Refactor/redesign video tiles

src/observable-utils.ts

@@ -0,0 +1,37 @@
+/*
+Copyright 2023 New Vector Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { Observable, defer, finalize, tap } from "rxjs";
+
+const nothing = Symbol("nothing");
+
+/**
+ * RxJS operator that invokes a callback when the Observable is finalized,
+ * passing the most recently emitted value. If no value was emitted, the
+ * callback will not be invoked.
+ */
+export function finalizeValue<T>(callback: (finalValue: T) => void) {
+  return (source: Observable<T>): Observable<T> =>
+    defer(() => {
+      let finalValue: T | typeof nothing = nothing;
+      return source.pipe(
+        tap((value) => (finalValue = value)),
+        finalize(() => {
+          if (finalValue !== nothing) callback(finalValue);
+        }),
+      );
+    });
+}