package main

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"strings"
	"sync"
	"time"

	"github.com/labstack/echo/v4"
	"github.com/labstack/echo/v4/middleware"
	"golang.org/x/time/rate"
)

var jwtSecret []byte

func init() {
	secret := os.Getenv("JWT_SECRET")
	if secret == "" {
		panic("JWT_SECRET environment variable is required")
	}
	jwtSecret = []byte(secret)
}

func createToken(userID int, username string, isAdmin bool) (string, error) {
	claims := Claims{
		UserID:   userID,
		Username: username,
		IsAdmin:  isAdmin,
	}

	header := base64.RawURLEncoding.EncodeToString([]byte(`{"alg":"HS256","typ":"JWT"}`))

	claimsWithExp := map[string]any{
		"user_id":  claims.UserID,
		"username": claims.Username,
		"is_admin": claims.IsAdmin,
		"exp":      time.Now().Add(2 * time.Hour).Unix(),
	}

	payload, _ := json.Marshal(claimsWithExp)
	payloadEncoded := base64.RawURLEncoding.EncodeToString(payload)

	message := header + "." + payloadEncoded

	h := hmac.New(sha256.New, jwtSecret)
	h.Write([]byte(message))
	signature := base64.RawURLEncoding.EncodeToString(h.Sum(nil))

	return message + "." + signature, nil
}

func verifyToken(tokenString string) (*Claims, error) {
	parts := strings.Split(tokenString, ".")
	if len(parts) != 3 {
		return nil, fmt.Errorf("invalid token format")
	}

	message := parts[0] + "." + parts[1]
	h := hmac.New(sha256.New, jwtSecret)
	h.Write([]byte(message))
	expectedSignature := base64.RawURLEncoding.EncodeToString(h.Sum(nil))

	if parts[2] != expectedSignature {
		return nil, fmt.Errorf("invalid signature")
	}

	payload, err := base64.RawURLEncoding.DecodeString(parts[1])
	if err != nil {
		return nil, err
	}

	var claimsMap map[string]any
	if err := json.Unmarshal(payload, &claimsMap); err != nil {
		return nil, err
	}

	if exp, ok := claimsMap["exp"].(float64); ok {
		if time.Now().Unix() > int64(exp) {
			return nil, fmt.Errorf("token expired")
		}
	}

	claims := &Claims{
		UserID:   int(claimsMap["user_id"].(float64)),
		Username: claimsMap["username"].(string),
		IsAdmin:  claimsMap["is_admin"].(bool),
	}

	return claims, nil
}

func JWTMiddleware() echo.MiddlewareFunc {
	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			authHeader := c.Request().Header.Get("Authorization")
			if authHeader == "" {
				return echo.NewHTTPError(http.StatusUnauthorized, "Unauthorized")
			}

			tokenString := strings.TrimPrefix(authHeader, "Bearer ")
			claims, err := verifyToken(tokenString)
			if err != nil {
				return echo.NewHTTPError(http.StatusUnauthorized, "Unauthorized")
			}

			c.Set("user_id", claims.UserID)
			c.Set("username", claims.Username)
			c.Set("is_admin", claims.IsAdmin)

			c.Logger().Infof("Authenticated user: ID=%d, Username=%s", claims.UserID, claims.Username)

			return next(c)
		}
	}
}

func AdminMiddleware() echo.MiddlewareFunc {
	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			isAdmin, ok := c.Get("is_admin").(bool)
			if !ok || !isAdmin {
				return echo.NewHTTPError(http.StatusForbidden, "Access denied")
			}
			return next(c)
		}
	}
}

func CustomLogger() echo.MiddlewareFunc {
	return middleware.LoggerWithConfig(middleware.LoggerConfig{
		Format: "${time_rfc3339} | ${status} | ${latency_human} | ${method} ${uri}\n",
	})
}

type LoginRateLimiter struct {
	limiters map[string]*rate.Limiter
	mu       sync.Mutex
}

func NewLoginRateLimiter() *LoginRateLimiter {
	limiter := &LoginRateLimiter{
		limiters: make(map[string]*rate.Limiter),
	}

	go func() {
		ticker := time.NewTicker(10 * time.Minute)
		defer ticker.Stop()
		for range ticker.C {
			limiter.mu.Lock()
			limiter.limiters = make(map[string]*rate.Limiter)
			limiter.mu.Unlock()
		}
	}()

	return limiter
}

func (l *LoginRateLimiter) GetLimiter(ip string) *rate.Limiter {
	l.mu.Lock()
	defer l.mu.Unlock()

	limiter, exists := l.limiters[ip]
	if !exists {
		limiter = rate.NewLimiter(rate.Every(time.Minute/5), 5)
		l.limiters[ip] = limiter
	}

	return limiter
}

func (l *LoginRateLimiter) Middleware() echo.MiddlewareFunc {
	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			ip := c.RealIP()
			limiter := l.GetLimiter(ip)

			if !limiter.Allow() {
				return echo.NewHTTPError(http.StatusTooManyRequests, "Too many login attempts. Please try again later.")
			}

			return next(c)
		}
	}
}

func HTTPSRedirectMiddleware() echo.MiddlewareFunc {
	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			if os.Getenv("ENVIRONMENT") == "production" {
				if c.Request().Header.Get("X-Forwarded-Proto") != "https" {
					return c.Redirect(http.StatusMovedPermanently,
						"https://"+c.Request().Host+c.Request().RequestURI)
				}
			}
			return next(c)
		}
	}
}