Make WidgetAPI an EventEmitter + use for terminate + cleanups

Use EventEmitter for emitting events, rename terminate event code,
plus misc cleanups from review.

Signed-off-by: Pauli Virtanen <pav@iki.fi>

src/WidgetMessaging.js

@@ -89,8 +89,6 @@ export default class WidgetMessaging {
 
     /**
      * Tells the widget that it should terminate now.
-     * It is not necessarily called in all instances before the widget is removed,
-     * and the client may force termination with a timeout.
      * @returns {Promise<*>} Resolves when widget has acknowledged the message.
      */
     terminate() {

src/components/views/elements/AppTile.js

@@ -346,7 +346,7 @@ export default class AppTile extends React.Component {
     _endWidgetActions() {
         let promise;
 
-        if (this._hasCapability('m.receive_terminate')) {
+        if (this._hasCapability('im.vector.receive_terminate')) {
             // Wait for widget to terminate within a timeout
             const timeout = 2000;
             const messaging = ActiveWidgetStore.getWidgetMessaging(this.props.app.id);
@@ -396,10 +396,11 @@ export default class AppTile extends React.Component {
                     this.setState({deleting: true});
 
                     this._endWidgetActions().then(() => {
-                        WidgetUtils.setRoomWidget(
+                        return WidgetUtils.setRoomWidget(
                             this.props.room.roomId,
                             this.props.app.id,
-                        ).catch((e) => {
+                        );
+                    }).catch((e) => {
                         console.error('Failed to delete widget', e);
                         const ErrorDialog = sdk.getComponent("dialogs.ErrorDialog");
 
@@ -410,7 +411,6 @@ export default class AppTile extends React.Component {
                     }).finally(() => {
                         this.setState({deleting: false});
                     });
-                    });
                 },
             });
         }

src/widgets/WidgetApi.ts

@@ -18,12 +18,13 @@ limitations under the License.
 // https://github.com/turt2live/matrix-dimension/blob/4f92d560266635e5a3c824606215b84e8c0b19f5/web/app/shared/services/scalar/scalar-widget.api.ts
 
 import { randomString } from "matrix-js-sdk/src/randomstring";
+import { EventEmitter } from "events";
 
 export enum Capability {
     Screenshot = "m.capability.screenshot",
     Sticker = "m.sticker",
     AlwaysOnScreen = "m.always_on_screen",
-    ReceiveTerminate = "m.receive_terminate",
+    ReceiveTerminate = "im.vector.receive_terminate",
 }
 
 export enum KnownWidgetActions {
@@ -64,14 +65,17 @@ export interface FromWidgetRequest extends WidgetRequest {
 
 /**
  * Handles Riot <--> Widget interactions for embedded/standalone widgets.
+ *
+ * Emitted events:
+ * - terminate(wait): client requested the widget to terminate.
+ *   Call the argument 'wait(promise)' to postpone the finalization until
+ *   the given promise resolves.
  */
-export class WidgetApi {
+export class WidgetApi extends EventEmitter {
     private origin: string;
     private inFlightRequests: { [requestId: string]: (reply: FromWidgetRequest) => void } = {};
     private readyPromise: Promise<any>;
     private readyPromiseResolve: () => void;
-    private terminatePromise: Promise<any>;
-    private terminatePromiseResolve: () => void;
 
     /**
      * Set this to true if your widget is expecting a ready message from the client. False otherwise (default).
@@ -79,10 +83,11 @@ export class WidgetApi {
     public expectingExplicitReady = false;
 
     constructor(currentUrl: string, private widgetId: string, private requestedCapabilities: string[]) {
+        super();
+
         this.origin = new URL(currentUrl).origin;
 
         this.readyPromise = new Promise<any>(resolve => this.readyPromiseResolve = resolve);
-        this.terminatePromise = new Promise<any>(resolve => this.terminatePromiseResolve = resolve);
 
         window.addEventListener("message", event => {
             if (event.origin !== this.origin) return; // ignore: invalid origin
@@ -104,11 +109,15 @@ export class WidgetApi {
                     // Automatically acknowledge so we can move on
                     this.replyToRequest(<ToWidgetRequest>payload, {});
                 } else if (payload.action === KnownWidgetActions.Terminate) {
-                    // Reply after resolving
-                    this.terminatePromise.then(() => {
+                    // Finalization needs to be async, so postpone with a promise
+                    let finalizePromise = Promise.resolve();
+                    const wait = promise => {
+                        finalizePromise = finalizePromise.then(value => promise);
+                    }
+                    this.emit('terminate', wait);
+                    Promise.resolve(finalizePromise).then(() => {
                         this.replyToRequest(<ToWidgetRequest>payload, {});
                     });
-                    this.terminatePromiseResolve();
                 } else {
                     console.warn(`[WidgetAPI] Got unexpected action: ${payload.action}`);
                 }
@@ -127,10 +136,6 @@ export class WidgetApi {
         return this.readyPromise;
     }
 
-    public addTerminateCallback(action) {
-        this.terminatePromise = this.terminatePromise.then(action);
-    }
-
     private replyToRequest(payload: ToWidgetRequest, reply: any) {
         if (!window.parent) return;