package middleware

import (
	"context"
	"net/http"
	"os"
	"strings"

	"github.com/golang-jwt/jwt/v5"
)

type contextKey string

const UserIDKey contextKey = "userID"

func JWTAuth(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		authHeader := r.Header.Get("Authorization")
		if authHeader == "" {
			http.Error(w, `{"code":401, "message":"Unauthorized: missing token"}`, http.StatusUnauthorized)
			return
		}

		parts := strings.Split(authHeader, " ")
		if len(parts) != 2 || parts[0] != "Bearer" {
			http.Error(w, `{"code":401, "message":"Unauthorized: invalid token format"}`, http.StatusUnauthorized)
			return
		}

		tokenString := parts[1]
		secret := os.Getenv("JWT_SECRET")

		token, err := jwt.Parse(tokenString, func(t *jwt.Token) (interface{}, error) {
			if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
				return nil, jwt.ErrSignatureInvalid
			}
			return []byte(secret), nil
		})

		if err != nil || !token.Valid {
			http.Error(w, `{"code":401, "message":"Unauthorized: invalid or expired token"}`, http.StatusUnauthorized)
			return
		}

		claims, ok := token.Claims.(jwt.MapClaims)
		if !ok {
			http.Error(w, `{"code":401, "message":"Unauthorized: invalid token claims"}`, http.StatusUnauthorized)
			return
		}

		userID, ok := claims["sub"].(string)
		if !ok || userID == "" {
			// fallback check inside user_id or id if sub doesn't exist
			userID, _ = claims["user_id"].(string)
		}

		if userID == "" {
			http.Error(w, `{"code":401, "message":"Unauthorized: user ID not found in token"}`, http.StatusUnauthorized)
			return
		}

		ctx := context.WithValue(r.Context(), UserIDKey, userID)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}