Refactor ring$ observable

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

src/state/CallViewModel.ts

@@ -898,58 +898,59 @@ export class CallViewModel extends ViewModel {
   // 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.
-  private readonly ring$: Behavior<
-    Observable<"ringing" | "timeout" | "decline"> | Observable<never>
-  > = this.scope.behavior(
-    this.didSendCallNotification$.pipe(
-      filter(
-        ([notificationEvent]) => notificationEvent.notification_type === "ring",
-      ),
-      map(([notificationEvent]) => {
-        const lifetimeMs = notificationEvent?.lifetime ?? 0;
-        return concat(
-          lifetimeMs === 0
-            ? // If no lifetime, skip the ring state
-              EMPTY
-            : // 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),
-          NEVER,
-        ).pipe(
-          takeUntil(
-            (
-              fromEvent(this.matrixRoom, RoomEvent.Timeline) as Observable<
-                Parameters<EventTimelineSetHandlerMap[RoomEvent.Timeline]>
-              >
-            ).pipe(
-              filter(
-                ([event]) =>
-                  event.getType() === EventType.RTCDecline &&
-                  event.getRelation()?.rel_type === "m.reference" &&
-                  event.getRelation()?.event_id ===
-                    notificationEvent.event_id &&
-                  event.getSender() !== this.userId,
+  private readonly ring$: Behavior<"ringing" | "timeout" | "decline" | null> =
+    this.scope.behavior(
+      this.didSendCallNotification$.pipe(
+        filter(
+          ([notificationEvent]) =>
+            notificationEvent.notification_type === "ring",
+        ),
+        switchMap(([notificationEvent]) => {
+          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(
+              (
+                fromEvent(this.matrixRoom, RoomEvent.Timeline) as Observable<
+                  Parameters<EventTimelineSetHandlerMap[RoomEvent.Timeline]>
+                >
+              ).pipe(
+                filter(
+                  ([event]) =>
+                    event.getType() === EventType.RTCDecline &&
+                    event.getRelation()?.rel_type === "m.reference" &&
+                    event.getRelation()?.event_id ===
+                      notificationEvent.event_id &&
+                    event.getSender() !== this.userId,
+                ),
               ),
             ),
-          ),
-          endWith("decline" as const),
-        );
-      }),
-    ),
-    EMPTY,
-  );
+            endWith("decline" as const),
+          );
+        }),
+      ),
+      null,
+    );
 
   /**
    * Whether some Matrix user other than ourself is joined to the call.
    */
   private readonly someoneElseJoined$ = this.memberships$.pipe(
     map((ms) => ms.some((m) => m.sender !== this.userId)),
-  );
+  ) as Behavior<boolean>;
 
   /**
    * The current call pickup state of the call.
@@ -968,27 +969,19 @@ export class CallViewModel extends ViewModel {
     ? this.scope.behavior<
         "unknown" | "ringing" | "timeout" | "decline" | "success"
       >(
-        combineLatest([
-          this.livekitConnectionState$,
-          this.someoneElseJoined$,
-        ]).pipe(
-          switchMap(([livekitConnectionState, someoneElseJoined]) => {
+        combineLatest(
+          [this.livekitConnectionState$, this.someoneElseJoined$, this.ring$],
+          (livekitConnectionState, someoneElseJoined, ring) => {
             if (livekitConnectionState === ConnectionState.Disconnected) {
               // Do not ring until we're connected.
-              return of("unknown" as const);
-            } else if (someoneElseJoined) {
-              return of("success" as const);
+              return "unknown" as const;
+            } else if (someoneElseJoined && ring !== null) {
+              return "success" as const;
             }
             // Show the ringing state of the most recent ringing attempt.
-            // ring$ is a behavior so it will emit the latest observable which very well might already have a running timer.
-            // this is important in case livekitConnectionState$ after didSendCallNotification$ has already emitted.
-            return this.ring$.pipe(switchAll());
-          }),
-          // The state starts as 'unknown' because we don't know if the RTC
-          // session will actually send a notify event yet. It will only be
-          // known once we send our own membership and see that we were the
-          // first one to join.
-          startWith("unknown" as const),
+            // as long as we have not yet sent an RTC notification event, ring will be null -> callPickupState$ = unknown.
+            return ring ?? ("unknown" as const);
+          },
         ),
       )
     : constant(null);
@@ -1700,7 +1693,7 @@ export class CallViewModel extends ViewModel {
     private readonly livekitRoom: LivekitRoom,
     private readonly mediaDevices: MediaDevices,
     private readonly options: CallViewModelOptions,
-    public readonly livekitConnectionState$: Observable<ECConnectionState>,
+    public readonly livekitConnectionState$: Behavior<ECConnectionState>,
     private readonly handsRaisedSubject$: Observable<
       Record<string, RaisedHandInfo>
     >,