/*
 * Copyright 2024 Jonas Kaninda
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package middlewares

import (
	"fmt"
	"github.com/golang-jwt/jwt"
	"net/http"
	"time"
)

func (oauth Oauth) AuthMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		oauthConf := oauth2Config(oauth)
		// Check if the user is authenticated
		token, err := r.Cookie("goma.oauth")
		if err != nil {
			// If no token, redirect to OAuth provider
			url := oauthConf.AuthCodeURL(oauth.State)
			http.Redirect(w, r, url, http.StatusTemporaryRedirect)
			return
		}
		ok, err := validateJWT(token.Value, oauth)
		if err != nil {
			// If no token, redirect to OAuth provider
			url := oauthConf.AuthCodeURL(oauth.State)
			http.Redirect(w, r, url, http.StatusTemporaryRedirect)
			return
		}
		if !ok {
			// If no token, redirect to OAuth provider
			url := oauthConf.AuthCodeURL(oauth.State)
			http.Redirect(w, r, url, http.StatusTemporaryRedirect)
			return
		}
		// Token exists, proceed with request
		next.ServeHTTP(w, r)
	})
}

func validateJWT(signedToken string, oauth Oauth) (bool, error) {
	// Parse the JWT token and provide the key function
	token, err := jwt.Parse(signedToken, func(token *jwt.Token) (interface{}, error) {
		// Ensure the signing method is HMAC and specifically HS256
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
		}
		// Return the shared secret key for validation
		return []byte(oauth.JWTSecret), nil
	})

	// If there's an error or token is invalid, return false
	if err != nil || !token.Valid {
		return false, fmt.Errorf("token is invalid: %v", err)
	}

	// Check if token claims are valid
	if claims, ok := token.Claims.(jwt.MapClaims); ok && token.Valid {
		// Optional: Check token expiration
		if exp, ok := claims["exp"].(float64); ok {
			if time.Unix(int64(exp), 0).Before(time.Now()) {
				return false, fmt.Errorf("token has expired")
			}
		}

		// Token is valid and not expired
		return true, nil
	}

	return false, fmt.Errorf("token is invalid or missing claims")
}