Hide the invite button in non-public rooms

src/room/useRoomState.ts

@@ -0,0 +1,51 @@
+/*
+Copyright 2022 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 { RoomState, RoomStateEvent } from "matrix-js-sdk/src/models/room-state";
+import { useCallback, useMemo, useState } from "react";
+
+import type { Room } from "matrix-js-sdk/src/models/room";
+import { useTypedEventEmitter } from "../useEvents";
+
+/**
+ * A React hook for values computed from room state.
+ * @param room The room.
+ * @param f A mapping from the current room state to the computed value.
+ * @returns The computed value.
+ */
+export const useRoomState = <T>(room: Room, f: (state: RoomState) => T): T => {
+  const [numUpdates, setNumUpdates] = useState(0);
+  useTypedEventEmitter(
+    room,
+    RoomStateEvent.Update,
+    useCallback(() => setNumUpdates((n) => n + 1), [setNumUpdates])
+  );
+  // We want any change to the update counter to trigger an update here
+  // eslint-disable-next-line react-hooks/exhaustive-deps
+  return useMemo(() => f(room.currentState), [room, f, numUpdates]);
+};
+
+export const useRoomAvatar = (room: Room) =>
+  useRoomState(
+    room,
+    useCallback(() => room.getMxcAvatarUrl(), [room])
+  );
+
+export const useJoinRule = (room: Room) =>
+  useRoomState(
+    room,
+    useCallback((state) => state.getJoinRule(), [])
+  );