discourse/app/assets/javascripts/discourse/lib/ajax.js.es6

import pageVisible from 'discourse/lib/page-visible';

let _trackView = false;
let _transientHeader = null;

export function setTransientHeader(key, value) {
  _transientHeader = {key, value};
}

export function viewTrackingRequired() {
  _trackView = true;
}

/**
  Our own $.ajax method. Makes sure the .then method executes in an Ember runloop
  for performance reasons. Also automatically adjusts the URL to support installs
  in subfolders.
**/

export function ajax() {
  let url, args;
  let ajaxObj;

  if (arguments.length === 1) {
    if (typeof arguments[0] === "string") {
      url = arguments[0];
      args = {};
    } else {
      args = arguments[0];
      url = args.url;
      delete args.url;
    }
  } else if (arguments.length === 2) {
    url = arguments[0];
    args = arguments[1];
  }

  function performAjax(resolve, reject) {

    args.headers = args.headers || {};

    if (_transientHeader) {
      args.headers[_transientHeader.key] = _transientHeader.value;
      _transientHeader = null;
    }

    if (_trackView && (!args.type || args.type === "GET")) {
      _trackView = false;
      // DON'T CHANGE: rack is prepending "HTTP_" in the header's name
      args.headers['Discourse-Track-View'] = "true";
    }

    if (pageVisible()) {
      args.headers['Discourse-Visible'] = "true";
    }

    args.success = (data, textStatus, xhr) => {
      if (xhr.getResponseHeader('Discourse-Readonly')) {
        Ember.run(() => Discourse.Site.currentProp('isReadOnly', true));
      }

      if (args.returnXHR) {
        data = { result: data, xhr: xhr };
      }

      Ember.run(null, resolve, data);
    };

    args.error = (xhr, textStatus, errorThrown) => {
      // note: for bad CSRF we don't loop an extra request right away.
      //  this allows us to eliminate the possibility of having a loop.
      if (xhr.status === 403 && xhr.responseText === "[\"BAD CSRF\"]") {
        Discourse.Session.current().set('csrfToken', null);
      }

      // If it's a parsererror, don't reject
      if (xhr.status === 200) return args.success(xhr);

      // Fill in some extra info
      xhr.jqTextStatus = textStatus;
      xhr.requestedUrl = url;

      Ember.run(null, reject, {
        jqXHR: xhr,
        textStatus: textStatus,
        errorThrown: errorThrown
      });
    };

    // We default to JSON on GET. If we don't, sometimes if the server doesn't return the proper header
    // it will not be parsed as an object.
    if (!args.type) args.type = 'GET';
    if (!args.dataType && args.type.toUpperCase() === 'GET') args.dataType = 'json';

    if (args.dataType === "script") {
      args.headers['Discourse-Script'] = true;
    }

    if (args.type === 'GET' && args.cache !== true) {
      args.cache = false;
    }

    ajaxObj = $.ajax(Discourse.getURL(url), args);
  };

  let promise;

  // For cached pages we strip out CSRF tokens, need to round trip to server prior to sending the
  //  request (bypass for GET, not needed)
  if(args.type && args.type.toUpperCase() !== 'GET' && !Discourse.Session.currentProp('csrfToken')){
    promise = new Ember.RSVP.Promise((resolve, reject) => {
      ajaxObj = $.ajax(Discourse.getURL('/session/csrf'), {cache: false})
        .success(result => {
          Discourse.Session.currentProp('csrfToken', result.csrf);
          performAjax(resolve, reject);
        });
    });
  } else {
    promise = new Ember.RSVP.Promise(performAjax);
  }

  promise.abort = () => {
    if (ajaxObj) {
      ajaxObj.abort();
    }
  };

  return promise;
}