/* OpenBills-server - Server for libre billing software OpenBills-web
 * Copyright (C) 2022  Vidhu Kant Sharma <vidhukant@vidhukant.xyz>

 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.

 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

package auth

import (
	"context"
	"github.com/MikunoNaka/OpenBills-server/database"
	"github.com/MikunoNaka/OpenBills-server/user"
	"github.com/MikunoNaka/OpenBills-server/util"
	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v4"
	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/bson/primitive"
	"go.mongodb.org/mongo-driver/mongo"
	"net/http"
	"time"
)

var db *mongo.Collection = database.DB.Collection("Users")

var (
	refreshSecret []byte
)

func init() {
	conf := util.GetConfig().Crypto
	refreshSecret = []byte(conf.RefreshTokenSecret)
}

// TODO: check if user even exists and send response accordingly
// middleware to check refresh token
func verifyRefreshToken() gin.HandlerFunc {
	return func(ctx *gin.Context) {
		refreshToken, err := ctx.Cookie("refreshToken")
		if err == nil {
			token, err := jwt.ParseWithClaims(refreshToken, &jwt.StandardClaims{}, func(token *jwt.Token) (interface{}, error) {
				return []byte(refreshSecret), nil
			})
			if err != nil { // invalid token
				ctx.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"message": "invalid token"})
			} else { // valid token
				// convert id from string to ObjectID
				id, _ := primitive.ObjectIDFromHex(token.Claims.(*jwt.StandardClaims).Issuer)

				// check if user exists
				var u user.User
				if err := db.FindOne(context.TODO(), bson.M{"_id": id}).Decode(&u); err != nil {
					ctx.AbortWithStatusJSON(http.StatusNotFound, gin.H{"message": "user not found"})
				} else {
					// check if this refreshToken is in DB
					for _, i := range u.Sessions {
						if i.Token == refreshToken {
							ctx.Set("user", u)
							ctx.Next()
							return
						}
					}
					ctx.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"message": "refresh token expired"})
				}
			}
		} else {
			// invalid Authorization header
			ctx.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"message": "not logged in"})
		}
	}
}

/*
 * the refresh token has a long lifespan and is stored in
 * the database in case it needs to be revoked.
 *
 * this can be stored as an HTTP only cookie and will be used
 * when creating a new access token
 *
 * I'm using a different secret key for refresh tokens
 * for enhanced security
 */
func newRefreshToken(userId string) (string, int64, error) {
	// convert id from string to ObjectID
	id, _ := primitive.ObjectIDFromHex(userId)

	// check if user exists
	var u user.User
	if err := db.FindOne(context.TODO(), bson.M{"_id": id}).Decode(&u); err != nil {
		return "", 0, user.ErrUserNotFound
	}

	// generate refresh token
	expiresAt := time.Now().Add(time.Hour * 12).Unix()
	claims := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.StandardClaims{
		Issuer:    userId,
		ExpiresAt: expiresAt,
	})
	token, err := claims.SignedString(refreshSecret)
	if err != nil {
		return "", expiresAt, err
	}

	// store refresh token in db with unique session name for ease in identification
	sessionName := time.Now().Format("01-02-2006.15:04:05") + "-" + u.UserName
	u.Sessions = append(u.Sessions, user.Session{Name: sessionName, Token: token})
	db.UpdateOne(context.TODO(), bson.M{"_id": id}, bson.D{{"$set", u}})

	return token, expiresAt, nil
}