.Nil, nil
	}

	userID, err := uuid.Parse(userIDStr.(string))
	if err != nil {
		return uuid.Nil, err
	}

	return userID, nil
}

// GetClientIP returns the client's IP address
func GetClientIP(c *gin.Context) string {
	// Check X-Forwarded-For header first (for proxied requests)
	if xff := c.GetHeader("X-Forwarded-For"); xff != "" {
		ips := strings.Split(xff, ",")
		return strings.TrimSpace(ips[0])
	}

	// Check X-Real-IP header
	if xri := c.GetHeader("X-Real-IP"); xri != "" {
		return xri
	}

	return c.ClientIP()
}

// GetUserAgent returns the client's User-Agent
func GetUserAgent(c *gin.Context) string {
	return c.GetHeader("User-Agent")
}