Invent an AsyncStore and use it for room lists

This is to get around the problem of a slow dispatch loop. Instead of slowing the whole app down to deal with room lists, we'll just raise events to say we're ready.

Based upon the EventEmitter class.

package.json

@@ -55,6 +55,7 @@
   },
   "dependencies": {
     "@babel/runtime": "^7.8.3",
+    "await-lock": "^2.0.1",
     "blueimp-canvas-to-blob": "^3.5.0",
     "browser-encrypt-attachment": "^0.3.0",
     "browser-request": "^0.3.3",

src/components/views/rooms/RoomList2.tsx

@@ -21,7 +21,7 @@ import { _t } from "../../../languageHandler";
 import { Layout } from '../../../resizer/distributors/roomsublist2';
 import { RovingTabIndexProvider } from "../../../accessibility/RovingTabIndex";
 import { ResizeNotifier } from "../../../utils/ResizeNotifier";
-import RoomListStore from "../../../stores/room-list/RoomListStore2";
+import RoomListStore, { LISTS_UPDATE_EVENT } from "../../../stores/room-list/RoomListStore2";
 
 interface IProps {
     onKeyDown: (ev: React.KeyboardEvent) => void;
@@ -56,8 +56,8 @@ export default class RoomList2 extends React.Component<IProps, IState> {
     }
 
     public componentDidMount(): void {
-        RoomListStore.instance.addListener(() => {
-            console.log(RoomListStore.instance.orderedLists);
+        RoomListStore.instance.on(LISTS_UPDATE_EVENT, (store) => {
+            console.log("new lists", store.orderedLists);
         });
     }
 

src/stores/AsyncStore.ts

@@ -0,0 +1,105 @@
+/*
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { EventEmitter } from 'events';
+import AwaitLock from 'await-lock';
+import { ActionPayload } from "../dispatcher-types";
+import { Dispatcher } from "flux";
+
+/**
+ * The event/channel to listen for in an AsyncStore.
+ */
+export const UPDATE_EVENT = "update";
+
+/**
+ * Represents a minimal store which works similar to Flux stores. Instead
+ * of everything needing to happen in a dispatch cycle, everything can
+ * happen async to that cycle.
+ *
+ * The store's core principle is Object.assign(), therefore it is recommended
+ * to break out your state to be as safe as possible. The state mutations are
+ * also locked, preventing concurrent writes.
+ *
+ * All updates to the store happen on the UPDATE_EVENT event channel with the
+ * one argument being the instance of the store.
+ *
+ * To update the state, use updateState() and preferably await the result to
+ * help prevent lock conflicts.
+ */
+export abstract class AsyncStore<T extends Object> extends EventEmitter {
+    private storeState: T = <T>{};
+    private lock = new AwaitLock();
+    private readonly dispatcherRef: string;
+
+    /**
+     * Creates a new AsyncStore using the given dispatcher.
+     * @param {Dispatcher<ActionPayload>} dispatcher The dispatcher to rely upon.
+     */
+    protected constructor(private dispatcher: Dispatcher<ActionPayload>) {
+        super();
+
+        this.dispatcherRef = dispatcher.register(this.onDispatch.bind(this));
+    }
+
+    /**
+     * The current state of the store. Cannot be mutated.
+     */
+    protected get state(): T {
+        return Object.freeze(this.storeState);
+    }
+
+    /**
+     * Stops the store's listening functions, such as the listener to the dispatcher.
+     */
+    protected stop() {
+        if (this.dispatcherRef) this.dispatcher.unregister(this.dispatcherRef);
+    }
+
+    /**
+     * Updates the state of the store.
+     * @param {T|*} newState The state to update in the store using Object.assign()
+     */
+    protected async updateState(newState: T | Object) {
+        await this.lock.acquireAsync();
+        try {
+            this.storeState = Object.assign(<T>{}, this.storeState, newState);
+            this.emit(UPDATE_EVENT, this);
+        } finally {
+            await this.lock.release();
+        }
+    }
+
+    /**
+     * Resets the store's to the provided state or an empty object.
+     * @param {T|*} newState The new state of the store.
+     * @param {boolean} quiet If true, the function will not raise an UPDATE_EVENT.
+     */
+    protected async reset(newState: T | Object = null, quiet = false) {
+        await this.lock.acquireAsync();
+        try {
+            this.storeState = <T>(newState || {});
+            if (!quiet) this.emit(UPDATE_EVENT, this);
+        } finally {
+            await this.lock.release();
+        }
+    }
+
+    /**
+     * Called when the dispatcher broadcasts a dispatch event.
+     * @param {ActionPayload} payload The event being dispatched.
+     */
+    protected abstract onDispatch(payload: ActionPayload);
+}

src/stores/room-list/RoomListStore2.ts

@@ -15,15 +15,14 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {Store} from 'flux/utils';
-import {Room} from "matrix-js-sdk/src/models/room";
-import {MatrixClient} from "matrix-js-sdk/src/client";
+import { MatrixClient } from "matrix-js-sdk/src/client";
 import { ActionPayload, defaultDispatcher } from "../../dispatcher-types";
 import SettingsStore from "../../settings/SettingsStore";
-import { OrderedDefaultTagIDs, DefaultTagID, TagID } from "./models";
+import { DefaultTagID, OrderedDefaultTagIDs, TagID } from "./models";
 import { IAlgorithm, ITagMap, ITagSortingMap, ListAlgorithm, SortAlgorithm } from "./algorithms/IAlgorithm";
 import TagOrderStore from "../TagOrderStore";
 import { getAlgorithmInstance } from "./algorithms";
+import { AsyncStore } from "../AsyncStore";
 
 interface IState {
     tagsEnabled?: boolean;
@@ -32,8 +31,13 @@ interface IState {
     preferredAlgorithm?: ListAlgorithm;
 }
 
-class _RoomListStore extends Store<ActionPayload> {
-    private state: IState = {};
+/**
+ * The event/channel which is called when the room lists have been changed. Raised
+ * with one argument: the instance of the store.
+ */
+export const LISTS_UPDATE_EVENT = "lists_update";
+
+class _RoomListStore extends AsyncStore<ActionPayload> {
     private matrixClient: MatrixClient;
     private initialListsGenerated = false;
     private enabled = false;
@@ -49,7 +53,6 @@ class _RoomListStore extends Store<ActionPayload> {
         super(defaultDispatcher);
 
         this.checkEnabled();
-        this.reset();
         for (const settingName of this.watchedSettings) SettingsStore.monitorSetting(settingName, null);
     }
 
@@ -66,17 +69,11 @@ class _RoomListStore extends Store<ActionPayload> {
         }
     }
 
-    private reset(): void {
-        // We don't call setState() because it'll cause changes to emitted which could
-        // crash the app during logout/signin/etc.
-        this.state = {};
-    }
-
-    private readAndCacheSettingsFromStore() {
+    private async readAndCacheSettingsFromStore() {
         const tagsEnabled = SettingsStore.isFeatureEnabled("feature_custom_tags");
         const orderByImportance = SettingsStore.getValue("RoomList.orderByImportance");
         const orderAlphabetically = SettingsStore.getValue("RoomList.orderAlphabetically");
-        this.setState({
+        await this.updateState({
             tagsEnabled,
             preferredSort: orderAlphabetically ? SortAlgorithm.Alphabetic : SortAlgorithm.Recent,
             preferredAlgorithm: orderByImportance ? ListAlgorithm.Importance : ListAlgorithm.Natural,
@@ -84,23 +81,23 @@ class _RoomListStore extends Store<ActionPayload> {
         this.setAlgorithmClass();
     }
 
-    protected __onDispatch(payload: ActionPayload): void {
+    protected async onDispatch(payload: ActionPayload) {
         if (payload.action === 'MatrixActions.sync') {
             // Filter out anything that isn't the first PREPARED sync.
             if (!(payload.prevState === 'PREPARED' && payload.state !== 'PREPARED')) {
                 return;
             }
 
+            // TODO: Remove this once the RoomListStore becomes default
             this.checkEnabled();
             if (!this.enabled) return;
 
             this.matrixClient = payload.matrixClient;
 
             // Update any settings here, as some may have happened before we were logically ready.
-            this.readAndCacheSettingsFromStore();
-
-            // noinspection JSIgnoredPromiseFromCall
-            this.regenerateAllLists();
+            console.log("Regenerating room lists: Startup");
+            await this.readAndCacheSettingsFromStore();
+            await this.regenerateAllLists();
         }
 
         // TODO: Remove this once the RoomListStore becomes default
@@ -109,7 +106,7 @@ class _RoomListStore extends Store<ActionPayload> {
         if (payload.action === 'on_client_not_viable' || payload.action === 'on_logged_out') {
             // Reset state without causing updates as the client will have been destroyed
             // and downstream code will throw NPE errors.
-            this.reset();
+            this.reset(null, true);
             this.matrixClient = null;
             this.initialListsGenerated = false; // we'll want to regenerate them
         }
@@ -120,14 +117,15 @@ class _RoomListStore extends Store<ActionPayload> {
 
         if (payload.action === 'setting_updated') {
             if (this.watchedSettings.includes(payload.settingName)) {
-                this.readAndCacheSettingsFromStore();
+                console.log("Regenerating room lists: Settings changed");
+                await this.readAndCacheSettingsFromStore();
 
-                // noinspection JSIgnoredPromiseFromCall
-                this.regenerateAllLists(); // regenerate the lists now
+                await this.regenerateAllLists(); // regenerate the lists now
             }
         } else if (payload.action === 'MatrixActions.Room.receipt') {
             // First see if the receipt event is for our own user. If it was, trigger
             // a room update (we probably read the room on a different device).
+            // noinspection JSObjectNullOrUndefined - this.matrixClient can't be null by this point in the lifecycle
             const myUserId = this.matrixClient.getUserId();
             for (const eventId of Object.keys(payload.event.getContent())) {
                 const receiptUsers = Object.keys(payload.event.getContent()[eventId]['m.read'] || {});
@@ -167,11 +165,10 @@ class _RoomListStore extends Store<ActionPayload> {
         }
     }
 
-    private setState(newState: IState) {
+    protected async updateState(newState: IState) {
         if (!this.enabled) return;
 
-        this.state = Object.assign(this.state, newState);
-        this.__emitChange();
+        await super.updateState(newState);
     }
 
     private setAlgorithmClass() {
@@ -179,7 +176,7 @@ class _RoomListStore extends Store<ActionPayload> {
     }
 
     private async regenerateAllLists() {
-        console.log("REGEN");
+        console.warn("Regenerating all room lists");
         const tags: ITagSortingMap = {};
         for (const tagId of OrderedDefaultTagIDs) {
             tags[tagId] = this.getSortAlgorithmFor(tagId);
@@ -196,7 +193,7 @@ class _RoomListStore extends Store<ActionPayload> {
 
         this.initialListsGenerated = true;
 
-        // TODO: How do we asynchronously update the store's state? or do we just give in and make it all sync?
+        this.emit(LISTS_UPDATE_EVENT, this);
     }
 }
 

src/stores/room-list/RoomListStoreTempProxy.ts

@@ -19,6 +19,8 @@ import { Room } from "matrix-js-sdk/src/models/room";
 import SettingsStore from "../../settings/SettingsStore";
 import RoomListStore from "./RoomListStore2";
 import OldRoomListStore from "../RoomListStore";
+import { ITagMap } from "./algorithms/IAlgorithm";
+import { UPDATE_EVENT } from "../AsyncStore";
 
 /**
  * Temporary RoomListStore proxy. Should be replaced with RoomListStore2 when
@@ -33,13 +35,13 @@ export class RoomListStoreTempProxy {
 
     public static addListener(handler: () => void) {
         if (RoomListStoreTempProxy.isUsingNewStore()) {
-            return RoomListStore.instance.addListener(handler);
+            return RoomListStore.instance.on(UPDATE_EVENT, handler);
         } else {
             return OldRoomListStore.addListener(handler);
         }
     }
 
-    public static getRoomLists(): {[tagId in TagID]: Room[]} {
+    public static getRoomLists(): ITagMap {
         if (RoomListStoreTempProxy.isUsingNewStore()) {
             return RoomListStore.instance.orderedLists;
         } else {

src/stores/room-list/algorithms/ChaoticAlgorithm.ts

@@ -65,7 +65,6 @@ export class ChaoticAlgorithm implements IAlgorithm {
         }
 
         // TODO: Remove logging
-        console.log('setting known rooms - regen in progress');
         console.log({alg: this.representativeAlgorithm});
 
         // Step through each room and determine which tags it should be in.

yarn.lock

@@ -1834,6 +1834,11 @@ autoprefixer@^9.0.0:
     postcss "^7.0.27"
     postcss-value-parser "^4.0.3"
 
+await-lock@^2.0.1:
+  version "2.0.1"
+  resolved "https://registry.yarnpkg.com/await-lock/-/await-lock-2.0.1.tgz#b3f65fdf66e08f7538260f79b46c15bcfc18cadd"
+  integrity sha512-ntLi9fzlMT/vWjC1wwVI11/cSRJ3nTS35qVekNc9WnaoMOP2eWH0RvIqwLQkDjX4a4YynsKEv+Ere2VONp9wxg==
+
 aws-sign2@~0.7.0:
   version "0.7.0"
   resolved "https://registry.yarnpkg.com/aws-sign2/-/aws-sign2-0.7.0.tgz#b46e890934a9591f2d2f6f86d7e6a9f1b3fe76a8"