Add probablyLeft event to the MatrixRTCSession (#4962)

* Add probablyLeft emission to the MatrixRTCSession

Signed-off-by: Timo K <toger5@hotmail.de>

* add docstring

Signed-off-by: Timo K <toger5@hotmail.de>

* Review: add additional test + fix pending promises issue.

Signed-off-by: Timo K <toger5@hotmail.de>

* review: `Pick` only a subset of membership manager events

Signed-off-by: Timo K <toger5@hotmail.de>

* reveiw: update probablyLeft logic to be more straight forward

Signed-off-by: Timo K <toger5@hotmail.de>

* fix test

Signed-off-by: Timo K <toger5@hotmail.de>

* make test not wait for 5s

Signed-off-by: Timo K <toger5@hotmail.de>

* review

Signed-off-by: Timo K <toger5@hotmail.de>

* fix linter (rebase)

Signed-off-by: Timo K <toger5@hotmail.de>

* fix import

Signed-off-by: Timo K <toger5@hotmail.de>

---------

Signed-off-by: Timo K <toger5@hotmail.de>

spec/unit/matrixrtc/MembershipManager.spec.ts

@@ -16,7 +16,14 @@ limitations under the License.
 
 import { type MockedFunction, type Mock } from "jest-mock";
 
-import { EventType, HTTPError, MatrixError, UnsupportedDelayedEventsEndpointError, type Room } from "../../../src";
+import {
+    type EmptyObject,
+    EventType,
+    HTTPError,
+    MatrixError,
+    UnsupportedDelayedEventsEndpointError,
+    type Room,
+} from "../../../src";
 import {
     MembershipManagerEvent,
     Status,
@@ -611,6 +618,7 @@ describe("MembershipManager", () => {
             await testExpires(10_000, 1_000);
         });
     });
+
     describe("status updates", () => {
         it("starts 'Disconnected'", () => {
             const manager = new MembershipManager({}, room, client, () => undefined, callSession);
@@ -836,6 +844,63 @@ describe("MembershipManager", () => {
             expect(client.sendStateEvent).toHaveBeenCalled();
         });
     });
+    describe("probablyLeft", () => {
+        it("emits probablyLeft when the membership manager could not hear back from the server for the duration of the delayed event", async () => {
+            const manager = new MembershipManager(
+                { delayedLeaveEventDelayMs: 10000 },
+                room,
+                client,
+                () => undefined,
+                callSession,
+            );
+            const { promise: stuckPromise, reject: rejectStuckPromise } = Promise.withResolvers<EmptyObject>();
+            const probablyLeftEmit = jest.fn();
+            manager.on(MembershipManagerEvent.ProbablyLeft, probablyLeftEmit);
+            manager.join([focus], focusActive);
+            try {
+                // Let the scheduler run one iteration so that we can send the join state event
+                await waitForMockCall(client._unstable_updateDelayedEvent);
+
+                // We never resolve the delayed event so that we can test the probablyLeft event.
+                // This simulates the case where the server does not respond to the delayed event.
+                client._unstable_updateDelayedEvent = jest.fn(() => stuckPromise);
+                expect(client.sendStateEvent).toHaveBeenCalledTimes(1);
+                expect(manager.status).toBe(Status.Connected);
+                expect(probablyLeftEmit).not.toHaveBeenCalledWith(true);
+                // We expect the probablyLeft event to be emitted after the `delayedLeaveEventDelayMs` = 10000.
+                // We also track the calls to updated the delayed event that all will never resolve to simulate the server not responding.
+                // The numbers are a bit arbitrary since we use the local timeout that does not perfectly match the 5s check interval in this test.
+                await jest.advanceTimersByTimeAsync(5000);
+                // No emission after 5s
+                expect(probablyLeftEmit).not.toHaveBeenCalledWith(true);
+                expect(client._unstable_updateDelayedEvent).toHaveBeenCalledTimes(1);
+
+                await jest.advanceTimersByTimeAsync(4999);
+                expect(client._unstable_updateDelayedEvent).toHaveBeenCalledTimes(3);
+                expect(probablyLeftEmit).not.toHaveBeenCalledWith(true);
+
+                // Reset mocks before we setup the next delayed event restart by advancing the timers 1 more ms.
+                (client._unstable_updateDelayedEvent as Mock<any>).mockResolvedValue({});
+
+                // Emit after 10s
+                await jest.advanceTimersByTimeAsync(1);
+                expect(client._unstable_updateDelayedEvent).toHaveBeenCalledTimes(4);
+                expect(probablyLeftEmit).toHaveBeenCalledWith(true);
+
+                // Mock a sync which does not include our own membership
+                await manager.onRTCSessionMemberUpdate([]);
+                // Wait for the current ongoing delayed event sending to finish
+                await jest.advanceTimersByTimeAsync(1);
+                // We should send a new state event and an associated delayed leave event.
+                expect(client._unstable_sendDelayedStateEvent).toHaveBeenCalledTimes(2);
+                expect(client.sendStateEvent).toHaveBeenCalledTimes(2);
+                // At the same time we expect the probablyLeft event to be emitted with false so we are back operational.
+                expect(probablyLeftEmit).toHaveBeenCalledWith(false);
+            } finally {
+                rejectStuckPromise();
+            }
+        });
+    });
 });
 
 it("Should prefix log with MembershipManager used", () => {

src/matrixrtc/IMembershipManager.ts

@@ -17,13 +17,21 @@ limitations under the License.
 import type { CallMembership } from "./CallMembership.ts";
 import type { Focus } from "./focus.ts";
 import type { Status } from "./types.ts";
+import { type TypedEventEmitter } from "../models/typed-event-emitter.ts";
 
 export enum MembershipManagerEvent {
     StatusChanged = "StatusChanged",
+    /**
+     * Emitted when the membership manager has not heard back from the server for the duration
+     * of the delayed event and hence failed to restart the delayed event.
+     * This means that the user is probably not joined anymore and the leave event was distributed to other session members.
+     */
+    ProbablyLeft = "ProbablyLeft",
 }
 
 export type MembershipManagerEventHandlerMap = {
     [MembershipManagerEvent.StatusChanged]: (prefStatus: Status, newStatus: Status) => void;
+    [MembershipManagerEvent.ProbablyLeft]: (probablyLeft: boolean) => void;
 };
 
 /**
@@ -33,7 +41,8 @@ export type MembershipManagerEventHandlerMap = {
  *
  * @internal
  */
-export interface IMembershipManager {
+export interface IMembershipManager
+    extends TypedEventEmitter<MembershipManagerEvent, MembershipManagerEventHandlerMap> {
     /**
      * If we are trying to join, or have successfully joined the session.
      * It does not reflect if the room state is already configured to represent us being joined.
@@ -85,8 +94,4 @@ export interface IMembershipManager {
      * @returns the used active focus in the currently joined session or undefined if not joined.
      */
     getActiveFocus(): Focus | undefined;
-
-    // TypedEventEmitter methods:
-    on(event: MembershipManagerEvent.StatusChanged, listener: (oldStatus: Status, newStatus: Status) => void): this;
-    off(event: MembershipManagerEvent.StatusChanged, listener: (oldStatus: Status, newStatus: Status) => void): this;
 }

src/matrixrtc/MatrixRTCSession.ts

@@ -29,7 +29,11 @@ import { EncryptionManager, type IEncryptionManager } from "./EncryptionManager.
 import { deepCompare, logDurationSync } from "../utils.ts";
 import { type Statistics, type RTCNotificationType } from "./types.ts";
 import { RoomKeyTransport } from "./RoomKeyTransport.ts";
-import type { IMembershipManager } from "./IMembershipManager.ts";
+import {
+    MembershipManagerEvent,
+    type MembershipManagerEventHandlerMap,
+    type IMembershipManager,
+} from "./IMembershipManager.ts";
 import { RTCEncryptionManager } from "./RTCEncryptionManager.ts";
 import {
     RoomAndToDeviceEvents,
@@ -220,8 +224,10 @@ export type JoinSessionConfig = SessionConfig & MembershipConfig & EncryptionCon
  * This class doesn't deal with media at all, just membership & properties of a session.
  */
 export class MatrixRTCSession extends TypedEventEmitter<
-    MatrixRTCSessionEvent | RoomAndToDeviceEvents,
+    MatrixRTCSessionEvent | RoomAndToDeviceEvents | MembershipManagerEvent.ProbablyLeft,
-    MatrixRTCSessionEventHandlerMap & RoomAndToDeviceEventsHandlerMap
+    MatrixRTCSessionEventHandlerMap &
+        RoomAndToDeviceEventsHandlerMap &
+        Pick<MembershipManagerEventHandlerMap, MembershipManagerEvent.ProbablyLeft>
 > {
     private membershipManager?: IMembershipManager;
     private encryptionManager?: IEncryptionManager;
@@ -456,8 +462,8 @@ export class MatrixRTCSession extends TypedEventEmitter<
         roomState?.off(RoomStateEvent.Members, this.onRoomMemberUpdate);
     }
     private reEmitter = new TypedReEmitter<
-        MatrixRTCSessionEvent | RoomAndToDeviceEvents,
+        MatrixRTCSessionEvent | RoomAndToDeviceEvents | MembershipManagerEvent,
-        MatrixRTCSessionEventHandlerMap & RoomAndToDeviceEventsHandlerMap
+        MatrixRTCSessionEventHandlerMap & RoomAndToDeviceEventsHandlerMap & MembershipManagerEventHandlerMap
     >(this);
 
     /**
@@ -490,6 +496,7 @@ export class MatrixRTCSession extends TypedEventEmitter<
                 this.logger,
             );
 
+            this.reEmitter.reEmit(this.membershipManager!, [MembershipManagerEvent.ProbablyLeft]);
             // Create Encryption manager
             let transport;
             if (joinConfig?.useExperimentalToDeviceTransport) {

src/matrixrtc/MembershipManager.ts

@@ -129,6 +129,12 @@ export interface MembershipManagerState {
     rateLimitRetries: Map<MembershipActionType, number>;
     /** Retry counter for other errors */
     networkErrorRetries: Map<MembershipActionType, number>;
+    /** The time at which we expect the server to send the delayed leave event. */
+    expectedServerDelayLeaveTs?: number;
+    /** This is used to track if the client expects the scheduled delayed leave event to have
+     * been sent because restarting failed during the available time.
+     * Once we resend the delayed event or successfully restarted it will get unset. */
+    probablyLeft: boolean;
 }
 
 /**
@@ -343,6 +349,7 @@ export class MembershipManager
             rateLimitRetries: new Map(),
             networkErrorRetries: new Map(),
             expireUpdateIterations: 1,
+            probablyLeft: false,
         };
     }
     // Membership Event static parameters:
@@ -466,6 +473,8 @@ export class MembershipManager
                 this.stateKey,
             )
             .then((response) => {
+                this.state.expectedServerDelayLeaveTs = Date.now() + this.delayedLeaveEventDelayMs;
+                this.setAndEmitProbablyLeft(false);
                 // On success we reset retries and set delayId.
                 this.resetRateLimitCounter(MembershipActionType.SendDelayedEvent);
                 this.state.delayId = response.delay_id;
@@ -545,27 +554,58 @@ export class MembershipManager
             });
     }
 
+    private setAndEmitProbablyLeft(probablyLeft: boolean): void {
+        if (this.state.probablyLeft === probablyLeft) {
+            return;
+        }
+        this.state.probablyLeft = probablyLeft;
+        this.emit(MembershipManagerEvent.ProbablyLeft, this.state.probablyLeft);
+    }
+
     private async restartDelayedEvent(delayId: string): Promise<ActionUpdate> {
+        // Compute the duration until we expect the server to send the delayed leave event.
+        const durationUntilServerDelayedLeave = this.state.expectedServerDelayLeaveTs
+            ? this.state.expectedServerDelayLeaveTs - Date.now()
+            : undefined;
         const abortPromise = new Promise((_, reject) => {
-            setTimeout(() => {
+            setTimeout(
+                () => {
                     reject(new AbortError("Restart delayed event timed out before the HS responded"));
-            }, this.delayedLeaveEventRestartLocalTimeoutMs);
+                },
+                // We abort immediately at the time where we expect the server to send the delayed leave event.
+                // At this point we want the catch block to run and set the `probablyLeft` state.
+                //
+                // While we are already in probablyLeft state, we use the unaltered delayedLeaveEventRestartLocalTimeoutMs.
+                durationUntilServerDelayedLeave !== undefined && !this.state.probablyLeft
+                    ? Math.min(this.delayedLeaveEventRestartLocalTimeoutMs, durationUntilServerDelayedLeave)
+                    : this.delayedLeaveEventRestartLocalTimeoutMs,
+            );
         });
 
         // The obvious choice here would be to use the `IRequestOpts` to set the timeout. Since this call might be forwarded
-        // to the widget driver this information would ge lost. That is why we mimic the AbortError using the race.
+        // to the widget driver this information would get lost. That is why we mimic the AbortError using the race.
         return await Promise.race([
             this.client._unstable_updateDelayedEvent(delayId, UpdateDelayedEventAction.Restart),
             abortPromise,
         ])
             .then(() => {
+                // Whenever we successfully restart the delayed event we update the `state.expectedServerDelayLeaveTs`
+                // which stores the predicted timestamp at which the server will send the delayed leave event if there wont be any further
+                // successful restart requests.
+                this.state.expectedServerDelayLeaveTs = Date.now() + this.delayedLeaveEventDelayMs;
                 this.resetRateLimitCounter(MembershipActionType.RestartDelayedEvent);
+                this.setAndEmitProbablyLeft(false);
                 return createInsertActionUpdate(
                     MembershipActionType.RestartDelayedEvent,
                     this.delayedLeaveEventRestartMs,
                 );
             })
             .catch((e) => {
+                if (this.state.expectedServerDelayLeaveTs && this.state.expectedServerDelayLeaveTs <= Date.now()) {
+                    // Once we reach this point it's likely that the server is sending the delayed leave event so we emit `probablyLeft = true`.
+                    // It will emit `probablyLeft = false` once we notice about our leave through sync and successfully setup a new state event.
+                    this.setAndEmitProbablyLeft(true);
+                }
                 const repeatActionType = MembershipActionType.RestartDelayedEvent;
                 if (this.isNotFoundError(e)) {
                     this.state.delayId = undefined;
@@ -620,6 +660,7 @@ export class MembershipManager
                 this.stateKey,
             )
             .then(() => {
+                this.setAndEmitProbablyLeft(false);
                 this.state.startTime = Date.now();
                 // The next update should already use twice the membershipEventExpiryTimeout
                 this.state.expireUpdateIterations = 1;