ljm_j1/modules/RTC/RTCUtils.js

/* global $,
          __filename,
          attachMediaStream,
          MediaStreamTrack,
          RTCIceCandidate,
          RTCPeerConnection,
          RTCSessionDescription,
          mozRTCIceCandidate,
          mozRTCPeerConnection,
          mozRTCSessionDescription,
          webkitMediaStream,
          webkitRTCPeerConnection,
          webkitURL
*/
import CameraFacingMode from '../../service/RTC/CameraFacingMode';
import EventEmitter from 'events';
import { getLogger } from 'jitsi-meet-logger';
import GlobalOnErrorHandler from '../util/GlobalOnErrorHandler';
import JitsiTrackError from '../../JitsiTrackError';
import Listenable from '../util/Listenable';
import * as MediaType from '../../service/RTC/MediaType';
import Resolutions from '../../service/RTC/Resolutions';
import RTCBrowserType from './RTCBrowserType';
import RTCEvents from '../../service/RTC/RTCEvents';
import screenObtainer from './ScreenObtainer';
import SDPUtil from '../xmpp/SDPUtil';
import VideoType from '../../service/RTC/VideoType';

const logger = getLogger(__filename);

// XXX Don't require Temasys unless it's to be used because it doesn't run on
// React Native, for example.
const AdapterJS
    = RTCBrowserType.isTemasysPluginUsed()
        ? require('./adapter.screenshare')
        : undefined;

const eventEmitter = new EventEmitter();

const AVAILABLE_DEVICES_POLL_INTERVAL_TIME = 3000; // ms

const devices = {
    audio: false,
    video: false
};

// Currently audio output device change is supported only in Chrome and
// default output always has 'default' device ID
let audioOutputDeviceId = 'default'; // default device
// whether user has explicitly set a device to use
let audioOutputChanged = false;
// Disables Acoustic Echo Cancellation
let disableAEC = false;
// Disables Noise Suppression
let disableNS = false;

const featureDetectionAudioEl = document.createElement('audio');
const isAudioOutputDeviceChangeAvailable
    = typeof featureDetectionAudioEl.setSinkId !== 'undefined';

let currentlyAvailableMediaDevices;

let rawEnumerateDevicesWithCallback = undefined;
/**
 * "rawEnumerateDevicesWithCallback" will be initialized only after WebRTC is
 * ready. Otherwise it is too early to assume that the devices listing is not
 * supported.
 */
function initRawEnumerateDevicesWithCallback() {
    rawEnumerateDevicesWithCallback = navigator.mediaDevices
        && navigator.mediaDevices.enumerateDevices
        ? function(callback) {
            navigator.mediaDevices.enumerateDevices().then(
                callback, function() {
                    callback([]);
                });
        }
        // Safari:
        // "ReferenceError: Can't find variable: MediaStreamTrack"
        // when Temasys plugin is not installed yet, have to delay this call
        // until WebRTC is ready.
        : MediaStreamTrack && MediaStreamTrack.getSources
        ? function(callback) {
            MediaStreamTrack.getSources(function(sources) {
                callback(sources.map(convertMediaStreamTrackSource));
            });
        }
        : undefined;
}

// TODO: currently no browser supports 'devicechange' event even in nightly
// builds so no feature/browser detection is used at all. However in future this
// should be changed to some expression. Progress on 'devicechange' event
// implementation for Chrome/Opera/NWJS can be tracked at
// https://bugs.chromium.org/p/chromium/issues/detail?id=388648, for Firefox -
// at https://bugzilla.mozilla.org/show_bug.cgi?id=1152383. More information on
// 'devicechange' event can be found in spec -
// http://w3c.github.io/mediacapture-main/#event-mediadevices-devicechange
// TODO: check MS Edge
const isDeviceChangeEventSupported = false;

let rtcReady = false;

function setResolutionConstraints(constraints, resolution) {
    const isAndroid = RTCBrowserType.isAndroid();

    if (Resolutions[resolution]) {
        constraints.video.mandatory.minWidth = Resolutions[resolution].width;
        constraints.video.mandatory.minHeight = Resolutions[resolution].height;
    } else if (isAndroid) {
        // FIXME can't remember if the purpose of this was to always request
        //       low resolution on Android ? if yes it should be moved up front
        constraints.video.mandatory.minWidth = 320;
        constraints.video.mandatory.minHeight = 180;
        constraints.video.mandatory.maxFrameRate = 15;
    }

    if (constraints.video.mandatory.minWidth) {
        constraints.video.mandatory.maxWidth
            = constraints.video.mandatory.minWidth;
    }
    if (constraints.video.mandatory.minHeight) {
        constraints.video.mandatory.maxHeight
            = constraints.video.mandatory.minHeight;
    }
}

/**
 * @param {string[]} um required user media types
 *
 * @param {Object} [options={}] optional parameters
 * @param {string} options.resolution
 * @param {number} options.bandwidth
 * @param {number} options.fps
 * @param {string} options.desktopStream
 * @param {string} options.cameraDeviceId
 * @param {string} options.micDeviceId
 * @param {CameraFacingMode} options.facingMode
 * @param {bool} firefox_fake_device
 */
function getConstraints(um, options) {
    const constraints = {audio: false, video: false};

    // Don't mix new and old style settings for Chromium as this leads
    // to TypeError in new Chromium versions. @see
    // https://bugs.chromium.org/p/chromium/issues/detail?id=614716
    // This is a temporary solution, in future we will fully split old and
    // new style constraints when new versions of Chromium and Firefox will
    // have stable support of new constraints format. For more information
    // @see https://github.com/jitsi/lib-jitsi-meet/pull/136
    const isNewStyleConstraintsSupported
        = RTCBrowserType.isFirefox()
        || RTCBrowserType.isReactNative()
        || RTCBrowserType.isTemasysPluginUsed();

    if (um.indexOf('video') >= 0) {
        // same behaviour as true
        constraints.video = { mandatory: {}, optional: [] };

        if (options.cameraDeviceId) {
            if (isNewStyleConstraintsSupported) {
                // New style of setting device id.
                constraints.video.deviceId = options.cameraDeviceId;
            }
            // Old style.
            constraints.video.optional.push({
                sourceId: options.cameraDeviceId
            });
        } else {
            // Prefer the front i.e. user-facing camera (to the back i.e.
            // environment-facing camera, for example).
            // TODO: Maybe use "exact" syntax if options.facingMode is defined,
            // but this probably needs to be decided when updating other
            // constraints, as we currently don't use "exact" syntax anywhere.
            const facingMode = options.facingMode || CameraFacingMode.USER;

            if (isNewStyleConstraintsSupported) {
                constraints.video.facingMode = facingMode;
            }
            constraints.video.optional.push({
                facingMode
            });
        }

        if (options.minFps || options.maxFps || options.fps) {
            // for some cameras it might be necessary to request 30fps
            // so they choose 30fps mjpg over 10fps yuy2
            if (options.minFps || options.fps) {
                options.minFps = options.minFps || options.fps; // Fall back to options.fps for backwards compatibility
                constraints.video.mandatory.minFrameRate = options.minFps;
            }
            if (options.maxFps) {
                constraints.video.mandatory.maxFrameRate = options.maxFps;
            }
        }

        setResolutionConstraints(constraints, options.resolution);
    }
    if (um.indexOf('audio') >= 0) {
        if (RTCBrowserType.isReactNative()) {
            // The react-native-webrtc project that we're currently using
            // expects the audio constraint to be a boolean.
            constraints.audio = true;
        } else if (!RTCBrowserType.isFirefox()) {
            // same behaviour as true
            constraints.audio = { mandatory: {}, optional: []};
            if (options.micDeviceId) {
                if (isNewStyleConstraintsSupported) {
                    // New style of setting device id.
                    constraints.audio.deviceId = options.micDeviceId;
                }
                // Old style.
                constraints.audio.optional.push({
                    sourceId: options.micDeviceId
                });
            }
            // if it is good enough for hangouts...
            constraints.audio.optional.push(
                {googEchoCancellation: !disableAEC},
                {googAutoGainControl: true},
                {googNoiseSupression: !disableNS},
                {googHighpassFilter: true},
                {googNoiseSuppression2: !disableNS},
                {googEchoCancellation2: !disableAEC},
                {googAutoGainControl2: true}
            );
        } else {
            if (options.micDeviceId) {
                constraints.audio = {
                    mandatory: {},
                    deviceId: options.micDeviceId, // new style
                    optional: [{
                        sourceId: options.micDeviceId // old style
                    }]};
            } else {
                constraints.audio = true;
            }
        }
    }
    if (um.indexOf('screen') >= 0) {
        if (RTCBrowserType.isChrome()) {
            constraints.video = {
                mandatory: {
                    chromeMediaSource: 'screen',
                    maxWidth: window.screen.width,
                    maxHeight: window.screen.height,
                    maxFrameRate: 3
                },
                optional: []
            };
        } else if (RTCBrowserType.isTemasysPluginUsed()) {
            constraints.video = {
                optional: [
                    {
                        sourceId: AdapterJS.WebRTCPlugin.plugin.screensharingKey
                    }
                ]
            };
        } else if (RTCBrowserType.isFirefox()) {
            constraints.video = {
                mozMediaSource: 'window',
                mediaSource: 'window'
            };

        } else {
            const errmsg
                = '\'screen\' WebRTC media source is supported only in Chrome'
                    + ' and with Temasys plugin';
            GlobalOnErrorHandler.callErrorHandler(new Error(errmsg));
            logger.error(errmsg);
        }
    }
    if (um.indexOf('desktop') >= 0) {
        constraints.video = {
            mandatory: {
                chromeMediaSource: 'desktop',
                chromeMediaSourceId: options.desktopStream,
                maxWidth: window.screen.width,
                maxHeight: window.screen.height,
                maxFrameRate: 3
            },
            optional: []
        };
    }

    if (options.bandwidth) {
        if (!constraints.video) {
            // same behaviour as true
            constraints.video = {mandatory: {}, optional: []};
        }
        constraints.video.optional.push({bandwidth: options.bandwidth});
    }

    // we turn audio for both audio and video tracks, the fake audio & video seems to work
    // only when enabled in one getUserMedia call, we cannot get fake audio separate by fake video
    // this later can be a problem with some of the tests
    if(RTCBrowserType.isFirefox() && options.firefox_fake_device) {
        // seems to be fixed now, removing this experimental fix, as having
        // multiple audio tracks brake the tests
        // constraints.audio = true;
        constraints.fake = true;
    }

    return constraints;
}

/**
 * Sets the availbale devices based on the options we requested and the
 * streams we received.
 * @param um the options we requested to getUserMedia.
 * @param stream the stream we received from calling getUserMedia.
 */
function setAvailableDevices(um, stream) {
    const audioTracksReceived = stream && stream.getAudioTracks().length > 0;
    const videoTracksReceived = stream && stream.getVideoTracks().length > 0;

    if (um.indexOf('video') != -1) {
        devices.video = videoTracksReceived;
    }
    if (um.indexOf('audio') != -1) {
        devices.audio = audioTracksReceived;
    }

    eventEmitter.emit(RTCEvents.AVAILABLE_DEVICES_CHANGED, devices);
}

/**
 * Checks if new list of available media devices differs from previous one.
 * @param {MediaDeviceInfo[]} newDevices - list of new devices.
 * @returns {boolean} - true if list is different, false otherwise.
 */
function compareAvailableMediaDevices(newDevices) {
    if (newDevices.length !== currentlyAvailableMediaDevices.length) {
        return true;
    }

    return newDevices.map(mediaDeviceInfoToJSON).sort().join('')
        !== currentlyAvailableMediaDevices.map(mediaDeviceInfoToJSON).sort().join('');

    function mediaDeviceInfoToJSON(info) {
        return JSON.stringify({
            kind: info.kind,
            deviceId: info.deviceId,
            groupId: info.groupId,
            label: info.label,
            facing: info.facing
        });
    }
}

/**
 * Periodically polls enumerateDevices() method to check if list of media
 * devices has changed. This is temporary workaround until 'devicechange' event
 * will be supported by browsers.
 */
function pollForAvailableMediaDevices() {
    // Here we use plain navigator.mediaDevices.enumerateDevices instead of
    // wrapped because we just need to know the fact the devices changed, labels
    // do not matter. This fixes situation when we have no devices initially,
    // and then plug in a new one.
    if (rawEnumerateDevicesWithCallback) {
        rawEnumerateDevicesWithCallback(function(devices) {
            // We don't fire RTCEvents.DEVICE_LIST_CHANGED for the first time
            // we call enumerateDevices(). This is the initial step.
            if (typeof currentlyAvailableMediaDevices === 'undefined') {
                currentlyAvailableMediaDevices = devices.slice(0);
            } else if (compareAvailableMediaDevices(devices)) {
                onMediaDevicesListChanged(devices);
            }

            window.setTimeout(pollForAvailableMediaDevices,
                AVAILABLE_DEVICES_POLL_INTERVAL_TIME);
        });
    }
}

/**
 * Event handler for the 'devicechange' event.
 *
 * @param {MediaDeviceInfo[]} devices - list of media devices.
 * @emits RTCEvents.DEVICE_LIST_CHANGED
 */
function onMediaDevicesListChanged(devicesReceived) {
    currentlyAvailableMediaDevices = devicesReceived.slice(0);
    logger.info('list of media devices has changed:', currentlyAvailableMediaDevices);

    const videoInputDevices
        = currentlyAvailableMediaDevices.filter(d => d.kind === 'videoinput');
    const audioInputDevices
        = currentlyAvailableMediaDevices.filter(d => d.kind === 'audioinput');
    const videoInputDevicesWithEmptyLabels
        = videoInputDevices.filter(d => d.label === '');
    const audioInputDevicesWithEmptyLabels
        = audioInputDevices.filter(d => d.label === '');

    if (videoInputDevices.length
        && videoInputDevices.length === videoInputDevicesWithEmptyLabels.length) {
        devices.video = false;
    }

    if (audioInputDevices.length
        && audioInputDevices.length === audioInputDevicesWithEmptyLabels.length) {
        devices.audio = false;
    }

    eventEmitter.emit(RTCEvents.DEVICE_LIST_CHANGED, devicesReceived);
}

// In case of IE we continue from 'onReady' callback
// passed to RTCUtils constructor. It will be invoked by Temasys plugin
// once it is initialized.
function onReady(options, GUM) {
    rtcReady = true;
    eventEmitter.emit(RTCEvents.RTC_READY, true);
    screenObtainer.init(options, GUM);

    // Initialize rawEnumerateDevicesWithCallback
    initRawEnumerateDevicesWithCallback();

    if (rtcUtils.isDeviceListAvailable() && rawEnumerateDevicesWithCallback) {
        rawEnumerateDevicesWithCallback(function(devices) {
            currentlyAvailableMediaDevices = devices.splice(0);

            eventEmitter.emit(RTCEvents.DEVICE_LIST_AVAILABLE,
                currentlyAvailableMediaDevices);

            if (isDeviceChangeEventSupported) {
                navigator.mediaDevices.addEventListener(
                    'devicechange',
                    function() {
                        rtcUtils.enumerateDevices(
                            onMediaDevicesListChanged);
                    });
            } else {
                pollForAvailableMediaDevices();
            }
        });
    }
}

/**
 * Apply function with arguments if function exists.
 * Do nothing if function not provided.
 * @param {function} [fn] function to apply
 * @param {Array} [args=[]] arguments for function
 */
function maybeApply(fn, args) {
    fn && fn(...args);
}

const getUserMediaStatus = {
    initialized: false,
    callbacks: []
};

/**
 * Wrap `getUserMedia` to allow others to know if it was executed at least
 * once or not. Wrapper function uses `getUserMediaStatus` object.
 * @param {Function} getUserMedia native function
 * @returns {Function} wrapped function
 */
function wrapGetUserMedia(getUserMedia) {
    return function(constraints, successCallback, errorCallback) {
        getUserMedia(constraints, function(stream) {
            maybeApply(successCallback, [stream]);
            if (!getUserMediaStatus.initialized) {
                getUserMediaStatus.initialized = true;
                getUserMediaStatus.callbacks.forEach(function(callback) {
                    callback();
                });
                getUserMediaStatus.callbacks.length = 0;
            }
        }, function(error) {
            maybeApply(errorCallback, [error]);
        });
    };
}

/**
 * Execute function after getUserMedia was executed at least once.
 * @param {Function} callback function to execute after getUserMedia
 */
function afterUserMediaInitialized(callback) {
    if (getUserMediaStatus.initialized) {
        callback();
    } else {
        getUserMediaStatus.callbacks.push(callback);
    }
}

/**
 * Wrapper function which makes enumerateDevices to wait
 * until someone executes getUserMedia first time.
 * @param {Function} enumerateDevices native function
 * @returns {Funtion} wrapped function
 */
function wrapEnumerateDevices(enumerateDevices) {
    return function(callback) {
        // enumerate devices only after initial getUserMedia
        afterUserMediaInitialized(function() {
            enumerateDevices().then(callback, function(err) {
                logger.error('cannot enumerate devices: ', err);
                callback([]);
            });
        });
    };
}

/**
 * Use old MediaStreamTrack to get devices list and
 * convert it to enumerateDevices format.
 * @param {Function} callback function to call when received devices list.
 */
function enumerateDevicesThroughMediaStreamTrack(callback) {
    MediaStreamTrack.getSources(function(sources) {
        callback(sources.map(convertMediaStreamTrackSource));
    });
}

/**
 * Converts MediaStreamTrack Source to enumerateDevices format.
 * @param {Object} source
 */
function convertMediaStreamTrackSource(source) {
    const kind = (source.kind || '').toLowerCase();

    return {
        facing: source.facing || null,
        label: source.label,
        // theoretically deprecated MediaStreamTrack.getSources should
        // not return 'audiooutput' devices but let's handle it in any
        // case
        kind: kind
            ? kind === 'audiooutput' ? kind : `${kind}input`
            : null,
        deviceId: source.id,
        groupId: source.groupId || null
    };
}

function obtainDevices(options) {
    if(!options.devices || options.devices.length === 0) {
        return options.successCallback(options.streams || {});
    }

    const device = options.devices.splice(0, 1);
    const devices = [];
    devices.push(device);
    options.deviceGUM[device](function(stream) {
        options.streams = options.streams || {};
        options.streams[device] = stream;
        obtainDevices(options);
    },
        function(error) {
            Object.keys(options.streams).forEach(function(device) {
                rtcUtils.stopMediaStream(options.streams[device]);
            });
            logger.error(
                `failed to obtain ${device} stream - stop`, error);

            options.errorCallback(error);
        });
}


/**
 * Handles the newly created Media Streams.
 * @param streams the new Media Streams
 * @param resolution the resolution of the video streams
 * @returns {*[]} object that describes the new streams
 */
function handleLocalStream(streams, resolution) {
    let audioStream, desktopStream, videoStream;
    const res = [];

    // XXX The function obtainAudioAndVideoPermissions has examined the type of
    // the browser, its capabilities, etc. and has taken the decision whether to
    // invoke getUserMedia per device (e.g. Firefox) or once for both audio and
    // video (e.g. Chrome). In order to not duplicate the logic here, examine
    // the specified streams and figure out what we've received based on
    // obtainAudioAndVideoPermissions' decision.
    if (streams) {
        // As mentioned above, certian types of browser (e.g. Chrome) support
        // (with a result which meets our requirements expressed bellow) calling
        // getUserMedia once for both audio and video.
        const audioVideo = streams.audioVideo;
        if (audioVideo) {
            const audioTracks = audioVideo.getAudioTracks();
            if (audioTracks.length) {
                // eslint-disable-next-line new-cap
                audioStream = new webkitMediaStream();
                for (let i = 0; i < audioTracks.length; i++) {
                    audioStream.addTrack(audioTracks[i]);
                }
            }

            const videoTracks = audioVideo.getVideoTracks();
            if (videoTracks.length) {
                // eslint-disable-next-line new-cap
                videoStream = new webkitMediaStream();
                for (let j = 0; j < videoTracks.length; j++) {
                    videoStream.addTrack(videoTracks[j]);
                }
            }
        } else {
          // On other types of browser (e.g. Firefox) we choose (namely,
          // obtainAudioAndVideoPermissions) to call getUsermedia per device
          // (type).
            audioStream = streams.audio;
            videoStream = streams.video;
        }
        // Again, different choices on different types of browser.
        desktopStream = streams.desktopStream || streams.desktop;
    }

    if (desktopStream) {
        res.push({
            stream: desktopStream,
            track: desktopStream.getVideoTracks()[0],
            mediaType: MediaType.VIDEO,
            videoType: VideoType.DESKTOP
        });
    }
    if (audioStream) {
        res.push({
            stream: audioStream,
            track: audioStream.getAudioTracks()[0],
            mediaType: MediaType.AUDIO,
            videoType: null
        });
    }
    if (videoStream) {
        res.push({
            stream: videoStream,
            track: videoStream.getVideoTracks()[0],
            mediaType: MediaType.VIDEO,
            videoType: VideoType.CAMERA,
            resolution
        });
    }

    return res;
}

/**
 * Wraps original attachMediaStream function to set current audio output device
 * if this is supported.
 * @param {Function} origAttachMediaStream
 * @returns {Function}
 */
function wrapAttachMediaStream(origAttachMediaStream) {
    return function(element, stream) {
        const res = origAttachMediaStream.apply(rtcUtils, arguments);

        if (stream
                && rtcUtils.isDeviceChangeAvailable('output')
                && stream.getAudioTracks
                && stream.getAudioTracks().length
                // we skip setting audio output if there was no explicit change
                && audioOutputChanged) {
            element.setSinkId(rtcUtils.getAudioOutputDevice())
                .catch(function(ex) {
                    const err = new JitsiTrackError(ex, null, ['audiooutput']);

                    GlobalOnErrorHandler.callUnhandledRejectionHandler(
                        {promise: this, reason: err});

                    logger.warn('Failed to set audio output device for the '
                        + 'element. Default audio output device will be used '
                        + 'instead',
                        element, err);
                });
        }

        return res;
    };
}

/**
 * Represents a default implementation of setting a <tt>MediaStream</tt> as the
 * source of a video element that tries to be browser-agnostic through feature
 * checking. Note though that it was not completely clear from the predating
 * browser-specific implementations what &quot;videoSrc&quot; was because one
 * implementation of {@link RTCUtils#getVideoSrc} would return
 * <tt>MediaStream</tt> (e.g. Firefox), another a <tt>string</tt> representation
 * of the <tt>URL</tt> of the <tt>MediaStream</tt> (e.g. Chrome) and the return
 * value was only used by {@link RTCUIHelper#getVideoId} which itself did not
 * appear to be used anywhere. Generally, the implementation will try to follow
 * the related standards i.e. work with the <tt>srcObject</tt> and <tt>src</tt>
 * properties of the specified <tt>element</tt> taking into account vender
 * prefixes.
 *
 * @param element the element whose video source/src is to be set to the
 * specified <tt>stream</tt>
 * @param {MediaStream} stream the <tt>MediaStream</tt> to set as the video
 * source/src of <tt>element</tt>
 */
function defaultSetVideoSrc(element, stream) {
    // srcObject
    let srcObjectPropertyName = 'srcObject';
    if (!(srcObjectPropertyName in element)) {
        srcObjectPropertyName = 'mozSrcObject';
        if (!(srcObjectPropertyName in element)) {
            srcObjectPropertyName = null;
        }
    }
    if (srcObjectPropertyName) {
        element[srcObjectPropertyName] = stream;
        return;
    }

    // src
    let src;
    if (stream) {
        src = stream.jitsiObjectURL;
        // Save the created URL for stream so we can reuse it and not keep
        // creating URLs.
        if (!src) {
            stream.jitsiObjectURL
                = src
                    = (URL || webkitURL).createObjectURL(stream);
        }
    }
    element.src = src || '';
}

// Options parameter is to pass config options. Currently uses only "useIPv6".
class RTCUtils extends Listenable {
    constructor() {
        super(eventEmitter);
    }

    init(options) {
        if (typeof options.disableAEC === 'boolean') {
            disableAEC = options.disableAEC;
            logger.info(`Disable AEC: ${disableAEC}`);
        }
        if (typeof options.disableNS === 'boolean') {
            disableNS = options.disableNS;
            logger.info(`Disable NS: ${disableNS}`);
        }

        return new Promise(function(resolve, reject) {
            if (RTCBrowserType.isFirefox()) {
                const FFversion = RTCBrowserType.getFirefoxVersion();
                if (FFversion < 40) {
                    rejectWithWebRTCNotSupported(
                        `Firefox version too old: ${FFversion}.`
                            + ' Required >= 40.',
                        reject);

                    return;
                }
                this.peerconnection = mozRTCPeerConnection;
                this.getUserMedia = wrapGetUserMedia(navigator.mozGetUserMedia.bind(navigator));
                this.enumerateDevices = wrapEnumerateDevices(
                    navigator.mediaDevices.enumerateDevices.bind(navigator.mediaDevices)
                );
                this.pc_constraints = {};
                this.attachMediaStream = wrapAttachMediaStream(function(element, stream) {
                    //  srcObject is being standardized and FF will eventually
                    //  support that unprefixed. FF also supports the
                    //  "element.src = URL.createObjectURL(...)" combo, but that
                    //  will be deprecated in favour of srcObject.
                    //
                    // https://groups.google.com/forum/#!topic/mozilla.dev.media/pKOiioXonJg
                    // https://github.com/webrtc/samples/issues/302
                    if (element) {
                        defaultSetVideoSrc(element, stream);
                        if (stream) {
                            element.play();
                        }
                    }
                    return element;
                });
                this.getStreamID = function(stream) {
                    let id = stream.id;
                    if (!id) {
                        let tracks = stream.getVideoTracks();
                        if (!tracks || tracks.length === 0) {
                            tracks = stream.getAudioTracks();
                        }
                        id = tracks[0].id;
                    }
                    return SDPUtil.filter_special_chars(id);
                };
                RTCSessionDescription = mozRTCSessionDescription; // eslint-disable-line
                RTCIceCandidate = mozRTCIceCandidate;             // eslint-disable-line
            } else if (RTCBrowserType.isChrome()
                    || RTCBrowserType.isOpera()
                    || RTCBrowserType.isNWJS()
                    || RTCBrowserType.isElectron()
                    || RTCBrowserType.isReactNative()) {

                this.peerconnection = webkitRTCPeerConnection;
                const getUserMedia = navigator.webkitGetUserMedia.bind(navigator);
                if (navigator.mediaDevices) {
                    this.getUserMedia = wrapGetUserMedia(getUserMedia);
                    this.enumerateDevices = wrapEnumerateDevices(
                        navigator.mediaDevices.enumerateDevices.bind(navigator.mediaDevices)
                    );
                } else {
                    this.getUserMedia = getUserMedia;
                    this.enumerateDevices = enumerateDevicesThroughMediaStreamTrack;
                }
                this.attachMediaStream = wrapAttachMediaStream(function(element, stream) {
                    defaultSetVideoSrc(element, stream);
                    return element;
                });
                this.getStreamID = function(stream) {
                    // A. MediaStreams from FF endpoints have the characters '{'
                    // and '}' that make jQuery choke.
                    // B. The react-native-webrtc implementation that we use on
                    // React Native at the time of this writing returns a number
                    // for the id of MediaStream. Let's just say that a number
                    // contains no special characters.
                    const id = stream.id;
                    // XXX The return statement is affected by automatic
                    // semicolon insertion (ASI). No line terminator is allowed
                    // between the return keyword and the expression.
                    return (
                        typeof id === 'number'
                            ? id
                            : SDPUtil.filter_special_chars(id));
                };

                this.pc_constraints = {optional: [] };

                // Allows sending of video to be suspended if the bandwidth
                // estimation is too low.
                if (!options.disableSuspendVideo) {
                    this.pc_constraints.optional.push(
                        {googSuspendBelowMinBitrate: true});
                }

                if (options.useIPv6) {
                    // https://code.google.com/p/webrtc/issues/detail?id=2828
                    this.pc_constraints.optional.push({googIPv6: true});
                }

                if (!webkitMediaStream.prototype.getVideoTracks) {
                    webkitMediaStream.prototype.getVideoTracks = function() {
                        return this.videoTracks;
                    };
                }
                if (!webkitMediaStream.prototype.getAudioTracks) {
                    webkitMediaStream.prototype.getAudioTracks = function() {
                        return this.audioTracks;
                    };
                }
            } else if (RTCBrowserType.isTemasysPluginUsed()) {
                // Detect IE/Safari
                const webRTCReadyCb = () => {
                    this.peerconnection = RTCPeerConnection;
                    this.getUserMedia = window.getUserMedia;
                    this.enumerateDevices = enumerateDevicesThroughMediaStreamTrack;
                    this.attachMediaStream = wrapAttachMediaStream((element, stream) => {
                        if (stream) {
                            if (stream.id === 'dummyAudio'
                                    || stream.id === 'dummyVideo') {
                                return;
                            }

                            // The container must be visible in order to play or
                            // attach the stream when Temasys plugin is in use
                            const containerSel = $(element);
                            if (RTCBrowserType.isTemasysPluginUsed()
                                    && !containerSel.is(':visible')) {
                                containerSel.show();
                            }
                            const video = stream.getVideoTracks().length > 0;
                            if (video && !$(element).is(':visible')) {
                                throw new Error(
                                    'video element must be visible to attach'
                                        + ' video stream');
                            }
                        }

                        return attachMediaStream(element, stream);
                    });
                    this.getStreamID
                        = stream => SDPUtil.filter_special_chars(stream.label);

                    onReady(
                        options,
                        this.getUserMediaWithConstraints.bind(this));
                };
                const webRTCReadyPromise
                    = new Promise(resolve => AdapterJS.webRTCReady(resolve));

                // Resolve or reject depending on whether the Temasys plugin is
                // installed.
                AdapterJS.WebRTCPlugin.isPluginInstalled(
                    AdapterJS.WebRTCPlugin.pluginInfo.prefix,
                    AdapterJS.WebRTCPlugin.pluginInfo.plugName,
                    AdapterJS.WebRTCPlugin.pluginInfo.type,
                    /* installed */ () => {
                        webRTCReadyPromise.then(() => {
                            webRTCReadyCb();
                            resolve();
                        });
                    },
                    /* not installed */ () => {
                        const error
                            = new Error('Temasys plugin is not installed');

                        error.name = 'WEBRTC_NOT_READY';
                        error.webRTCReadyPromise = webRTCReadyPromise;

                        reject(error);
                    });
            } else {
                rejectWithWebRTCNotSupported(
                    'Browser does not appear to be WebRTC-capable',
                    reject);

                return;
            }

            // Call onReady() if Temasys plugin is not used
            if (!RTCBrowserType.isTemasysPluginUsed()) {
                onReady(options, this.getUserMediaWithConstraints.bind(this));
                resolve();
            }
        }.bind(this));
    }

    /**
    * @param {string[]} um required user media types
    * @param {function} success_callback
    * @param {Function} failure_callback
    * @param {Object} [options] optional parameters
    * @param {string} options.resolution
    * @param {number} options.bandwidth
    * @param {number} options.fps
    * @param {string} options.desktopStream
    * @param {string} options.cameraDeviceId
    * @param {string} options.micDeviceId
    **/
    getUserMediaWithConstraints(um, success_callback, failure_callback, options) {
        options = options || {};
        const constraints = getConstraints(um, options);

        logger.info('Get media constraints', constraints);

        try {
            this.getUserMedia(constraints,
                function(stream) {
                    logger.log('onUserMediaSuccess');
                    setAvailableDevices(um, stream);
                    success_callback(stream);
                },
                function(error) {
                    setAvailableDevices(um, undefined);
                    logger.warn('Failed to get access to local media. Error ',
                        error, constraints);

                    if (failure_callback) {
                        failure_callback(
                            new JitsiTrackError(error, constraints, um));
                    }
                });
        } catch (e) {
            logger.error('GUM failed: ', e);

            if (failure_callback) {
                failure_callback(new JitsiTrackError(e, constraints, um));
            }
        }
    }

    /**
     * Creates the local MediaStreams.
     * @param {Object} [options] optional parameters
     * @param {Array} options.devices the devices that will be requested
     * @param {string} options.resolution resolution constraints
     * @param {bool} options.dontCreateJitsiTrack if <tt>true</tt> objects with the following structure {stream: the Media Stream,
     * type: "audio" or "video", videoType: "camera" or "desktop"}
     * will be returned trough the Promise, otherwise JitsiTrack objects will be returned.
     * @param {string} options.cameraDeviceId
     * @param {string} options.micDeviceId
     * @returns {*} Promise object that will receive the new JitsiTracks
     */
    obtainAudioAndVideoPermissions(options) {
        const self = this;

        options = options || {};
        const dsOptions = options.desktopSharingExtensionExternalInstallation;
        return new Promise(function(resolve, reject) {
            const successCallback = function(stream) {
                resolve(handleLocalStream(stream, options.resolution));
            };

            options.devices = options.devices || ['audio', 'video'];
            if(!screenObtainer.isSupported()
                && options.devices.indexOf('desktop') !== -1) {
                reject(new Error('Desktop sharing is not supported!'));
            }
            if (RTCBrowserType.isFirefox()
                    // XXX The react-native-webrtc implementation that we
                    // utilize on React Native at the time of this writing does
                    // not support the MediaStream constructors defined by
                    // https://www.w3.org/TR/mediacapture-streams/#constructors
                    // and instead has a single constructor which expects (an
                    // NSNumber as) a MediaStream ID.
                    || RTCBrowserType.isReactNative()
                    || RTCBrowserType.isTemasysPluginUsed()) {
                const GUM = function(device, s, e) {
                    this.getUserMediaWithConstraints(device, s, e, options);
                };

                const deviceGUM = {
                    'audio': GUM.bind(self, ['audio']),
                    'video': GUM.bind(self, ['video'])
                };

                if(screenObtainer.isSupported()) {
                    deviceGUM.desktop = screenObtainer.obtainStream.bind(
                        screenObtainer,
                        dsOptions);
                }
                // With FF/IE we can't split the stream into audio and video because FF
                // doesn't support media stream constructors. So, we need to get the
                // audio stream separately from the video stream using two distinct GUM
                // calls. Not very user friendly :-( but we don't have many other
                // options neither.
                //
                // Note that we pack those 2 streams in a single object and pass it to
                // the successCallback method.
                obtainDevices({
                    devices: options.devices,
                    streams: [],
                    successCallback,
                    errorCallback: reject,
                    deviceGUM
                });
            } else {
                const hasDesktop = options.devices.indexOf('desktop') > -1;
                if (hasDesktop) {
                    options.devices.splice(options.devices.indexOf('desktop'), 1);
                }
                options.resolution = options.resolution || '360';
                if(options.devices.length) {
                    this.getUserMediaWithConstraints(
                        options.devices,
                        function(stream) {
                            const audioDeviceRequested
                                = options.devices.indexOf('audio') !== -1;
                            const videoDeviceRequested
                                = options.devices.indexOf('video') !== -1;
                            const audioTracksReceived
                                = stream.getAudioTracks().length > 0;
                            const videoTracksReceived
                                = stream.getVideoTracks().length > 0;

                            if((audioDeviceRequested && !audioTracksReceived)
                                || (videoDeviceRequested && !videoTracksReceived)) {
                                self.stopMediaStream(stream);

                                // We are getting here in case if we requested
                                // 'audio' or 'video' devices or both, but
                                // didn't get corresponding MediaStreamTrack in
                                // response stream. We don't know the reason why
                                // this happened, so reject with general error.
                                const devices = [];

                                if (audioDeviceRequested && !audioTracksReceived) {
                                    devices.push('audio');
                                }

                                if (videoDeviceRequested && !videoTracksReceived) {
                                    devices.push('video');
                                }

                                // we are missing one of the media we requested
                                // in order to get the actual error that caused
                                // this missing media we will call one more time
                                // getUserMedia so we can obtain the actual
                                // error (Example usecases are requesting
                                // audio and video and video device is missing
                                // or device is denied to be used and chrome is
                                // set to not ask for permissions)
                                self.getUserMediaWithConstraints(
                                    devices,
                                    function() {
                                        // we already failed to obtain this
                                        // media, so we are not supposed in any
                                        // way to receive success for this call
                                        // any way we will throw an error to be
                                        // sure the promise will finish
                                        reject(new JitsiTrackError(
                                            { name: 'UnknownError' },
                                            getConstraints(
                                                options.devices, options),
                                            devices)
                                        );
                                    },
                                    function(error) {
                                        // rejects with real error for not
                                        // obtaining the media
                                        reject(error);
                                    },options);

                                return;
                            }
                            if(hasDesktop) {
                                screenObtainer.obtainStream(
                                    dsOptions,
                                    function(desktopStream) {
                                        successCallback({audioVideo: stream,
                                            desktopStream});
                                    }, function(error) {
                                        self.stopMediaStream(stream);

                                        reject(error);
                                    });
                            } else {
                                successCallback({audioVideo: stream});
                            }
                        },
                        function(error) {
                            reject(error);
                        },
                        options);
                } else if (hasDesktop) {
                    screenObtainer.obtainStream(
                        dsOptions,
                        function(stream) {
                            successCallback({desktopStream: stream});
                        }, function(error) {
                            reject(error);
                        });
                }
            }
        }.bind(this));
    }

    getDeviceAvailability() {
        return devices;
    }

    isRTCReady() {
        return rtcReady;
    }

    _isDeviceListAvailable() {
        if (!rtcReady) {
            throw new Error('WebRTC not ready yet');
        }
        return Boolean(navigator.mediaDevices
            && navigator.mediaDevices.enumerateDevices
            && typeof MediaStreamTrack !== 'undefined'
            && MediaStreamTrack.getSources);
    }

    /**
     * Returns a promise which can be used to make sure that the WebRTC stack
     * has been initialized.
     *
     * @returns {Promise} which is resolved only if the WebRTC stack is ready.
     * Note that currently we do not detect stack initialization failure and
     * the promise is never rejected(unless unexpected error occurs).
     */
    onRTCReady() {
        if (rtcReady) {
            return Promise.resolve();
        }
        return new Promise(resolve => {
            const listener = () => {
                eventEmitter.removeListener(RTCEvents.RTC_READY, listener);
                resolve();
            };
            eventEmitter.addListener(RTCEvents.RTC_READY, listener);
                // We have no failed event, so... it either resolves or nothing
                // happens
        });

    }

    /**
     * Checks if its possible to enumerate available cameras/microphones.
     *
     * @returns {Promise<boolean>} a Promise which will be resolved only once
     * the WebRTC stack is ready, either with true if the device listing is
     * available available or with false otherwise.
     */
    isDeviceListAvailable() {
        return this.onRTCReady().then(this._isDeviceListAvailable.bind(this));
    }

    /**
     * Returns true if changing the input (camera / microphone) or output
     * (audio) device is supported and false if not.
     * @params {string} [deviceType] - type of device to change. Default is
     *      undefined or 'input', 'output' - for audio output device change.
     * @returns {boolean} true if available, false otherwise.
     */
    isDeviceChangeAvailable(deviceType) {
        return deviceType === 'output' || deviceType === 'audiooutput'
            ? isAudioOutputDeviceChangeAvailable
            : RTCBrowserType.isChrome()
                || RTCBrowserType.isFirefox()
                || RTCBrowserType.isOpera()
                || RTCBrowserType.isTemasysPluginUsed()
                || RTCBrowserType.isNWJS()
                || RTCBrowserType.isElectron();
    }
    /**
     * A method to handle stopping of the stream.
     * One point to handle the differences in various implementations.
     * @param mediaStream MediaStream object to stop.
     */
    stopMediaStream(mediaStream) {
        mediaStream.getTracks().forEach(function(track) {
            // stop() not supported with IE
            if (!RTCBrowserType.isTemasysPluginUsed() && track.stop) {
                track.stop();
            }
        });

        // leave stop for implementation still using it
        if (mediaStream.stop) {
            mediaStream.stop();
        }

        // The MediaStream implementation of the react-native-webrtc project has
        // an explicit release method that is to be invoked in order to release
        // used resources such as memory.
        if (mediaStream.release) {
            mediaStream.release();
        }

        // if we have done createObjectURL, lets clean it
        const url = mediaStream.jitsiObjectURL;
        if (url) {
            delete mediaStream.jitsiObjectURL;
            (URL || webkitURL).revokeObjectURL(url);
        }
    }

    /**
     * Returns whether the desktop sharing is enabled or not.
     * @returns {boolean}
     */
    isDesktopSharingEnabled() {
        return screenObtainer.isSupported();
    }

    /**
     * Sets current audio output device.
     * @param {string} deviceId - id of 'audiooutput' device from
     *      navigator.mediaDevices.enumerateDevices(), 'default' for default
     *      device
     * @returns {Promise} - resolves when audio output is changed, is rejected
     *      otherwise
     */
    setAudioOutputDevice(deviceId) {
        if (!this.isDeviceChangeAvailable('output')) {
            Promise.reject(
                new Error('Audio output device change is not supported'));
        }

        return featureDetectionAudioEl.setSinkId(deviceId)
            .then(function() {
                audioOutputDeviceId = deviceId;
                audioOutputChanged = true;

                logger.log(`Audio output device set to ${deviceId}`);

                eventEmitter.emit(RTCEvents.AUDIO_OUTPUT_DEVICE_CHANGED,
                    deviceId);
            });
    }

    /**
     * Returns currently used audio output device id, '' stands for default
     * device
     * @returns {string}
     */
    getAudioOutputDevice() {
        return audioOutputDeviceId;
    }

    /**
     * Returns list of available media devices if its obtained, otherwise an
     * empty array is returned/
     * @returns {Array} list of available media devices.
     */
    getCurrentlyAvailableMediaDevices() {
        return currentlyAvailableMediaDevices;
    }

    /**
     * Returns event data for device to be reported to stats.
     * @returns {MediaDeviceInfo} device.
     */
    getEventDataForActiveDevice(device) {
        const devices = [];
        const deviceData = {
            'deviceId': device.deviceId,
            'kind':     device.kind,
            'label':    device.label,
            'groupId':  device.groupId
        };
        devices.push(deviceData);
        return { deviceList: devices };
    }
}

/**
 * Rejects a Promise because WebRTC is not supported.
 *
 * @param {string} errorMessage - The human-readable message of the Error which
 * is the reason for the rejection.
 * @param {Function} reject - The reject function of the Promise.
 * @returns {void}
 */
function rejectWithWebRTCNotSupported(errorMessage, reject) {
    const error = new Error(errorMessage);

    // WebRTC is not supported either natively or via a known plugin such as
    // Temasys.
    // XXX The Error class already has a property name which is commonly used to
    // detail the represented error in a non-human-readable way (in contrast to
    // the human-readable property message). I explicitly did not want to
    // introduce a new specific property.
    // FIXME None of the existing JitsiXXXErrors seemed to be appropriate
    // recipients of the constant WEBRTC_NOT_SUPPORTED so I explicitly chose to
    // leave it as a magic string at the time of this writing.
    error.name = 'WEBRTC_NOT_SUPPORTED';

    logger.error(errorMessage);
    reject(error);
}

const rtcUtils = new RTCUtils();

export default rtcUtils;