Implement enough of the new store to get a list of rooms

src/@types/global.d.ts

@@ -47,6 +47,7 @@ import { type DeepReadonly } from "./common";
 import type MatrixChat from "../components/structures/MatrixChat";
 import { type InitialCryptoSetupStore } from "../stores/InitialCryptoSetupStore";
 import { type ModuleApiType } from "../modules/Api.ts";
+import type RoomListStoreV3 from "../stores/room-list-v3/RoomListStoreV3.ts";
 
 /* eslint-disable @typescript-eslint/naming-convention */
 
@@ -99,6 +100,7 @@ declare global {
         mxToastStore: ToastStore;
         mxDeviceListener: DeviceListener;
         mxRoomListStore: RoomListStore;
+        mxRoomListStoreV3: RoomListStoreV3;
         mxRoomListLayoutStore: RoomListLayoutStore;
         mxPlatformPeg: PlatformPeg;
         mxIntegrationManagers: typeof IntegrationManagers;

src/stores/room-list-v3/RoomListStoreV3.ts

@@ -0,0 +1,69 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import type { EmptyObject, Room } from "matrix-js-sdk/src/matrix";
+import type { MatrixDispatcher } from "../../dispatcher/dispatcher";
+import type { ActionPayload } from "../../dispatcher/payloads";
+import { AsyncStoreWithClient } from "../AsyncStoreWithClient";
+import SettingsStore from "../../settings/SettingsStore";
+import { VisibilityProvider } from "../room-list/filters/VisibilityProvider";
+import defaultDispatcher from "../../dispatcher/dispatcher";
+import { LISTS_UPDATE_EVENT } from "../room-list/RoomListStore";
+import { RoomSkipList } from "./skip-list/RoomSkipList";
+import { RecencySorter } from "./skip-list/sorters/RecencySorter";
+
+export class RoomListStoreV3Class extends AsyncStoreWithClient<EmptyObject> {
+    private roomSkipList?: RoomSkipList;
+    private readonly msc3946ProcessDynamicPredecessor: boolean;
+
+    public constructor(dispatcher: MatrixDispatcher) {
+        super(dispatcher);
+        this.msc3946ProcessDynamicPredecessor = SettingsStore.getValue("feature_dynamic_room_predecessors");
+    }
+
+    public getSortedRooms(): Room[] {
+        if (this.roomSkipList?.initialized) return Array.from(this.roomSkipList);
+        else return [];
+    }
+
+    protected async onReady(): Promise<any> {
+        if (this.roomSkipList?.initialized || !this.matrixClient) return;
+        const sorter = new RecencySorter(this.matrixClient.getSafeUserId() ?? "");
+        this.roomSkipList = new RoomSkipList(sorter);
+        const rooms = this.fetchRoomsFromSdk();
+        if (!rooms) return;
+        this.roomSkipList.seed(rooms);
+        this.emit(LISTS_UPDATE_EVENT);
+    }
+
+    protected async onAction(payload: ActionPayload): Promise<void> {
+        return;
+    }
+
+    private fetchRoomsFromSdk(): Room[] | null {
+        if (!this.matrixClient) return null;
+        let rooms = this.matrixClient.getVisibleRooms(this.msc3946ProcessDynamicPredecessor);
+        rooms = rooms.filter((r) => VisibilityProvider.instance.isRoomVisible(r));
+        return rooms;
+    }
+}
+
+export default class RoomListStoreV3 {
+    private static internalInstance: RoomListStoreV3Class;
+
+    public static get instance(): RoomListStoreV3Class {
+        if (!RoomListStoreV3.internalInstance) {
+            const instance = new RoomListStoreV3Class(defaultDispatcher);
+            instance.start();
+            RoomListStoreV3.internalInstance = instance;
+        }
+
+        return this.internalInstance;
+    }
+}
+
+window.mxRoomListStoreV3 = RoomListStoreV3.instance;