Room List Store: Save preferred sorting algorithm and use that on app launch

src/settings/Settings.tsx

@@ -44,6 +44,7 @@ import { type ReleaseAnnouncementData } from "../stores/ReleaseAnnouncementStore
 import { type Json, type JsonValue } from "../@types/json.ts";
 import { type RecentEmojiData } from "../emojipicker/recent.ts";
 import { type Assignable } from "../@types/common.ts";
+import { SortingAlgorithm } from "../stores/room-list-v3/skip-list/sorters/index.ts";
 
 export const defaultWatchManager = new WatchManager();
 
@@ -311,6 +312,7 @@ export interface Settings {
     "lowBandwidth": IBaseSetting<boolean>;
     "fallbackICEServerAllowed": IBaseSetting<boolean | null>;
     "showImages": IBaseSetting<boolean>;
+    "RoomList.preferredSorting": IBaseSetting<SortingAlgorithm>;
     "RightPanel.phasesGlobal": IBaseSetting<IRightPanelForRoomStored | null>;
     "RightPanel.phases": IBaseSetting<IRightPanelForRoomStored | null>;
     "enableEventIndexing": IBaseSetting<boolean>;
@@ -1114,6 +1116,10 @@ export const SETTINGS: Settings = {
         displayName: _td("settings|image_thumbnails"),
         default: true,
     },
+    "RoomList.preferredSorting": {
+        supportedLevels: [SettingLevel.DEVICE],
+        default: SortingAlgorithm.Recency,
+    },
     "RightPanel.phasesGlobal": {
         supportedLevels: [SettingLevel.DEVICE],
         default: null,

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

@@ -31,6 +31,8 @@ import { RoomsFilter } from "./skip-list/filters/RoomsFilter";
 import { InvitesFilter } from "./skip-list/filters/InvitesFilter";
 import { MentionsFilter } from "./skip-list/filters/MentionsFilter";
 import { LowPriorityFilter } from "./skip-list/filters/LowPriorityFilter";
+import { type Sorter, SortingAlgorithm } from "./skip-list/sorters";
+import { SettingLevel } from "../../settings/SettingLevel";
 
 /**
  * These are the filters passed to the room skip list.
@@ -93,28 +95,32 @@ export class RoomListStoreV3Class extends AsyncStoreWithClient<EmptyObject> {
     }
 
     /**
-     * Re-sort the list of rooms by alphabetic order.
+     * Resort the list of rooms using a different algorithm.
+     * @param algorithm The sorting algorithm to use.
      */
-    public useAlphabeticSorting(): void {
-        if (this.roomSkipList) {
-            const sorter = new AlphabeticSorter();
-            this.roomSkipList.useNewSorter(sorter, this.getRooms());
-        }
+    public resort(algorithm: SortingAlgorithm): void {
+        if (!this.roomSkipList) throw new Error("Cannot resort room list before skip list is created.");
+        if (!this.matrixClient) throw new Error("Cannot resort room list without matrix client.");
+        if (this.roomSkipList.activeSortAlgorithm === algorithm) return;
+        const sorter =
+            algorithm === SortingAlgorithm.Alphabetic
+                ? new AlphabeticSorter()
+                : new RecencySorter(this.matrixClient.getSafeUserId());
+        this.roomSkipList.useNewSorter(sorter, this.getRooms());
+        this.emit(LISTS_UPDATE_EVENT);
+        SettingsStore.setValue("RoomList.preferredSorting", null, SettingLevel.DEVICE, algorithm);
     }
 
     /**
-     * Re-sort the list of rooms by recency.
+     * Currently active sorting algorithm if the store is ready or undefined otherwise.
      */
-    public useRecencySorting(): void {
-        if (this.roomSkipList && this.matrixClient) {
-            const sorter = new RecencySorter(this.matrixClient?.getSafeUserId() ?? "");
-            this.roomSkipList.useNewSorter(sorter, this.getRooms());
-        }
+    public get activeSortAlgorithm(): SortingAlgorithm | undefined {
+        return this.roomSkipList?.activeSortAlgorithm;
     }
 
     protected async onReady(): Promise<any> {
         if (this.roomSkipList?.initialized || !this.matrixClient) return;
-        const sorter = new RecencySorter(this.matrixClient.getSafeUserId());
+        const sorter = this.getPreferredSorter(this.matrixClient.getSafeUserId());
         this.roomSkipList = new RoomSkipList(sorter, FILTERS);
         await SpaceStore.instance.storeReadyPromise;
         const rooms = this.getRooms();
@@ -214,6 +220,23 @@ export class RoomListStoreV3Class extends AsyncStoreWithClient<EmptyObject> {
         }
     }
 
+    /**
+     * Create the correct sorter depending on the persisted user preference.
+     * @param myUserId The user-id of our user.
+     * @returns Sorter object that can be passed to the skip list.
+     */
+    private getPreferredSorter(myUserId: string): Sorter {
+        const preferred = SettingsStore.getValue("RoomList.preferredSorting");
+        switch (preferred) {
+            case SortingAlgorithm.Alphabetic:
+                return new AlphabeticSorter();
+            case SortingAlgorithm.Recency:
+                return new RecencySorter(myUserId);
+            default:
+                throw new Error(`Got unknown sort preference from RoomList.preferredSorting setting`);
+        }
+    }
+
     /**
      * Add a room to the skiplist and emit an update.
      * @param room The room to add to the skiplist

src/stores/room-list-v3/skip-list/RoomSkipList.ts

@@ -6,7 +6,7 @@ Please see LICENSE files in the repository root for full details.
 */
 
 import type { Room } from "matrix-js-sdk/src/matrix";
-import type { Sorter } from "./sorters";
+import type { Sorter, SortingAlgorithm } from "./sorters";
 import type { Filter, FilterKey } from "./filters";
 import { RoomNode } from "./RoomNode";
 import { shouldPromote } from "./utils";
@@ -204,4 +204,11 @@ export class RoomSkipList implements Iterable<Room> {
     public get size(): number {
         return this.levels[0].size;
     }
+
+    /**
+     * The currently active sorting algorithm.
+     */
+    public get activeSortAlgorithm(): SortingAlgorithm {
+        return this.sorter.type;
+    }
 }

src/stores/room-list-v3/skip-list/sorters/AlphabeticSorter.ts

@@ -6,7 +6,7 @@ Please see LICENSE files in the repository root for full details.
 */
 
 import type { Room } from "matrix-js-sdk/src/matrix";
-import type { Sorter } from ".";
+import { type Sorter, SortingAlgorithm } from ".";
 
 export class AlphabeticSorter implements Sorter {
     private readonly collator = new Intl.Collator();
@@ -20,4 +20,8 @@ export class AlphabeticSorter implements Sorter {
     public comparator(roomA: Room, roomB: Room): number {
         return this.collator.compare(roomA.name, roomB.name);
     }
+
+    public get type(): SortingAlgorithm.Alphabetic {
+        return SortingAlgorithm.Alphabetic;
+    }
 }

src/stores/room-list-v3/skip-list/sorters/RecencySorter.ts

@@ -6,7 +6,7 @@ Please see LICENSE files in the repository root for full details.
 */
 
 import type { Room } from "matrix-js-sdk/src/matrix";
-import type { Sorter } from ".";
+import { type Sorter, SortingAlgorithm } from ".";
 import { getLastTs } from "../../../room-list/algorithms/tag-sorting/RecentAlgorithm";
 
 export class RecencySorter implements Sorter {
@@ -23,6 +23,10 @@ export class RecencySorter implements Sorter {
         return roomBLastTs - roomALastTs;
     }
 
+    public get type(): SortingAlgorithm.Recency {
+        return SortingAlgorithm.Recency;
+    }
+
     private getTs(room: Room, cache?: { [roomId: string]: number }): number {
         const ts = cache?.[room.roomId] ?? getLastTs(room, this.myUserId);
         if (cache) {

src/stores/room-list-v3/skip-list/sorters/index.ts

@@ -8,6 +8,29 @@ Please see LICENSE files in the repository root for full details.
 import type { Room } from "matrix-js-sdk/src/matrix";
 
 export interface Sorter {
+    /**
+     * Performs an initial sort of rooms and returns a new array containing
+     * the result.
+     * @param rooms An array of rooms.
+     */
     sort(rooms: Room[]): Room[];
+    /**
+     * The comparator used for sorting.
+     * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort#comparefn
+     * @param roomA Room
+     * @param roomB Room
+     */
     comparator(roomA: Room, roomB: Room): number;
+    /**
+     * A string that uniquely identifies this given sorter.
+     */
+    type: SortingAlgorithm;
+}
+
+/**
+ * All the available sorting algorithms.
+ */
+export const enum SortingAlgorithm {
+    Recency = "Recency",
+    Alphabetic = "Alphabetic",
 }

test/unit-tests/stores/room-list-v3/RoomListStoreV3-test.ts

@@ -24,6 +24,8 @@ import { DefaultTagID } from "../../../../src/stores/room-list/models";
 import { FilterKey } from "../../../../src/stores/room-list-v3/skip-list/filters";
 import { RoomNotificationStateStore } from "../../../../src/stores/notifications/RoomNotificationStateStore";
 import DMRoomMap from "../../../../src/utils/DMRoomMap";
+import { SortingAlgorithm } from "../../../../src/stores/room-list-v3/skip-list/sorters";
+import SettingsStore from "../../../../src/settings/SettingsStore";
 
 describe("RoomListStoreV3", () => {
     async function getRoomListStore() {
@@ -53,6 +55,10 @@ describe("RoomListStoreV3", () => {
         }) as () => DMRoomMap);
     });
 
+    afterEach(() => {
+        jest.restoreAllMocks();
+    });
+
     it("Provides an unsorted list of rooms", async () => {
         const { store, rooms } = await getRoomListStore();
         expect(store.getRooms()).toEqual(rooms);
@@ -69,14 +75,24 @@ describe("RoomListStoreV3", () => {
         const { store, rooms, client } = await getRoomListStore();
 
         // List is sorted by recency, sort by alphabetical now
-        store.useAlphabeticSorting();
+        store.resort(SortingAlgorithm.Alphabetic);
         let sortedRooms = new AlphabeticSorter().sort(rooms);
         expect(store.getSortedRooms()).toEqual(sortedRooms);
+        expect(store.activeSortAlgorithm).toEqual(SortingAlgorithm.Alphabetic);
 
         // Go back to recency sorting
-        store.useRecencySorting();
+        store.resort(SortingAlgorithm.Recency);
         sortedRooms = new RecencySorter(client.getSafeUserId()).sort(rooms);
         expect(store.getSortedRooms()).toEqual(sortedRooms);
+        expect(store.activeSortAlgorithm).toEqual(SortingAlgorithm.Recency);
+    });
+
+    it("Uses preferred sorter on startup", async () => {
+        jest.spyOn(SettingsStore, "getValue").mockImplementation(() => {
+            return SortingAlgorithm.Alphabetic;
+        });
+        const { store } = await getRoomListStore();
+        expect(store.activeSortAlgorithm).toEqual(SortingAlgorithm.Alphabetic);
     });
 
     describe("Updates", () => {