const connection = new RTCPeerConnection({ iceServers: [{ urls: 'stun:stun.l.google.com:19302' }] });

connection.onicecandidate = (e) => {
  if (e.candidate) {
    localStorage.setItem('candidate', JSON.stringify(e.candidate));
  }
};

connection.oniceconnectionstatechange = (e) => {
  console.log(connection.iceConnectionState);
}

const channel = connection.createDataChannel('chat', { negociated: true, id: 'very secret' });
channel.onmessage = ({ data }) => console.log(data);

window.sendMessage = (message) => {
  channel.send(message)
}

async function createOffer() {
  const offer = await connection.createOffer();
  connection.setLocalDescription(offer)
  localStorage.setItem('offer', JSON.stringify(offer));
}

async function createAnswer(offer) {
  connection.setRemoteDescription(
    new RTCSessionDescription(offer)
  );

  const answer = await connection.createAnswer();
  connection.setLocalDescription(answer)
  localStorage.setItem('answer', JSON.stringify(answer))
}

async function acceptAnswer(answer) {
  connection.setRemoteDescription(new RTCSessionDescription(answer));
};

window.addEventListener('storage', ({ key, newValue }) => {
  switch(key) {
    case 'offer':
      createAnswer(JSON.parse(newValue));
      break;
    case 'answer':
      acceptAnswer(JSON.parse(newValue));
      break;
    case 'candidate':
      connection.addIceCandidate(JSON.parse(newValue));
      break;
  }
});