class VideoRTC extends HTMLElement {
  constructor() {
    super();

    this.DISCONNECT_TIMEOUT = 5000;
    this.RECONNECT_TIMEOUT = 30000;

    this.CODECS = [
      'avc1.640029', // H.264 high 4.1 (Chromecast 1st and 2nd Gen)
      'avc1.64002A', // H.264 high 4.2 (Chromecast 3rd Gen)
      'avc1.640033', // H.264 high 5.1 (Chromecast with Google TV)
      'hvc1.1.6.L153.B0', // H.265 main 5.1 (Chromecast Ultra)
      'mp4a.40.2', // AAC LC
      'mp4a.40.5', // AAC HE
      'flac', // FLAC (PCM compatible)
      'opus', // OPUS Chrome, Firefox
    ];

    /**
     * [config] Supported modes (webrtc, mse, mp4, mjpeg).
     * @type {string}
     */
    this.mode = 'webrtc,mse,mp4,mjpeg';

    /**
     * [config] Run stream when not displayed on the screen. Default `false`.
     * @type {boolean}
     */
    this.background = false;

    /**
     * [config] Run stream only when player in the viewport. Stop when user scroll out player.
     * Value is percentage of visibility from `0` (not visible) to `1` (full visible).
     * Default `0` - disable;
     * @type {number}
     */
    this.visibilityThreshold = 0;

    /**
     * [config] Run stream only when browser page on the screen. Stop when user change browser
     * tab or minimise browser windows.
     * @type {boolean}
     */
    this.visibilityCheck = true;

    /**
     * [config] WebRTC configuration
     * @type {RTCConfiguration}
     */
    this.pcConfig = {
      iceServers: [{ urls: 'stun:stun.l.google.com:19302' }],
      sdpSemantics: 'unified-plan', // important for Chromecast 1
    };

    /**
     * [info] WebSocket connection state. Values: CONNECTING, OPEN, CLOSED
     * @type {number}
     */
    this.wsState = WebSocket.CLOSED;

    /**
     * [info] WebRTC connection state.
     * @type {number}
     */
    this.pcState = WebSocket.CLOSED;

    /**
     * @type {HTMLVideoElement}
     */
    this.video = null;

    /**
     * @type {WebSocket}
     */
    this.ws = null;

    /**
     * @type {string|URL}
     */
    this.wsURL = '';

    /**
     * @type {RTCPeerConnection}
     */
    this.pc = null;

    /**
     * @type {number}
     */
    this.connectTS = 0;

    /**
     * @type {string}
     */
    this.mseCodecs = '';

    /**
     * [internal] Disconnect TimeoutID.
     * @type {number}
     */
    this.disconnectTID = 0;

    /**
     * [internal] Reconnect TimeoutID.
     * @type {number}
     */
    this.reconnectTID = 0;

    /**
     * [internal] Handler for receiving Binary from WebSocket.
     * @type {Function}
     */
    this.ondata = null;

    /**
     * [internal] Handlers list for receiving JSON from WebSocket
     * @type {Object.<string,Function>}}
     */
    this.onmessage = null;
  }

  /**
   * Set video source (WebSocket URL). Support relative path.
   * @param {string|URL} value
   */
  set src(value) {
    if (typeof value !== 'string') value = value.toString();
    if (value.startsWith('http')) {
      value = `ws${value.substring(4)}`;
    } else if (value.startsWith('/')) {
      value = `ws${location.origin.substring(4)}${value}`;
    }

    this.wsURL = value;

    this.onconnect();
  }

  /**
   * Play video. Support automute when autoplay blocked.
   * https://developer.chrome.com/blog/autoplay/
   */
  play() {
    this.video.play().catch((er) => {
      if (er.name === 'NotAllowedError' && !this.video.muted) {
        this.video.muted = true;
        this.video.play().catch(() => { });
      }
    });
  }

  /**
   * Send message to server via WebSocket
   * @param {Object} value
   */
  send(value) {
    if (this.ws) this.ws.send(JSON.stringify(value));
  }

  codecs(type) {
    const test =
      type === 'mse'
        ? (codec) => MediaSource.isTypeSupported(`video/mp4; codecs="${codec}"`)
        : (codec) => this.video.canPlayType(`video/mp4; codecs="${codec}"`);
    return this.CODECS.filter(test).join();
  }

  /**
   * `CustomElement`. Invoked each time the custom element is appended into a
   * document-connected element.
   */
  connectedCallback() {
    if (this.disconnectTID) {
      clearTimeout(this.disconnectTID);
      this.disconnectTID = 0;
    }

    // because video autopause on disconnected from DOM
    if (this.video) {
      const seek = this.video.seekable;
      if (seek.length > 0) {
        this.video.currentTime = seek.end(seek.length - 1);
      }
      this.play();
    } else {
      this.oninit();
    }

    this.onconnect();
  }

  /**
   * `CustomElement`. Invoked each time the custom element is disconnected from the
   * document's DOM.
   */
  disconnectedCallback() {
    if (this.background || this.disconnectTID) return;
    if (this.wsState === WebSocket.CLOSED && this.pcState === WebSocket.CLOSED) return;

    this.disconnectTID = setTimeout(() => {
      if (this.reconnectTID) {
        clearTimeout(this.reconnectTID);
        this.reconnectTID = 0;
      }

      this.disconnectTID = 0;

      this.ondisconnect();
    }, this.DISCONNECT_TIMEOUT);
  }

  /**
   * Creates child DOM elements. Called automatically once on `connectedCallback`.
   */
  oninit() {
    this.video = document.createElement('video');
    this.video.controls = true;
    this.video.playsInline = true;
    this.video.preload = 'auto';

    this.video.style.display = 'block'; // fix bottom margin 4px
    this.video.style.width = '100%';
    this.video.style.height = '100%';

    this.appendChild(this.video);

    if (this.background) return;

    if ('hidden' in document && this.visibilityCheck) {
      document.addEventListener('visibilitychange', () => {
        if (document.hidden) {
          this.disconnectedCallback();
        } else if (this.isConnected) {
          this.connectedCallback();
        }
      });
    }

    if ('IntersectionObserver' in window && this.visibilityThreshold) {
      const observer = new IntersectionObserver(
        (entries) => {
          entries.forEach((entry) => {
            if (!entry.isIntersecting) {
              this.disconnectedCallback();
            } else if (this.isConnected) {
              this.connectedCallback();
            }
          });
        },
        { threshold: this.visibilityThreshold }
      );
      observer.observe(this);
    }
  }

  /**
   * Connect to WebSocket. Called automatically on `connectedCallback`.
   * @return {boolean} true if the connection has started.
   */
  onconnect() {
    if (!this.isConnected || !this.wsURL || this.ws || this.pc) return false;

    // CLOSED or CONNECTING => CONNECTING
    this.wsState = WebSocket.CONNECTING;

    this.connectTS = Date.now();

    this.ws = new WebSocket(this.wsURL);
    this.ws.binaryType = 'arraybuffer';
    this.ws.addEventListener('open', (ev) => this.onopen(ev));
    this.ws.addEventListener('close', (ev) => this.onclose(ev));

    return true;
  }

  ondisconnect() {
    this.wsState = WebSocket.CLOSED;
    if (this.ws) {
      this.ws.close();
      this.ws = null;
    }

    this.pcState = WebSocket.CLOSED;
    if (this.pc) {
      this.pc.close();
      this.pc = null;
    }
  }

  /**
   * @returns {Array.<string>} of modes (mse, webrtc, etc.)
   */
  onopen() {
    // CONNECTING => OPEN
    this.wsState = WebSocket.OPEN;

    this.ws.addEventListener('message', (ev) => {
      if (typeof ev.data === 'string') {
        const msg = JSON.parse(ev.data);
        for (const mode in this.onmessage) {
          this.onmessage[mode](msg);
        }
      } else {
        this.ondata(ev.data);
      }
    });

    this.ondata = null;
    this.onmessage = {};

    const modes = [];

    if (this.mode.indexOf('mse') >= 0 && 'MediaSource' in window) {
      // iPhone
      modes.push('mse');
      this.onmse();
    } else if (this.mode.indexOf('mp4') >= 0) {
      modes.push('mp4');
      this.onmp4();
    }

    if (this.mode.indexOf('webrtc') >= 0 && 'RTCPeerConnection' in window) {
      // macOS Desktop app
      modes.push('webrtc');
      this.onwebrtc();
    }

    if (this.mode.indexOf('mjpeg') >= 0) {
      if (modes.length) {
        this.onmessage['mjpeg'] = (msg) => {
          if (msg.type !== 'error' || msg.value.indexOf(modes[0]) !== 0) return;
          this.onmjpeg();
        };
      } else {
        modes.push('mjpeg');
        this.onmjpeg();
      }
    }

    return modes;
  }

  /**
   * @return {boolean} true if reconnection has started.
   */
  onclose() {
    if (this.wsState === WebSocket.CLOSED) return false;

    // CONNECTING, OPEN => CONNECTING
    this.wsState = WebSocket.CONNECTING;
    this.ws = null;

    // reconnect no more than once every X seconds
    const delay = Math.max(this.RECONNECT_TIMEOUT - (Date.now() - this.connectTS), 0);

    this.reconnectTID = setTimeout(() => {
      this.reconnectTID = 0;
      this.onconnect();
    }, delay);

    return true;
  }

  onmse() {
    const ms = new MediaSource();
    ms.addEventListener(
      'sourceopen',
      () => {
        URL.revokeObjectURL(this.video.src);
        this.send({ type: 'mse', value: this.codecs('mse') });
      },
      { once: true }
    );

    this.video.src = URL.createObjectURL(ms);
    this.video.srcObject = null;
    this.play();

    this.mseCodecs = '';

    this.onmessage['mse'] = (msg) => {
      if (msg.type !== 'mse') return;

      this.mseCodecs = msg.value;

      const sb = ms.addSourceBuffer(msg.value);
      sb.mode = 'segments'; // segments or sequence
      sb.addEventListener('updateend', () => {
        if (sb.updating) return;

        try {
          if (bufLen > 0) {
            const data = buf.slice(0, bufLen);
            bufLen = 0;
            sb.appendBuffer(data);
          } else if (sb.buffered && sb.buffered.length) {
            const end = sb.buffered.end(sb.buffered.length - 1) - 15;
            const start = sb.buffered.start(0);
            if (end > start) {
              sb.remove(start, end);
              ms.setLiveSeekableRange(end, end + 15);
            }
            // console.debug("VideoRTC.buffered", start, end);
          }
        } catch (e) {
          // console.debug(e);
        }
      });

      const buf = new Uint8Array(2 * 1024 * 1024);
      let bufLen = 0;

      this.ondata = (data) => {
        if (sb.updating || bufLen > 0) {
          const b = new Uint8Array(data);
          buf.set(b, bufLen);
          bufLen += b.byteLength;
          // console.debug("VideoRTC.buffer", b.byteLength, bufLen);
        } else {
          try {
            sb.appendBuffer(data);
          } catch (e) {
            // console.debug(e);
          }
        }
      };
    };
  }

  onwebrtc() {
    const pc = new RTCPeerConnection(this.pcConfig);

    /** @type {HTMLVideoElement} */
    const video2 = document.createElement('video');
    video2.addEventListener('loadeddata', (ev) => this.onpcvideo(ev), { once: true });

    pc.addEventListener('icecandidate', (ev) => {
      const candidate = ev.candidate ? ev.candidate.toJSON().candidate : '';
      this.send({ type: 'webrtc/candidate', value: candidate });
    });

    pc.addEventListener('track', (ev) => {
      // when stream already init
      if (video2.srcObject !== null) return;

      // when audio track not exist in Chrome
      if (ev.streams.length === 0) return;

      // when audio track not exist in Firefox
      if (ev.streams[0].id[0] === '{') return;

      video2.srcObject = ev.streams[0];
    });

    pc.addEventListener('connectionstatechange', () => {
      if (pc.connectionState === 'failed' || pc.connectionState === 'disconnected') {
        pc.close(); // stop next events

        this.pcState = WebSocket.CLOSED;
        this.pc = null;

        this.onconnect();
      }
    });

    this.onmessage['webrtc'] = (msg) => {
      switch (msg.type) {
        case 'webrtc/candidate':
          pc.addIceCandidate({
            candidate: msg.value,
            sdpMid: '0',
          }).catch(() => { });
          break;
        case 'webrtc/answer':
          pc.setRemoteDescription({
            type: 'answer',
            sdp: msg.value,
          }).catch(() => { });
          break;
        case 'error':
          if (msg.value.indexOf('webrtc/offer') < 0) return;
          pc.close();
      }
    };

    // Safari doesn't support "offerToReceiveVideo"
    pc.addTransceiver('video', { direction: 'recvonly' });
    pc.addTransceiver('audio', { direction: 'recvonly' });

    pc.createOffer().then((offer) => {
      pc.setLocalDescription(offer).then(() => {
        this.send({ type: 'webrtc/offer', value: offer.sdp });
      });
    });

    this.pcState = WebSocket.CONNECTING;
    this.pc = pc;
  }

  /**
   * @param ev {Event}
   */
  onpcvideo(ev) {
    if (!this.pc) return;

    /** @type {HTMLVideoElement} */
    const video2 = ev.target;
    const state = this.pc.connectionState;

    // Firefox doesn't support pc.connectionState
    if (state === 'connected' || state === 'connecting' || !state) {
      // Video+Audio > Video, H265 > H264, Video > Audio, WebRTC > MSE
      let rtcPriority = 0,
        msePriority = 0;

      /** @type {MediaStream} */
      const ms = video2.srcObject;
      if (ms.getVideoTracks().length > 0) rtcPriority += 0x220;
      if (ms.getAudioTracks().length > 0) rtcPriority += 0x102;

      if (this.mseCodecs.indexOf('hvc1.') >= 0) msePriority += 0x230;
      if (this.mseCodecs.indexOf('avc1.') >= 0) msePriority += 0x210;
      if (this.mseCodecs.indexOf('mp4a.') >= 0) msePriority += 0x101;

      if (rtcPriority >= msePriority) {
        this.video.srcObject = ms;
        this.play();

        this.pcState = WebSocket.OPEN;

        this.wsState = WebSocket.CLOSED;
        this.ws.close();
        this.ws = null;
      } else {
        this.pcState = WebSocket.CLOSED;
        this.pc.close();
        this.pc = null;
      }
    }

    video2.srcObject = null;
  }

  onmjpeg() {
    this.ondata = (data) => {
      this.video.controls = false;
      this.video.poster = `data:image/jpeg;base64,${VideoRTC.btoa(data)}`;
    };

    this.send({ type: 'mjpeg' });
  }

  onmp4() {
    /** @type {HTMLCanvasElement} **/
    const canvas = document.createElement('canvas');
    /** @type {CanvasRenderingContext2D} */
    let context;

    /** @type {HTMLVideoElement} */
    const video2 = document.createElement('video');
    video2.autoplay = true;
    video2.playsInline = true;
    video2.muted = true;

    video2.addEventListener('loadeddata', (_) => {
      if (!context) {
        canvas.width = video2.videoWidth;
        canvas.height = video2.videoHeight;
        context = canvas.getContext('2d');
      }

      context.drawImage(video2, 0, 0, canvas.width, canvas.height);

      this.video.controls = false;
      this.video.poster = canvas.toDataURL('image/jpeg');
    });

    this.ondata = (data) => {
      video2.src = `data:video/mp4;base64,${VideoRTC.btoa(data)}`;
    };

    this.send({ type: 'mp4', value: this.codecs('mp4') });
  }

  static btoa(buffer) {
    const bytes = new Uint8Array(buffer);
    const len = bytes.byteLength;
    let binary = '';
    for (let i = 0; i < len; i++) {
      binary += String.fromCharCode(bytes[i]);
    }
    return window.btoa(binary);
  }
}

class VideoStream extends VideoRTC {


  /**
   * Custom GUI
   */
  oninit() {
    super.oninit();
    const info = this.querySelector('.info');
    this.insertBefore(this.video, info);
  }

  onconnect() {
    const result = super.onconnect();
    if (result) this.divMode = 'loading';
    return result;
  }

  ondisconnect() {;
    super.ondisconnect();
  }

  onopen() {
    const result = super.onopen();

    this.onmessage['stream'] = (_) => {
    };

    return result;
  }

  onclose() {
    return super.onclose();
  }

  onpcvideo(ev) {
    super.onpcvideo(ev);

    if (this.pcState !== WebSocket.CLOSED) {
      this.divMode = 'RTC';
    }
  }
}

customElements.define('video-stream', VideoStream);