// Copyright (c) 2025 Nikolai Papin
//
// This file is part of Easywish
//
// 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 middleware

import (
	"context"
	"easywish/config"
	"easywish/internal/database"
	"easywish/internal/utils/enums"
	"errors"
	"fmt"
	"net/http"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/go-redis/redis/v8"
	"github.com/golang-jwt/jwt/v5"
	"github.com/jackc/pgx/v5"
	"go.uber.org/zap"
)

type Claims struct {
	Username string     				`json:"username"`
	Role     enums.Role 			  `json:"role"`
	Type 		 enums.JwtTokenType `json:"type"`
	Session  string 					  `json:"session"`	
	jwt.RegisteredClaims
}

// XXX: cluttered; move cache & database check to auth service
func AuthMiddleware(log *zap.Logger, dbctx database.DbContext, redisClient *redis.Client) gin.HandlerFunc {
	return func(c *gin.Context) {
		cfg := config.GetConfig()
		authHeader := c.GetHeader("Authorization")

		if authHeader == "" {
			c.Set("username", nil)
			c.Set("role", enums.GuestRole)
			c.Next()
			return
		}

		tokenString := authHeader

		token, err := jwt.ParseWithClaims(
			tokenString, 
			&Claims{}, 
			func(token *jwt.Token) (any, error) {
				if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
					return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
				}
				return []byte(cfg.JwtSecret), nil
			},
		)

		if err != nil {
			if errors.Is(err, jwt.ErrTokenExpired) {
				c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "Token expired"})
			} else {
				c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "Invalid token"})
			}
			return
		}

		if claims, ok := token.Claims.(*Claims); ok && token.Valid {

			if claims.Type != enums.JwtAccessTokenType {
				c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "Not an access token"})
				return
			}

			ctx := context.TODO()
			isTerminated, redisErr := redisClient.Get(ctx, fmt.Sprintf("session::%s::is_terminated", claims.Session)).Bool()
			if redisErr != nil && redisErr != redis.Nil {
				log.Error(
					"Failed to lookup cache to check whether session is not terminated",	
					zap.Error(redisErr))
				c.AbortWithStatus(http.StatusInternalServerError)
				return
			}

			// Cache if nil
			if redisErr == redis.Nil {
				db := database.NewDbHelper(dbctx)

				session, err := db.Queries.GetSessionByGuid(db.CTX, claims.Session)
				if err != nil {

					if errors.Is(err, pgx.ErrNoRows) {
						log.Warn(
							"Session does not exist or was deleted",
							zap.String("session", claims.Session))
						c.AbortWithStatus(http.StatusUnauthorized)
						return
					}

					log.Error(
						"Failed to lookup session in database",	
						zap.String("session", claims.Session),
						zap.Error(err))
					c.AbortWithStatus(http.StatusInternalServerError)
					return
				}

				if err := redisClient.Set(
					ctx, 
					fmt.Sprintf("session::%s::is_terminated", claims.Session), 
					session.Terminated, 
					time.Duration(8 * time.Hour), // XXX: magic number
				).Err(); err != nil {
					log.Error(
						"Failed to cache session's is_terminated state",	
						zap.String("session", claims.Session),
						zap.Error(err))
					c.AbortWithStatus(http.StatusInternalServerError)
					return
				}

				isTerminated = *session.Terminated
			}

			if isTerminated {
				log.Warn(
					"Attempt to access resource from a terminated session",	
					zap.String("session", claims.Session))
				c.AbortWithStatus(http.StatusUnauthorized)
				return
			}

			c.Set("username", claims.Username)
			c.Set("role", claims.Role)
			c.Next()
		} else {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "Invalid claims"})
		}
	}
}