/**
 * package utils
 * 作用：IP归属地查询工具
 * 说明：使用第三方API查询IP归属地信息
 */
package utils

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
)

// IPLocationInfo IP归属地信息
type IPLocationInfo struct {
	Country   string `json:"country"`   // 国家
	Region    string `json:"region"`    // 省份
	City      string `json:"city"`      // 城市
	ISP       string `json:"isp"`       // 运营商
	FullLocation string `json:"full_location"` // 完整归属地
}

// 缓存结构（简单内存缓存）
var (
	ipCache      = make(map[string]*IPLocationInfo)
	cacheTimeout = 24 * time.Hour
)

/**
 * GetIPLocation
 * 功能：获取IP归属地信息
 * @param ip IP地址
 * @returns 归属地信息字符串
 */
func GetIPLocation(ip string) string {
	// 排除本地IP
	if isLocalIP(ip) {
		return "本地"
	}

	// 检查缓存
	if info, ok := ipCache[ip]; ok {
		return info.FullLocation
	}

	// 查询IP归属地
	info := queryIPLocation(ip)
	if info != nil {
		// 构建完整归属地字符串
		parts := []string{}
		if info.Country != "" {
			parts = append(parts, info.Country)
		}
		if info.Region != "" {
			parts = append(parts, info.Region)
		}
		if info.City != "" {
			parts = append(parts, info.City)
		}
		if info.ISP != "" {
			parts = append(parts, info.ISP)
		}

		if len(parts) > 0 {
			info.FullLocation = strings.Join(parts, " ")
		} else {
			info.FullLocation = "未知"
		}

		// 存入缓存
		ipCache[ip] = info
		return info.FullLocation
	}

	return "未知"
}

/**
 * isLocalIP
 * 功能：判断是否为本地IP
 */
func isLocalIP(ip string) bool {
	// 本地回环地址
	if ip == "127.0.0.1" || ip == "localhost" || ip == "::1" {
		return true
	}

	// 内网地址
	if strings.HasPrefix(ip, "192.168.") ||
		strings.HasPrefix(ip, "10.") ||
		strings.HasPrefix(ip, "172.16.") ||
		strings.HasPrefix(ip, "172.17.") ||
		strings.HasPrefix(ip, "172.18.") ||
		strings.HasPrefix(ip, "172.19.") ||
		strings.HasPrefix(ip, "172.20.") ||
		strings.HasPrefix(ip, "172.21.") ||
		strings.HasPrefix(ip, "172.22.") ||
		strings.HasPrefix(ip, "172.23.") ||
		strings.HasPrefix(ip, "172.24.") ||
		strings.HasPrefix(ip, "172.25.") ||
		strings.HasPrefix(ip, "172.26.") ||
		strings.HasPrefix(ip, "172.27.") ||
		strings.HasPrefix(ip, "172.28.") ||
		strings.HasPrefix(ip, "172.29.") ||
		strings.HasPrefix(ip, "172.30.") ||
		strings.HasPrefix(ip, "172.31.") {
		return true
	}

	return false
}

/**
 * queryIPLocation
 * 功能：查询IP归属地（使用ip-api.com免费API）
 */
func queryIPLocation(ip string) *IPLocationInfo {
	// 使用ip-api.com免费API（限制：每分钟45次请求）
	url := fmt.Sprintf("http://ip-api.com/json/%s?lang=zh-CN&fields=status,message,country,regionName,city,isp", ip)

	client := &http.Client{
		Timeout: 3 * time.Second,
	}

	resp, err := client.Get(url)
	if err != nil {
		return nil
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil
	}

	var result struct {
		Status    string `json:"status"`
		Message   string `json:"message"`
		Country   string `json:"country"`
		Region    string `json:"regionName"`
		City      string `json:"city"`
		ISP       string `json:"isp"`
	}

	if err := json.Unmarshal(body, &result); err != nil {
		return nil
	}

	if result.Status != "success" {
		return nil
	}

	return &IPLocationInfo{
		Country: result.Country,
		Region:  result.Region,
		City:    result.City,
		ISP:     result.ISP,
	}
}