Show authenticated unique online player count on home screen

tests/presence.test.ts

@@ -0,0 +1,35 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { createServer } from 'node:http';
+import { Server } from 'socket.io';
+import { io as client, type Socket } from 'socket.io-client';
+import { registerPresence } from '../src/server/presence.js';
+import type { GameSessionStore } from '../src/server/game-session-store.js';
+
+test('presence counts authenticated players once across tabs and removes disconnected players', async () => {
+  const http = createServer(), io = new Server(http);
+  registerPresence(io, { async get(auth: { token: string; gameSessionId: string }) {
+    if (auth.token !== 'valid') throw new Error('INVALID_SESSION');
+    return { playerId: auth.gameSessionId.startsWith('a') ? 'a' : 'b' };
+  } } as unknown as GameSessionStore);
+  await new Promise<void>(resolve => http.listen(0, '127.0.0.1', resolve));
+  const url = `http://127.0.0.1:${(http.address() as { port: number }).port}/presence`;
+  const sockets: Socket[] = [];
+  const open = (id: string, token = 'valid') => {
+    const socket = client(url, { autoConnect: false, forceNew: true, auth: { gameSessionId: id, token }, reconnection: false });
+    sockets.push(socket); return socket;
+  };
+  const next = (socket: Socket) => new Promise<number>((resolve, reject) => {
+    const timer = setTimeout(() => reject(new Error('PRESENCE_TIMEOUT')), 3000);
+    socket.once('presence:count', n => { clearTimeout(timer); resolve(n); });
+  });
+  try {
+    const a = open('a1'), aFirst = next(a); a.connect(); assert.equal(await aFirst, 1);
+    const secondTab = open('a2'), tabFirst = next(secondTab); secondTab.connect(); assert.equal(await tabFirst, 1);
+    const b = open('b1'), bFirst = next(b), aUpdate = next(a); b.connect();
+    assert.equal(await bFirst, 2); assert.equal(await aUpdate, 2);
+    const bad = open('bad', 'invalid');
+    const rejected = new Promise<void>(resolve => bad.once('connect_error', () => resolve())); bad.connect(); await rejected;
+    const lastA = next(secondTab); a.disconnect(); b.disconnect(); assert.equal(await lastA, 1);
+  } finally { for (const socket of sockets) socket.disconnect(); await new Promise<void>(resolve => io.close(() => resolve())); }
+});