import * as JitsiConferenceEvents from '../../JitsiConferenceEvents';
import RTCEvents from '../../service/RTC/RTCEvents';
import FeatureFlags from '../flags/FeatureFlags';
import MediaSessionEvents from '../xmpp/MediaSessionEvents';

/**
 * The class manages send video constraints across media sessions({@link JingleSessionPC}) which belong to
 * {@link JitsiConference}. It finds the lowest common value, between the local user's send preference and
 * the remote party's receive preference. Also this module will consider only the active session's receive value,
 * because local tracks are shared and while JVB may have no preference, the remote p2p may have and they may be totally
 * different.
 */
export default class SendVideoController {
    /**
     * Creates new instance for a given conference.
     *
     * @param {JitsiConference} conference - the conference instance for which the new instance will be managing
     * the send video quality constraints.
     * @param {RTC} rtc - the rtc instance that is responsible for sending the messages on the bridge channel.
     */
    constructor(conference, rtc) {
        this._conference = conference;
        this._rtc = rtc;

        /**
         * Source name based sender constraints.
         * @type {Map<string, number>};
         */

        this._sourceSenderConstraints = new Map();
        this._conference.on(
            JitsiConferenceEvents._MEDIA_SESSION_STARTED,
            session => this._onMediaSessionStarted(session));
        this._conference.on(
            JitsiConferenceEvents._MEDIA_SESSION_ACTIVE_CHANGED,
            () => this._propagateSendMaxFrameHeight());
        this._rtc.on(
            RTCEvents.SENDER_VIDEO_CONSTRAINTS_CHANGED,
            videoConstraints => this._onSenderConstraintsReceived(videoConstraints));
    }

    /**
     * Handles the {@link JitsiConferenceEvents.MEDIA_SESSION_STARTED}, that is when the conference creates new media
     * session. It doesn't mean it's already active though. For example the JVB connection may be created after
     * the conference has entered the p2p mode already.
     *
     * @param {JingleSessionPC} mediaSession - the started media session.
     * @private
     */
    _onMediaSessionStarted(mediaSession) {
        mediaSession.addListener(
            MediaSessionEvents.REMOTE_VIDEO_CONSTRAINTS_CHANGED,
            session => {
                if (session === this._conference.getActiveMediaSession()) {
                    this._propagateSendMaxFrameHeight();
                }
            });
    }

    /**
     * Propagates the video constraints if they have changed.
     *
     * @param {Object} videoConstraints - The sender video constraints received from the bridge.
     */
    _onSenderConstraintsReceived(videoConstraints) {
        if (FeatureFlags.isSourceNameSignalingEnabled()) {
            const { idealHeight, sourceName } = videoConstraints;
            const localVideoTracks = this._conference.getLocalVideoTracks() ?? [];

            for (const track of localVideoTracks) {
                // Propagate the sender constraint only if it has changed.
                if (track.getSourceName() === sourceName
                    && (!this._sourceSenderConstraints.has(sourceName)
                    || this._sourceSenderConstraints.get(sourceName) !== idealHeight)) {
                    this._sourceSenderConstraints.set(sourceName, idealHeight);
                    this._propagateSendMaxFrameHeight(sourceName);
                }
            }
        } else if (this._senderVideoConstraints?.idealHeight !== videoConstraints.idealHeight) {
            this._senderVideoConstraints = videoConstraints;
            this._propagateSendMaxFrameHeight();
        }
    }

    /**
     * Figures out the send video constraint as specified by {@link selectSendMaxFrameHeight} and sets it on all media
     * sessions for the reasons mentioned in this class description.
     *
     * @param {string} sourceName - The source for which sender constraints have changed.
     * @returns {Promise<void[]>}
     * @private
     */
    _propagateSendMaxFrameHeight(sourceName = null) {
        const sendMaxFrameHeight = this.selectSendMaxFrameHeight(sourceName);
        const promises = [];

        if (sendMaxFrameHeight >= 0) {
            for (const session of this._conference.getMediaSessions()) {
                promises.push(session.setSenderVideoConstraint(sendMaxFrameHeight, sourceName));
            }
        }

        return Promise.all(promises);
    }

    /**
     * Selects the lowest common value for the local video send constraint by looking at local user's preference and
     * the active media session's receive preference set by the remote party.
     *
     * @param {string} sourceName - The source for which sender constraints have changed.
     * @returns {number|undefined}
     */
    selectSendMaxFrameHeight(sourceName = null) {
        const activeMediaSession = this._conference.getActiveMediaSession();
        const remoteRecvMaxFrameHeight = activeMediaSession
            ? activeMediaSession.isP2P
                ? activeMediaSession.getRemoteRecvMaxFrameHeight()
                : sourceName ? this._sourceSenderConstraints.get(sourceName) : this._senderVideoConstraints?.idealHeight
            : undefined;

        if (this._preferredSendMaxFrameHeight >= 0 && remoteRecvMaxFrameHeight >= 0) {
            return Math.min(this._preferredSendMaxFrameHeight, remoteRecvMaxFrameHeight);
        } else if (remoteRecvMaxFrameHeight >= 0) {
            return remoteRecvMaxFrameHeight;
        }

        return this._preferredSendMaxFrameHeight;
    }

    /**
     * Sets local preference for max send video frame height.
     *
     * @param {number} maxFrameHeight - the new value to set.
     * @returns {Promise<void[]>} - resolved when the operation is complete.
     */
    setPreferredSendMaxFrameHeight(maxFrameHeight) {
        this._preferredSendMaxFrameHeight = maxFrameHeight;

        return this._propagateSendMaxFrameHeight();
    }
}