package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"net"
	"net/http"
	"os"
	"strings"
	"time"
)

// User 用户数据结构
type User struct {
	IP         string `json:"ip"`
	Username   string `json:"username"`
	ExpiryDate string `json:"expiryDate"`
	Phone      string `json:"phone"`
}

// UserData 用户数据容器
type UserData struct {
	Users []User `json:"users"`
}

// APIResponse API响应结构
type APIResponse struct {
	Expiry     string `json:"expiry"`
	ServerTime string `json:"serverTime"`
}

// getClientIP 获取客户端真实IP地址
func getClientIP(r *http.Request) string {
	// 优先检查代理头
	if xForwardedFor := r.Header.Get("X-Forwarded-For"); xForwardedFor != "" {
		// X-Forwarded-For 可能包含多个IP，取第一个
		ips := strings.Split(xForwardedFor, ",")
		if len(ips) > 0 {
			return strings.TrimSpace(ips[0])
		}
	}

	if xRealIP := r.Header.Get("X-Real-IP"); xRealIP != "" {
		return xRealIP
	}

	if xClientIP := r.Header.Get("X-Client-IP"); xClientIP != "" {
		return xClientIP
	}

	// 从RemoteAddr获取IP
	ip, _, err := net.SplitHostPort(r.RemoteAddr)
	if err != nil {
		return r.RemoteAddr
	}

	// 处理IPv6回环地址
	if ip == "::1" {
		return "127.0.0.1"
	}

	// 移除IPv6前缀
	if strings.HasPrefix(ip, "::ffff:") {
		return strings.TrimPrefix(ip, "::ffff:")
	}

	return ip
}

// loadUserData 加载用户数据
func loadUserData() ([]User, error) {
	data, err := os.ReadFile("users.json")
	if err != nil {
		return nil, err
	}

	var userData UserData
	err = json.Unmarshal(data, &userData)
	if err != nil {
		return nil, err
	}

	return userData.Users, nil
}

// findUserByIP 根据IP查找用户
func findUserByIP(users []User, ip string) *User {
	for _, user := range users {
		if user.IP == ip {
			return &user
		}
	}
	return nil
}

// setCORSHeaders 设置CORS头
func setCORSHeaders(w http.ResponseWriter) {
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
	w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, Authorization")
}

// healthHandler 健康检查处理器
func healthHandler(w http.ResponseWriter, r *http.Request) {
	setCORSHeaders(w)

	if r.Method == "OPTIONS" {
		w.WriteHeader(http.StatusOK)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)

	response := map[string]interface{}{
		"status": "ok",
		"time":   time.Now().Format(time.RFC3339),
	}

	json.NewEncoder(w).Encode(response)
}

// checkExpiryHandler 检查到期时间处理器
func checkExpiryHandler(w http.ResponseWriter, r *http.Request) {
	setCORSHeaders(w)

	if r.Method == "OPTIONS" {
		w.WriteHeader(http.StatusOK)
		return
	}

	// 获取客户端IP
	clientIP := getClientIP(r)
	log.Printf("收到来自 %s 的请求", clientIP)

	// 获取当前服务器时间
	serverTime := time.Now().Format(time.RFC3339)

	// 加载用户数据
	users, err := loadUserData()
	if err != nil {
		log.Printf("读取用户数据失败: %v", err)
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(map[string]interface{}{})
		return
	}

	// 查找用户
	user := findUserByIP(users, clientIP)
	if user == nil {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(map[string]interface{}{})
		return
	}

	// 找到用户，返回到期时间
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(APIResponse{
		Expiry:     user.ExpiryDate,
		ServerTime: serverTime,
	})
}

func main() {
	// 定义命令行参数
	portFlag := flag.String("port", "3763", "服务器端口号")
	flag.Parse()

	// 设置路由
	http.HandleFunc("/health", healthHandler)
	http.HandleFunc("/api/check-expiry", checkExpiryHandler)

	port := ":" + *portFlag
	fmt.Printf("服务器运行在端口 %s\n", port)
	fmt.Printf("健康检查: http://localhost%s/health\n", port)
	fmt.Printf("API接口: http://localhost%s/api/check-expiry\n", port)

	// 启动服务器
	log.Fatal(http.ListenAndServe(port, nil))
}