/*!
 * Copyright 2016 Amazon.com,
 * Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Amazon Software License (the "License").
 * You may not use this file except in compliance with the
 * License. A copy of the License is located at
 *
 *     http://aws.amazon.com/asl/
 *
 * or in the "license" file accompanying this file. This file is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, express or implied. See the License
 * for the specific language governing permissions and
 * limitations under the License.
 */

import { AsyncStorage } from 'react-native';

const MEMORY_KEY_PREFIX = '@MemoryStorage:';
let dataMemory = {};

/** @class */
class MemoryStorage {

  /**
   * This is used to set a specific item in storage
   * @param {string} key - the key for the item
   * @param {object} value - the value
   * @returns {string} value that was set
   */
  static setItem(key, value) {
    AsyncStorage.setItem(MEMORY_KEY_PREFIX + key, value);
    dataMemory[key] = value;
    return dataMemory[key];
  }

  /**
   * This is used to get a specific key from storage
   * @param {string} key - the key for the item
   * This is used to clear the storage
   * @returns {string} the data item
   */
  static getItem(key) {
    return Object.prototype.hasOwnProperty.call(dataMemory, key) ? dataMemory[key] : undefined;
  }

  /**
   * This is used to remove an item from storage
   * @param {string} key - the key being set
   * @returns {string} value - value that was deleted
   */
  static removeItem(key) {
    AsyncStorage.removeItem(MEMORY_KEY_PREFIX + key);
    return delete dataMemory[key];
  }

  /**
   * This is used to clear the storage
   * @returns {string} nothing
   */
  static clear() {
    dataMemory = {};
    return dataMemory;
  }

  /**
  * Will sync the MemoryStorage data from AsyncStorage to storageWindow MemoryStorage
  * @param {nodeCallback<string>} callback callback with (err, 'SUCCESS')
  * @returns {void}
  */
  static sync(callback) {
    AsyncStorage.getAllKeys((errKeys, keys) => {
      if (errKeys) return callback(errKeys, null);
      const memoryKeys = keys.filter((key) => key.startsWith(MEMORY_KEY_PREFIX));
      AsyncStorage.multiGet(memoryKeys, (err, stores) => {
        if (err) return callback(err, null);
        stores.map((result, index, store) => {
          const key = store[index][0];
          const value = store[index][1];
          const memoryKey = key.replace(MEMORY_KEY_PREFIX, '');
          dataMemory[memoryKey] = value;
          return undefined;
        });
        callback(null, 'SUCCESS');
        return undefined;
      });
      return undefined;
    });
  }
}

/** @class */
export default class StorageHelper {

  /**
   * This is used to get a storage object
   * @returns {object} the storage
   */
  constructor() {
    this.storageWindow = MemoryStorage;
  }

  /**
   * This is used to return the storage
   * @returns {object} the storage
   */
  getStorage() {
    return this.storageWindow;
  }
}
