Implement deep-linking for threads (matrix.to) (#7003)

src/utils/EventUtils.ts

@@ -21,6 +21,9 @@ import shouldHideEvent from "../shouldHideEvent";
 import { getHandlerTile, haveTileForEvent } from "../components/views/rooms/EventTile";
 import SettingsStore from "../settings/SettingsStore";
 import { EventType } from "matrix-js-sdk/src/@types/event";
+import { MatrixClient } from 'matrix-js-sdk/src/client';
+import { Thread } from 'matrix-js-sdk/src/models/thread';
+import { logger } from 'matrix-js-sdk/src/logger';
 
 /**
  * Returns whether an event should allow actions like reply, reactions, edit, etc.
@@ -158,3 +161,37 @@ export function isVoiceMessage(mxEvent: MatrixEvent): boolean {
         !!content['org.matrix.msc3245.voice']
     );
 }
+
+export async function fetchInitialEvent(
+    client: MatrixClient,
+    roomId: string,
+    eventId: string): Promise<MatrixEvent | null> {
+    let initialEvent: MatrixEvent;
+
+    try {
+        const eventData = await client.fetchRoomEvent(roomId, eventId);
+        initialEvent = new MatrixEvent(eventData);
+    } catch (e) {
+        logger.warn("Could not find initial event: " + initialEvent.threadRootId);
+        initialEvent = null;
+    }
+
+    if (initialEvent?.isThreadRelation) {
+        try {
+            const rootEventData = await client.fetchRoomEvent(roomId, initialEvent.threadRootId);
+            const rootEvent = new MatrixEvent(rootEventData);
+            const room = client.getRoom(roomId);
+            const thread = new Thread(
+                [rootEvent],
+                room,
+                client,
+            );
+            thread.addEvent(initialEvent);
+            room.threads.set(thread.id, thread);
+        } catch (e) {
+            logger.warn("Could not find root event: " + initialEvent.threadRootId);
+        }
+    }
+
+    return initialEvent;
+}