pull out all screen share related logic.

src/state/CallViewModel/CallNotificationLifecycle.ts

@@ -0,0 +1,210 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import {
+  type CallMembership,
+  type MatrixRTCSession,
+  MatrixRTCSessionEvent,
+  type MatrixRTCSessionEventHandlerMap,
+} from "matrix-js-sdk/lib/matrixrtc";
+import {
+  combineLatest,
+  concat,
+  endWith,
+  filter,
+  fromEvent,
+  ignoreElements,
+  map,
+  merge,
+  NEVER,
+  type Observable,
+  of,
+  pairwise,
+  startWith,
+  switchMap,
+  takeUntil,
+  timer,
+} from "rxjs";
+import {
+  type EventTimelineSetHandlerMap,
+  EventType,
+  type Room as MatrixRoom,
+  RoomEvent,
+} from "matrix-js-sdk";
+
+import { type Behavior } from "../Behavior";
+import { type Epoch, mapEpoch, type ObservableScope } from "../ObservableScope";
+export type AutoLeaveReason = "allOthersLeft" | "timeout" | "decline";
+export type CallPickupState =
+  | "unknown"
+  | "ringing"
+  | "timeout"
+  | "decline"
+  | "success"
+  | null;
+export type CallNotificationWrapper = Parameters<
+  MatrixRTCSessionEventHandlerMap[MatrixRTCSessionEvent.DidSendCallNotification]
+>;
+export function createSentCallNotification$(
+  scope: ObservableScope,
+  matrixRTCSession: MatrixRTCSession,
+): Behavior<CallNotificationWrapper | null> {
+  const sentCallNotification$ = scope.behavior(
+    fromEvent(matrixRTCSession, MatrixRTCSessionEvent.DidSendCallNotification),
+    null,
+  ) as Behavior<CallNotificationWrapper | null>;
+  return sentCallNotification$;
+}
+
+export function createReceivedDecline$(
+  matrixRoom: MatrixRoom,
+): Observable<Parameters<EventTimelineSetHandlerMap[RoomEvent.Timeline]>> {
+  return (
+    fromEvent(matrixRoom, RoomEvent.Timeline) as Observable<
+      Parameters<EventTimelineSetHandlerMap[RoomEvent.Timeline]>
+    >
+  ).pipe(filter(([event]) => event.getType() === EventType.RTCDecline));
+}
+
+interface Props {
+  scope: ObservableScope;
+  memberships$: Behavior<Epoch<CallMembership[]>>;
+  sentCallNotification$: Observable<CallNotificationWrapper | null>;
+  receivedDecline$: Observable<
+    Parameters<EventTimelineSetHandlerMap[RoomEvent.Timeline]>
+  >;
+  options: { waitForCallPickup?: boolean; autoLeaveWhenOthersLeft?: boolean };
+  localUser: { deviceId: string; userId: string };
+}
+/**
+ * @returns {callPickupState$, autoLeave$}
+ * `callPickupState$` The current call pickup state of the call.
+ *  - "unknown": The client has not yet sent the notification event. We don't know if it will because it first needs to send its own membership.
+ *     Then we can conclude if we were the first one to join or not.
+ *     This may also be set if we are disconnected.
+ *  - "ringing": The call is ringing on other devices in this room (This client should give audiovisual feedback that this is happening).
+ *  - "timeout": No-one picked up in the defined time this call should be ringing on others devices.
+ *     The call failed. If desired this can be used as a trigger to exit the call.
+ *  - "success": Someone else joined. The call is in a normal state. No audiovisual feedback.
+ *  - null: EC is configured to never show any waiting for answer state.
+ *
+ * `autoLeave$` An observable that emits (null) when the call should be automatically left.
+ *  - if options.autoLeaveWhenOthersLeft is set to true it emits when all others left.
+ *  - if options.waitForCallPickup is set to true it emits if noone picked up the ring or if the ring got declined.
+ *  - if options.autoLeaveWhenOthersLeft && options.waitForCallPickup is false it will never emit.
+ *
+ */
+export function createCallNotificationLifecycle$({
+  scope,
+  memberships$,
+  sentCallNotification$,
+  receivedDecline$,
+  options,
+  localUser,
+}: Props): {
+  callPickupState$: Behavior<CallPickupState>;
+  autoLeave$: Observable<AutoLeaveReason>;
+} {
+  // TODO convert all ring and all others left logic into one callLifecycleTracker$(didSendCallNotification$,matrixLivekitItem$): {autoLeave$,callPickupState$}
+  const allOthersLeft$ = memberships$.pipe(
+    pairwise(),
+    filter(
+      ([{ value: prev }, { value: current }]) =>
+        current.every((m) => m.userId === localUser.userId) &&
+        prev.some((m) => m.userId !== localUser.userId),
+    ),
+    map(() => {}),
+  );
+
+  /**
+   * Whether some Matrix user other than ourself is joined to the call.
+   */
+  const someoneElseJoined$ = memberships$.pipe(
+    mapEpoch((ms) => ms.some((m) => m.userId !== localUser.userId)),
+  ) as Behavior<Epoch<boolean>>;
+
+  /**
+   * Whenever the RTC session tells us that it intends to ring the remote
+   * participant's devices, this emits an Observable tracking the current state of
+   * that ringing process.
+   */
+  // This is a behavior since we need to store the latest state for when we subscribe to this after `didSendCallNotification$`
+  // has already emitted but we still need the latest observable with a timeout timer that only gets created on after receiving `notificationEvent`.
+  // A behavior will emit the latest observable with the running timer to new subscribers.
+  // see also: callPickupState$ and in particular the line: `return this.ring$.pipe(mergeAll());` here we otherwise might get an EMPTY observable if
+  // `ring$` would not be a behavior.
+  const remoteRingState$: Behavior<"ringing" | "timeout" | "decline" | null> =
+    scope.behavior(
+      sentCallNotification$.pipe(
+        filter(
+          (newAndLegacyEvents) =>
+            // only care about new events (legacy do not have decline pattern)
+            newAndLegacyEvents?.[0].notification_type === "ring",
+        ),
+        map((e) => e as CallNotificationWrapper),
+        switchMap(([notificastionEvent]) => {
+          const lifetimeMs = notificationEvent?.lifetime ?? 0;
+          return concat(
+            lifetimeMs === 0
+              ? // If no lifetime, skip the ring state
+                of(null)
+              : // Ring until lifetime ms have passed
+                timer(lifetimeMs).pipe(
+                  ignoreElements(),
+                  startWith("ringing" as const),
+                ),
+            // The notification lifetime has timed out, meaning ringing has likely
+            // stopped on all receiving clients.
+            of("timeout" as const),
+            // This makes sure we will not drop into the `endWith("decline" as const)` state
+            NEVER,
+          ).pipe(
+            takeUntil(
+              receivedDecline$.pipe(
+                filter(
+                  ([event]) =>
+                    event.getRelation()?.rel_type === "m.reference" &&
+                    event.getRelation()?.event_id ===
+                      notificationEvent.event_id &&
+                    event.getSender() !== localUser.userId,
+                ),
+              ),
+            ),
+            endWith("decline" as const),
+          );
+        }),
+      ),
+      null,
+    );
+
+  const callPickupState$ = scope.behavior(
+    options.waitForCallPickup === true
+      ? combineLatest(
+          [someoneElseJoined$, remoteRingState$],
+          (someoneElseJoined, ring) => {
+            if (someoneElseJoined) {
+              return "success" as const;
+            }
+            // Show the ringing state of the most recent ringing attempt.
+            // as long as we have not yet sent an RTC notification event, ring will be null -> callPickupState$ = unknown.
+            return ring ?? ("unknown" as const);
+          },
+        )
+      : NEVER,
+    null,
+  );
+
+  const autoLeave$ = merge(
+    options.autoLeaveWhenOthersLeft === true
+      ? allOthersLeft$.pipe(map(() => "allOthersLeft" as const))
+      : NEVER,
+    callPickupState$.pipe(
+      filter((state) => state === "timeout" || state === "decline"),
+    ),
+  );
+  return { autoLeave$, callPickupState$ };
+}