src/api/Fetcher.js

/**
 * Base api fetcher.
 */
export default class Fetcher {
  /**
   * @param {Http} http
   * @param {string} [territory = 'TW'] - ['TW', 'HK', 'SG', 'MY', 'JP'] The territory for the fetcher.
   */
  constructor(http, territory = 'TW') {
    /**
     * @ignore
     */
    this.http = http;

    /**
     * @ignore
     */
    this.territory = territory;
  }

  /**
   * Set the fetcher's territory.
   * @param {string} [territory = 'TW'] - ['TW', 'HK', 'SG', 'MY', 'JP'] The territory for the fetcher.
   * @return {Fetcher}
   */
  setTerritory(territory) {
    this.territory = territory;
    return this;
  }

  /**
   * Gets an object's nested property by path.
   * @ignore
   */
  getPropertyByPath(object, path) {
    path = path.replace(/\[(\w+)\]/g, '.$1'); // convert indexes to properties
    path = path.replace(/^\./, ''); // strip a leading dot
    var keys = path.split('.');
    for (var i = 0, n = keys.length; i < n; ++i) {
      var key = keys[i];
      if (key in object) {
        object = object[key];
      } else {
        return;
      }
    }
    return object;
  }

  /**
   * Fetches next page of various paged APIs.
   *
   * @param {fulfillment} fulfillment - The fulfillment get from Promose's onFulfillment function
   * @param {String} nextUriPath - The next uri's path. Defaults to 'data.paging.next',
   * which means we will get the next uri path from 'fulfillment.data.paging.next'.
   * The correct next uri path depends on respective api's response.
   * @return {Promise}
   * @example
   * api.albumFetcher
   *   .setAlbumID('KmRKnW5qmUrTnGRuxF')
   *   .fetchTracks()
   *   .then(response => {
   *     api.albumFetcher.fetchNextPage(response));
   *   });
   */
  fetchNextPage(fulfillment, nextUriPath = 'data.paging.next') {
    var nextUri = this.getPropertyByPath(fulfillment, nextUriPath);
    if (nextUri != null && nextUri !== undefined) {
      return this.http.get(nextUri);
    } else {
      return new Promise((resolve, reject) => {
        reject(new Error('Cannot fetch next page'));
      });
    }
  }

  /**
   * Is next page available for various paged APIs.
   * @param {fulfillment} fulfillment - The fulfillment get from Promose's onFulfillment function
   * @param {String} nextUriPath - The next uri's path. Defaults to 'data.paging.next',
   * which means we will get the next uri path from 'fulfillment.data.paging.next'.
   * The correct next uri path depends on respective api's response.
   * @return {Boolean}
   * @example
   * api.albumFetcher
   *   .setAlbumID('KmRKnW5qmUrTnGRuxF')
   *   .fetchTracks()
   *   .then(response => {
   *     if (api.albumFetcher.hasNextPage(response)) {
   *       // more data available
   *     }
   *   });
   */
  hasNextPage(fulfillment, nextUriPath = 'data.paging.next') {
    var nextUri = this.getPropertyByPath(fulfillment, nextUriPath);
    return nextUri != null && nextUri !== undefined;
  }
}