room-state.js

/*
Copyright 2015, 2016 OpenMarket Ltd

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
"use strict";
/**
 * @module models/room-state
 */
const EventEmitter = require("events").EventEmitter;

const utils = require("../utils");
const RoomMember = require("./room-member");

// possible statuses for out-of-band member loading
const OOB_STATUS_NOTSTARTED = 1;
const OOB_STATUS_INPROGRESS = 2;
const OOB_STATUS_FINISHED = 3;

/**
 * Construct room state.
 *
 * Room State represents the state of the room at a given point.
 * It can be mutated by adding state events to it.
 * There are two types of room member associated with a state event:
 * normal member objects (accessed via getMember/getMembers) which mutate
 * with the state to represent the current state of that room/user, eg.
 * the object returned by getMember('@bob:example.com') will mutate to
 * get a different display name if Bob later changes his display name
 * in the room.
 * There are also 'sentinel' members (accessed via getSentinelMember).
 * These also represent the state of room members at the point in time
 * represented by the RoomState object, but unlike objects from getMember,
 * sentinel objects will always represent the room state as at the time
 * getSentinelMember was called, so if Bob subsequently changes his display
 * name, a room member object previously acquired with getSentinelMember
 * will still have his old display name. Calling getSentinelMember again
 * after the display name change will return a new RoomMember object
 * with Bob's new display name.
 *
 * @constructor
 * @param {?string} roomId Optional. The ID of the room which has this state.
 * If none is specified it just tracks paginationTokens, useful for notifTimelineSet
 * @param {?object} oobMemberFlags Optional. The state of loading out of bound members.
 * As the timeline might get reset while they are loading, this state needs to be inherited
 * and shared when the room state is cloned for the new timeline.
 * This should only be passed from clone.
 * @prop {Object.<string, RoomMember>} members The room member dictionary, keyed
 * on the user's ID.
 * @prop {Object.<string, Object.<string, MatrixEvent>>} events The state
 * events dictionary, keyed on the event type and then the state_key value.
 * @prop {string} paginationToken The pagination token for this state.
 */
function RoomState(roomId, oobMemberFlags = undefined) {
    this.roomId = roomId;
    this.members = {
        // userId: RoomMember
    };
    this.events = {
        // eventType: { stateKey: MatrixEvent }
    };
    this.paginationToken = null;

    this._sentinels = {
        // userId: RoomMember
    };
    this._updateModifiedTime();
    this._displayNameToUserIds = {};
    this._userIdsToDisplayNames = {};
    this._tokenToInvite = {}; // 3pid invite state_key to m.room.member invite
    this._joinedMemberCount = null; // cache of the number of joined members
    // joined members count from summary api
    // once set, we know the server supports the summary api
    // and we should only trust that
    // we could also only trust that before OOB members
    // are loaded but doesn't seem worth the hassle atm
    this._summaryJoinedMemberCount = null;
    // same for invited member count
    this._invitedMemberCount = null;
    this._summaryInvitedMemberCount = null;

    if (!oobMemberFlags) {
        oobMemberFlags = {
            status: OOB_STATUS_NOTSTARTED,
        };
    }
    this._oobMemberFlags = oobMemberFlags;
}
utils.inherits(RoomState, EventEmitter);

/**
 * Returns the number of joined members in this room
 * This method caches the result.
 * @return {integer} The number of members in this room whose membership is 'join'
 */
RoomState.prototype.getJoinedMemberCount = function() {
    if (this._summaryJoinedMemberCount !== null) {
        return this._summaryJoinedMemberCount;
    }
    if (this._joinedMemberCount === null) {
        this._joinedMemberCount = this.getMembers().reduce((count, m) => {
            return m.membership === 'join' ? count + 1 : count;
        }, 0);
    }
    return this._joinedMemberCount;
};

/**
 * Set the joined member count explicitly (like from summary part of the sync response)
 * @param {number} count the amount of joined members
 */
RoomState.prototype.setJoinedMemberCount = function(count) {
    this._summaryJoinedMemberCount = count;
};
/**
 * Returns the number of invited members in this room
 * @return {integer} The number of members in this room whose membership is 'invite'
 */
RoomState.prototype.getInvitedMemberCount = function() {
    if (this._summaryInvitedMemberCount !== null) {
        return this._summaryInvitedMemberCount;
    }
    if (this._invitedMemberCount === null) {
        this._invitedMemberCount = this.getMembers().reduce((count, m) => {
            return m.membership === 'invite' ? count + 1 : count;
        }, 0);
    }
    return this._invitedMemberCount;
};

/**
 * Set the amount of invited members in this room
 * @param {number} count the amount of invited members
 */
RoomState.prototype.setInvitedMemberCount = function(count) {
    this._summaryInvitedMemberCount = count;
};

/**
 * Get all RoomMembers in this room.
 * @return {Array<RoomMember>} A list of RoomMembers.
 */
RoomState.prototype.getMembers = function() {
    return utils.values(this.members);
};

/**
 * Get a room member by their user ID.
 * @param {string} userId The room member's user ID.
 * @return {RoomMember} The member or null if they do not exist.
 */
RoomState.prototype.getMember = function(userId) {
    return this.members[userId] || null;
};

/**
 * Get a room member whose properties will not change with this room state. You
 * typically want this if you want to attach a RoomMember to a MatrixEvent which
 * may no longer be represented correctly by Room.currentState or Room.oldState.
 * The term 'sentinel' refers to the fact that this RoomMember is an unchanging
 * guardian for state at this particular point in time.
 * @param {string} userId The room member's user ID.
 * @return {RoomMember} The member or null if they do not exist.
 */
RoomState.prototype.getSentinelMember = function(userId) {
    if (!userId) return null;
    let sentinel = this._sentinels[userId];

    if (sentinel === undefined) {
        sentinel = new RoomMember(this.roomId, userId);
        const member = this.members[userId];
        if (member) {
            sentinel.setMembershipEvent(member.events.member);
        }
        this._sentinels[userId] = sentinel;
    }
    return sentinel;
};

/**
 * Get state events from the state of the room.
 * @param {string} eventType The event type of the state event.
 * @param {string} stateKey Optional. The state_key of the state event. If
 * this is <code>undefined</code> then all matching state events will be
 * returned.
 * @return {MatrixEvent[]|MatrixEvent} A list of events if state_key was
 * <code>undefined</code>, else a single event (or null if no match found).
 */
RoomState.prototype.getStateEvents = function(eventType, stateKey) {
    if (!this.events[eventType]) {
        // no match
        return stateKey === undefined ? [] : null;
    }
    if (stateKey === undefined) { // return all values
        return utils.values(this.events[eventType]);
    }
    const event = this.events[eventType][stateKey];
    return event ? event : null;
};

/**
 * Creates a copy of this room state so that mutations to either won't affect the other.
 * @return {RoomState} the copy of the room state
 */
RoomState.prototype.clone = function() {
    const copy = new RoomState(this.roomId, this._oobMemberFlags);

    // Ugly hack: because setStateEvents will mark
    // members as susperseding future out of bound members
    // if loading is in progress (through _oobMemberFlags)
    // since these are not new members, we're merely copying them
    // set the status to not started
    // after copying, we set back the status and
    // copy the superseding flag from the current state
    const status = this._oobMemberFlags.status;
    this._oobMemberFlags.status = OOB_STATUS_NOTSTARTED;

    Object.values(this.events).forEach((eventsByStateKey) => {
        const eventsForType = Object.values(eventsByStateKey);
        copy.setStateEvents(eventsForType);
    });

    // Ugly hack: see above
    this._oobMemberFlags.status = status;

    if (this._summaryInvitedMemberCount !== null) {
        copy.setInvitedMemberCount(this.getInvitedMemberCount());
    }
    if (this._summaryJoinedMemberCount !== null) {
        copy.setJoinedMemberCount(this.getJoinedMemberCount());
    }

    // copy out of band flags if needed
    if (this._oobMemberFlags.status == OOB_STATUS_FINISHED) {
        // copy markOutOfBand flags
        this.getMembers().forEach((member) => {
            if (member.isOutOfBand()) {
                const copyMember = copy.getMember(member.userId);
                copyMember.markOutOfBand();
            }
        });
    } else if (this._oobMemberFlags.status == OOB_STATUS_INPROGRESS) {
        // copy markSupersedesOutOfBand flags
        this.getMembers().forEach((member) => {
            if (member.supersedesOutOfBand()) {
                const copyMember = copy.getMember(member.userId);
                copyMember.markSupersedesOutOfBand();
            }
        });
    }

    return copy;
};

/**
 * Add previously unknown state events.
 * When lazy loading members while back-paginating,
 * the relevant room state for the timeline chunk at the end
 * of the chunk can be set with this method.
 * @param {MatrixEvent[]} events state events to prepend
 */
RoomState.prototype.setUnknownStateEvents = function(events) {
    const unknownStateEvents = events.filter((event) => {
        return this.events[event.getType()] === undefined ||
            this.events[event.getType()][event.getStateKey()] === undefined;
    });

    this.setStateEvents(unknownStateEvents);
};

/**
 * Add an array of one or more state MatrixEvents, overwriting
 * any existing state with the same {type, stateKey} tuple. Will fire
 * "RoomState.events" for every event added. May fire "RoomState.members"
 * if there are <code>m.room.member</code> events.
 * @param {MatrixEvent[]} stateEvents a list of state events for this room.
 * @fires module:client~MatrixClient#event:"RoomState.members"
 * @fires module:client~MatrixClient#event:"RoomState.newMember"
 * @fires module:client~MatrixClient#event:"RoomState.events"
 */
RoomState.prototype.setStateEvents = function(stateEvents) {
    const self = this;
    this._updateModifiedTime();

    // update the core event dict
    utils.forEach(stateEvents, function(event) {
        if (event.getRoomId() !== self.roomId) {
            return;
        }
        if (!event.isState()) {
            return;
        }

        self._setStateEvent(event);
        if (event.getType() === "m.room.member") {
            _updateDisplayNameCache(
                self, event.getStateKey(), event.getContent().displayname,
            );
            _updateThirdPartyTokenCache(self, event);
        }
        self.emit("RoomState.events", event, self);
    });

    // update higher level data structures. This needs to be done AFTER the
    // core event dict as these structures may depend on other state events in
    // the given array (e.g. disambiguating display names in one go to do both
    // clashing names rather than progressively which only catches 1 of them).
    utils.forEach(stateEvents, function(event) {
        if (event.getRoomId() !== self.roomId) {
            return;
        }
        if (!event.isState()) {
            return;
        }

        if (event.getType() === "m.room.member") {
            const userId = event.getStateKey();

            // leave events apparently elide the displayname or avatar_url,
            // so let's fake one up so that we don't leak user ids
            // into the timeline
            if (event.getContent().membership === "leave" ||
                event.getContent().membership === "ban") {
                event.getContent().avatar_url =
                    event.getContent().avatar_url ||
                    event.getPrevContent().avatar_url;
                event.getContent().displayname =
                    event.getContent().displayname ||
                    event.getPrevContent().displayname;
            }

            const member = self._getOrCreateMember(userId, event);
            member.setMembershipEvent(event, self);
            // if out of band members are loading,
            // mark the member as more recent
            if (self._oobMemberFlags.status == OOB_STATUS_INPROGRESS) {
                member.markSupersedesOutOfBand();
            }

            self._updateMember(member);
            self.emit("RoomState.members", event, self, member);
        } else if (event.getType() === "m.room.power_levels") {
            const members = utils.values(self.members);
            utils.forEach(members, function(member) {
                member.setPowerLevelEvent(event);
                self.emit("RoomState.members", event, self, member);
            });

            // assume all our sentinels are now out-of-date
            self._sentinels = {};
        }
    });
};

/**
 * Looks up a member by the given userId, and if it doesn't exist,
 * create it and emit the `RoomState.newMember` event.
 * This method makes sure the member is added to the members dictionary
 * before emitting, as this is done from setStateEvents and _setOutOfBandMember.
 * @param {string} userId the id of the user to look up
 * @param {MatrixEvent} event the membership event for the (new) member. Used to emit.
 * @fires module:client~MatrixClient#event:"RoomState.newMember"
 * @returns {RoomMember} the member, existing or newly created.
 */
RoomState.prototype._getOrCreateMember = function(userId, event) {
    let member = this.members[userId];
    if (!member) {
        member = new RoomMember(this.roomId, userId);
        // add member to members before emitting any events,
        // as event handlers often lookup the member
        this.members[userId] = member;
        this.emit("RoomState.newMember", event, this, member);
    }
    return member;
};

RoomState.prototype._setStateEvent = function(event) {
    if (this.events[event.getType()] === undefined) {
        this.events[event.getType()] = {};
    }
    this.events[event.getType()][event.getStateKey()] = event;
};

RoomState.prototype._updateMember = function(member) {
    // this member may have a power level already, so set it.
    const pwrLvlEvent = this.getStateEvents("m.room.power_levels", "");
    if (pwrLvlEvent) {
        member.setPowerLevelEvent(pwrLvlEvent);
    }

    // blow away the sentinel which is now outdated
    delete this._sentinels[member.userId];

    this.members[member.userId] = member;
    this._joinedMemberCount = null;
    this._invitedMemberCount = null;
};

/**
 * Get the out-of-band members loading state, whether loading is needed or not.
 * Note that loading might be in progress and hence isn't needed.
 * @return {bool} whether or not the members of this room need to be loaded
 */
RoomState.prototype.needsOutOfBandMembers = function() {
    return this._oobMemberFlags.status === OOB_STATUS_NOTSTARTED;
};

/**
 * Mark this room state as waiting for out-of-band members,
 * ensuring it doesn't ask for them to be requested again
 * through needsOutOfBandMembers
 */
RoomState.prototype.markOutOfBandMembersStarted = function() {
    if (this._oobMemberFlags.status !== OOB_STATUS_NOTSTARTED) {
        return;
    }
    this._oobMemberFlags.status = OOB_STATUS_INPROGRESS;
};

/**
 * Mark this room state as having failed to fetch out-of-band members
 */
RoomState.prototype.markOutOfBandMembersFailed = function() {
    if (this._oobMemberFlags.status !== OOB_STATUS_INPROGRESS) {
        return;
    }
    // the request failed, there is nothing to supersede
    // in case of a retry, these event would not supersede the
    // retry anymore.
    this.getMembers().forEach((m) => {
        m.clearSupersedesOutOfBand();
    });
    this._oobMemberFlags.status = OOB_STATUS_NOTSTARTED;
};

/**
 * Clears the loaded out-of-band members
 */
RoomState.prototype.clearOutOfBandMembers = function() {
    let count = 0;
    Object.keys(this.members).forEach((userId) => {
        const member = this.members[userId];
        if (member.isOutOfBand()) {
            ++count;
            delete this.members[userId];
        }
    });
    console.log(`LL: RoomState removed ${count} members...`);
    this._oobMemberFlags.status = OOB_STATUS_NOTSTARTED;
};

/**
 * Sets the loaded out-of-band members.
 * @param {MatrixEvent[]} stateEvents array of membership state events
 */
RoomState.prototype.setOutOfBandMembers = function(stateEvents) {
    console.log(`LL: RoomState about to set ${stateEvents.length} OOB members ...`);
    if (this._oobMemberFlags.status !== OOB_STATUS_INPROGRESS) {
        return;
    }
    console.log(`LL: RoomState put in OOB_STATUS_FINISHED state ...`);
    this._oobMemberFlags.status = OOB_STATUS_FINISHED;
    stateEvents.forEach((e) => this._setOutOfBandMember(e));
};

/**
 * Sets a single out of band member, used by both setOutOfBandMembers and clone
 * @param {MatrixEvent} stateEvent membership state event
 */
RoomState.prototype._setOutOfBandMember = function(stateEvent) {
    if (stateEvent.getType() !== 'm.room.member') {
        return;
    }
    const userId = stateEvent.getStateKey();
    const existingMember = this.getMember(userId);
    if (existingMember) {
        const existingMemberEvent = existingMember.events.member;
        // ignore out of band members with events we are
        // already aware of.
        if (existingMemberEvent.getId() === stateEvent.getId()) {
            return;
        }
        // this member was updated since we started
        // loading the out of band members.
        // Ignore the out of band member and clear
        // the "supersedes" flag as the out of members are now loaded
        if (existingMember.supersedesOutOfBand()) {
            existingMember.clearSupersedesOutOfBand();
            return;
        }
    }

    const member = this._getOrCreateMember(userId, stateEvent);
    member.setMembershipEvent(stateEvent);
    // needed to know which members need to be stored seperately
    // as the are not part of the sync accumulator
    // this is cleared by setMembershipEvent so when it's updated through /sync
    member.markOutOfBand();

    _updateDisplayNameCache(this, member.userId, member.name);

    this._setStateEvent(stateEvent);
    this._updateMember(member);
    this.emit("RoomState.members", stateEvent, this, member);
};

/**
 * Set the current typing event for this room.
 * @param {MatrixEvent} event The typing event
 */
RoomState.prototype.setTypingEvent = function(event) {
    utils.forEach(utils.values(this.members), function(member) {
        member.setTypingEvent(event);
    });
};

/**
 * Get the m.room.member event which has the given third party invite token.
 *
 * @param {string} token The token
 * @return {?MatrixEvent} The m.room.member event or null
 */
RoomState.prototype.getInviteForThreePidToken = function(token) {
    return this._tokenToInvite[token] || null;
};

/**
 * Update the last modified time to the current time.
 */
RoomState.prototype._updateModifiedTime = function() {
    this._modified = Date.now();
};

/**
 * Get the timestamp when this room state was last updated. This timestamp is
 * updated when this object has received new state events.
 * @return {number} The timestamp
 */
RoomState.prototype.getLastModifiedTime = function() {
    return this._modified;
};

/**
 * Get user IDs with the specified display name.
 * @param {string} displayName The display name to get user IDs from.
 * @return {string[]} An array of user IDs or an empty array.
 */
RoomState.prototype.getUserIdsWithDisplayName = function(displayName) {
    return this._displayNameToUserIds[displayName] || [];
};

/**
 * Returns true if userId is in room, event is not redacted and either sender of
 * mxEvent or has power level sufficient to redact events other than their own.
 * @param {MatrixEvent} mxEvent The event to test permission for
 * @param {string} userId The user ID of the user to test permission for
 * @return {boolean} true if the given used ID can redact given event
 */
RoomState.prototype.maySendRedactionForEvent = function(mxEvent, userId) {
    const member = this.getMember(userId);
    if (!member || member.membership === 'leave') return false;

    if (mxEvent.status || mxEvent.isRedacted()) return false;

    // The user may have been the sender, but they can't redact their own message
    // if redactions are blocked.
    const canRedact = this.maySendEvent("m.room.redaction", userId);
    if (mxEvent.getSender() === userId) return canRedact;

    return this._hasSufficientPowerLevelFor('redact', member.powerLevel);
};

/**
 * Returns true if the given power level is sufficient for action
 * @param {string} action The type of power level to check
 * @param {number} powerLevel The power level of the member
 * @return {boolean} true if the given power level is sufficient
 */
RoomState.prototype._hasSufficientPowerLevelFor = function(action, powerLevel) {
    const powerLevelsEvent = this.getStateEvents('m.room.power_levels', '');

    let powerLevels = {};
    if (powerLevelsEvent) {
        powerLevels = powerLevelsEvent.getContent();
    }

    let requiredLevel = 50;
    if (utils.isNumber(powerLevels[action])) {
        requiredLevel = powerLevels[action];
    }

    return powerLevel >= requiredLevel;
};

/**
 * Short-form for maySendEvent('m.room.message', userId)
 * @param {string} userId The user ID of the user to test permission for
 * @return {boolean} true if the given user ID should be permitted to send
 *                   message events into the given room.
 */
RoomState.prototype.maySendMessage = function(userId) {
    return this._maySendEventOfType('m.room.message', userId, false);
};

/**
 * Returns true if the given user ID has permission to send a normal
 * event of type `eventType` into this room.
 * @param {string} eventType The type of event to test
 * @param {string} userId The user ID of the user to test permission for
 * @return {boolean} true if the given user ID should be permitted to send
 *                        the given type of event into this room,
 *                        according to the room's state.
 */
RoomState.prototype.maySendEvent = function(eventType, userId) {
    return this._maySendEventOfType(eventType, userId, false);
};

/**
 * Returns true if the given MatrixClient has permission to send a state
 * event of type `stateEventType` into this room.
 * @param {string} stateEventType The type of state events to test
 * @param {MatrixClient} cli The client to test permission for
 * @return {boolean} true if the given client should be permitted to send
 *                        the given type of state event into this room,
 *                        according to the room's state.
 */
RoomState.prototype.mayClientSendStateEvent = function(stateEventType, cli) {
    if (cli.isGuest()) {
        return false;
    }
    return this.maySendStateEvent(stateEventType, cli.credentials.userId);
};

/**
 * Returns true if the given user ID has permission to send a state
 * event of type `stateEventType` into this room.
 * @param {string} stateEventType The type of state events to test
 * @param {string} userId The user ID of the user to test permission for
 * @return {boolean} true if the given user ID should be permitted to send
 *                        the given type of state event into this room,
 *                        according to the room's state.
 */
RoomState.prototype.maySendStateEvent = function(stateEventType, userId) {
    return this._maySendEventOfType(stateEventType, userId, true);
};

/**
 * Returns true if the given user ID has permission to send a normal or state
 * event of type `eventType` into this room.
 * @param {string} eventType The type of event to test
 * @param {string} userId The user ID of the user to test permission for
 * @param {boolean} state If true, tests if the user may send a state
                          event of this type. Otherwise tests whether
                          they may send a regular event.
 * @return {boolean} true if the given user ID should be permitted to send
 *                        the given type of event into this room,
 *                        according to the room's state.
 */
RoomState.prototype._maySendEventOfType = function(eventType, userId, state) {
    const power_levels_event = this.getStateEvents('m.room.power_levels', '');

    let power_levels;
    let events_levels = {};

    let state_default = 0;
    let events_default = 0;
    let powerLevel = 0;
    if (power_levels_event) {
        power_levels = power_levels_event.getContent();
        events_levels = power_levels.events || {};

        if (Number.isFinite(power_levels.state_default)) {
            state_default = power_levels.state_default;
        } else {
            state_default = 50;
        }

        const userPowerLevel = power_levels.users && power_levels.users[userId];
        if (Number.isFinite(userPowerLevel)) {
            powerLevel = userPowerLevel;
        } else if(Number.isFinite(power_levels.users_default)) {
            powerLevel = power_levels.users_default;
        }

        if (Number.isFinite(power_levels.events_default)) {
            events_default = power_levels.events_default;
        }
    }

    let required_level = state ? state_default : events_default;
    if (Number.isFinite(events_levels[eventType])) {
        required_level = events_levels[eventType];
    }
    return powerLevel >= required_level;
};

/**
 * Returns true if the given user ID has permission to trigger notification
 * of type `notifLevelKey`
 * @param {string} notifLevelKey The level of notification to test (eg. 'room')
 * @param {string} userId The user ID of the user to test permission for
 * @return {boolean} true if the given user ID has permission to trigger a
 *                        notification of this type.
 */
RoomState.prototype.mayTriggerNotifOfType = function(notifLevelKey, userId) {
    const member = this.getMember(userId);
    if (!member) {
        return false;
    }

    const powerLevelsEvent = this.getStateEvents('m.room.power_levels', '');

    let notifLevel = 50;
    if (
        powerLevelsEvent &&
        powerLevelsEvent.getContent() &&
        powerLevelsEvent.getContent().notifications &&
        utils.isNumber(powerLevelsEvent.getContent().notifications[notifLevelKey])
    ) {
        notifLevel = powerLevelsEvent.getContent().notifications[notifLevelKey];
    }

    return member.powerLevel >= notifLevel;
};

/**
 * The RoomState class.
 */
module.exports = RoomState;


function _updateThirdPartyTokenCache(roomState, memberEvent) {
    if (!memberEvent.getContent().third_party_invite) {
        return;
    }
    const token = (memberEvent.getContent().third_party_invite.signed || {}).token;
    if (!token) {
        return;
    }
    const threePidInvite = roomState.getStateEvents(
        "m.room.third_party_invite", token,
    );
    if (!threePidInvite) {
        return;
    }
    roomState._tokenToInvite[token] = memberEvent;
}

function _updateDisplayNameCache(roomState, userId, displayName) {
    const oldName = roomState._userIdsToDisplayNames[userId];
    delete roomState._userIdsToDisplayNames[userId];
    if (oldName) {
        // Remove the old name from the cache.
        // We clobber the user_id > name lookup but the name -> [user_id] lookup
        // means we need to remove that user ID from that array rather than nuking
        // the lot.
        const strippedOldName = utils.removeHiddenChars(oldName);

        const existingUserIds = roomState._displayNameToUserIds[strippedOldName];
        if (existingUserIds) {
            // remove this user ID from this array
            const filteredUserIDs = existingUserIds.filter((id) => id !== userId);
            roomState._displayNameToUserIds[strippedOldName] = filteredUserIDs;
        }
    }

    roomState._userIdsToDisplayNames[userId] = displayName;

    const strippedDisplayname = displayName && utils.removeHiddenChars(displayName);
    // an empty stripped displayname (undefined/'') will be set to MXID in room-member.js
    if (strippedDisplayname) {
        if (!roomState._displayNameToUserIds[strippedDisplayname]) {
            roomState._displayNameToUserIds[strippedDisplayname] = [];
        }
        roomState._displayNameToUserIds[strippedDisplayname].push(userId);
    }
}

/**
 * Fires whenever the event dictionary in room state is updated.
 * @event module:client~MatrixClient#"RoomState.events"
 * @param {MatrixEvent} event The matrix event which caused this event to fire.
 * @param {RoomState} state The room state whose RoomState.events dictionary
 * was updated.
 * @example
 * matrixClient.on("RoomState.events", function(event, state){
 *   var newStateEvent = event;
 * });
 */

/**
 * Fires whenever a member in the members dictionary is updated in any way.
 * @event module:client~MatrixClient#"RoomState.members"
 * @param {MatrixEvent} event The matrix event which caused this event to fire.
 * @param {RoomState} state The room state whose RoomState.members dictionary
 * was updated.
 * @param {RoomMember} member The room member that was updated.
 * @example
 * matrixClient.on("RoomState.members", function(event, state, member){
 *   var newMembershipState = member.membership;
 * });
 */

 /**
 * Fires whenever a member is added to the members dictionary. The RoomMember
 * will not be fully populated yet (e.g. no membership state) but will already
 * be available in the members dictionary.
 * @event module:client~MatrixClient#"RoomState.newMember"
 * @param {MatrixEvent} event The matrix event which caused this event to fire.
 * @param {RoomState} state The room state whose RoomState.members dictionary
 * was updated with a new entry.
 * @param {RoomMember} member The room member that was added.
 * @example
 * matrixClient.on("RoomState.newMember", function(event, state, member){
 *   // add event listeners on 'member'
 * });
 */