/* global __filename */

import { getLogger } from 'jitsi-meet-logger';
import debounce from 'lodash.debounce';

import * as JitsiConferenceEvents from '../../JitsiConferenceEvents';
import RTCEvents from '../../service/RTC/RTCEvents';
import browser from '../browser';

import E2EEContext from './E2EEContext';
import { OlmAdapter } from './OlmAdapter';

const logger = getLogger(__filename);

// Period which we'll wait before updating / rotating our keys when a participant
// joins or leaves.
const DEBOUNCE_PERIOD = 5000;

/**
 * This module integrates {@link E2EEContext} with {@link JitsiConference} in order to enable E2E encryption.
 */
export class E2EEncryption {
    /**
     * A constructor.
     * @param {JitsiConference} conference - The conference instance for which E2E encryption is to be enabled.
     */
    constructor(conference) {
        this.conference = conference;

        this._conferenceJoined = false;
        this._enabled = false;
        this._initialized = false;

        this._e2eeCtx = new E2EEContext({ salt: conference.getName() });
        this._olmAdapter = new OlmAdapter(conference);

        // Debounce key rotation / ratcheting to avoid a storm of messages.
        this._ratchetKey = debounce(this._ratchetKeyImpl, DEBOUNCE_PERIOD);
        this._rotateKey = debounce(this._rotateKeyImpl, DEBOUNCE_PERIOD);

        // Participant join / leave operations. Used for key advancement / rotation.
        //

        this.conference.on(
            JitsiConferenceEvents.USER_JOINED,
            this._onParticipantJoined.bind(this));
        this.conference.on(
            JitsiConferenceEvents.USER_LEFT,
            this._onParticipantLeft.bind(this));
        this.conference.on(
            JitsiConferenceEvents.CONFERENCE_JOINED,
            () => {
                this._conferenceJoined = true;
            });

        // Conference media events in order to attach the encryptor / decryptor.
        // FIXME add events to TraceablePeerConnection which will allow to see when there's new receiver or sender
        // added instead of shenanigans around conference track events and track muted.
        //

        this.conference.on(
            JitsiConferenceEvents._MEDIA_SESSION_STARTED,
            this._onMediaSessionStarted.bind(this));
        this.conference.on(
            JitsiConferenceEvents.TRACK_ADDED,
            track => track.isLocal() && this._onLocalTrackAdded(track));
        this.conference.rtc.on(
            RTCEvents.REMOTE_TRACK_ADDED,
            (track, tpc) => this._setupReceiverE2EEForTrack(tpc, track));
        this.conference.on(
            JitsiConferenceEvents.TRACK_MUTE_CHANGED,
            this._trackMuteChanged.bind(this));

        // Olm signalling events.
        this._olmAdapter.on(
            OlmAdapter.events.PARTICIPANT_E2EE_CHANNEL_READY,
            this._onParticipantE2EEChannelReady.bind(this));
        this._olmAdapter.on(
            OlmAdapter.events.PARTICIPANT_KEY_UPDATED,
            this._onParticipantKeyUpdated.bind(this));
    }

    /**
     * Indicates if E2EE is supported in the current platform.
     *
     * @param {object} config - Global configuration.
     * @returns {boolean}
     */
    static isSupported(config) {
        return browser.supportsInsertableStreams()
            && OlmAdapter.isSupported()
            && !(config.testing && config.testing.disableE2EE);
    }

    /**
     * Indicates whether E2EE is currently enabled or not.
     *
     * @returns {boolean}
     */
    isEnabled() {
        return this._enabled;
    }

    /**
     * Enables / disables End-To-End encryption.
     *
     * @param {boolean} enabled - whether E2EE should be enabled or not.
     * @returns {void}
     */
    setEnabled(enabled) {
        if (enabled === this._enabled) {
            return;
        }

        this._enabled = enabled;

        if (!this._initialized && enabled) {
            // Need to re-create the peerconnections in order to apply the insertable streams constraint.
            // TODO: this was necessary due to some audio issues when indertable streams are used
            // even though encryption is not performed. This should be fixed in the browser eventually.
            // https://bugs.chromium.org/p/chromium/issues/detail?id=1103280
            this.conference._restartMediaSessions();

            this._initialized = true;
        }

        // Generate a random key in case we are enabling.
        const key = enabled ? this._generateKey() : false;

        // Send it to others using the E2EE olm channel.
        this._olmAdapter.updateKey(key).then(index => {
            // Set our key so we begin encrypting.
            this._e2eeCtx.setKey(this.conference.myUserId(), key, index);
        });
    }

    /**
     * Generates a new 256 bit random key.
     *
     * @returns {Uint8Array}
     * @private
     */
    _generateKey() {
        return window.crypto.getRandomValues(new Uint8Array(32));
    }

    /**
     * Setup E2EE on the new track that has been added to the conference, apply it on all the open peerconnections.
     * @param {JitsiLocalTrack} track - the new track that's being added to the conference.
     * @private
     */
    _onLocalTrackAdded(track) {
        for (const session of this.conference._getMediaSessions()) {
            this._setupSenderE2EEForTrack(session, track);
        }
    }

    /**
     * Setups E2E encryption for the new session.
     * @param {JingleSessionPC} session - the new media session.
     * @private
     */
    _onMediaSessionStarted(session) {
        const localTracks = this.conference.getLocalTracks();

        for (const track of localTracks) {
            this._setupSenderE2EEForTrack(session, track);
        }
    }

    /**
     * Advances (using ratcheting) the current key whern a new participant joins the conference.
     * @private
     */
    _onParticipantJoined(id) {
        logger.debug(`Participant ${id} joined`);

        if (this._conferenceJoined && this._enabled) {
            this._ratchetKey();
        }
    }

    /**
     * Rotates the current key when a participant leaves the conference.
     * @private
     */
    _onParticipantLeft(id) {
        logger.debug(`Participant ${id} left`);

        this._e2eeCtx.cleanup(id);

        if (this._enabled) {
            this._rotateKey();
        }
    }

    /**
     * Event posted when the E2EE signalling channel has been establioshed with the given participant.
     * @private
     */
    _onParticipantE2EEChannelReady(id) {
        logger.debug(`E2EE channel with participant ${id} is ready`);
    }

    /**
     * Handles an update in a participant's key.
     *
     * @param {string} id - The participant ID.
     * @param {Uint8Array | boolean} key - The new key for the participant.
     * @param {Number} index - The new key's index.
     * @private
     */
    _onParticipantKeyUpdated(id, key, index) {
        logger.debug(`Participant ${id} updated their key`);

        this._e2eeCtx.setKey(id, key, index);
    }

    /**
     * Advances the current key by using ratcheting.
     * TODO: not yet implemented, we are just rotating the key at the moment,
     * which is a heavier operation.
     *
     * @private
     */
    async _ratchetKeyImpl() {
        logger.debug('Ratchetting key');

        return this._rotateKey();
    }

    /**
     * Rotates the local key. Rotating the key implies creating a new one, then distributing it
     * to all participants and once they all received it, start using it.
     *
     * @private
     */
    async _rotateKeyImpl() {
        logger.debug('Rotating key');

        const key = this._generateKey();
        const index = await this._olmAdapter.updateKey(key);

        this._e2eeCtx.setKey(this.conference.myUserId(), key, index);
    }

    /**
     * Setup E2EE for the receiving side.
     *
     * @private
     */
    _setupReceiverE2EEForTrack(tpc, track) {
        if (!this._enabled) {
            return;
        }

        const receiver = tpc.findReceiverForTrack(track.track);

        if (receiver) {
            this._e2eeCtx.handleReceiver(receiver, track.getType(), track.getParticipantId());
        } else {
            logger.warn(`Could not handle E2EE for ${track}: receiver not found in: ${tpc}`);
        }
    }

    /**
     * Setup E2EE for the sending side.
     *
     * @param {JingleSessionPC} session - the session which sends the media produced by the track.
     * @param {JitsiLocalTrack} track - the local track for which e2e encoder will be configured.
     * @private
     */
    _setupSenderE2EEForTrack(session, track) {
        if (!this._enabled) {
            return;
        }

        const pc = session.peerconnection;
        const sender = pc && pc.findSenderForTrack(track.track);

        if (sender) {
            this._e2eeCtx.handleSender(sender, track.getType(), track.getParticipantId());
        } else {
            logger.warn(`Could not handle E2EE for ${track}: sender not found in ${pc}`);
        }
    }

    /**
     * Setup E2EE on the sender that is created for the unmuted local video track.
     * @param {JitsiLocalTrack} track - the track for which muted status has changed.
     * @private
     */
    _trackMuteChanged(track) {
        if (browser.doesVideoMuteByStreamRemove() && track.isLocal() && track.isVideoTrack() && !track.isMuted()) {
            for (const session of this.conference._getMediaSessions()) {
                this._setupSenderE2EEForTrack(session, track);
            }
        }
    }
}