refactor: prevent overwriting existing session on reconnect and improve player identity handling

public/js/main.js

@@ -19,8 +19,12 @@ function showToast(msg) {
 function handleConnected(msg) {
   state.playerId = msg.playerId;
   if (msg.sessionId) {
+    // Don't clobber an existing session on reconnect; only set if none exists yet.
+    const existing = localStorage.getItem('sessionId');
+    if (!existing) {
       cacheSessionId(msg.sessionId);
     }
+  }
   const stored = localStorage.getItem('playerName');
   if (stored) {
     if ($nameLobby && $nameLobby.value !== stored) {

src/server/game.js

@@ -20,11 +20,24 @@ function drawNextTrack(room) {
 export function setupWebSocket(server) {
   const wss = new WebSocketServer({ server });
   wss.on('connection', (ws) => {
-  const id = uuidv4();
+  // Create a tentative player identity, but don't immediately commit or send it.
-  const sessionId = uuidv4();
+  const newId = uuidv4();
-  let player = { id, sessionId, name: `Player-${id.slice(0, 4)}`, ws, connected: true, roomId: null };
+  const newSessionId = uuidv4();
+  let player = { id: newId, sessionId: newSessionId, name: `Player-${newId.slice(0, 4)}`, ws, connected: true, roomId: null };
     const send = (type, payload) => { try { ws.send(JSON.stringify({ type, ...payload })); } catch {} };
-  send('connected', { playerId: id, sessionId });
+
+    // To avoid overwriting an existing session on reconnect, delay the initial
+    // welcome until we see if the client sends a resume message.
+    let helloSent = false;
+    const sendHello = (p) => {
+      if (helloSent) return;
+      helloSent = true;
+      send('connected', { playerId: p.id, sessionId: p.sessionId });
+    };
+    // Fallback: if no resume arrives shortly, treat as a fresh connection.
+    const helloTimer = setTimeout(() => {
+      sendHello(player);
+    }, 400);
 
     function isParticipant(room, pid) {
       if (!room) return false;
@@ -39,6 +52,7 @@ export function setupWebSocket(server) {
 
       // Allow client to resume by session token
       if (msg.type === 'resume') {
+        clearTimeout(helloTimer);
         const reqSession = String(msg.sessionId || '');
         if (!reqSession) { send('resume_result', { ok: false, reason: 'no_session' }); return; }
         let found = null; let foundRoom = null;
@@ -61,7 +75,10 @@ export function setupWebSocket(server) {
           // Notify room
           broadcast(foundRoom, 'room_update', { room: roomSummary(foundRoom) });
         }
+  // Send resume result and an explicit connected that preserves their original session.
   send('resume_result', { ok: true, playerId: found.id, roomId: foundRoom?.id });
+  helloSent = true;
+  send('connected', { playerId: found.id, sessionId: found.sessionId });
         return;
       }
 
@@ -109,6 +126,13 @@ export function setupWebSocket(server) {
       if (msg.type === 'create_room') { const room = createRoom(msg.name, player); player.roomId = room.id; broadcast(room, 'room_update', { room: roomSummary(room) }); return; }
       if (msg.type === 'join_room') {
         const code = String(msg.code || '').toUpperCase(); const room = rooms.get(code); if (!room) return send('error', { message: 'Room not found' });
+        // If there's an existing player in this room with the same session, merge to avoid duplicates.
+        let existing = null;
+        for (const p of room.players.values()) { if (p.sessionId && p.sessionId === player.sessionId && p.id !== player.id) { existing = p; break; } }
+        if (existing) {
+          try { if (existing.ws && existing.ws !== ws) { try { existing.ws.terminate(); } catch {} } } catch {}
+          existing.ws = ws; existing.connected = true; existing.roomId = room.id; player = existing;
+        }
         room.players.set(player.id, player); player.roomId = room.id; if (!room.state.ready) room.state.ready = {}; if (room.state.ready[player.id] == null) room.state.ready[player.id] = false;
         const inProgress = room.state.status === 'playing' || room.state.status === 'ended';
         const wasParticipant = isParticipant(room, player.id);
@@ -161,6 +185,7 @@ export function setupWebSocket(server) {
     });
 
     ws.on('close', () => {
+      clearTimeout(helloTimer);
       // Mark player disconnected but keep them in the room for resume
       try {
         if (player) {
@@ -172,7 +197,5 @@ export function setupWebSocket(server) {
         }
       } catch {}
     });
-
-    ws.on('close', () => { player.connected = false; if (player.roomId && rooms.has(player.roomId)) { const room = rooms.get(player.roomId); broadcast(room, 'room_update', { room: roomSummary(room) }); } });
   });
 }