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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+ KeyValueService: "resource://gre/modules/kvstore.sys.mjs",
+});
+
+/**
+ * A helper to keep track of synchronization statuses.
+ *
+ * We rely on a different storage backend than for storing Remote Settings data,
+ * because the eventual goal is to be able to detect `IndexedDB` issues and act
+ * accordingly.
+ */
+export class SyncHistory {
+ // Internal reference to underlying rkv store.
+ #store;
+
+ /**
+ * @param {String} source the synchronization source (eg. `"settings-sync"`)
+ * @param {Object} options
+ * @param {int} options.size Maximum number of entries per source.
+ */
+ constructor(source, { size } = { size: 100 }) {
+ this.source = source;
+ this.size = size;
+ }
+
+ /**
+ * Store the synchronization status. The ETag is converted and stored as
+ * a millisecond epoch timestamp.
+ * The entries with the oldest timestamps will be deleted to maintain the
+ * history size under the configured maximum.
+ *
+ * @param {String} etag the ETag value from the server (eg. `"1647961052593"`)
+ * @param {String} status the synchronization status (eg. `"success"`)
+ * @param {Object} infos optional additional information to keep track of
+ */
+ async store(etag, status, infos = {}) {
+ const rkv = await this.#init();
+ const timestamp = parseInt(etag.replace('"', ""), 10);
+ if (Number.isNaN(timestamp)) {
+ throw new Error(`Invalid ETag value ${etag}`);
+ }
+ const key = `v1-${this.source}\t${timestamp}`;
+ const value = { timestamp, status, infos };
+ await rkv.put(key, JSON.stringify(value));
+ // Trim old entries.
+ const allEntries = await this.list();
+ for (let i = this.size; i < allEntries.length; i++) {
+ let { timestamp } = allEntries[i];
+ await rkv.delete(`v1-${this.source}\t${timestamp}`);
+ }
+ }
+
+ /**
+ * Retrieve the stored history entries for a certain source, sorted by
+ * timestamp descending.
+ *
+ * @returns {Array<Object>} a list of objects
+ */
+ async list() {
+ const rkv = await this.#init();
+ const entries = [];
+ // The "from" and "to" key parameters to nsIKeyValueStore.enumerate()
+ // are inclusive and exclusive, respectively, and keys are tuples
+ // of source and datetime joined by a tab (\t), which is character code 9;
+ // so enumerating ["source", "source\n"), where the line feed (\n)
+ // is character code 10, enumerates all pairs with the given source.
+ for (const { value } of await rkv.enumerate(
+ `v1-${this.source}`,
+ `v1-${this.source}\n`
+ )) {
+ try {
+ const stored = JSON.parse(value);
+ entries.push({ ...stored, datetime: new Date(stored.timestamp) });
+ } catch (e) {
+ // Ignore malformed entries.
+ console.error(e);
+ }
+ }
+ // Sort entries by `timestamp` descending.
+ entries.sort((a, b) => (a.timestamp > b.timestamp ? -1 : 1));
+ return entries;
+ }
+
+ /**
+ * Return the most recent entry.
+ */
+ async last() {
+ // List is sorted from newer to older.
+ return (await this.list())[0];
+ }
+
+ /**
+ * Wipe out the **whole** store.
+ */
+ async clear() {
+ const rkv = await this.#init();
+ await rkv.clear();
+ }
+
+ /**
+ * Initialize the rkv store in the user profile.
+ *
+ * @returns {Object} the underlying `KeyValueService` instance.
+ */
+ async #init() {
+ if (!this.#store) {
+ // Get and cache a handle to the kvstore.
+ const dir = PathUtils.join(PathUtils.profileDir, "settings");
+ await IOUtils.makeDirectory(dir);
+ this.#store = await lazy.KeyValueService.getOrCreate(dir, "synchistory");
+ }
+ return this.#store;
+ }
+}