Convert RoomAliasCache to Typescript

src/RoomAliasCache.ts

@@ -0,0 +1,35 @@
+/*
+Copyright 2019, 2021 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.
+*/
+
+/**
+ * This is meant to be a cache of room alias to room ID so that moving between
+ * rooms happens smoothly (for example using browser back / forward buttons).
+ *
+ * For the moment, it's in memory only and so only applies for the current
+ * session for simplicity, but could be extended further in the future.
+ *
+ * A similar thing could also be achieved via `pushState` with a state object,
+ * but keeping it separate like this seems easier in case we do want to extend.
+ */
+const aliasToIDMap = new Map<string, string>();
+
+export function storeRoomAliasInCache(alias: string, id: string): void {
+    aliasToIDMap.set(alias, id);
+}
+
+export function getCachedRoomIDForAlias(alias: string): string {
+    return aliasToIDMap.get(alias);
+}