package main

import (
	"context"
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"log"
	"net/http"
	"os"
	"time"

	"github.com/gin-contrib/cors"
	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt"
	"github.com/google/go-github/v50/github"
	"github.com/joho/godotenv"
	"golang.org/x/oauth2"
	"gorm.io/driver/mysql"
	"gorm.io/gorm"
)

var db *gorm.DB
var jwtSecret = []byte("JWT_SECRET")
var oauthConf *oauth2.Config

func main() {
	err := godotenv.Load()
	if err != nil {
		log.Fatal("Error loading .env file")
	}
	oauthConf = &oauth2.Config{
		ClientID:     os.Getenv("GITHUB_CLIENT_ID"),
		ClientSecret: os.Getenv("GITHUB_CLIENT_SECRET"),
		// Scopes:       []string{"read:user", "user:email"},
		Endpoint: oauth2.Endpoint{
			AuthURL:  "https://github.com/login/oauth/authorize",
			TokenURL: "https://github.com/login/oauth/access_token",
		}}

	initDB()

	router := gin.Default()

	router.Use(cors.New(cors.Config{
		AllowOrigins:     []string{"*"},
		AllowMethods:     []string{"GET", "POST", "PUT", "DELETE", "OPTIONS", "HEAD"},
		AllowHeaders:     []string{"Accept", "Authorization", "Content-Type", "X-CSRF-Token"},
		AllowCredentials: true,
	}))
	router.GET("/", func(ctx *gin.Context) { ctx.Writer.WriteString("hello world") })
	router.GET("/auth/github", githubLoginHandler)
	router.GET("/auth/github/callback", githubCallbackHandler)

	router.Run(":8000")
}

func githubLoginHandler(c *gin.Context) {
	// state := generateState()
	// code := generateCode()

	// err := storeStateToDB(state, code)
	// if err != nil {
	// 	log.Println("Error storing state to DB:", err)
	// 	c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"message": "Internal server error"})
	// 	return
	// }

	url := oauthConf.AuthCodeURL("state")
	log.Println(url)
	c.Redirect(http.StatusFound, url)
}

func githubCallbackHandler(c *gin.Context) {
	state := c.Query("state")
	code := c.Query("code")
	log.Println(state, code)

	// if !verifyState(state, code) {
	// 	c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{"message": "Invalid state"})
	// 	return
	// }

	// 使用 code 换取 token
	token, err := oauthConf.Exchange(context.Background(), code)
	if err != nil {
		// c.String(http.StatusBadRequest, "授权失败: %s", err.Error())
		c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{"error": fmt.Errorf("授权失败: %s", err.Error())})
		return
	}
	log.Println("token:", token)

	// 使用 token 获取 GitHub 用户信息
	// client := github.NewClient(oauthConf.Client(context.Background(), token))
	client := github.NewClient(oauth2.NewClient(context.Background(), oauth2.StaticTokenSource(token)))
	user, _, err := client.Users.Get(c.Request.Context(), "")
	if err != nil {
		// c.String(http.StatusInternalServerError, "获取用户信息失败: %s", err.Error())
		c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": fmt.Errorf("获取用户信息失败: %s", err.Error())})
		return
	}

	// err = storeUserToDB(user)
	// if err != nil {
	// 	log.Println("Error storing user to DB:", err)
	// 	c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"message": "Internal server error"})
	// 	return
	// }

	log.Printf("%#v\n", user)
	log.Println(user.GetEmail(), user.GetName(), user.GetID(), user.GetAvatarURL())
	// 处理用户信息
	c.JSON(http.StatusOK, gin.H{
		"login":    user.Login,
		"name":     user.Name,
		"email":    user.Email,
		"location": user.Location,
		"scopes":   token.Extra("scope"),
	})
	// jwtToken, err := generateJWTToken(*user.ID)
	// if err != nil {
	// 	log.Println("Error generating JWT token:", err)
	// 	c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"message": "Internal server error"})
	// 	return
	// }

	// c.SetCookie("token", jwtToken, 60*60*24, "/", "localhost", false, true)
	// c.Redirect(http.StatusFound, "http://152.70.110.4:8000")
}

func initDB() {
	dsn := os.Getenv("MYSQL_DSN")
	db, err := gorm.Open(mysql.Open(dsn), &gorm.Config{})
	if err != nil {
		log.Fatal("Error opening database:", err)
	}
	// db.AutoMigrate()
	sqlDB, err := db.DB()
	if err != nil {
		log.Fatal("Error connecting to database:", err)
	}
	sqlDB.SetMaxIdleConns(10)
	sqlDB.SetMaxOpenConns(100)
	sqlDB.SetConnMaxLifetime(time.Hour)

	log.Println("Database connection established")
}

func generateState() string {
	return generateRandomString(20)
}

func generateCode() string {
	return generateRandomString(20)
}

func generateRandomString(length int) string {
	byteArr := make([]byte, length)
	_, err := rand.Read(byteArr)
	if err != nil {
		log.Fatal("Error generating random string:", err)
	}

	return base64.URLEncoding.EncodeToString(byteArr)
}

func storeStateToDB(state, code string) error {
	query := "INSERT INTO oauth_state (state, code) VALUES (?, ?)"
	err := db.Exec(query, state, code).Error
	if err != nil {
		return err
	}

	return nil
}

func verifyState(state, code string) bool {
	query := "SELECT COUNT(*) FROM oauth_state WHERE state = ? AND code = ?"
	row := db.Exec(query, state, code)

	var count int
	err := row.Scan(&count)
	if err != nil {
		log.Println("Error verifying state:", err)
		return false
	}

	if count == 0 {
		return false
	}

	return true
}

func storeUserToDB(user *github.User) error {
	query := "INSERT INTO users (id, login, email) VALUES (?, ?, ?) ON DUPLICATE KEY UPDATE login = VALUES(login), email = VALUES(email)"

	err := db.Exec(query, user.GetID(), user.GetLogin(), user.GetEmail()).Error
	if err != nil {
		return err
	}

	return nil
}

func generateJWTToken(userID int64) (string, error) {
	token := jwt.New(jwt.SigningMethodHS256)

	claims := token.Claims.(jwt.MapClaims)
	claims["user"] = userID
	claims["exp"] = time.Now().Add(time.Hour * 24).Unix()

	jwtToken, err := token.SignedString(jwtSecret)
	if err != nil {
		return "", err
	}

	return jwtToken, nil
}

func verifyJWTToken(tokenString string) {
	// 验证 token
	tokenValue, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
		// 该函数用于验证令牌的签名方法是否正确
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("Unexpected signing method: %v", token.Header["alg"])
		}

		return jwtSecret, nil
	})
	if err != nil {
		fmt.Println("Error parsing token string:", err)
		return
	}

	// 获取声明信息
	if claims, ok := tokenValue.Claims.(jwt.MapClaims); ok && tokenValue.Valid {
		// fmt.Println("Authorized:", claims["authorized"])
		fmt.Println("User:", claims["user"])
		fmt.Println("Expiration time:", time.Unix(int64(claims["exp"].(float64)), 0))
	} else {
		fmt.Println("Invalid token.")
	}
}