Add voice broadcast pre-recoding PiP (#9548)

src/voice-broadcast/stores/VoiceBroadcastPreRecordingStore.ts

@@ -0,0 +1,70 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+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 { TypedEventEmitter } from "matrix-js-sdk/src/models/typed-event-emitter";
+
+import { VoiceBroadcastPreRecording } from "..";
+import { IDestroyable } from "../../utils/IDestroyable";
+
+export type VoiceBroadcastPreRecordingEvent = "changed";
+
+interface EventMap {
+    changed: (preRecording: VoiceBroadcastPreRecording | null) => void;
+}
+
+export class VoiceBroadcastPreRecordingStore
+    extends TypedEventEmitter<VoiceBroadcastPreRecordingEvent, EventMap>
+    implements IDestroyable {
+    private current: VoiceBroadcastPreRecording | null = null;
+
+    public setCurrent(current: VoiceBroadcastPreRecording): void {
+        if (this.current === current) return;
+
+        if (this.current) {
+            this.current.off("dismiss", this.onCancel);
+        }
+
+        this.current = current;
+        current.on("dismiss", this.onCancel);
+        this.emit("changed", current);
+    }
+
+    public clearCurrent(): void {
+        if (this.current === null) return;
+
+        this.current.off("dismiss", this.onCancel);
+        this.current = null;
+        this.emit("changed", null);
+    }
+
+    public getCurrent(): VoiceBroadcastPreRecording | null {
+        return this.current;
+    }
+
+    public destroy(): void {
+        this.removeAllListeners();
+
+        if (this.current) {
+            this.current.off("dismiss", this.onCancel);
+        }
+    }
+
+    private onCancel = (voiceBroadcastPreRecording: VoiceBroadcastPreRecording): void => {
+        if (this.current === voiceBroadcastPreRecording) {
+            this.clearCurrent();
+        }
+    };
+}