Delegate delayed leaves in LocalMember rather than LocalTransport

IMO this is where the delegation calls should have lived all along, since the leave event is part of the membership lifecycle, and we otherwise end up with an awkward hack to ignore transport updates.

Doing this now ensures that the client won't send any delegation requests if delegation is unsupported, and prepares the code for a future change in which we use the dedicated delegation endpoint from the CS API.

src/state/CallViewModel/localMember/LocalMember.ts

@@ -15,6 +15,7 @@ import {
   MediaDeviceFailure,
 } from "livekit-client";
 import { observeParticipantEvents } from "@livekit/components-core";
+import { type MatrixClient } from "matrix-js-sdk";
 import {
   Status as RTCSessionStatus,
   type LivekitTransport,
@@ -76,6 +77,7 @@ import { type HomeserverConnected } from "./HomeserverConnected.ts";
 import { type LocalTransport } from "./LocalTransport.ts";
 import { areLivekitTransportsEqual } from "../remoteMembers/MatrixLivekitMembers.ts";
 import { or$ } from "../../../utils/observable.ts";
+import { getSFUConfigWithOpenID } from "../../../livekit/openIDSFU.ts";
 
 export enum TransportState {
   /** Not even a transport is available to the LocalMembership */
@@ -143,12 +145,16 @@ interface Props {
   ) => void;
   homeserverConnected: HomeserverConnected;
   roomId: string;
+  ownMembershipIdentity: CallMembershipIdentityParts;
   localTransport: LocalTransport;
+  client: Pick<MatrixClient, "getDeviceId" | "getOpenIdToken">;
   matrixRTCSession: Pick<
     MatrixRTCSession,
     "updateCallIntent" | "leaveRoomSession"
   >;
   baseUrl: string;
+  delayId$: Behavior<string | null>;
+  matrixRTCMode: MatrixRTCMode;
   logger: Logger;
 }
 
@@ -168,6 +174,7 @@ interface Props {
  * @param props.muteStates The mute states for video and audio.
  * @param props.matrixRTCSession The matrix RTC session to join.
  * @param props.baseUrl Base URL of the homeserver.
+ * @param props.delayId$ ID of the delayed leave event to delegate to the SFU.
  * @param props.roomId The room ID used as the call identifier in analytics events.
  * @returns
  *  - publisher: The handle to create tracks and publish them to the room.
@@ -179,15 +186,19 @@ interface Props {
 export const createLocalMembership$ = ({
   scope,
   connectionManager,
-  localTransport$,
+  localTransport,
   homeserverConnected,
   createPublisherFactory,
   joinMatrixRTC,
   logger: parentLogger,
   muteStates,
+  client,
   matrixRTCSession,
   baseUrl,
   roomId,
+  ownMembershipIdentity,
+  delayId$,
+  matrixRTCMode,
 }: Props): {
   /**
    * This request to start audio and video tracks.
@@ -711,6 +722,34 @@ export const createLocalMembership$ = ({
     ),
   );
 
+  // Delegate delayed leaves to the SFU
+  scope.reconcile(
+    scope.behavior(combineLatest([joinParams$, delayId$])),
+    async ([joinParams, delayId]) => {
+      if (joinParams?.delegationSupported && delayId !== null) {
+        try {
+          // This will technically cause the service to issue a new JWT token,
+          // but it's safe to discard. We're only interested in triggering
+          // delegation.
+          await getSFUConfigWithOpenID(
+            client,
+            ownMembershipIdentity,
+            joinParams.transport.livekit_service_url,
+            roomId,
+            { matrixRTCMode, delayEndpointBaseUrl: baseUrl, delayId },
+            logger,
+          );
+        } catch (e) {
+          // TODO: Surface this to the user as a service interruption?
+          logger.error(
+            `Failed to delegate leave to ${joinParams.transport.livekit_service_url}`,
+            e,
+          );
+        }
+      }
+    },
+  );
+
   // Pause upstream of all local media tracks when we're disconnected from
   // MatrixRTC, because it can be an unpleasant surprise for the app to say
   // 'reconnecting' and yet still be transmitting your media to others.