90 lines
2.5 KiB
JavaScript
90 lines
2.5 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/**
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* A file (disk) based persistent cache of a JSON serializable object.
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*/
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export class PersistentCache {
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/**
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* Create a cache object based on a name.
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*
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* @param {string} name Name of the cache. It will be used to create the filename.
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* @param {boolean} preload (optional). Whether the cache should be preloaded from file. Defaults to false.
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*/
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constructor(name, preload = false) {
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this.name = name;
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this._filename = `activity-stream.${name}.json`;
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if (preload) {
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this._load();
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}
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}
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/**
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* Set a value to be cached with the specified key.
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*
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* @param {string} key The cache key.
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* @param {object} value The data to be cached.
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*/
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async set(key, value) {
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const data = await this._load();
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data[key] = value;
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await this._persist(data);
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}
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/**
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* Get a value from the cache.
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*
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* @param {string} key (optional) The cache key. If not provided, we return the full cache.
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* @returns {object} The cached data.
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*/
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async get(key) {
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const data = await this._load();
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return key ? data[key] : data;
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}
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/**
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* Load the cache into memory if it isn't already.
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*/
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_load() {
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return (
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this._cache ||
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// eslint-disable-next-line no-async-promise-executor
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(this._cache = new Promise(async (resolve, reject) => {
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let filepath;
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try {
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filepath = PathUtils.join(PathUtils.localProfileDir, this._filename);
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} catch (error) {
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reject(error);
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return;
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}
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let data = {};
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try {
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data = await IOUtils.readJSON(filepath);
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} catch (error) {
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if (
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// isInstance() is not available in node unit test. It should be safe to use instanceof as it's directly from IOUtils.
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// eslint-disable-next-line mozilla/use-isInstance
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!(error instanceof DOMException) ||
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error.name !== "NotFoundError"
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) {
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console.error(`Failed to parse ${this._filename}:`, error.message);
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}
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}
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resolve(data);
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}))
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);
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}
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/**
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* Persist the cache to file.
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*/
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async _persist(data) {
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const filepath = PathUtils.join(PathUtils.localProfileDir, this._filename);
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await IOUtils.writeJSON(filepath, data, {
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tmpPath: `${filepath}.tmp`,
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});
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}
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}
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