Allow modules to access a part of MatrixClient functionality

packages/element-web-module-api/element-web-module-api.api.md

@@ -24,6 +24,13 @@ export interface AccountAuthInfo {
     userId: string;
 }
 
+// @public
+export interface AccountDataApi {
+    delete(eventType: string): Promise<void>;
+    get(eventType: string): Watchable<unknown>;
+    set(eventType: string, content: unknown): Promise<void>;
+}
+
 // @alpha @deprecated (undocumented)
 export interface AliasCustomisations {
     // (undocumented)
@@ -37,6 +44,7 @@ export interface AliasCustomisations {
 export interface Api extends LegacyModuleApiExtension, LegacyCustomisationsApiExtension, DialogApiExtension, AccountAuthApiExtension, ProfileApiExtension {
     // @alpha
     readonly builtins: BuiltinsApi;
+    readonly client: ClientApi;
     readonly config: ConfigApi;
     createRoot(element: Element): Root;
     // @alpha
@@ -46,6 +54,7 @@ export interface Api extends LegacyModuleApiExtension, LegacyCustomisationsApiEx
     readonly i18n: I18nApi;
     readonly navigation: NavigationApi;
     readonly rootNode: HTMLElement;
+    readonly stores: StoresApi;
 }
 
 // @alpha
@@ -64,6 +73,12 @@ export interface ChatExportCustomisations<ExportFormat, ExportType> {
     };
 }
 
+// @public
+export interface ClientApi {
+    accountData: AccountDataApi;
+    getRoom: (id: string) => Room | null;
+}
+
 // @alpha @deprecated (undocumented)
 export interface ComponentVisibilityCustomisations {
     shouldShowComponent?(component: "UIComponent.sendInvites" | "UIComponent.roomCreation" | "UIComponent.spaceCreation" | "UIComponent.exploreRooms" | "UIComponent.addIntegrations" | "UIComponent.filterContainer" | "UIComponent.roomOptionsMenu"): boolean;
@@ -311,11 +326,24 @@ export interface ProfileApiExtension {
     readonly profile: Watchable<Profile>;
 }
 
+// @public
+export interface Room {
+    getLastActiveTimestamp: () => number;
+    id: string;
+    name: Watchable<string>;
+}
+
 // @alpha @deprecated (undocumented)
 export interface RoomListCustomisations<Room> {
     isRoomVisible?(room: Room): boolean;
 }
 
+// @public
+export interface RoomListStoreApi {
+    getRooms(): Watchable<Room[]>;
+    waitForReady(): Promise<void>;
+}
+
 // @alpha
 export interface RoomViewProps {
     roomId?: string;
@@ -334,6 +362,11 @@ export interface SpacePanelItemProps {
     tooltip?: string;
 }
 
+// @public
+export interface StoresApi {
+    roomListStore: RoomListStoreApi;
+}
+
 // @public
 export type Translations = Record<string, {
     [ietfLanguageTag: string]: string;
@@ -359,9 +392,14 @@ export type Variables = {
 // @public
 export class Watchable<T> {
     constructor(currentValue: T);
+    // Warning: (ae-forgotten-export) The symbol "WatchFn" needs to be exported by the entry point index.d.ts
+    //
     // (undocumented)
-    unwatch(listener: (value: T) => void): void;
+    protected readonly listeners: Set<WatchFn<T>>;
+    protected onFirstWatch(): void;
+    protected onLastWatch(): void;
     // (undocumented)
+    unwatch(listener: (value: T) => void): void;
     get value(): T;
     set value(value: T);
     // (undocumented)

packages/element-web-module-api/src/api/client.ts

@@ -0,0 +1,46 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import type { Room } from "../models/Room";
+import { Watchable } from "./watchable";
+
+/**
+ * Modify account data stored on the homeserver.
+ * @public
+ */
+export interface AccountDataApi {
+    /**
+     * Returns a watchable with account data for this event type.
+     */
+    get(eventType: string): Watchable<unknown>;
+    /**
+     * Set account data on the homeserver.
+     */
+    set(eventType: string, content: unknown): Promise<void>;
+    /**
+     * Changes the content of this event to be empty.
+     */
+    delete(eventType: string): Promise<void>;
+}
+
+/**
+ * Access some limited functionality from the SDK.
+ * @public
+ */
+export interface ClientApi {
+    /**
+     * Use this to modify account data on the homeserver.
+     */
+    accountData: AccountDataApi;
+
+    /**
+     * Fetch room by id from SDK.
+     * @param id - Id of the room to get
+     * @returns Room object from SDK
+     */
+    getRoom: (id: string) => Room | null;
+}

packages/element-web-module-api/src/api/index.ts

@@ -17,6 +17,8 @@ import { AccountAuthApiExtension } from "./auth.ts";
 import { ProfileApiExtension } from "./profile.ts";
 import { ExtrasApi } from "./extras.ts";
 import { BuiltinsApi } from "./builtins.ts";
+import { StoresApi } from "./stores.ts";
+import { ClientApi } from "./client.ts";
 
 /**
  * Module interface for modules to implement.
@@ -123,6 +125,16 @@ export interface Api
      */
     readonly extras: ExtrasApi;
 
+    /**
+     * Allows modules to access a limited functionality of certain stores from Element Web.
+     */
+    readonly stores: StoresApi;
+
+    /**
+     * Access some very specific functionality from the client.
+     */
+    readonly client: ClientApi;
+
     /**
      * Create a ReactDOM root for rendering React components.
      * Exposed to allow modules to avoid needing to bundle their own ReactDOM.

packages/element-web-module-api/src/api/stores.ts

@@ -0,0 +1,36 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import type { Room } from "../models/Room";
+import { Watchable } from "./watchable";
+
+/**
+ * Provides some basic functionality of the Room List Store from element-web.
+ * @public
+ */
+export interface RoomListStoreApi {
+    /**
+     * Returns a watchable holding a flat list of sorted room.
+     */
+    getRooms(): Watchable<Room[]>;
+
+    /**
+     * Returns a promise that resolves when RLS is ready.
+     */
+    waitForReady(): Promise<void>;
+}
+
+/**
+ * Provides access to certain stores from element-web.
+ * @public
+ */
+export interface StoresApi {
+    /**
+     * Use this to access limited functionality of the RLS from element-web.
+     */
+    roomListStore: RoomListStoreApi;
+}

packages/element-web-module-api/src/api/watchable.test.ts

@@ -5,7 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE files in the repository root for full details.
 */
 
-import { expect, test, vitest } from "vitest";
+import { expect, test, vi, vitest } from "vitest";
 
 import { Watchable } from "./watchable";
 
@@ -56,3 +56,44 @@ test("when value is an object, shallow comparison works", () => {
 
     watchable.unwatch(listener); // Clean up after the test
 });
+
+test("onFirstWatch and onLastWatch are called when appropriate", () => {
+    const onFirstWatch = vi.fn();
+    const onLastWatch = vi.fn();
+    class CustomWatchable extends Watchable<number> {
+        protected onFirstWatch(): void {
+            onFirstWatch();
+        }
+        protected onLastWatch(): void {
+            onLastWatch();
+        }
+    }
+
+    const watchable = new CustomWatchable(10);
+    // No listeners yet, so expect no calls
+    expect(onFirstWatch).not.toHaveBeenCalled();
+    expect(onLastWatch).not.toHaveBeenCalled();
+
+    // Let's say that we have three listeners
+    const listeners = [vi.fn(), vi.fn(), vi.fn()];
+
+    // Let's add all of them via watch
+    for (const listener of listeners) {
+        watchable.watch(listener);
+    }
+
+    // Only expect onFirstWatch() to have been called once
+    expect(onFirstWatch).toHaveBeenCalledOnce();
+
+    // Let's remove all the listeners
+    for (const listener of listeners) {
+        watchable.unwatch(listener);
+    }
+
+    // Only expect onLastWatch to have been called once
+    expect(onLastWatch).toHaveBeenCalledOnce();
+
+    // Should call onFirstWatch again once we have more listeners
+    watchable.watch(vi.fn());
+    expect(onFirstWatch).toHaveBeenCalledTimes(2);
+});

packages/element-web-module-api/src/api/watchable.ts

@@ -26,10 +26,14 @@ function isObject(value: unknown): value is object {
  * @public
  */
 export class Watchable<T> {
-    private readonly listeners = new Set<WatchFn<T>>();
+    protected readonly listeners = new Set<WatchFn<T>>();
 
     public constructor(private currentValue: T) {}
 
+    /**
+     * The value stored in this watchable.
+     * Warning: Could potentially return stale data if you haven't called {@link Watchable#watch}.
+     */
     public get value(): T {
         return this.currentValue;
     }
@@ -50,12 +54,32 @@ export class Watchable<T> {
     }
 
     public watch(listener: (value: T) => void): void {
+        // Call onFirstWatch if there was no listener before.
+        if (this.listeners.size === 0) {
+            this.onFirstWatch();
+        }
         this.listeners.add(listener);
     }
 
     public unwatch(listener: (value: T) => void): void {
-        this.listeners.delete(listener);
+        const hasDeleted = this.listeners.delete(listener);
+        // Call onLastWatch if every listener has been removed.
+        if (hasDeleted && this.listeners.size === 0) {
+            this.onLastWatch();
+        }
     }
+
+    /**
+     * This is called when the number of listeners go from zero to one.
+     * Could be used to add external event listeners.
+     */
+    protected onFirstWatch(): void {}
+
+    /**
+     * This is called when the number of listeners go from one to zero.
+     * Could be used to remove external event listeners.
+     */
+    protected onLastWatch(): void {}
 }
 
 /**

packages/element-web-module-api/src/index.ts

@@ -10,6 +10,7 @@ export type { Api, Module, ModuleFactory } from "./api";
 export type { Config, ConfigApi } from "./api/config";
 export type { I18nApi, Variables, Translations } from "./api/i18n";
 export type * from "./models/event";
+export type * from "./models/Room";
 export type * from "./api/custom-components";
 export type * from "./api/extras";
 export type * from "./api/legacy-modules";
@@ -19,4 +20,6 @@ export type * from "./api/dialog";
 export type * from "./api/profile";
 export type * from "./api/navigation";
 export type * from "./api/builtins";
+export type * from "./api/stores";
+export type * from "./api/client";
 export * from "./api/watchable";

packages/element-web-module-api/src/models/Room.ts

@@ -0,0 +1,28 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { Watchable } from "../api/watchable";
+
+/**
+ * Represents a room from element-web.
+ * @public
+ */
+export interface Room {
+    /**
+     * Id of this room.
+     */
+    id: string;
+    /**
+     * {@link Watchable} holding the name for this room.
+     */
+    name: Watchable<string>;
+    /**
+     * Get the timestamp of the last message in this room.
+     * @returns last active timestamp
+     */
+    getLastActiveTimestamp: () => number;
+}