var pc = null;

function negotiate() {
    pc.addTransceiver('video', { direction: 'recvonly' });
    pc.addTransceiver('audio', { direction: 'recvonly' });
    return pc.createOffer().then((offer) => {
        console.log('Created offer: type=' + offer.type + ', sdp_length=' + offer.sdp.length);
        return pc.setLocalDescription(offer).then(() => {
            console.log('Set local description complete, iceGatheringState=' + pc.iceGatheringState);
        });
    }).then(() => {
        // wait for ICE gathering to complete
        return new Promise((resolve, reject) => {
            if (pc.iceGatheringState === 'complete') {
                console.log('ICE gathering already complete');
                resolve();
            } else {
                const checkState = () => {
                    if (pc.iceGatheringState === 'complete') {
                        pc.removeEventListener('icegatheringstatechange', checkState);
                        console.log('ICE gathering complete');
                        resolve();
                    }
                };
                pc.addEventListener('icegatheringstatechange', checkState);
                
                // 5秒超时
                setTimeout(() => {
                    pc.removeEventListener('icegatheringstatechange', checkState);
                    resolve(); // 继续执行，即使 ICE 汇集未完成
                }, 5000);
            }
        });
    }).then(() => {
        var offer = pc.localDescription;
        console.log('Sending offer: type=' + offer.type + ', sdp_length=' + offer.sdp.length);
        return fetch('/offer', {
            body: JSON.stringify({
                sdp: offer.sdp,
                type: offer.type,
            }),
            headers: {
                'Content-Type': 'application/json'
            },
            method: 'POST'
        }).then((response) => {
            console.log('Received response status:', response.status);
            return response;
        });
    }).then((response) => {
        if (!response.ok) {
            throw new Error('服务器返回错误: ' + response.status);
        }
        return response.json();
    }).then((answer) => {
        console.log('Received answer: type=' + answer.type + ', sdp_length=' + answer.sdp.length);
        document.getElementById('sessionid').value = answer.sessionid
        return pc.setRemoteDescription(answer).then(() => {
            console.log('Successfully set remote description');
        });
    }).catch((e) => {
        console.error('Error in negotiate:', e);
        let errorMsg = '连接失败: ';
        if (e.name === 'InvalidStateError') {
            errorMsg += '连接状态异常，请刷新页面后重试';
        } else if (e.name === 'SyntaxError') {
            errorMsg += '服务器响应格式错误，请检查服务器状态';
        } else if (e.message && e.message.includes('state')) {
            errorMsg += '连接状态错误，请刷新页面后重试';
        } else if (e.message && e.message.includes('服务器返回错误')) {
            errorMsg += e.message + '，请检查后端日志';
        } else {
            errorMsg += e.message || e.toString();
        }
        alert(errorMsg);
    });
}

function start() {
    var config = {
        sdpSemantics: 'unified-plan'
    };

    // 使用多个 STUN 服务器（提高连接成功率）
    config.iceServers = [
        { urls: ['stun:stun.l.google.com:19302'] },
        { urls: ['stun:stun1.l.google.com:19302'] },
        { urls: ['stun:stun.services.mozilla.com'] },
        { urls: ['stun:stun.voip.blackberry.com:3478'] }
    ];

    pc = new RTCPeerConnection(config);

    // 添加连接状态日志
    pc.addEventListener('connectionstatechange', function() {
        console.log('PeerConnection state:', pc.connectionState);
        // 将日志发送到后端
        fetch('/log', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ type: 'webrtc', message: 'PeerConnection state: ' + pc.connectionState })
        }).catch(() => {});
        
        // 连接成功时的提示
        if (pc.connectionState === 'connected') {
            console.log('✅ WebRTC connection established successfully!');
            document.getElementById('startBtn').style.display = 'none';
            document.getElementById('stopBtn').style.display = 'inline-block';
        } else if (pc.connectionState === 'failed') {
            console.error('❌ WebRTC connection failed!');
            alert('WebRTC 连接失败，请检查网络连接或刷新页面重试');
        }
    });
    
    pc.addEventListener('iceconnectionstatechange', function() {
        console.log('ICE connection state:', pc.iceConnectionState);
        fetch('/log', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ type: 'webrtc', message: 'ICE connection state: ' + pc.iceConnectionState })
        }).catch(() => {});
            
        // ICE 连接超时处理
        if (pc.iceConnectionState === 'disconnected') {
            console.warn('⚠️ ICE disconnected, attempting to reconnect...');
        } else if (pc.iceConnectionState === 'failed') {
            console.error('❌ ICE connection failed!');
            alert('ICE 连接失败，可能是网络防火墙阻止了 WebRTC 连接');
        }
    });
    
    pc.addEventListener('icegatheringstatechange', function() {
        console.log('ICE gathering state:', pc.iceGatheringState);
        fetch('/log', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ type: 'webrtc', message: 'ICE gathering state: ' + pc.iceGatheringState })
        }).catch(() => {});
    });

    // 收集 ICE 候选
    pc.addEventListener('icecandidate', function(event) {
        if (event.candidate) {
            console.log('ICE candidate:', event.candidate.candidate);
            fetch('/log', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ type: 'webrtc', message: 'ICE candidate: ' + event.candidate.candidate })
            }).catch(() => {});
        } else {
            console.log('ICE gathering complete');
            fetch('/log', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ type: 'webrtc', message: 'ICE gathering complete' })
            }).catch(() => {});
        }
    });

    // connect audio / video
    pc.addEventListener('track', (evt) => {
        if (evt.track.kind == 'video') {
            const video = document.getElementById('video');
            if (video) {
                video.srcObject = evt.streams[0];
                console.log('Video track attached successfully');
            } else {
                console.error('Video element not found in DOM');
            }
        } else if (evt.track.kind == 'audio') {
            const audio = document.getElementById('audio');
            if (audio) {
                audio.srcObject = evt.streams[0];
                console.log('Audio track attached successfully');
                // 尝试播放音频（处理浏览器自动播放策略）
                audio.play().catch(e => {
                    console.warn('Auto-play was prevented, user interaction needed:', e);
                });
            } else {
                console.warn('Audio element not found in DOM, but continuing with video only');
            }
        }
    });

    document.getElementById('startBtn').style.display = 'none';
    negotiate();
    document.getElementById('stopBtn').style.display = 'inline-block';
}

function stop() {
    document.getElementById('stopBtn').style.display = 'none';

    // close peer connection
    setTimeout(() => {
        pc.close();
    }, 500);
}

window.onunload = function(event) {
    // 在这里执行你想要的操作
    setTimeout(() => {
        pc.close();
    }, 500);
};

window.onbeforeunload = function (e) {
        setTimeout(() => {
                pc.close();
            }, 500);
        e = e || window.event
        // 兼容IE8和Firefox 4之前的版本
        if (e) {
          e.returnValue = '关闭提示'
        }
        // Chrome, Safari, Firefox 4+, Opera 12+ , IE 9+
        return '关闭提示'
      }