RoomListViewModel: Provide a way to resort the room list and track the active sort method

src/components/viewmodels/roomlist/RoomListViewModel.tsx

@@ -12,6 +12,7 @@ import type { ViewRoomPayload } from "../../../dispatcher/payloads/ViewRoomPaylo
 import dispatcher from "../../../dispatcher/dispatcher";
 import { Action } from "../../../dispatcher/actions";
 import { type PrimaryFilter, type SecondaryFilters, useFilteredRooms } from "./useFilteredRooms";
+import { type SortOption, useSorter } from "./useSorter";
 
 export interface RoomListViewState {
     /**
@@ -39,6 +40,16 @@ export interface RoomListViewState {
      * The currently active secondary filter.
      */
     activeSecondaryFilter: SecondaryFilters;
+
+    /**
+     * Change the sort order of the room-list.
+     */
+    sort: (option: SortOption) => void;
+
+    /**
+     * The currently active sort option.
+     */
+    activeSortOption: SortOption;
 }
 
 /**
@@ -47,6 +58,7 @@ export interface RoomListViewState {
  */
 export function useRoomListViewModel(): RoomListViewState {
     const { primaryFilters, rooms, activateSecondaryFilter, activeSecondaryFilter } = useFilteredRooms();
+    const { activeSortOption, sort } = useSorter();
 
     const openRoom = useCallback((roomId: string): void => {
         dispatcher.dispatch<ViewRoomPayload>({
@@ -62,5 +74,7 @@ export function useRoomListViewModel(): RoomListViewState {
         primaryFilters,
         activateSecondaryFilter,
         activeSecondaryFilter,
+        activeSortOption,
+        sort,
     };
 }

src/components/viewmodels/roomlist/useSorter.ts

@@ -0,0 +1,62 @@
+/*
+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 { useState } from "react";
+
+import RoomListStoreV3 from "../../../stores/room-list-v3/RoomListStoreV3";
+import { SortingAlgorithm } from "../../../stores/room-list-v3/skip-list/sorters";
+import SettingsStore from "../../../settings/SettingsStore";
+
+/**
+ * Sorting options made available to the view.
+ */
+export const enum SortOption {
+    Activity = SortingAlgorithm.Recency,
+    AToZ = SortingAlgorithm.Alphabetic,
+}
+
+/**
+ * {@link SortOption} holds almost the same information as
+ * {@link SortingAlgorithm}. This is done intentionally to
+ * prevent the view from having a dependence on the
+ * model (which is the store in this case).
+ */
+const sortingAlgorithmToSortingOption = {
+    [SortingAlgorithm.Alphabetic]: SortOption.AToZ,
+    [SortingAlgorithm.Recency]: SortOption.Activity,
+};
+
+const sortOptionToSortingAlgorithm = {
+    [SortOption.AToZ]: SortingAlgorithm.Alphabetic,
+    [SortOption.Activity]: SortingAlgorithm.Recency,
+};
+
+interface SortState {
+    sort: (option: SortOption) => void;
+    activeSortOption: SortOption;
+}
+
+/**
+ * This hook does two things:
+ * - Provides a way to track the currently active sort option.
+ * - Provides a function to resort the room list.
+ */
+export function useSorter(): SortState {
+    const [activeSortingAlgorithm, setActiveSortingAlgorithm] = useState(() =>
+        SettingsStore.getValue("RoomList.preferredSorting"),
+    );
+
+    const sort = (option: SortOption): void => {
+        const sortingAlgorithm = sortOptionToSortingAlgorithm[option];
+        RoomListStoreV3.instance.resort(sortingAlgorithm);
+        setActiveSortingAlgorithm(sortingAlgorithm);
+    };
+
+    return {
+        sort,
+        activeSortOption: sortingAlgorithmToSortingOption[activeSortingAlgorithm!],
+    };
+}

test/unit-tests/components/viewmodels/roomlist/RoomListViewModel-test.tsx

@@ -16,6 +16,9 @@ import dispatcher from "../../../../../src/dispatcher/dispatcher";
 import { Action } from "../../../../../src/dispatcher/actions";
 import { FilterKey } from "../../../../../src/stores/room-list-v3/skip-list/filters";
 import { SecondaryFilters } from "../../../../../src/components/viewmodels/roomlist/useFilteredRooms";
+import { SortingAlgorithm } from "../../../../../src/stores/room-list-v3/skip-list/sorters";
+import { SortOption } from "../../../../../src/components/viewmodels/roomlist/useSorter";
+import SettingsStore from "../../../../../src/settings/SettingsStore";
 
 describe("RoomListViewModel", () => {
     function mockAndCreateRooms() {
@@ -26,6 +29,10 @@ describe("RoomListViewModel", () => {
         return { rooms, fn };
     }
 
+    afterEach(() => {
+        jest.restoreAllMocks();
+    });
+
     it("should return a list of rooms", async () => {
         const { rooms } = mockAndCreateRooms();
         const { result: vm } = renderHook(() => useRoomListViewModel());
@@ -203,5 +210,29 @@ describe("RoomListViewModel", () => {
                 expect(vm.current.primaryFilters.find((f) => f.name === primaryFilterName)).toBeUndefined();
             });
         });
+
+        it("should change sort order", () => {
+            mockAndCreateRooms();
+            const { result: vm } = renderHook(() => useRoomListViewModel());
+
+            const resort = jest.spyOn(RoomListStoreV3.instance, "resort").mockImplementation(() => {});
+
+            // Change the sort option
+            act(() => {
+                vm.current.sort(SortOption.AToZ);
+            });
+
+            // Resort method in RLS must have been called
+            expect(resort).toHaveBeenCalledWith(SortingAlgorithm.Alphabetic);
+        });
+
+        it("should set activeSortOption based on value from settings", () => {
+            // Let's say that the user's preferred sorting is alphabetic
+            jest.spyOn(SettingsStore, "getValue").mockImplementation(() => SortingAlgorithm.Alphabetic);
+
+            mockAndCreateRooms();
+            const { result: vm } = renderHook(() => useRoomListViewModel());
+            expect(vm.current.activeSortOption).toEqual(SortOption.AToZ);
+        });
     });
 });

test/unit-tests/components/views/rooms/RoomListPanel/RoomList-test.tsx

@@ -15,6 +15,7 @@ import { type RoomListViewState } from "../../../../../../src/components/viewmod
 import { RoomList } from "../../../../../../src/components/views/rooms/RoomListPanel/RoomList";
 import DMRoomMap from "../../../../../../src/utils/DMRoomMap";
 import { SecondaryFilters } from "../../../../../../src/components/viewmodels/roomlist/useFilteredRooms";
+import { SortOption } from "../../../../../../src/components/viewmodels/roomlist/useSorter";
 
 describe("<RoomList />", () => {
     let matrixClient: MatrixClient;
@@ -34,6 +35,8 @@ describe("<RoomList />", () => {
             primaryFilters: [],
             activateSecondaryFilter: () => {},
             activeSecondaryFilter: SecondaryFilters.AllActivity,
+            sort: jest.fn(),
+            activeSortOption: SortOption.Activity,
         };
 
         // Needed to render a room list cell

test/unit-tests/components/views/rooms/RoomListPanel/RoomListPrimaryFilters-test.tsx

@@ -12,6 +12,7 @@ import userEvent from "@testing-library/user-event";
 import { type RoomListViewState } from "../../../../../../src/components/viewmodels/roomlist/RoomListViewModel";
 import { SecondaryFilters } from "../../../../../../src/components/viewmodels/roomlist/useFilteredRooms";
 import { RoomListPrimaryFilters } from "../../../../../../src/components/views/rooms/RoomListPanel/RoomListPrimaryFilters";
+import { SortOption } from "../../../../../../src/components/viewmodels/roomlist/useSorter";
 
 describe("<RoomListPrimaryFilters />", () => {
     let vm: RoomListViewState;
@@ -26,6 +27,8 @@ describe("<RoomListPrimaryFilters />", () => {
             ],
             activateSecondaryFilter: () => {},
             activeSecondaryFilter: SecondaryFilters.AllActivity,
+            sort: jest.fn(),
+            activeSortOption: SortOption.Activity,
         };
     });