ljm_j1/modules/RTC/JitsiTrack.js

/* global __filename, module */
import EventEmitter from 'events';
import { getLogger } from 'jitsi-meet-logger';
import * as JitsiTrackEvents from '../../JitsiTrackEvents';
import * as MediaType from '../../service/RTC/MediaType';
import RTCBrowserType from './RTCBrowserType';
import RTCUtils from './RTCUtils';

const logger = getLogger(__filename);

/**
 * Maps our handler types to MediaStreamTrack properties.
 */
const trackHandler2Prop = {
    'track_mute': 'onmute', // Not supported on FF
    'track_unmute': 'onunmute',
    'track_ended': 'onended'
};

/**
 * This implements 'onended' callback normally fired by WebRTC after the stream
 * is stopped. There is no such behaviour yet in FF, so we have to add it.
 * @param jitsiTrack our track object holding the original WebRTC stream object
 * to which 'onended' handling will be added.
 */
function implementOnEndedHandling(jitsiTrack) {
    const stream = jitsiTrack.getOriginalStream();

    if (!stream) {
        return;
    }

    const originalStop = stream.stop;

    stream.stop = function() {
        originalStop.apply(stream);
        if (jitsiTrack.isActive()) {
            stream.onended();
        }
    };
}

/**
 * Adds onended/oninactive handler to a MediaStream.
 * @param mediaStream a MediaStream to attach onended/oninactive handler
 * @param handler the handler
 */
function addMediaStreamInactiveHandler(mediaStream, handler) {
    // Temasys will use onended
    if (typeof mediaStream.active === 'undefined') {
        mediaStream.onended = handler;
    } else {
        mediaStream.oninactive = handler;
    }
}

/**
 * Represents a single media track (either audio or video).
 */
export default class JitsiTrack extends EventEmitter {
    /* eslint-disable max-params */
    /**
     * Represents a single media track (either audio or video).
     * @constructor
     * @param conference the rtc instance
     * @param stream the WebRTC MediaStream instance
     * @param track the WebRTC MediaStreamTrack instance, must be part of
     * the given <tt>stream</tt>.
     * @param streamInactiveHandler the function that will handle
     *        onended/oninactive events of the stream.
     * @param trackMediaType the media type of the JitsiTrack
     * @param videoType the VideoType for this track if any
     */
    constructor(
            conference,
            stream,
            track,
            streamInactiveHandler,
            trackMediaType,
            videoType) {
        super();

        // aliases for addListener/removeListener
        this.addEventListener = this.addListener;
        this.removeEventListener = this.off = this.removeListener;

        /**
         * Array with the HTML elements that are displaying the streams.
         * @type {Array}
         */
        this.containers = [];
        this.conference = conference;
        this.audioLevel = -1;
        this.type = trackMediaType;
        this.track = track;
        this.videoType = videoType;
        this.handlers = new Map();

        /**
         * Indicates whether this JitsiTrack has been disposed. If true, this
         * JitsiTrack is to be considered unusable and operations involving it
         * are to fail (e.g. {@link JitsiConference#addTrack(JitsiTrack)},
         * {@link JitsiConference#removeTrack(JitsiTrack)}).
         * @type {boolean}
         */
        this.disposed = false;

        /**
         * The inactive handler which will be triggered when the underlying
         * <tt>MediaStream</tt> ends.
         *
         * @private
         * @type {Function}
         */
        this._streamInactiveHandler = streamInactiveHandler;

        this._setStream(stream);
    }

    /* eslint-enable max-params */

    /**
     * Binds the inactive handler.
     * @param {Function} streamInactiveHandler
     * @private
     */
    _bindInactiveHandler(streamInactiveHandler) {
        if (RTCBrowserType.isFirefox()) {
            implementOnEndedHandling(this);
        }
        addMediaStreamInactiveHandler(this.stream, streamInactiveHandler);
    }

    /**
     * Sets handler to the WebRTC MediaStream or MediaStreamTrack object
     * depending on the passed type.
     * @param {string} type the type of the handler that is going to be set
     * @param {Function} handler the handler.
     */
    _setHandler(type, handler) {
        if (!trackHandler2Prop.hasOwnProperty(type)) {
            logger.error(`Invalid handler type ${type}`);

            return;
        }
        if (handler) {
            this.handlers.set(type, handler);
        } else {
            this.handlers.delete(type);
        }

        if (this.stream) {
            // FIXME Why only video tracks?
            for (const track of this.stream.getVideoTracks()) {
                track[trackHandler2Prop[type]] = handler;
            }
        }
    }

    /**
     * Unregisters all event handlers bound to the underlying media stream/track
     * @private
     */
    _unregisterHandlers() {
        if (!this.stream) {
            logger.warn(
                `${this}: unable to unregister handlers - no stream object`);

            return;
        }

        for (const type of this.handlers.keys()) {
            // FIXME Why only video tracks?
            for (const videoTrack of this.stream.getVideoTracks()) {
                videoTrack[trackHandler2Prop[type]] = undefined;
            }
        }
        if (this._streamInactiveHandler) {
            addMediaStreamInactiveHandler(this.stream, undefined);
        }
    }

    /**
     * Sets the stream property of JitsiTrack object and sets all stored
     * handlers to it.
     *
     * @param {MediaStream} stream the new stream.
     * @protected
     */
    _setStream(stream) {
        if (this.stream === stream) {
            return;
        }

        this.stream = stream;

        // TODO Practically, that's like the opposite of _unregisterHandlers
        // i.e. may be abstracted into a function/method called
        // _registerHandlers for clarity and easing the maintenance of the two
        // pieces of source code.
        if (this.stream) {
            for (const type of this.handlers.keys()) {
                this._setHandler(type, this.handlers.get(type));
            }
            if (this._streamInactiveHandler) {
                this._bindInactiveHandler(this._streamInactiveHandler);
            }
        }
    }

    /**
     * Returns the type (audio or video) of this track.
     */
    getType() {
        return this.type;
    }

    /**
     * Check if this is an audio track.
     */
    isAudioTrack() {
        return this.getType() === MediaType.AUDIO;
    }

    /**
     * Checks whether the underlying WebRTC <tt>MediaStreamTrack</tt> is muted
     * according to it's 'muted' field status.
     * @return {boolean} <tt>true</tt> if the underlying
     * <tt>MediaStreamTrack</tt> is muted or <tt>false</tt> otherwise.
     */
    isWebRTCTrackMuted() {
        return this.track && this.track.muted;
    }

    /**
     * Check if this is a video track.
     */
    isVideoTrack() {
        return this.getType() === MediaType.VIDEO;
    }

    /**
     * Checks whether this is a local track.
     * @abstract
     * @return {boolean} 'true' if it's a local track or 'false' otherwise.
     */
    isLocal() {
        throw new Error('Not implemented by subclass');
    }

    /**
     * Returns the WebRTC MediaStream instance.
     */
    getOriginalStream() {
        return this.stream;
    }

    /**
     * Returns the ID of the underlying WebRTC Media Stream(if any)
     * @returns {String|null}
     */
    getStreamId() {
        return this.stream ? this.stream.id : null;
    }

    /**
     * Return the underlying WebRTC MediaStreamTrack
     * @returns {MediaStreamTrack}
     */
    getTrack() {
        return this.track;
    }

    /**
     * Returns the ID of the underlying WebRTC MediaStreamTrack(if any)
     * @returns {String|null}
     */
    getTrackId() {
        return this.track ? this.track.id : null;
    }

    /**
     * Return meaningful usage label for this track depending on it's media and
     * eventual video type.
     * @returns {string}
     */
    getUsageLabel() {
        if (this.isAudioTrack()) {
            return 'mic';
        }

        return this.videoType ? this.videoType : 'default';
    }

    /**
     * Eventually will trigger RTCEvents.TRACK_ATTACHED event.
     * @param container the video/audio container to which this stream is
     *        attached and for which event will be fired.
     * @private
     */
    _maybeFireTrackAttached(container) {
        if (this.conference && container) {
            this.conference._onTrackAttach(this, container);
        }
    }

    /**
     * Attaches the MediaStream of this track to an HTML container.
     * Adds the container to the list of containers that are displaying the
     * track. Note that Temasys plugin will replace original audio/video element
     * with 'object' when stream is being attached to the container for the
     * first time.
     * * NOTE * if given container element is not visible when the stream is
     * being attached it will be shown back given that Temasys plugin is
     * currently in use.
     *
     * @param container the HTML container which can be 'video' or 'audio'
     * element. It can also be 'object' element if Temasys plugin is in use and
     * this method has been called previously on video or audio HTML element.
     *
     * @returns potentially new instance of container if it was replaced by the
     *          library. That's the case when Temasys plugin is in use.
     */
    attach(container) {
        let c = container;

        if (this.stream) {
            c = RTCUtils.attachMediaStream(container, this.stream);
        }
        this.containers.push(c);
        this._maybeFireTrackAttached(c);
        this._attachTTFMTracker(c);

        return c;
    }

    /**
     * Removes this JitsiTrack from the passed HTML container.
     *
     * @param container the HTML container to detach from this JitsiTrack. If
     * <tt>null</tt> or <tt>undefined</tt>, all containers are removed. A
     * container can be a 'video', 'audio' or 'object' HTML element instance to
     * which this JitsiTrack is currently attached.
     */
    detach(container) {
        for (let cs = this.containers, i = cs.length - 1; i >= 0; --i) {
            const c = cs[i];

            if (!container) {
                RTCUtils.attachMediaStream(c, null);
            }
            if (!container || c === container) {
                cs.splice(i, 1);
            }
        }

        if (container) {
            RTCUtils.attachMediaStream(container, null);
        }
    }

    /**
     * Attach time to first media tracker only if there is conference and only
     * for the first element.
     *
     * @param {HTMLElement} container the HTML container which can be 'video' or
     * 'audio' element. It can also be 'object' element if Temasys plugin is in
     * use and this method has been called previously on video or audio HTML
     * element.
     * @private
     */
    _attachTTFMTracker(container) { // eslint-disable-line no-unused-vars
        // Should be defined by the classes that are extending JitsiTrack
    }

    /**
     * Removes attached event listeners.
     *
     * @returns {Promise}
     */
    dispose() {
        this.removeAllListeners();

        this.disposed = true;

        return Promise.resolve();
    }

    /**
     * Returns true if this is a video track and the source of the video is a
     * screen capture as opposed to a camera.
     */
    isScreenSharing() {
        // FIXME: Should be fixed or removed.
    }

    /**
     * Returns id of the track.
     * @returns {string|null} id of the track or null if this is fake track.
     */
    getId() {
        if (this.stream) {
            return RTCUtils.getStreamID(this.stream);
        }

        return null;
    }

    /**
     * Checks whether the MediaStream is active/not ended.
     * When there is no check for active we don't have information and so
     * will return that stream is active (in case of FF).
     * @returns {boolean} whether MediaStream is active.
     */
    isActive() {
        if (typeof this.stream.active !== 'undefined') {
            return this.stream.active;
        }

        return true;
    }

    /**
     * Sets the audio level for the stream
     * @param {number} audioLevel value between 0 and 1
     * @param {TraceablePeerConnection} [tpc] the peerconnection instance which
     * is source for the audio level. It can be <tt>undefined</tt> for
     * a local track if the audio level was measured outside of the
     * peerconnection (see /modules/statistics/LocalStatsCollector.js).
     */
    setAudioLevel(audioLevel, tpc) {
        if (this.audioLevel !== audioLevel) {
            this.audioLevel = audioLevel;
            this.emit(
                JitsiTrackEvents.TRACK_AUDIO_LEVEL_CHANGED,
                audioLevel,
                tpc);
        }
    }

    /**
     * Returns the msid of the stream attached to the JitsiTrack object or null
     * if no stream is attached.
     */
    getMSID() {
        const streamId = this.getStreamId();
        const trackId = this.getTrackId();

        return streamId && trackId ? `${streamId} ${trackId}` : null;
    }

    /**
     * Sets new audio output device for track's DOM elements. Video tracks are
     * ignored.
     * @param {string} audioOutputDeviceId - id of 'audiooutput' device from
     *      navigator.mediaDevices.enumerateDevices(), '' for default device
     * @emits JitsiTrackEvents.TRACK_AUDIO_OUTPUT_CHANGED
     * @returns {Promise}
     */
    setAudioOutput(audioOutputDeviceId) {
        if (!RTCUtils.isDeviceChangeAvailable('output')) {
            return Promise.reject(
                new Error('Audio output device change is not supported'));
        }

        // All audio communication is done through audio tracks, so ignore
        // changing audio output for video tracks at all.
        if (this.isVideoTrack()) {
            return Promise.resolve();
        }

        return (
            Promise.all(
                this.containers.map(
                    element =>
                        element.setSinkId(audioOutputDeviceId)
                            .catch(error => {
                                logger.warn(
                                    'Failed to change audio output device on'
                                        + ' element. Default or previously set'
                                        + ' audio output device will be used.',
                                    element,
                                    error);
                                throw error;
                            }))
            )
                .then(() => {
                    this.emit(
                        JitsiTrackEvents.TRACK_AUDIO_OUTPUT_CHANGED,
                        audioOutputDeviceId);
                }));
    }
}