var pc = null;
function negotiate() {
    pc.addTransceiver('video', { direction: 'recvonly' });
    return pc.createOffer().then((offer) => {
        return pc.setLocalDescription(offer);
    }).then(() => {
        // wait for ICE gathering to complete
        return new Promise((resolve) => {
            if (pc.iceGatheringState === 'complete') {
                resolve();
            } else {
                const checkState = () => {
                    if (pc.iceGatheringState === 'complete') {
                        pc.removeEventListener('icegatheringstatechange', checkState);
                        resolve();
                    }
                };
                pc.addEventListener('icegatheringstatechange', checkState);
            }
        });
    }).then(() => {
        var offer = pc.localDescription;
        return fetch('/api/offer', {
            body: JSON.stringify({
                sdp: offer.sdp,
                type: offer.type,
            }),
            headers: {
                'Content-Type': 'application/json'
            },
            method: 'POST'
        });
    }).then((response) => {
        return response.json();
    }).then((answer) => {
        return pc.setRemoteDescription(answer);
    }).catch((e) => {
        alert(e);
    });
}

function start() {
    console.log('开始执行！');
    var config = {
        sdpSemantics: 'unified-plan'
    };
    //config.iceServers = [{ urls: ['stun:stun.voiparound.com'] }];
    pc = new RTCPeerConnection();
    pc.addEventListener('track', (evt) => {
        if (evt.track.kind == 'video') {
            //document.getElementById('video').srcObject = evt.streams[0];
            document.getElementById('u33_video').srcObject = evt.streams[0];
        }
    });
    negotiate();
}

function showView(){
    console.log('status:',document.getElementById('u33_video').paused)
    if (document.getElementById('u33_video').paused) {
        document.getElementById('u33_video').play().catch(error => {
            console.error('Error playing video:', error);
        });
    }
}

function getChannellist(){

}