From f5cd079a16abf3099de37c0521bffd655c567617 Mon Sep 17 00:00:00 2001
From: Travis Ralston <travpc@gmail.com>
Date: Mon, 2 Nov 2020 21:32:49 -0700
Subject: [PATCH] Add support for sending/receiving events from widgets

Part of MSC2762: https://github.com/matrix-org/matrix-doc/pull/2762
Requires: https://github.com/matrix-org/matrix-widget-api/pull/9

This is the bare minimum required to send an event to a widget and receive events from widgets. Like the view_room action, this is controlled by a well-known permission key.

**Danger**: This allows widgets to potentially modify room state. Use the permissions with care.
---
 src/stores/widgets/StopGapWidget.ts       | 32 +++++++++++++++++++++++
 src/stores/widgets/StopGapWidgetDriver.ts | 26 +++++++++++++++++-
 2 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/src/stores/widgets/StopGapWidget.ts b/src/stores/widgets/StopGapWidget.ts
index 441e037ddf..1c26b67faf 100644
--- a/src/stores/widgets/StopGapWidget.ts
+++ b/src/stores/widgets/StopGapWidget.ts
@@ -55,6 +55,8 @@ import ThemeWatcher from "../../settings/watchers/ThemeWatcher";
 import {getCustomTheme} from "../../theme";
 import CountlyAnalytics from "../../CountlyAnalytics";
 import { ElementWidgetCapabilities } from "./ElementWidgetCapabilities";
+import { MatrixEvent } from "matrix-js-sdk/src/models/event";
+import ActiveRoomObserver from "../../ActiveRoomObserver";
 
 // TODO: Destroy all of this code
 
@@ -329,6 +331,10 @@ export class StopGapWidget extends EventEmitter {
             this.messaging.transport.reply(ev.detail, <IWidgetApiRequestEmptyData>{});
         });
 
+        // Attach listeners for feeding events - the underlying widget classes handle permissions for us
+        MatrixClientPeg.get().on('event', this.onEvent);
+        MatrixClientPeg.get().on('Event.decrypted', this.onEventDecrypted);
+
         if (WidgetType.JITSI.matches(this.mockWidget.type)) {
             this.messaging.on("action:set_always_on_screen",
                 (ev: CustomEvent<IStickyActionRequest>) => {
@@ -422,5 +428,31 @@ export class StopGapWidget extends EventEmitter {
         if (!this.started) return;
         WidgetMessagingStore.instance.stopMessaging(this.mockWidget);
         ActiveWidgetStore.delRoomId(this.mockWidget.id);
+
+        if (MatrixClientPeg.get()) {
+            MatrixClientPeg.get().off('event', this.onEvent);
+            MatrixClientPeg.get().off('Event.decrypted', this.onEventDecrypted);
+        }
+    }
+
+    private onEvent = (ev: MatrixEvent) => {
+        if (ev.isBeingDecrypted() || ev.isDecryptionFailure()) return;
+        if (ev.getRoomId() !== ActiveRoomObserver.activeRoomId) return;
+        this.feedEvent(ev);
+    };
+
+    private onEventDecrypted = (ev: MatrixEvent) => {
+        if (ev.isDecryptionFailure()) return;
+        if (ev.getRoomId() !== ActiveRoomObserver.activeRoomId) return;
+        this.feedEvent(ev);
+    };
+
+    private feedEvent(ev: MatrixEvent) {
+        if (!this.messaging) return;
+
+        const raw = ev.event;
+        this.messaging.feedEvent(raw).catch(e => {
+            console.error("Error sending event to widget: ", e);
+        });
     }
 }
diff --git a/src/stores/widgets/StopGapWidgetDriver.ts b/src/stores/widgets/StopGapWidgetDriver.ts
index 9b455ac481..5c2d1868aa 100644
--- a/src/stores/widgets/StopGapWidgetDriver.ts
+++ b/src/stores/widgets/StopGapWidgetDriver.ts
@@ -14,11 +14,12 @@
  * limitations under the License.
  */
 
-import { Capability, WidgetDriver, WidgetType } from "matrix-widget-api";
+import { Capability, ISendEventDetails, WidgetDriver, WidgetEventCapability, WidgetType } from "matrix-widget-api";
 import { iterableUnion } from "../../utils/iterables";
 import { MatrixClientPeg } from "../../MatrixClientPeg";
 import { arrayFastClone } from "../../utils/arrays";
 import { ElementWidgetCapabilities } from "./ElementWidgetCapabilities";
+import ActiveRoomObserver from "../../ActiveRoomObserver";
 
 // TODO: Purge this from the universe
 
@@ -47,7 +48,30 @@ export class StopGapWidgetDriver extends WidgetDriver {
                     allowedCaps.push(ElementWidgetCapabilities.CanChangeViewedRoom);
                 }
             }
+            if (Array.isArray(wkPerms["event_actions"])) {
+                if (wkPerms["event_actions"].includes(this.forType)) {
+                    allowedCaps.push(...WidgetEventCapability.findEventCapabilities(requested).map(c => c.raw));
+                }
+            }
         }
         return new Set(iterableUnion(requested, allowedCaps));
     }
+
+    public async sendEvent(eventType: string, content: any, stateKey: string = null): Promise<ISendEventDetails> {
+        const client = MatrixClientPeg.get();
+        const roomId = ActiveRoomObserver.activeRoomId;
+
+        if (!client || !roomId) throw new Error("Not in a room or not attached to a client");
+
+        let r: {event_id: string} = null;
+        if (stateKey !== null) {
+            // state event
+            r = await client.sendStateEvent(roomId, eventType, content, stateKey);
+        } else {
+            // message event
+            r = await client.sendEvent(roomId, eventType, content);
+        }
+
+        return {roomId, eventId: r.event_id};
+    }
 }