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