MultiRoombaRover/server/src/services/roverSnapshotSocketService.js

const io = require('../globals/io');
const logger = require('../globals/logger').child('roverSnapshotSocket');
const { getMode, MODES } = require('./modeManager');
const { isAdmin, isLockdownAdmin, getRole } = require('./roleService');
const roverManager = require('./roverManager');
const { roverSnapshotEvents, getRoverSnapshotState } = require('./roverSnapshotService');

const SUBSCRIBE_LIMIT = 50;
const SUBSCRIBE_WINDOW_MS = 10000;
const STREAM_INTERVAL_MS = 333;

function passesMode(socket) {
  const mode = getMode();
  if (mode === MODES.LOCKDOWN) {
    return isLockdownAdmin(socket);
  }
  if (mode === MODES.ADMIN) {
    const role = getRole(socket);
    return role === 'spectator' || isAdmin(socket);
  }
  return true;
}

function canViewSnapshots(socket) {
  return passesMode(socket);
}

const roverSubscribers = new Map(); // id -> Set(socketId)
const socketSubscriptions = new Map(); // socketId -> Set(id)
const subscribeBuckets = new Map(); // socketId -> { start, count }
const lastSentBySocket = new Map(); // socketId -> Map(roverId -> ts)

function addSubscription(socket, roverId) {
  if (!roverSubscribers.has(roverId)) {
    roverSubscribers.set(roverId, new Set());
  }
  roverSubscribers.get(roverId).add(socket.id);

  if (!socketSubscriptions.has(socket.id)) {
    socketSubscriptions.set(socket.id, new Set());
  }
  socketSubscriptions.get(socket.id).add(roverId);
}

function removeSubscription(socketId, roverId) {
  const bucket = roverSubscribers.get(roverId);
  if (bucket) {
    bucket.delete(socketId);
    if (bucket.size === 0) {
      roverSubscribers.delete(roverId);
    }
  }
  const socketBucket = socketSubscriptions.get(socketId);
  if (socketBucket) {
    socketBucket.delete(roverId);
    if (socketBucket.size === 0) {
      socketSubscriptions.delete(socketId);
    }
  }
}

function removeAllSubscriptions(socketId) {
  const bucket = socketSubscriptions.get(socketId);
  if (!bucket) return;
  bucket.forEach((roverId) => removeSubscription(socketId, roverId));
}

function allowSubscribe(socketId) {
  const now = Date.now();
  let bucket = subscribeBuckets.get(socketId);
  if (!bucket || now - bucket.start >= SUBSCRIBE_WINDOW_MS) {
    bucket = { start: now, count: 0 };
  }
  bucket.count += 1;
  subscribeBuckets.set(socketId, bucket);
  return bucket.count <= SUBSCRIBE_LIMIT;
}

function sendFrame(socket, roverId, payload, buffer) {
  socket.emit('roverSnapshot:frame', { id: roverId, ...payload }, buffer);
}

function sendStatus(socket, roverId, status) {
  socket.emit('roverSnapshot:status', { id: roverId, ...status });
}

roverSnapshotEvents.on('frame', ({ id, buffer, ts }) => {
  const bucket = roverSubscribers.get(id);
  if (!bucket || !buffer) return;
  bucket.forEach((socketId) => {
    const socket = io.sockets.sockets.get(socketId);
    if (!socket) return;
    let lastMap = lastSentBySocket.get(socketId);
    if (!lastMap) {
      lastMap = new Map();
      lastSentBySocket.set(socketId, lastMap);
    }
    const lastSent = lastMap.get(id) || 0;
    const now = ts || Date.now();
    if (now - lastSent < STREAM_INTERVAL_MS) {
      return;
    }
    lastMap.set(id, now);
    sendFrame(socket, id, { ts }, buffer);
  });
});

roverSnapshotEvents.on('status', ({ id, error }) => {
  const bucket = roverSubscribers.get(id);
  if (!bucket) return;
  bucket.forEach((socketId) => {
    const socket = io.sockets.sockets.get(socketId);
    if (!socket) return;
    sendStatus(socket, id, { error: error || null });
  });
});

io.on('connection', (socket) => {
  socket.on('roverSnapshot:subscribe', (payload = {}, cb = () => {}) => {
    const list = Array.isArray(payload?.ids)
      ? payload.ids.map(String)
      : payload?.roverId || payload?.id
      ? [String(payload.roverId || payload.id)]
      : roverManager.getRoster().map((rover) => rover.id);
    const uniqueIds = Array.from(new Set(list));
    try {
      if (!allowSubscribe(socket.id)) {
        cb({ error: 'Rate limited' });
        return;
      }
      if (!canViewSnapshots(socket)) {
        throw new Error('Not authorized for rover snapshots');
      }
      const rosterIds = new Set(roverManager.getRoster().map((entry) => String(entry.id)));
      const validIds = uniqueIds.filter((id) => rosterIds.has(String(id)));
      validIds.forEach((roverId) => addSubscription(socket, roverId));
      validIds.forEach((roverId) => {
        const state = getRoverSnapshotState(roverId);
        if (state?.frame) {
          sendFrame(socket, roverId, { ts: state.ts }, state.frame);
        }
        sendStatus(socket, roverId, {
          ts: state?.ts || null,
          error: state?.error || null,
        });
      });
      cb({ ok: true, subscribed: validIds });
    } catch (err) {
      logger.warn('Rover snapshot subscribe failed', { socketId: socket.id, err: err.message });
      cb({ error: err.message });
    }
  });

  socket.on('roverSnapshot:unsubscribe', (payload = {}) => {
    const list = Array.isArray(payload?.ids)
      ? payload.ids.map(String)
      : payload?.roverId || payload?.id
      ? [String(payload.roverId || payload.id)]
      : [];
    list.forEach((roverId) => removeSubscription(socket.id, roverId));
  });

  socket.on('disconnect', () => {
    removeAllSubscriptions(socket.id);
    subscribeBuckets.delete(socket.id);
    lastSentBySocket.delete(socket.id);
  });
});