feat(widget): Rtc transports discovery for widgets

apps/web/src/stores/widgets/ElementWidgetDriver.ts

@@ -26,6 +26,7 @@ import {
     type IWidgetApiErrorResponseDataDetails,
     type ISearchUserDirectoryResult,
     type IGetMediaConfigResult,
+    type IRtcTransportsResult,
 } from "matrix-widget-api";
 import {
     ClientEvent,
@@ -123,6 +124,7 @@ export class ElementWidgetDriver extends WidgetDriver {
             // This is a trusted Element Call widget that we control
             this.allowedCapabilities.add(MatrixCapabilities.AlwaysOnScreen);
             this.allowedCapabilities.add(MatrixCapabilities.MSC3846TurnServers);
+            this.allowedCapabilities.add(MatrixCapabilities.MSC4515RtcTransports);
             this.allowedCapabilities.add(`org.matrix.msc2762.timeline:${inRoomId}`);
             this.allowedCapabilities.add(MatrixCapabilities.MSC4157SendDelayedEvent);
             this.allowedCapabilities.add(MatrixCapabilities.MSC4157UpdateDelayedEvent);
@@ -765,6 +767,16 @@ export class ElementWidgetDriver extends WidgetDriver {
         }
     }
 
+    public async getRtcTransports(): Promise<IRtcTransportsResult> {
+        const client = MatrixClientPeg.safeGet();
+        // Delegate to the authenticated CS endpoint (MSC4143). Any error (e.g. the
+        // homeserver not supporting it) propagates and is turned into a widget error
+        // response by ClientWidgetApi. The js-sdk Transport and widget-api IRtcTransport
+        // types are structurally identical.
+        const transports = await client._unstable_getRTCTransports();
+        return { rtc_transports: transports };
+    }
+
     public async readEventRelations(
         eventId: string,
         roomId?: string,

apps/web/test/unit-tests/stores/widgets/ElementWidgetDriver-test.ts

@@ -14,6 +14,7 @@
     type ITurnServer as IClientTurnServer,
     Direction,
     EventType,
+    MatrixError,
     MatrixEvent,
     MsgType,
     RelationType,
@@ -89,6 +90,7 @@
         const requestedCapabilities = new Set([
             "m.always_on_screen",
             "town.robin.msc3846.turn_servers",
+            "org.matrix.msc4515.rtc_transports",
             "org.matrix.msc2762.timeline:!1:example.org",
             "org.matrix.msc2762.send.event:org.matrix.msc4075.call.notify",
             "org.matrix.msc2762.send.event:org.matrix.msc4075.rtc.notification",
@@ -148,7 +150,7 @@
         ]);
 
         const approvedCapabilities = await driver.validateCapabilities(requestedCapabilities);
         expect(approvedCapabilities).toEqual(requestedCapabilities);
     });
 
     it("approves capabilities via module api", async () => {
@@ -420,6 +422,34 @@
         });
     });
 
+    describe("getRtcTransports", () => {
+        let driver: WidgetDriver;
+
+        beforeEach(() => {
+            driver = mkDefaultDriver();
+        });
+
+        it("gets the RTC transports from the homeserver", async () => {
+            const transports = [{ type: "livekit", livekit_service_url: "https://livekit-jwt.example.com" }];
+            client._unstable_getRTCTransports.mockResolvedValue(transports);
+
+            await expect(driver.getRtcTransports()).resolves.toEqual({ rtc_transports: transports });
+
+            expect(client._unstable_getRTCTransports).toHaveBeenCalledWith();
+        });
+
+        it("propagates errors from the homeserver", async () => {
+            const error = new MatrixError(
+                { errcode: "M_NOT_FOUND", error: "Not found" },
+                404,
+            );
+
+            client._unstable_getRTCTransports.mockRejectedValue(error);
+
+            await expect(driver.getRtcTransports()).rejects.toBe(error);
+        });
+    });
+
     describe("readEventRelations", () => {
         let driver: WidgetDriver;