package clientgeo

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

const DefaultLookupURL = "https://cf-ip-geo.smyhub.com/api"

type apiPayload struct {
	Geo *struct {
		CountryName string `json:"countryName"`
		RegionName  string `json:"regionName"`
		CityName    string `json:"cityName"`
	} `json:"geo"`
}

func FormatDisplay(countryName, regionName, cityName string) string {
	parts := make([]string, 0, 3)
	for _, s := range []string{countryName, regionName, cityName} {
		s = strings.TrimSpace(s)
		if s != "" {
			parts = append(parts, s)
		}
	}
	return strings.Join(parts, " ")
}

// FetchDisplayLocation 使用 cf-ip-geo 的 ?ip= 查询展示用位置（服务端调用，避免浏览器 CORS）。
func FetchDisplayLocation(ctx context.Context, lookupURL, ip string) (string, error) {
	ip = strings.TrimSpace(ip)
	if ip == "" {
		return "", nil
	}
	base := strings.TrimSuffix(strings.TrimSpace(lookupURL), "/")
	u, err := url.Parse(base)
	if err != nil || u.Scheme == "" || u.Host == "" {
		return "", fmt.Errorf("invalid lookup URL")
	}
	q := u.Query()
	q.Set("ip", ip)
	u.RawQuery = q.Encode()

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
	if err != nil {
		return "", err
	}
	client := &http.Client{Timeout: 6 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("geo status %d", resp.StatusCode)
	}
	var payload apiPayload
	if err := json.NewDecoder(resp.Body).Decode(&payload); err != nil {
		return "", err
	}
	if payload.Geo == nil {
		return "", nil
	}
	return FormatDisplay(payload.Geo.CountryName, payload.Geo.RegionName, payload.Geo.CityName), nil
}