Clean up editor drafts for unknown rooms (#12850)

* Clean up editor drafts for unknown rooms and add tests.

* lint

* Call cleanUpDraftsIfRequired when we know a live update has completed.

* Fix test for new call site of draft cleaning

* fix test

src/DraftCleaner.ts

@@ -0,0 +1,78 @@
+/*
+Copyright 2024 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 { logger } from "matrix-js-sdk/src/logger";
+
+import { MatrixClientPeg } from "./MatrixClientPeg";
+import { EDITOR_STATE_STORAGE_PREFIX } from "./components/views/rooms/SendMessageComposer";
+
+// The key used to persist the the timestamp we last cleaned up drafts
+export const DRAFT_LAST_CLEANUP_KEY = "mx_draft_cleanup";
+// The period of time we wait between cleaning drafts
+export const DRAFT_CLEANUP_PERIOD = 1000 * 60 * 60 * 24 * 30;
+
+/**
+ * Checks if `DRAFT_CLEANUP_PERIOD` has expired, if so, deletes any stord editor drafts that exist for rooms that are not in the known list.
+ */
+export function cleanUpDraftsIfRequired(): void {
+    if (!shouldCleanupDrafts()) {
+        return;
+    }
+    logger.debug(`Cleaning up editor drafts...`);
+    cleaupDrafts();
+    try {
+        localStorage.setItem(DRAFT_LAST_CLEANUP_KEY, String(Date.now()));
+    } catch (error) {
+        logger.error("Failed to persist draft cleanup key", error);
+    }
+}
+
+/**
+ *
+ * @returns {bool} True if the timestamp has not been persisted or the `DRAFT_CLEANUP_PERIOD` has expired.
+ */
+function shouldCleanupDrafts(): boolean {
+    try {
+        const lastCleanupTimestamp = localStorage.getItem(DRAFT_LAST_CLEANUP_KEY);
+        if (!lastCleanupTimestamp) {
+            return true;
+        }
+        const parsedTimestamp = Number.parseInt(lastCleanupTimestamp || "", 10);
+        if (!Number.isInteger(parsedTimestamp)) {
+            return true;
+        }
+        return Date.now() > parsedTimestamp + DRAFT_CLEANUP_PERIOD;
+    } catch (error) {
+        return true;
+    }
+}
+
+/**
+ * Clear all drafts for the CIDER editor if the room does not exist in the known rooms.
+ */
+function cleaupDrafts(): void {
+    for (let i = 0; i < localStorage.length; i++) {
+        const keyName = localStorage.key(i);
+        if (!keyName?.startsWith(EDITOR_STATE_STORAGE_PREFIX)) continue;
+        // Remove the prefix and the optional event id suffix to leave the room id
+        const roomId = keyName.slice(EDITOR_STATE_STORAGE_PREFIX.length).split("_$")[0];
+        const room = MatrixClientPeg.safeGet().getRoom(roomId);
+        if (!room) {
+            logger.debug(`Removing draft for unknown room with key ${keyName}`);
+            localStorage.removeItem(keyName);
+        }
+    }
+}