Reduce complexity of ElementWidgetDriver.readRoomTimeline

src/stores/widgets/ElementWidgetDriver.ts

@@ -27,18 +27,18 @@
     type ISearchUserDirectoryResult,
     type IGetMediaConfigResult,
 } from "matrix-widget-api";
 import {
     ClientEvent,
     type ITurnServer as IClientTurnServer,
     EventType,
     type IContent,
     MatrixError,
-    type MatrixEvent,
     Direction,
     THREAD_RELATION_TYPE,
     type SendDelayedEventResponse,
     type StateEvents,
     type TimelineEvents,
+    Room,
 } from "matrix-js-sdk/src/matrix";
 import { logger } from "matrix-js-sdk/src/logger";
 import {
@@ -85,17 +85,17 @@
  * authorized actions on the widget's behalf). Essentially this is a glorified
  * set of callbacks.
  */
 // TODO: Consider alternative designs for matrix-widget-api?
 // Replace with matrix-rust-sdk?
 export class ElementWidgetDriver extends WidgetDriver {
     private allowedCapabilities: Set<Capability>;
 
     // TODO: Refactor widgetKind into the Widget class
     public constructor(
         private forWidget: Widget,
         private forWidgetKind: WidgetKind,
         virtual: boolean,
         private inRoomId?: string,
     ) {
         super();
 
@@ -258,7 +258,7 @@
             });
         }
 
         // TODO: Do something when the widget requests new capabilities not yet asked for
         let rememberApproved = false;
         if (missing.size > 0) {
             try {
@@ -275,7 +275,7 @@
         }
 
         // discard all previously allowed capabilities if they are not requested
         // TODO: this results in an unexpected behavior when this function is called during the capabilities renegotiation of MSC2974 that will be resolved later.
         const allAllowed = new Set(iterableIntersection(allowedSoFar, requested));
 
         if (rememberApproved) {
@@ -314,7 +314,7 @@
             r = await client.sendStateEvent(
                 roomId,
                 eventType as keyof StateEvents,
                 content as StateEvents[keyof StateEvents],
                 stateKey,
             );
         } else if (eventType === EventType.RoomRedaction) {
@@ -325,7 +325,7 @@
             r = await client.sendEvent(
                 roomId,
                 eventType as keyof TimelineEvents,
                 content as TimelineEvents[keyof TimelineEvents],
             );
 
             if (eventType === EventType.RoomMessage) {
@@ -387,7 +387,7 @@
                 delay,
                 ...(parentDelayId !== null && { parent_delay_id: parentDelayId }),
             };
         } else if (parentDelayId !== null) {
             delayOpts = {
                 parent_delay_id: parentDelayId,
             };
@@ -396,13 +396,13 @@
         }
 
         let r: SendDelayedEventResponse | null;
         if (stateKey !== null) {
             // state event
             r = await client._unstable_sendDelayedStateEvent(
                 roomId,
                 delayOpts,
                 eventType as keyof StateEvents,
                 content as StateEvents[keyof StateEvents],
                 stateKey,
             );
         } else {
@@ -412,7 +412,7 @@
                 delayOpts,
                 null,
                 eventType as keyof TimelineEvents,
                 content as TimelineEvents[keyof TimelineEvents],
             );
         }
 
@@ -507,6 +507,38 @@
         }
     }
 
+    /**
+     * Generator function that retrieves events for readRoomTimeline
+     * @param room The room to check the timeline of.
+     * @param eventType The event type to be read.
+     * @param msgtype The msgtype of the events to be read, if applicable/defined.
+     * @param stateKey The state key of the events to be read, if applicable/defined.
+     * @param limit The maximum number of events to retrieve. Will be zero to denote "as many as
+     * possible".
+     * @param since When null, retrieves the number of events specified by the "limit" parameter.
+     * Otherwise, the event ID at which only subsequent events will be returned, as many as specified
+     * in "limit".
+     * @returns A generator that emits events.
+     */
+    private *readRoomTimelineIterator(
+        room: Room,
+        eventType: string,
+        msgtype: string | undefined,
+        stateKey: string | undefined,
+        limit: number,
+        since: string | undefined,
+    ): Generator<IRoomEvent, void, void> {
+        let resultCount: number = 0;
+        const events = [...room.getLiveTimeline().getEvents()]; // timelines are most recent last
+        for (let ev = events.pop(); ev && resultCount < limit && ev.getId() !== since; ev = events.pop()) {
+            if (ev.getType() !== eventType) continue;
+            if (eventType === EventType.RoomMessage && msgtype && msgtype !== ev.getContent()["msgtype"]) continue;
+            if (stateKey !== undefined && ev.getStateKey() !== stateKey) continue;
+            yield ev.getEffectiveEvent() as IRoomEvent;
+            resultCount++;
+        }
+    }
+
     /**
      * Reads all events of the given type, and optionally `msgtype` (if applicable/defined),
      * the user has access to. The widget API will have already verified that the widget is
@@ -532,23 +564,9 @@
         since: string | undefined,
     ): Promise<IRoomEvent[]> {
         limit = limit > 0 ? Math.min(limit, Number.MAX_SAFE_INTEGER) : Number.MAX_SAFE_INTEGER; // relatively arbitrary
-
         const room = MatrixClientPeg.safeGet().getRoom(roomId);
         if (room === null) return [];
-        const results: MatrixEvent[] = [];
-        const events = room.getLiveTimeline().getEvents(); // timelines are most recent last
-        for (let i = events.length - 1; i >= 0; i--) {
-            const ev = events[i];
-            if (results.length >= limit) break;
-            if (since !== undefined && ev.getId() === since) break;
-
-            if (ev.getType() !== eventType) continue;
-            if (eventType === EventType.RoomMessage && msgtype && msgtype !== ev.getContent()["msgtype"]) continue;
-            if (stateKey !== undefined && ev.getStateKey() !== stateKey) continue;
-            results.push(ev);
-        }
-
-        return results.map((e) => e.getEffectiveEvent() as IRoomEvent);
+        return [...this.readRoomTimelineIterator(room, eventType, msgtype, stateKey, limit, since)];
     }
 
     /**
@@ -607,7 +625,7 @@
             inRoomId: this.inRoomId,
         });
         const [confirm] = await finished;
         if (!confirm) {
             observer.update({ state: OpenIDRequestState.Blocked });
         } else {
             observer.update({ state: OpenIDRequestState.Allowed, token: await getToken() });
@@ -652,7 +670,7 @@
         }
     }
 
     public async readEventRelations(
         eventId: string,
         roomId?: string,
         relationType?: string,
@@ -667,7 +685,7 @@
         roomId = roomId ?? SdkContextClass.instance.roomViewStore.getRoomId() ?? undefined;
 
         if (typeof roomId !== "string") {
             throw new Error("Error while reading the current room");
         }
 
         const { events, nextBatch, prevBatch } = await client.relations(