import type { Server } from 'socket.io';
import { ApiError, type GameSessionStore } from './game-session-store.js';
import { PRESENCE_AUTH_REFRESH_MS } from '../../constants/presence.js';

// The application is deployed as one process, as is the ranked match service.
export function registerPresence(io: Server, sessions: GameSessionStore) {
  const namespace = io.of('/presence');
  let count = 0;
  function publish() {
    const next = new Set([...namespace.sockets.values()].filter(socket => socket.connected).map(socket => socket.data.playerId)).size;
    if (next !== count) { count = next; namespace.emit('presence:count', count); }
  }
  namespace.use((socket, next) => {
    const { gameSessionId, token } = socket.handshake.auth;
    void sessions.touchPresence({ gameSessionId, token }).then(session => {
      socket.data.playerId = session.playerId ?? session.gameSessionId;
      next();
    }, error => next(new Error(error instanceof ApiError && error.statusCode === 401 ? 'INVALID_SESSION' : 'PRESENCE_UNAVAILABLE')));
  });
  namespace.on('connection', socket => {
    const before = count; publish();
    if (before === count) socket.emit('presence:count', count);
    let checking = false;
    const timer = setInterval(() => {
      if (checking) return;
      checking = true;
      const { gameSessionId, token } = socket.handshake.auth;
      void sessions.touchPresence({ gameSessionId, token }).catch(error => {
        if (error instanceof ApiError && error.statusCode === 401) socket.disconnect(true);
        else socket.conn.close(); // Transport closure permits Socket.IO to reconnect after a transient outage.
      }).finally(() => { checking = false; });
    }, PRESENCE_AUTH_REFRESH_MS);
    timer.unref();
    socket.on('disconnect', () => { clearInterval(timer); publish(); });
  });
}