let peerConnection = new RTCPeerConnection({ "iceServers": [{ "urls": "stun:stun.l.google.com:19302" }] }),
    ws = new WebSocket((window.location.protocol === "https:" ? "wss://" : "ws://") + window.location.host + '/video/connections' + window.location.search);

navigator.mediaDevices.getUserMedia({ video: true, audio: true }).then(stream => {
    let element = document.getElementById('local_video');
    element.srcObject = stream;
    element.play().then(() => {
        stream.getTracks().forEach(track => peerConnection.addTrack(track, stream));
        peerConnection.onnegotiationneeded = () => {
            peerConnection.createOffer().then(offer => {
                return peerConnection.setLocalDescription(offer);
            }).then(() => {
                ws.send(JSON.stringify(peerConnection.localDescription));
            });
        }
    });
});

peerConnection.ontrack = evt => {
    let element = document.getElementById('remote_video');
    if (element.srcObject === evt.streams[0]) return;
    element.srcObject = evt.streams[0];
    element.play();
};

peerConnection.onicecandidate = evt => {
    if (evt.candidate) ws.send(JSON.stringify({ type: 'candidate', ice: evt.candidate }));
};

ws.onmessage = (evt) => {
    const message = JSON.parse(evt.data);
    switch (message.type) {
        case 'offer': {
            peerConnection.setRemoteDescription(message).then(() => {
                return peerConnection.createAnswer()
            }).then(answer => {
                return peerConnection.setLocalDescription(answer)
            }).then(() => {
                ws.send(JSON.stringify(peerConnection.localDescription));
            });
            break;
        }
        case 'answer': {
            peerConnection.setRemoteDescription(message);
            break;
        }
        case 'candidate': {
            peerConnection.addIceCandidate(new RTCIceCandidate(message.ice));
            break;
        }
    }
};