super-auto-pets-board-game/internal/server/ws.go

package server

import (
	"context"
	"encoding/json"
	"log/slog"
	"net/http"
	"time"

	"github.com/coder/websocket"

	"github.com/greyson/super-auto-pets-board-game/internal/game"
)

// client is one WebSocket connection bound to a player in a room.
type client struct {
	ws       *websocket.Conn
	playerID string
	send     chan []byte
}

// clientMessage is anything a player can ask the server to do. Type decides
// which other fields matter.
type clientMessage struct {
	Type  string   `json:"type"`
	Row   int      `json:"row"`   // buy
	Cards []string `json:"cards"` // discard, trade
	Pick  int      `json:"pick"`  // tradeChoose
	Order []string `json:"order"` // arrange
}

type serverMessage struct {
	Type  string     `json:"type"`
	State *game.View `json:"state,omitempty"`
	Error string     `json:"error,omitempty"`
}

// handleWS upgrades the connection and pumps messages until the client
// leaves. Query params: game, player, token.
func (s *Server) handleWS(w http.ResponseWriter, req *http.Request) {
	q := req.URL.Query()
	gameID, playerID, token := q.Get("game"), q.Get("player"), q.Get("token")

	r, err := s.getRoom(gameID)
	if err != nil {
		httpError(w, http.StatusNotFound, "game not found")
		return
	}
	r.mu.Lock()
	p := r.game.PlayerByID(playerID)
	r.mu.Unlock()
	if p == nil || p.Token != token {
		httpError(w, http.StatusForbidden, "bad player credentials")
		return
	}

	ws, err := websocket.Accept(w, req, &websocket.AcceptOptions{
		// Same-origin in production; the Vite dev server proxies /api, so
		// cross-origin checks buy nothing here yet.
		InsecureSkipVerify: true,
	})
	if err != nil {
		return
	}
	c := &client{ws: ws, playerID: playerID, send: make(chan []byte, 16)}

	ctx, cancel := context.WithCancel(req.Context())
	defer cancel()
	go c.writeLoop(ctx)

	r.mu.Lock()
	r.conns[c] = struct{}{}
	p.Connected = true
	r.broadcastLocked()
	r.mu.Unlock()

	defer func() {
		r.mu.Lock()
		delete(r.conns, c)
		// Only mark disconnected if no other tab/connection remains.
		stillHere := false
		for other := range r.conns {
			if other.playerID == playerID {
				stillHere = true
			}
		}
		if !stillHere {
			p.Connected = false
		}
		r.broadcastLocked()
		r.mu.Unlock()
		ws.Close(websocket.StatusNormalClosure, "")
	}()

	for {
		_, data, err := ws.Read(ctx)
		if err != nil {
			return
		}
		var msg clientMessage
		if err := json.Unmarshal(data, &msg); err != nil {
			c.sendError("invalid message")
			continue
		}
		s.apply(r, c, msg)
	}
}

// apply runs one player action against the game under the room lock, then
// persists and broadcasts on success.
func (s *Server) apply(r *room, c *client, msg clientMessage) {
	r.mu.Lock()
	defer r.mu.Unlock()

	g := r.game
	var err error
	switch msg.Type {
	case "buy":
		err = g.Buy(c.playerID, msg.Row)
	case "discard":
		if g.Phase == game.PhaseCleanup {
			err = g.CleanupDiscard(c.playerID, msg.Cards)
		} else {
			err = g.Discard(c.playerID, msg.Cards)
		}
	case "trade":
		err = g.TradeStart(c.playerID, msg.Cards)
	case "tradeChoose":
		err = g.TradeChoose(c.playerID, msg.Pick)
	case "pass":
		err = g.Pass(c.playerID)
	case "arrange":
		err = g.SubmitOrder(c.playerID, msg.Order)
	case "ready":
		err = g.AcknowledgeBattle(c.playerID)
	default:
		err = game.ErrInvalidAction
	}
	if err != nil {
		c.sendError(err.Error())
		return
	}
	s.persist(r)
	r.broadcastLocked()
}

// broadcastLocked sends each connected client its own view of the game.
// Callers must hold r.mu.
func (r *room) broadcastLocked() {
	for c := range r.conns {
		view := r.game.ViewFor(c.playerID)
		data, err := json.Marshal(serverMessage{Type: "state", State: &view})
		if err != nil {
			slog.Error("failed to marshal view", "err", err)
			continue
		}
		c.trySend(data)
	}
}

func (c *client) sendError(msg string) {
	data, _ := json.Marshal(serverMessage{Type: "error", Error: msg})
	c.trySend(data)
}

// trySend queues a message, dropping it if the client's buffer is full (a
// stalled client will resync from the next state broadcast anyway).
func (c *client) trySend(data []byte) {
	select {
	case c.send <- data:
	default:
	}
}

func (c *client) writeLoop(ctx context.Context) {
	for {
		select {
		case <-ctx.Done():
			return
		case data := <-c.send:
			writeCtx, cancel := context.WithTimeout(ctx, 10*time.Second)
			err := c.ws.Write(writeCtx, websocket.MessageText, data)
			cancel()
			if err != nil {
				return
			}
		}
	}
}