Save room shared keys to local storage

Signed-off-by: Šimon Brandner <simon.bra.ag@gmail.com>

src/e2ee/sharedKeyManagement.ts

@@ -14,7 +14,27 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { useSetting } from "../settings/useSetting";
+import { useEffect, useMemo } from "react";
+import { randomString } from "matrix-js-sdk/src/randomstring";
 
-export const useRoomSharedKey = (roomId: string, initialValue?: string) =>
-  useSetting(`room-shared-key-${roomId}`, initialValue);
+import { useEnableE2EE } from "../settings/useSetting";
+import { useLocalStorage } from "../useLocalStorage";
+
+const getRoomSharedKeyLocalStorageKey = (roomId: string): string =>
+  `room-shared-key-${roomId}`;
+
+export const useRoomSharedKey = (
+  roomId: string
+): [string | null, ((value: string) => void) | null] => {
+  const key = useMemo(() => getRoomSharedKeyLocalStorageKey(roomId), [roomId]);
+  const [e2eeEnabled] = useEnableE2EE();
+  const [roomSharedKey, setRoomSharedKey] = useLocalStorage(key);
+
+  useEffect(() => {
+    if ((roomSharedKey && roomSharedKey !== "") || !e2eeEnabled) return;
+
+    setRoomSharedKey(randomString(32));
+  }, [roomSharedKey, e2eeEnabled, setRoomSharedKey]);
+
+  return e2eeEnabled ? [roomSharedKey, setRoomSharedKey] : [null, null];
+};