Room List - Implement a minimal view model (#29357)

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

* Make it possible to swap sorting algorithm

* Don't attach to window object

We don't want the store to be created if the labs flag is off

* Remove the store class

Probably best to include this PR with the minimal vm implmentation

* Create a new room list store that wraps around the skip list

* Create a minimal view model

* Fix CI

* Add some basic tests for the store

* Write more tests

* Add some jsdoc comments

* Add more documentation

* Add more docs

src/components/viewmodels/roomlist/RoomListViewModel.tsx

@@ -0,0 +1,25 @@
+/*
+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 { Room } from "matrix-js-sdk/src/matrix";
+import RoomListStoreV3 from "../../../stores/room-list-v3/RoomListStoreV3";
+
+export interface RoomListViewState {
+    /**
+     * A list of rooms to be displayed in the left panel.
+     */
+    rooms: Room[];
+}
+
+/**
+ * View model for the new room list
+ * @see {@link RoomListViewState} for more information about what this view model returns.
+ */
+export function useRoomListViewModel(): RoomListViewState {
+    const rooms = RoomListStoreV3.instance.getSortedRooms();
+    return { rooms };
+}

src/components/views/rooms/RoomListPanel/RoomListPanel.tsx

@@ -6,11 +6,14 @@ Please see LICENSE files in the repository root for full details.
 */
 
 import React from "react";
+import { AutoSizer, List } from "react-virtualized";
 
+import type { ListRowProps } from "react-virtualized";
 import { shouldShowComponent } from "../../../../customisations/helpers/UIComponents";
 import { UIComponent } from "../../../../settings/UIFeature";
 import { RoomListSearch } from "./RoomListSearch";
 import { RoomListHeaderView } from "./RoomListHeaderView";
+import { useRoomListViewModel } from "../../../viewmodels/roomlist/RoomListViewModel";
 
 type RoomListPanelProps = {
     /**
@@ -25,11 +28,31 @@ type RoomListPanelProps = {
  */
 export const RoomListPanel: React.FC<RoomListPanelProps> = ({ activeSpace }) => {
     const displayRoomSearch = shouldShowComponent(UIComponent.FilterContainer);
+    const { rooms } = useRoomListViewModel();
+
+    const rowRenderer = ({ key, index, style }: ListRowProps): React.JSX.Element => {
+        return (
+            <div key={key} style={style}>
+                {rooms[index].name}
+            </div>
+        );
+    };
 
     return (
         <section className="mx_RoomListPanel" data-testid="room-list-panel">
             {displayRoomSearch && <RoomListSearch activeSpace={activeSpace} />}
             <RoomListHeaderView />
+            <AutoSizer>
+                {({ height, width }) => (
+                    <List
+                        rowRenderer={rowRenderer}
+                        rowCount={rooms.length}
+                        rowHeight={20}
+                        height={height}
+                        width={width}
+                    />
+                )}
+            </AutoSizer>
         </section>
     );
 };

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

@@ -0,0 +1,97 @@
+/*
+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";
+import { AlphabeticSorter } from "./skip-list/sorters/AlphabeticSorter";
+
+/**
+ * This store allows for fast retrieval of the room list in a sorted and filtered manner.
+ * This is the third such implementation hence the "V3".
+ * This store is being actively developed so expect the methods to change in future.
+ */
+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");
+    }
+
+    /**
+     * Get a list of unsorted, unfiltered rooms.
+     */
+    public getRooms(): Room[] {
+        let rooms = this.matrixClient?.getVisibleRooms(this.msc3946ProcessDynamicPredecessor) ?? [];
+        rooms = rooms.filter((r) => VisibilityProvider.instance.isRoomVisible(r));
+        return rooms;
+    }
+
+    /**
+     * Get a list of sorted rooms.
+     */
+    public getSortedRooms(): Room[] {
+        if (this.roomSkipList?.initialized) return Array.from(this.roomSkipList);
+        else return [];
+    }
+
+    /**
+     * Re-sort the list of rooms by alphabetic order.
+     */
+    public useAlphabeticSorting(): void {
+        if (this.roomSkipList) {
+            const sorter = new AlphabeticSorter();
+            this.roomSkipList.useNewSorter(sorter, this.getRooms());
+        }
+    }
+
+    /**
+     * Re-sort the list of rooms by recency.
+     */
+    public useRecencySorting(): void {
+        if (this.roomSkipList && this.matrixClient) {
+            const sorter = new RecencySorter(this.matrixClient?.getSafeUserId() ?? "");
+            this.roomSkipList.useNewSorter(sorter, this.getRooms());
+        }
+    }
+
+    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.getRooms();
+        this.roomSkipList.seed(rooms);
+        this.emit(LISTS_UPDATE_EVENT);
+    }
+
+    protected async onAction(payload: ActionPayload): Promise<void> {
+        return;
+    }
+}
+
+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;
+    }
+}