nits fixes

src/hooks/useFavouriteMessages.ts

@@ -0,0 +1,41 @@
+
+/*
+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 { useState } from "react";
+
+const favouriteMessageIds = JSON.parse(
+    localStorage?.getItem("io_element_favouriteMessages")?? "[]") as string[];
+
+export default function useFavouriteMessages() {
+    const [, setX] = useState<string[]>();
+
+    //checks if an id already exist
+    const isFavourite = (eventId: string): boolean => favouriteMessageIds.includes(eventId);
+
+    const toggleFavourite = (eventId: string) => {
+        isFavourite(eventId) ? favouriteMessageIds.splice(favouriteMessageIds.indexOf(eventId), 1)
+            : favouriteMessageIds.push(eventId);
+
+        //update the local storage
+        localStorage.setItem('io_element_favouriteMessages', JSON.stringify(favouriteMessageIds));
+
+        // This forces a re-render to account for changes in appearance in real-time when the favourite button is toggled
+        setX([]);
+    };
+
+    return { isFavourite, toggleFavourite };
+}