MediaStream.js

'use strict';

import {NativeModules} from 'react-native';
import EventTarget from 'event-target-shim';
import uuid from 'uuid';

import MediaStreamTrack from './MediaStreamTrack';

const {WebRTCModule} = NativeModules;

const MEDIA_STREAM_EVENTS = [
  'active',
  'inactive',
  'addtrack',
  'removetrack',
];

export default class MediaStream extends EventTarget(MEDIA_STREAM_EVENTS) {
  id: string;
  active: boolean = true;

  onactive: ?Function;
  oninactive: ?Function;
  onaddtrack: ?Function;
  onremovetrack: ?Function;

  _tracks: Array<MediaStreamTrack> = [];

  /**
   * The identifier of this MediaStream unique within the associated
   * WebRTCModule instance. As the id of a remote MediaStream instance is unique
   * only within the associated RTCPeerConnection, it is not sufficiently unique
   * to identify this MediaStream across multiple RTCPeerConnections and to
   * unambiguously differentiate it from a local MediaStream instance not added
   * to an RTCPeerConnection.
   */
  _reactTag: string;

  /**
   * A MediaStream can be constructed in several ways, depending on the paramters
   * that are passed here.
   *
   * - undefined: just a new stream, with no tracks.
   * - MediaStream instance: a new stream, with a copy of the tracks of the passed stream.
   * - Array of MediaStreamTrack: a new stream with a copy of the tracks in the array.
   * - object: a new stream instance, represented by the passed info object, this is always
   *   done internally, when the stream is first created in native and the JS wrapper is
   *   built afterwards.
   */
  constructor(arg) {
      super();

      // Assigm a UUID to start with. It may get overridden for remote streams.
      this.id = uuid.v4();
      // Local MediaStreams are created by WebRTCModule to have their id and
      // reactTag equal because WebRTCModule follows the respective standard's
      // recommendation for id generation i.e. uses UUID which is unique enough
      // for the purposes of reactTag.
      this._reactTag = this.id;

      if (typeof arg === 'undefined') {
          WebRTCModule.mediaStreamCreate(this.id);
      } else if (arg instanceof MediaStream) {
          WebRTCModule.mediaStreamCreate(this.id);
          for (const track of arg.getTracks()) {
              this.addTrack(track);
          }
      } else if (Array.isArray(arg)) {
          WebRTCModule.mediaStreamCreate(this.id);
          for (const track of arg) {
              this.addTrack(track);
          }
      } else if (typeof arg === 'object' && arg.streamId && arg.streamReactTag && arg.tracks) {
          this.id = arg.streamId;
          this._reactTag = arg.streamReactTag;
          for (const trackInfo of arg.tracks) {
              // We are not using addTrack here because the track is already part of the
              // stream, so there is no need to add it on the native side.
              this._tracks.push(new MediaStreamTrack(trackInfo));
          }
      } else {
          throw new TypeError(`invalid type: ${typeof arg}`);
      }
  }

  addTrack(track: MediaStreamTrack) {
      const index = this._tracks.indexOf(track);
      if (index !== -1) {
          return;
      }
      this._tracks.push(track);
      WebRTCModule.mediaStreamAddTrack(this._reactTag, track.id);
  }

  removeTrack(track: MediaStreamTrack) {
      const index = this._tracks.indexOf(track);
      if (index === -1) {
        return;
      }
      this._tracks.splice(index, 1);
      WebRTCModule.mediaStreamRemoveTrack(this._reactTag, track.id);
  }

  getTracks(): Array<MediaStreamTrack> {
    return this._tracks.slice();
  }

  getTrackById(trackId): ?MediaStreamTrack {
    return this._tracks.find(track => track.id === trackId);
  }

  getAudioTracks(): Array<MediaStreamTrack> {
    return this._tracks.filter(track => track.kind === 'audio');
  }

  getVideoTracks(): Array<MediaStreamTrack> {
    return this._tracks.filter(track => track.kind === 'video');
  }

  clone() {
    throw new Error('Not implemented.');
  }

  toURL() {
    return this._reactTag;
  }

  release() {
    WebRTCModule.mediaStreamRelease(this._reactTag);
  }
}