package geoip

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

// ipLocation 缓存的 IP 归属地信息
type ipLocation struct {
	Location  string
	FetchedAt time.Time
}

// Service IP 归属地查询服务（基于 ip-api.com 免费接口 + 内存缓存）
type Service struct {
	cache sync.Map
}

// NewService 创建 IP 归属地查询服务
func NewService() *Service {
	return &Service{}
}

// ipApiResponse ip-api.com 返回结构
type ipApiResponse struct {
	Status     string `json:"status"`
	Country    string `json:"country"`
	RegionName string `json:"regionName"`
	City       string `json:"city"`
	ISP        string `json:"isp"`
	Query      string `json:"query"`
}

// Lookup 查询 IP 归属地，带内存缓存（24小时有效）
func (s *Service) Lookup(ip string) string {
	// 本地/内网 IP 直接返回
	if ip == "127.0.0.1" || ip == "::1" || ip == "" ||
		strings.HasPrefix(ip, "192.168.") ||
		strings.HasPrefix(ip, "10.") ||
		strings.HasPrefix(ip, "172.") {
		return "本地网络"
	}

	// 检查缓存（24小时有效）
	if v, ok := s.cache.Load(ip); ok {
		loc := v.(*ipLocation)
		if time.Since(loc.FetchedAt) < 24*time.Hour {
			return loc.Location
		}
		s.cache.Delete(ip)
	}

	// 查询 ip-api.com（免费接口，限制 45 次/分钟）
	location := s.queryIPAPI(ip)
	if location == "" {
		return "未知"
	}

	// 写入缓存
	s.cache.Store(ip, &ipLocation{
		Location:  location,
		FetchedAt: time.Now(),
	})

	return location
}

// queryIPAPI 调用 ip-api.com 查询
func (s *Service) queryIPAPI(ip string) string {
	client := &http.Client{Timeout: 3 * time.Second}
	url := fmt.Sprintf("http://ip-api.com/json/%s?lang=zh-CN", ip)

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

	var result ipApiResponse
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return ""
	}

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

	parts := []string{}
	if result.Country != "" {
		parts = append(parts, result.Country)
	}
	if result.RegionName != "" {
		parts = append(parts, result.RegionName)
	}
	if result.City != "" {
		parts = append(parts, result.City)
	}
	if result.ISP != "" {
		parts = append(parts, result.ISP)
	}

	return strings.Join(parts, " ")
}