back-end

io.on('connection', (socket) => {
  socket.on('up_ice', (candidate: RTCIceCandidate) => {
    const peer = upPeers.get(socket.id);
    if (peer) peer.pc.addIceCandidate(new webrtc.RTCIceCandidate(candidate));
  });

  socket.on('up', async (offer: RTCDataChannelInit, callback) => {
    console.log('[UP] peer joined', socket.id);

    const peer = upPeers
      .set(socket.id, { id: socket.id, pc: createPeerConnection() })
      .get(socket.id);
    if (!peer) return;

    peer.pc.ontrack = (event: RTCTrackEvent) => {
      if (event.streams && event.streams[0]) {
        peer.stream = event.streams[0];
        socket.broadcast.emit('newUp', peer.id);
      }
    };

    await peer.pc.setRemoteDescription(new webrtc.RTCSessionDescription(offer));
    const answer = await peer.pc.createAnswer();
    await peer.pc.setLocalDescription(answer);

    callback({
      upPeers: Array.from(upPeers.values()),
      answer: {
        sdp: answer.sdp,
        type: answer.type,
      },
    });
  });

  socket.on('down_ice', ({ consumerId, candidate }) => {
    const consumer = downPeers.get(consumerId);
    if (!!consumer)
      consumer.addIceCandidate(new webrtc.RTCIceCandidate(candidate));
  });

  socket.on('down', async ({ id, offer, consumerId }, callback) => {
    console.log('[DOWN] peer joined', socket.id);
    const consumer = downPeers
      .set(consumerId, createPeerConnection())
      .get(consumerId);
    if (!consumer) return;

    await consumer.setRemoteDescription(
      new webrtc.RTCSessionDescription(offer),
    );

    const peer = upPeers.get(id);
    if (!peer?.stream) return;

    const remoteStream = peer.stream;
    remoteStream.getTracks().forEach((track) => {
      consumer.addTrack(track, remoteStream);
    });

    const answer = await consumer.createAnswer();
    await consumer.setLocalDescription(answer);

    callback(answer);
  });

  socket.on('disconnect', () => {
    console.log('user disconnected', socket.id);

    upPeers.delete(socket.id);
    downPeers.delete(socket.id);

    socket.broadcast.emit('producerLeft', socket.id);
  });
});