shotgun/server.go

package main

import (
	"context"
	"errors"
	"log/slog"
	"net/http"
	"sync"
	"time"

	"nhooyr.io/websocket"
	"nhooyr.io/websocket/wsjson"

	"git.sunturtle.xyz/studio/shotgun/game"
	"git.sunturtle.xyz/studio/shotgun/lobby"
	"git.sunturtle.xyz/studio/shotgun/player"
	"git.sunturtle.xyz/studio/shotgun/serve"
)

type Server struct {
	l *lobby.Lobby

	mu sync.Mutex
	pp map[player.ID]*websocket.Conn
}

type person struct {
	conn *websocket.Conn
	id   player.ID
}

func (s *Server) person(p player.ID) person {
	s.mu.Lock()
	defer s.mu.Unlock()
	return person{conn: s.pp[p], id: p}
}

func (s *Server) accept(w http.ResponseWriter, r *http.Request, p player.ID) (person, error) {
	conn, err := websocket.Accept(w, r, nil)
	if err != nil {
		return person{}, err
	}
	slog.Debug("upgraded", "player", p)
	s.mu.Lock()
	defer s.mu.Unlock()
	s.pp[p] = conn
	return person{conn: conn, id: p}, nil
}

func (s *Server) left(p player.ID) {
	s.mu.Lock()
	// NOTE(zeph): neither map index nor map delete can panic, so this critical
	// section does not need a defer
	c := s.pp[p]
	delete(s.pp, p)
	s.mu.Unlock()
	if c != nil {
		// We don't care about the error here since the connection is leaving.
		// It's probably already closed anyway.
		slog.Debug("leaving", "player", p)
		c.Close(websocket.StatusNormalClosure, "bye")
	}
}

// Queue connects players to games. The connection immediately upgrades.
// This handler MUST be wrapped in [serve.WithPlayerID].
func (s *Server) Queue(w http.ResponseWriter, r *http.Request) {
	p := serve.PlayerID(r.Context())
	if p == (player.ID{}) {
		panic("missing player ID")
	}
	person, err := s.accept(w, r, p)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	s.joinAndServe(person)
}

func (s *Server) joinAndServe(p person) {
	slog.Debug("joining", "player", p.id)
	ctx, stop := context.WithTimeoutCause(context.Background(), 10*time.Minute, errQueueEmpty)
	id, chall, deal := s.l.Queue(ctx, p.id)
	stop()
	if id == (lobby.GameID{}) {
		// Context canceled.
		p.conn.Close(websocket.StatusTryAgainLater, "sorry, queue is empty...")
		return
	}
	if deal {
		g := game.New(p.id, chall)
		other := s.person(chall)
		// TODO(zeph): save the game state s.t. we can provide a join channel
		go gameActor(ctx, g, p, other, nil)
	}
	// Reply with the game ID so they can share.
	r := struct {
		Game lobby.GameID `json:"game"`
	}{
		Game: id,
	}
	if err := wsjson.Write(context.TODO(), p.conn, r); err != nil {
		slog.WarnContext(ctx, "got a game but player dropped", "game", id, "player", p.id)
		s.left(p.id)
		return
	}
}

var errQueueEmpty = errors.New("sorry, queue is empty")