package urltest

import (
	"context"
	"net"
	"net/http"
	"net/url"
	"sync"
	"time"

	M "github.com/sagernet/sing/common/metadata"
	N "github.com/sagernet/sing/common/network"
	"github.com/sagernet/sing/common/x/list"
)

type History struct {
	Time  time.Time `json:"time"`
	Delay uint16    `json:"delay"`
}

type HistoryStorage struct {
	access       sync.RWMutex
	delayHistory map[string]*History
	callbacks    list.List[func()]
}

func NewHistoryStorage() *HistoryStorage {
	return &HistoryStorage{
		delayHistory: make(map[string]*History),
	}
}

func (s *HistoryStorage) AddListener(listener func()) *list.Element[func()] {
	s.access.Lock()
	defer s.access.Unlock()
	return s.callbacks.PushBack(listener)
}

func (s *HistoryStorage) RemoveListener(element *list.Element[func()]) {
	s.access.Lock()
	defer s.access.Unlock()
	s.callbacks.Remove(element)
}

func (s *HistoryStorage) LoadURLTestHistory(tag string) *History {
	if s == nil {
		return nil
	}
	s.access.RLock()
	defer s.access.RUnlock()
	return s.delayHistory[tag]
}

func (s *HistoryStorage) DeleteURLTestHistory(tag string) {
	s.access.Lock()
	delete(s.delayHistory, tag)
	s.access.Unlock()
	s.notifyUpdated()
}

func (s *HistoryStorage) StoreURLTestHistory(tag string, history *History) {
	s.access.Lock()
	s.delayHistory[tag] = history
	s.access.Unlock()
	s.notifyUpdated()
}

func (s *HistoryStorage) notifyUpdated() {
	s.access.RLock()
	defer s.access.RUnlock()
	for element := s.callbacks.Front(); element != nil; element = element.Next() {
		element.Value()
	}
}

func URLTest(ctx context.Context, link string, detour N.Dialer) (t uint16, err error) {
	if link == "" {
		link = "https://www.gstatic.com/generate_204"
	}
	linkURL, err := url.Parse(link)
	if err != nil {
		return
	}
	hostname := linkURL.Hostname()
	port := linkURL.Port()
	if port == "" {
		switch linkURL.Scheme {
		case "http":
			port = "80"
		case "https":
			port = "443"
		}
	}

	start := time.Now()
	instance, err := detour.DialContext(ctx, "tcp", M.ParseSocksaddrHostPortStr(hostname, port))
	if err != nil {
		return
	}
	defer instance.Close()

	req, err := http.NewRequest(http.MethodHead, link, nil)
	if err != nil {
		return
	}
	req = req.WithContext(ctx)

	transport := &http.Transport{
		Dial: func(string, string) (net.Conn, error) {
			return instance, nil
		},
		// from http.DefaultTransport
		MaxIdleConns:          100,
		IdleConnTimeout:       90 * time.Second,
		TLSHandshakeTimeout:   10 * time.Second,
		ExpectContinueTimeout: 1 * time.Second,
	}

	client := http.Client{
		Transport: transport,
		CheckRedirect: func(req *http.Request, via []*http.Request) error {
			return http.ErrUseLastResponse
		},
	}
	defer client.CloseIdleConnections()

	resp, err := client.Do(req)
	if err != nil {
		return
	}
	resp.Body.Close()
	t = uint16(time.Since(start) / time.Millisecond)
	return
}