package monitor

import (
	"io"
	"net/http"
	"strings"
	"sync"
	"time"

	"github.com/nezhahq/agent/pkg/util"
	pb "github.com/nezhahq/agent/proto"
)

var (
	cfList = []string{
		"https://blog.cloudflare.com/cdn-cgi/trace",
		"https://dash.cloudflare.com/cdn-cgi/trace",
		"https://developers.cloudflare.com/cdn-cgi/trace",
	}
	GeoQueryIP, CachedCountryCode string
	GeoQueryIPChanged             bool = true
	httpClientV4                       = util.NewSingleStackHTTPClient(time.Second*20, time.Second*5, time.Second*10, false)
	httpClientV6                       = util.NewSingleStackHTTPClient(time.Second*20, time.Second*5, time.Second*10, true)
)

// UpdateIP 按设置时间间隔更新IP地址的缓存
func FetchIP(useIPv6CountryCode bool) *pb.GeoIP {
	util.Println(agentConfig.Debug, "正在更新本地缓存IP信息")
	wg := new(sync.WaitGroup)
	wg.Add(2)
	var ipv4, ipv6 string
	go func() {
		defer wg.Done()
		ipv4 = fetchIP(cfList, false)
	}()
	go func() {
		defer wg.Done()
		ipv6 = fetchIP(cfList, true)
	}()
	wg.Wait()

	if ipv6 != "" && (useIPv6CountryCode || ipv4 == "") {
		GeoQueryIPChanged = GeoQueryIP != ipv6 || GeoQueryIPChanged
		GeoQueryIP = ipv6
	} else {
		GeoQueryIPChanged = GeoQueryIP != ipv4 || GeoQueryIPChanged
		GeoQueryIP = ipv4
	}

	if GeoQueryIP != "" {
		return &pb.GeoIP{
			Use6: useIPv6CountryCode,
			Ip: &pb.IP{
				Ipv4: ipv4,
				Ipv6: ipv6,
			},
		}
	}

	return nil
}

func fetchIP(servers []string, isV6 bool) string {
	var ip string
	var resp *http.Response
	var err error

	// 双栈支持参差不齐，不能随机请求，有些 IPv6 取不到 IP
	for i := 0; i < len(servers); i++ {
		if isV6 {
			resp, err = httpGetWithUA(httpClientV6, servers[i])
		} else {
			resp, err = httpGetWithUA(httpClientV4, servers[i])
		}
		// 遇到单栈机器提前退出
		if err != nil && strings.Contains(err.Error(), "no route to host") {
			return ip
		}
		if err == nil {
			body, err := io.ReadAll(resp.Body)
			if err != nil {
				continue
			}
			resp.Body.Close()
			lines := strings.Split(string(body), "\n")
			var newIP string
			for _, line := range lines {
				if strings.HasPrefix(line, "ip=") {
					newIP = strings.TrimPrefix(line, "ip=")
					break
				}
			}
			// 没取到 v6 IP
			if isV6 && strings.IndexByte(newIP, ':') == -1 {
				continue
			}
			// 没取到 v4 IP
			if !isV6 && strings.IndexByte(newIP, '.') == -1 {
				continue
			}
			ip = newIP
			return ip
		}
	}
	return ip
}

func httpGetWithUA(client *http.Client, url string) (*http.Response, error) {
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Add("User-Agent", util.MacOSChromeUA)
	return client.Do(req)
}