More hacking on rtcsession

src/room/useActiveFocus.ts

@@ -0,0 +1,68 @@
+/*
+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 {
+  MatrixRTCSession,
+  MatrixRTCSessionEvent,
+} from "matrix-js-sdk/src/matrixrtc/MatrixRTCSession";
+import { useCallback, useEffect, useState } from "react";
+import { deepCompare } from "matrix-js-sdk/src/utils";
+
+import { LivekitFocus } from "../livekit/LivekitFocus";
+
+function getActiveFocus(
+  rtcSession: MatrixRTCSession
+): LivekitFocus | undefined {
+  const oldestMembership = rtcSession.getOldestMembership();
+  return oldestMembership?.getActiveFoci()[0] as LivekitFocus;
+}
+
+/**
+ * Gets the currently active (livekit) focus for a MatrixRTC session
+ * This logic is specific to livekit foci where the whole call must use one
+ * and the same focus.
+ */
+export function useActiveFocus(
+  rtcSession: MatrixRTCSession
+): LivekitFocus | undefined {
+  const [activeFocus, setActiveFocus] = useState(() =>
+    getActiveFocus(rtcSession)
+  );
+
+  const onMembershipsChanged = useCallback(() => {
+    const newActiveFocus = getActiveFocus(rtcSession);
+
+    if (!deepCompare(activeFocus, newActiveFocus)) {
+      setActiveFocus(newActiveFocus);
+    }
+  }, [activeFocus, rtcSession]);
+
+  useEffect(() => {
+    rtcSession.on(
+      MatrixRTCSessionEvent.MembershipsChanged,
+      onMembershipsChanged
+    );
+
+    return () => {
+      rtcSession.off(
+        MatrixRTCSessionEvent.MembershipsChanged,
+        onMembershipsChanged
+      );
+    };
+  });
+
+  return activeFocus;
+}