thread.ts

/*
Copyright 2021 The Matrix.org Foundation C.I.C.

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.
*/

import { Optional } from "matrix-events-sdk";

import { MatrixClient, PendingEventOrdering } from "../client";
import { TypedReEmitter } from "../ReEmitter";
import { RelationType } from "../@types/event";
import { EventStatus, IThreadBundledRelationship, MatrixEvent, MatrixEventEvent } from "./event";
import { EventTimeline } from "./event-timeline";
import { EventTimelineSet, EventTimelineSetHandlerMap } from './event-timeline-set';
import { NotificationCountType, Room, RoomEvent } from './room';
import { RoomState } from "./room-state";
import { ServerControlledNamespacedValue } from "../NamespacedValue";
import { logger } from "../logger";
import { ReadReceipt } from "./read-receipt";
import { ReceiptType } from "../@types/read_receipts";

export enum ThreadEvent {
    New = "Thread.new",
    Update = "Thread.update",
    NewReply = "Thread.newReply",
    ViewThread = "Thread.viewThread",
    Delete = "Thread.delete"
}

type EmittedEvents = Exclude<ThreadEvent, ThreadEvent.New>
    | RoomEvent.Timeline
    | RoomEvent.TimelineReset;

export type EventHandlerMap = {
    [ThreadEvent.Update]: (thread: Thread) => void;
    [ThreadEvent.NewReply]: (thread: Thread, event: MatrixEvent) => void;
    [ThreadEvent.ViewThread]: () => void;
    [ThreadEvent.Delete]: (thread: Thread) => void;
} & EventTimelineSetHandlerMap;

interface IThreadOpts {
    room: Room;
    client: MatrixClient;
    pendingEventOrdering?: PendingEventOrdering;
}

export enum FeatureSupport {
    None = 0,
    Experimental = 1,
    Stable = 2
}

export function determineFeatureSupport(stable: boolean, unstable: boolean): FeatureSupport {
    if (stable) {
        return FeatureSupport.Stable;
    } else if (unstable) {
        return FeatureSupport.Experimental;
    } else {
        return FeatureSupport.None;
    }
}

/**
 * @experimental
 */
export class Thread extends ReadReceipt<EmittedEvents, EventHandlerMap> {
    public static hasServerSideSupport = FeatureSupport.None;
    public static hasServerSideListSupport = FeatureSupport.None;
    public static hasServerSideFwdPaginationSupport = FeatureSupport.None;

    /**
     * A reference to all the events ID at the bottom of the threads
     */
    public readonly timelineSet: EventTimelineSet;
    public timeline: MatrixEvent[] = [];

    private _currentUserParticipated = false;

    private reEmitter: TypedReEmitter<EmittedEvents, EventHandlerMap>;

    private lastEvent: MatrixEvent | undefined;
    private replyCount = 0;
    private lastPendingEvent: MatrixEvent | undefined;
    private pendingReplyCount = 0;

    public readonly room: Room;
    public readonly client: MatrixClient;
    private readonly pendingEventOrdering: PendingEventOrdering;

    public initialEventsFetched = !Thread.hasServerSideSupport;

    public constructor(
        public readonly id: string,
        public rootEvent: MatrixEvent | undefined,
        opts: IThreadOpts,
    ) {
        super();

        if (!opts?.room) {
            // Logging/debugging for https://github.com/vector-im/element-web/issues/22141
            // Hope is that we end up with a more obvious stack trace.
            throw new Error("element-web#22141: A thread requires a room in order to function");
        }

        this.room = opts.room;
        this.client = opts.client;
        this.pendingEventOrdering = opts.pendingEventOrdering ?? PendingEventOrdering.Chronological;
        this.timelineSet = new EventTimelineSet(this.room, {
            timelineSupport: true,
            pendingEvents: true,
        }, this.client, this);
        this.reEmitter = new TypedReEmitter(this);

        this.reEmitter.reEmit(this.timelineSet, [
            RoomEvent.Timeline,
            RoomEvent.TimelineReset,
        ]);

        this.room.on(MatrixEventEvent.BeforeRedaction, this.onBeforeRedaction);
        this.room.on(RoomEvent.Redaction, this.onRedaction);
        this.room.on(RoomEvent.LocalEchoUpdated, this.onEcho);
        this.timelineSet.on(RoomEvent.Timeline, this.onTimelineEvent);

        // even if this thread is thought to be originating from this client, we initialise it as we may be in a
        // gappy sync and a thread around this event may already exist.
        this.updateThreadMetadata();
        this.setEventMetadata(this.rootEvent);
    }

    private async fetchRootEvent(): Promise<void> {
        this.rootEvent = this.room.findEventById(this.id);
        // If the rootEvent does not exist in the local stores, then fetch it from the server.
        try {
            const eventData = await this.client.fetchRoomEvent(this.roomId, this.id);
            const mapper = this.client.getEventMapper();
            this.rootEvent = mapper(eventData); // will merge with existing event object if such is known
        } catch (e) {
            logger.error("Failed to fetch thread root to construct thread with", e);
        }
        await this.processEvent(this.rootEvent);
    }

    public static setServerSideSupport(
        status: FeatureSupport,
    ): void {
        Thread.hasServerSideSupport = status;
        if (status !== FeatureSupport.Stable) {
            FILTER_RELATED_BY_SENDERS.setPreferUnstable(true);
            FILTER_RELATED_BY_REL_TYPES.setPreferUnstable(true);
            THREAD_RELATION_TYPE.setPreferUnstable(true);
        }
    }

    public static setServerSideListSupport(
        status: FeatureSupport,
    ): void {
        Thread.hasServerSideListSupport = status;
    }

    public static setServerSideFwdPaginationSupport(
        status: FeatureSupport,
    ): void {
        Thread.hasServerSideFwdPaginationSupport = status;
    }

    private onBeforeRedaction = (event: MatrixEvent, redaction: MatrixEvent): void => {
        if (event?.isRelation(THREAD_RELATION_TYPE.name) &&
            this.room.eventShouldLiveIn(event).threadId === this.id &&
            event.getId() !== this.id && // the root event isn't counted in the length so ignore this redaction
            !redaction.status // only respect it when it succeeds
        ) {
            this.replyCount--;
            this.emit(ThreadEvent.Update, this);
        }
    };

    private onRedaction = async (event: MatrixEvent): Promise<void> => {
        if (event.threadRootId !== this.id) return; // ignore redactions for other timelines
        if (this.replyCount <= 0) {
            for (const threadEvent of this.timeline) {
                this.clearEventMetadata(threadEvent);
            }
            this.lastEvent = this.rootEvent;
            this._currentUserParticipated = false;
            this.emit(ThreadEvent.Delete, this);
        } else {
            await this.updateThreadMetadata();
        }
    };

    private onTimelineEvent = (
        event: MatrixEvent,
        room: Room | undefined,
        toStartOfTimeline: boolean | undefined,
    ): void => {
        // Add a synthesized receipt when paginating forward in the timeline
        if (!toStartOfTimeline) {
            room!.addLocalEchoReceipt(event.getSender()!, event, ReceiptType.Read);
        }
        this.onEcho(event);
    };

    private onEcho = async (event: MatrixEvent): Promise<void> => {
        if (event.threadRootId !== this.id) return; // ignore echoes for other timelines
        if (this.lastEvent === event) return;
        if (!event.isRelation(THREAD_RELATION_TYPE.name)) return;

        await this.updateThreadMetadata();
        this.emit(ThreadEvent.NewReply, this, event);
    };

    public get roomState(): RoomState {
        return this.room.getLiveTimeline().getState(EventTimeline.FORWARDS)!;
    }

    private addEventToTimeline(event: MatrixEvent, toStartOfTimeline: boolean): void {
        if (!this.findEventById(event.getId()!)) {
            this.timelineSet.addEventToTimeline(
                event,
                this.liveTimeline,
                {
                    toStartOfTimeline,
                    fromCache: false,
                    roomState: this.roomState,
                },
            );
            this.timeline = this.events;
        }
    }

    public addEvents(events: MatrixEvent[], toStartOfTimeline: boolean): void {
        events.forEach(ev => this.addEvent(ev, toStartOfTimeline, false));
        this.updateThreadMetadata();
    }

    /**
     * Add an event to the thread and updates
     * the tail/root references if needed
     * Will fire "Thread.update"
     * @param event - The event to add
     * @param toStartOfTimeline - whether the event is being added
     * to the start (and not the end) of the timeline.
     * @param emit - whether to emit the Update event if the thread was updated or not.
     */
    public async addEvent(event: MatrixEvent, toStartOfTimeline: boolean, emit = true): Promise<void> {
        this.setEventMetadata(event);

        const lastReply = this.lastReply();
        const isNewestReply = !lastReply || event.localTimestamp > lastReply!.localTimestamp;

        // Add all incoming events to the thread's timeline set when there's  no server support
        if (!Thread.hasServerSideSupport) {
            // all the relevant membership info to hydrate events with a sender
            // is held in the main room timeline
            // We want to fetch the room state from there and pass it down to this thread
            // timeline set to let it reconcile an event with its relevant RoomMember
            this.addEventToTimeline(event, toStartOfTimeline);

            this.client.decryptEventIfNeeded(event, {});
        } else if (!toStartOfTimeline && this.initialEventsFetched && isNewestReply) {
            await this.fetchEditsWhereNeeded(event);
            this.addEventToTimeline(event, false);
        } else if (event.isRelation(RelationType.Annotation) || event.isRelation(RelationType.Replace)) {
            // Apply annotations and replace relations to the relations of the timeline only
            this.timelineSet.relations?.aggregateParentEvent(event);
            this.timelineSet.relations?.aggregateChildEvent(event, this.timelineSet);
            return;
        }

        // If no thread support exists we want to count all thread relation
        // added as a reply. We can't rely on the bundled relationships count
        if ((!Thread.hasServerSideSupport || !this.rootEvent) && event.isRelation(THREAD_RELATION_TYPE.name)) {
            this.replyCount++;
        }

        if (emit) {
            this.emit(ThreadEvent.NewReply, this, event);
            this.updateThreadMetadata();
        }
    }

    public async processEvent(event: Optional<MatrixEvent>): Promise<void> {
        if (event) {
            this.setEventMetadata(event);
            await this.fetchEditsWhereNeeded(event);
        }
        this.timeline = this.events;
    }

    private getRootEventBundledRelationship(rootEvent = this.rootEvent): IThreadBundledRelationship | undefined {
        return rootEvent?.getServerAggregatedRelation<IThreadBundledRelationship>(THREAD_RELATION_TYPE.name);
    }

    private async processRootEvent(): Promise<void> {
        const bundledRelationship = this.getRootEventBundledRelationship();
        if (Thread.hasServerSideSupport && bundledRelationship) {
            this.replyCount = bundledRelationship.count;
            this._currentUserParticipated = !!bundledRelationship.current_user_participated;

            const mapper = this.client.getEventMapper();
            // re-insert roomId
            this.lastEvent = mapper({
                ...bundledRelationship.latest_event,
                room_id: this.roomId,
            });
            await this.processEvent(this.lastEvent);
        }

        let pendingEvents: MatrixEvent[];
        if (this.pendingEventOrdering === PendingEventOrdering.Detached) {
            pendingEvents = this.room.getPendingEvents()
                .filter(ev => ev.isRelation(THREAD_RELATION_TYPE.name) && this.id === ev.threadRootId);
            await Promise.all(pendingEvents.map(ev => this.processEvent(ev)));
        } else {
            pendingEvents = this.events
                .filter(ev => ev.isRelation(THREAD_RELATION_TYPE.name))
                .filter(ev => ev.status !== EventStatus.SENT && ev.status !== EventStatus.CANCELLED);
        }
        this.lastPendingEvent = pendingEvents.length ? pendingEvents[pendingEvents.length - 1] : undefined;
        this.pendingReplyCount = pendingEvents.length;
    }

    private async updateThreadMetadata(): Promise<void> {
        if (Thread.hasServerSideSupport) {
            // Ensure we show *something* as soon as possible, we'll update it as soon as we get better data, but we
            // don't want the thread preview to be empty if we can avoid it
            if (!this.initialEventsFetched) {
                await this.processRootEvent();
            }
            await this.fetchRootEvent();
        }
        await this.processRootEvent();

        if (!this.initialEventsFetched) {
            this.initialEventsFetched = true;
            // fetch initial event to allow proper pagination
            try {
                // if the thread has regular events, this will just load the last reply.
                // if the thread is newly created, this will load the root event.
                await this.client.paginateEventTimeline(this.liveTimeline, { backwards: true, limit: 1 });
                // just to make sure that, if we've created a timeline window for this thread before the thread itself
                // existed (e.g. when creating a new thread), we'll make sure the panel is force refreshed correctly.
                this.emit(RoomEvent.TimelineReset, this.room, this.timelineSet, true);
            } catch (e) {
                logger.error("Failed to load start of newly created thread: ", e);
                this.initialEventsFetched = false;
            }
        }

        this.emit(ThreadEvent.Update, this);
    }

    // XXX: Workaround for https://github.com/matrix-org/matrix-spec-proposals/pull/2676/files#r827240084
    private async fetchEditsWhereNeeded(...events: MatrixEvent[]): Promise<unknown> {
        return Promise.all(events.filter(e => e.isEncrypted()).map((event: MatrixEvent) => {
            if (event.isRelation()) return; // skip - relations don't get edits
            return this.client.relations(this.roomId, event.getId()!, RelationType.Replace, event.getType(), {
                limit: 1,
            }).then(relations => {
                if (relations.events.length) {
                    event.makeReplaced(relations.events[0]);
                }
            }).catch(e => {
                logger.error("Failed to load edits for encrypted thread event", e);
            });
        }));
    }

    public setEventMetadata(event: Optional<MatrixEvent>): void {
        if (event) {
            EventTimeline.setEventMetadata(event, this.roomState, false);
            event.setThread(this);
        }
    }

    public clearEventMetadata(event: Optional<MatrixEvent>): void {
        if (event) {
            event.setThread(undefined);
            delete event.event?.unsigned?.["m.relations"]?.[THREAD_RELATION_TYPE.name];
        }
    }

    /**
     * Finds an event by ID in the current thread
     */
    public findEventById(eventId: string): MatrixEvent | undefined {
        // Check the lastEvent as it may have been created based on a bundled relationship and not in a timeline
        if (this.lastEvent?.getId() === eventId) {
            return this.lastEvent;
        }

        return this.timelineSet.findEventById(eventId);
    }

    /**
     * Return last reply to the thread, if known.
     */
    public lastReply(matches: (ev: MatrixEvent) => boolean = (): boolean => true): MatrixEvent | null {
        for (let i = this.timeline.length - 1; i >= 0; i--) {
            const event = this.timeline[i];
            if (matches(event)) {
                return event;
            }
        }
        return null;
    }

    public get roomId(): string {
        return this.room.roomId;
    }

    /**
     * The number of messages in the thread
     * Only count rel_type=m.thread as we want to
     * exclude annotations from that number
     */
    public get length(): number {
        return this.replyCount + this.pendingReplyCount;
    }

    /**
     * A getter for the last event added to the thread, if known.
     */
    public get replyToEvent(): Optional<MatrixEvent> {
        return this.lastPendingEvent ?? this.lastEvent ?? this.lastReply();
    }

    public get events(): MatrixEvent[] {
        return this.liveTimeline.getEvents();
    }

    public has(eventId: string): boolean {
        return this.timelineSet.findEventById(eventId) instanceof MatrixEvent;
    }

    public get hasCurrentUserParticipated(): boolean {
        return this._currentUserParticipated;
    }

    public get liveTimeline(): EventTimeline {
        return this.timelineSet.getLiveTimeline();
    }

    public getUnfilteredTimelineSet(): EventTimelineSet {
        return this.timelineSet;
    }

    public addReceipt(event: MatrixEvent, synthetic: boolean): void {
        throw new Error("Unsupported function on the thread model");
    }

    public hasUserReadEvent(userId: string, eventId: string): boolean {
        if (userId === this.client.getUserId()) {
            const publicReadReceipt = this.getReadReceiptForUserId(userId, false, ReceiptType.Read);
            const privateReadReceipt = this.getReadReceiptForUserId(userId, false, ReceiptType.ReadPrivate);
            const hasUnreads = this.room.getThreadUnreadNotificationCount(this.id, NotificationCountType.Total) > 0;

            if (!publicReadReceipt && !privateReadReceipt && !hasUnreads) {
                // Consider an event read if it's part of a thread that has no
                // read receipts and has no notifications. It is likely that it is
                // part of a thread that was created before read receipts for threads
                // were supported (via MSC3771)
                return true;
            }
        }

        return super.hasUserReadEvent(userId, eventId);
    }
}

export const FILTER_RELATED_BY_SENDERS = new ServerControlledNamespacedValue(
    "related_by_senders",
    "io.element.relation_senders",
);
export const FILTER_RELATED_BY_REL_TYPES = new ServerControlledNamespacedValue(
    "related_by_rel_types",
    "io.element.relation_types",
);
export const THREAD_RELATION_TYPE = new ServerControlledNamespacedValue(
    "m.thread",
    "io.element.thread",
);

export enum ThreadFilterType {
    "My",
    "All"
}

export function threadFilterTypeToFilter(type: ThreadFilterType | null): 'all' | 'participated' {
    switch (type) {
        case ThreadFilterType.My:
            return 'participated';
        default:
            return 'all';
    }
}