storage-helper.js

/*!
 * MIT License
 *
 * Copyright (c) 2018 Pablo Klaschka
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

const storage = require('uxp').storage;
const fs = storage.localFileSystem;

let data;

/**
 * Reads the current value from the storage file
 * @param dataFile - the reference to the storage file
 * @return {Promise<any>} resolves with the data for the file on success, rejects otherwise
 */
async function readStorageFile(dataFile) {
    return JSON.parse((await dataFile.read({format: storage.formats.utf8})).toString());
}

class storageHelper {
    /**
     * Creates a data file if none was previously existent.
     * @return {Promise<storage.File>} The data file
     * @private
     */
    static async init() {
        let dataFolder = await fs.getDataFolder();
        try {
            let returnFile = await dataFolder.getEntry('storage.json');
            data = await readStorageFile(returnFile);
            return returnFile;
        } catch (e) {
            const file = await dataFolder.createEntry('storage.json', {type: storage.types.file, overwrite: true});
            if (file.isFile) {
                await file.write('{}', {append: false});
                data = {};
                return file;
            } else {
                throw new Error('Storage file storage.json was not a file.');
            }
        }
    }

    /**
     * Retrieves a value from storage. Saves default value if none is set.
     * @param {string} key The identifier
     * @param {*} defaultValue The default value. Gets saved and returned if no value was previously set for the speciefied key.
     * @return {Promise<*>} The value retrieved from storage. If none is saved, the `defaultValue` is returned.
     */
    static async get(key, defaultValue) {
        if (!data) {
            const dataFile = await this.init();
            await readStorageFile(dataFile);
        }
        if (data[key] === undefined) {
            await this.set(key, defaultValue);
            return defaultValue;
        } else {
            return data[key];
        }
    }

    /**
     * Saves a certain key-value-pair to the storage.
     * @param {string} key The identifier
     * @param {*} value The value that get's saved
     * @return {Promise<void>}
     */
    static async set(key, value) {
        const dataFile = await this.init();
        data[key] = value;
        return await dataFile.write(JSON.stringify(data), {append: false, format: storage.formats.utf8})
    }

    /**
     * Deletes a certain key-value-pair from the storage
     * @param {string} key The key of the deleted pair
     * @return {Promise<void>}
     */
    static async delete(key) {
        return await this.set(key, undefined);
    }

    /**
     * Resets (i.e. purges) all stored settings.
     * @returns {Promise<void>}
     */
    static async reset() {
        const dataFile = await this.init();
        return await dataFile.write('{}', {append: false, format: storage.formats.utf8})

    }
}

module.exports = storageHelper;