package main

import (
	"context"
	"log"
	"net/http"
	"strings"
	"sync"

	"github.com/caddyserver/certmagic"
	"github.com/quic-go/quic-go/http3"
	"github.com/quic-go/webtransport-go"
)

type Room struct {
	conns map[*webtransport.Session]bool
	mu    sync.Mutex
}

type Server struct {
	rooms map[string]*Room
	mu    sync.Mutex
}

func NewServer() *Server {
	return &Server{rooms: make(map[string]*Room)}
}

func (s *Server) getRoom(name string) *Room {
	s.mu.Lock()
	defer s.mu.Unlock()
	if room, ok := s.rooms[name]; ok {
		return room
	}
	room := &Room{conns: make(map[*webtransport.Session]bool)}
	s.rooms[name] = room
	return room
}

func (s *Server) handleSession(roomName string, sess *webtransport.Session) {
	room := s.getRoom(roomName)
	room.mu.Lock()
	room.conns[sess] = true
	room.mu.Unlock()

	log.Printf("User joined room: %s", roomName)

	defer func() {
		room.mu.Lock()
		delete(room.conns, sess)
		room.mu.Unlock()
		log.Printf("User left room: %s", roomName)
	}()

	for {
		stream, err := sess.AcceptStream(context.Background())
		if err != nil {
			return
		}
		go s.handleStream(room, sess, stream)
	}
}

func (s *Server) handleStream(room *Room, sender *webtransport.Session, stream *webtransport.Stream) {
	buf := make([]byte, 4096)
	for {
		n, err := stream.Read(buf)
		if err != nil {
			return
		}
		data := append([]byte(nil), buf[:n]...)

		room.mu.Lock()
		for conn := range room.conns {
			if conn == sender {
				continue
			}
			go func(c *webtransport.Session, d []byte) {
				out, err := c.OpenStream()
				if err != nil {
					return
				}
				defer out.Close()
				out.Write(d)
			}(conn, data)
		}
		room.mu.Unlock()
	}
}

func main() {
	domain := "qgo-server.quizer.space"
	email := "serverussnap@outlook.com"

	// 1. Настройка CertMagic
	certmagic.DefaultACME.Email = email
	certmagic.DefaultACME.Agreed = true
	cfg := certmagic.NewDefault()

	// Важно: ManageSync получит сертификат ДО запуска серверов
	err := cfg.ManageSync(context.Background(), []string{domain})
	if err != nil {
		log.Fatal("CertMagic error:", err)
	}

	tlsConf := cfg.TLSConfig()
	// NextProtos критически важен для WebTransport
	tlsConf.NextProtos = []string{"h3", "http/1.1"}

	server := NewServer()
	mux := http.NewServeMux()

	// 2. WebTransport сервер
	wt := &webtransport.Server{
		H3: &http3.Server{
			Addr:      ":443",
			TLSConfig: tlsConf,
			Handler:   mux,
		},
		CheckOrigin: func(r *http.Request) bool { return true }, // Разрешаем подключения отовсюду
	}

	mux.HandleFunc("/room/", func(w http.ResponseWriter, r *http.Request) {
		// Сообщаем браузеру, что сервер поддерживает HTTP/3 на порту 443
		w.Header().Set("Alt-Svc", `h3=":443"; ma=86400`)

		roomName := strings.TrimPrefix(r.URL.Path, "/room/")
		if roomName == "" {
			http.Error(w, "Room name required", 400)
			return
		}

		sess, err := wt.Upgrade(w, r)
		if err != nil {
			log.Printf("Upgrade error (check if you use https): %v", err)
			return
		}
		go server.handleSession(roomName, sess)
	})

	// 3. Запуск UDP (HTTP/3 + WebTransport)
	go func() {
		log.Printf("Starting UDP (WebTransport) on https://%s/room/", domain)
		if err := wt.ListenAndServe(); err != nil {
			log.Fatalf("UDP Server Error: %v", err)
		}
	}()

	// 4. Запуск TCP (HTTPS + ACME Challenge)
	// Это нужно, чтобы браузер сначала зашел по TCP и узнал про Alt-Svc
	log.Printf("Starting TCP (HTTPS) on https://%s", domain)
	httpServer := &http.Server{
		Addr:      ":443",
		TLSConfig: tlsConf,
		Handler:   mux,
	}

	// Используем ListenAndServeTLS с пустыми путями, так как сертификаты в tlsConf
	log.Fatal(httpServer.ListenAndServeTLS("", ""))
}