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import {
  ScriptReceivers,
  ScriptReceiverFactory
} from './script_receiver_factory';
import Runtime from 'runtime';
import ScriptRequest from './script_request';

/** Handles loading dependency files.
 *
 * Dependency loaders don't remember whether a resource has been loaded or
 * not. It is caller's responsibility to make sure the resource is not loaded
 * twice. This is because it's impossible to detect resource loading status
 * without knowing its content.
 *
 * Options:
 * - cdn_http - url to HTTP CND
 * - cdn_https - url to HTTPS CDN
 * - version - version of pusher-js
 * - suffix - suffix appended to all names of dependency files
 *
 * @param {Object} options
 */
export default class DependencyLoader {
  options: any;
  receivers: ScriptReceiverFactory;
  loading: any;

  constructor(options: any) {
    this.options = options;
    this.receivers = options.receivers || ScriptReceivers;
    this.loading = {};
  }

  /** Loads the dependency from CDN.
   *
   * @param  {String} name
   * @param  {Function} callback
   */
  load(name: string, options: any, callback: Function) {
    var self = this;

    if (self.loading[name] && self.loading[name].length > 0) {
      self.loading[name].push(callback);
    } else {
      self.loading[name] = [callback];

      var request = Runtime.createScriptRequest(self.getPath(name, options));
      var receiver = self.receivers.create(function(error) {
        self.receivers.remove(receiver);

        if (self.loading[name]) {
          var callbacks = self.loading[name];
          delete self.loading[name];

          var successCallback = function(wasSuccessful) {
            if (!wasSuccessful) {
              request.cleanup();
            }
          };
          for (var i = 0; i < callbacks.length; i++) {
            callbacks[i](error, successCallback);
          }
        }
      });
      request.send(receiver);
    }
  }

  /** Returns a root URL for pusher-js CDN.
   *
   * @returns {String}
   */
  getRoot(options: any): string {
    var cdn;
    var protocol = Runtime.getDocument().location.protocol;
    if ((options && options.useTLS) || protocol === 'https:') {
      cdn = this.options.cdn_https;
    } else {
      cdn = this.options.cdn_http;
    }
    // make sure there are no double slashes
    return cdn.replace(/\/*$/, '') + '/' + this.options.version;
  }

  /** Returns a full path to a dependency file.
   *
   * @param {String} name
   * @returns {String}
   */
  getPath(name: string, options: any): string {
    return this.getRoot(options) + '/' + name + this.options.suffix + '.js';
  }
}