import browser from 'webextension-polyfill';
import log from 'loglevel';
import { captureException } from '@sentry/browser';
import { checkForError } from './util';

/**
 * A wrapper around the extension's storage local API
 */
export default class ExtensionStore {
  constructor() {
    this.isSupported = Boolean(browser.storage.local);
    if (!this.isSupported) {
      log.error('Storage local API not available.');
    }
    // we use this flag to avoid flooding sentry with a ton of errors:
    // once data persistence fails once and it flips true we don't send further
    // data persistence errors to sentry
    this.dataPersistenceFailing = false;
  }

  setMetadata(initMetaData) {
    this.metadata = initMetaData;
  }

  async set(state) {
    if (!this.isSupported) {
      throw new Error(
        'Metamask- cannot persist state to local store as this browser does not support this action',
      );
    }
    if (!state) {
      throw new Error('MetaMask - updated state is missing');
    }
    if (!this.metadata) {
      throw new Error(
        'MetaMask - metadata must be set on instance of ExtensionStore before calling "set"',
      );
    }
    try {
      // we format the data for storage as an object with the "data" key for the controller state object
      // and the "meta" key for a metadata object containing a version number that tracks how the data shape
      // has changed using migrations to adapt to backwards incompatible changes
      await this._set({ data: state, meta: this.metadata });
      if (this.dataPersistenceFailing) {
        this.dataPersistenceFailing = false;
      }
    } catch (err) {
      if (!this.dataPersistenceFailing) {
        this.dataPersistenceFailing = true;
        captureException(err);
      }
      log.error('error setting state in local store:', err);
    }
  }

  /**
   * Returns all of the keys currently saved
   *
   * @returns {Promise<*>}
   */
  async get() {
    if (!this.isSupported) {
      return undefined;
    }
    const result = await this._get();
    // extension.storage.local always returns an obj
    // if the object is empty, treat it as undefined
    if (isEmpty(result)) {
      return undefined;
    }
    return result;
  }

  /**
   * Returns all of the keys currently saved
   *
   * @private
   * @returns {object} the key-value map from local storage
   */
  _get() {
    const { local } = browser.storage;
    return new Promise((resolve, reject) => {
      local.get(null).then((/** @type {any} */ result) => {
        const err = checkForError();
        if (err) {
          reject(err);
        } else {
          resolve(result);
        }
      });
    });
  }

  /**
   * Sets the key in local state
   *
   * @param {object} obj - The key to set
   * @returns {Promise<void>}
   * @private
   */
  _set(obj) {
    const { local } = browser.storage;
    return new Promise((resolve, reject) => {
      local.set(obj).then(() => {
        const err = checkForError();
        if (err) {
          reject(err);
        } else {
          resolve();
        }
      });
    });
  }
}

/**
 * Returns whether or not the given object contains no keys
 *
 * @param {object} obj - The object to check
 * @returns {boolean}
 */
function isEmpty(obj) {
  return Object.keys(obj).length === 0;
}