NewsBlur-viq/node/node_modules/socket.io-client/lib/transports/jsonp-polling.js

/**
 * socket.io
 * Copyright(c) 2011 LearnBoost <dev@learnboost.com>
 * MIT Licensed
 */

(function (exports, io, global) {
  /**
   * There is a way to hide the loading indicator in Firefox. If you create and
   * remove a iframe it will stop showing the current loading indicator.
   * Unfortunately we can't feature detect that and UA sniffing is evil.
   *
   * @api private
   */

  var indicator = global.document && "MozAppearance" in
    global.document.documentElement.style;

  /**
   * Expose constructor.
   */

  exports['jsonp-polling'] = JSONPPolling;

  /**
   * The JSONP transport creates an persistent connection by dynamically
   * inserting a script tag in the page. This script tag will receive the
   * information of the Socket.IO server. When new information is received
   * it creates a new script tag for the new data stream.
   *
   * @constructor
   * @extends {io.Transport.xhr-polling}
   * @api public
   */

  function JSONPPolling (socket) {
    io.Transport['xhr-polling'].apply(this, arguments);

    this.index = io.j.length;

    var self = this;

    io.j.push(function (msg) {
      self._(msg);
    });
  };

  /**
   * Inherits from XHR polling transport.
   */

  io.util.inherit(JSONPPolling, io.Transport['xhr-polling']);

  /**
   * Transport name
   *
   * @api public
   */

  JSONPPolling.prototype.name = 'jsonp-polling';

  /**
   * Posts a encoded message to the Socket.IO server using an iframe.
   * The iframe is used because script tags can create POST based requests.
   * The iframe is positioned outside of the view so the user does not
   * notice it's existence.
   *
   * @param {String} data A encoded message.
   * @api private
   */

  JSONPPolling.prototype.post = function (data) {
    var self = this
      , query = io.util.query(
             this.socket.options.query
          , 't='+ (+new Date) + '&i=' + this.index
        );

    if (!this.form) {
      var form = document.createElement('form')
        , area = document.createElement('textarea')
        , id = this.iframeId = 'socketio_iframe_' + this.index
        , iframe;

      form.className = 'socketio';
      form.style.position = 'absolute';
      form.style.top = '-1000px';
      form.style.left = '-1000px';
      form.target = id;
      form.method = 'POST';
      form.setAttribute('accept-charset', 'utf-8');
      area.name = 'd';
      form.appendChild(area);
      document.body.appendChild(form);

      this.form = form;
      this.area = area;
    }

    this.form.action = this.prepareUrl() + query;

    function complete () {
      initIframe();
      self.socket.setBuffer(false);
    };

    function initIframe () {
      if (self.iframe) {
        self.form.removeChild(self.iframe);
      }

      try {
        // ie6 dynamic iframes with target="" support (thanks Chris Lambacher)
        iframe = document.createElement('<iframe name="'+ self.iframeId +'">');
      } catch (e) {
        iframe = document.createElement('iframe');
        iframe.name = self.iframeId;
      }

      iframe.id = self.iframeId;

      self.form.appendChild(iframe);
      self.iframe = iframe;
    };

    initIframe();

    // we temporarily stringify until we figure out how to prevent
    // browsers from turning `\n` into `\r\n` in form inputs
    this.area.value = io.JSON.stringify(data);

    try {
      this.form.submit();
    } catch(e) {}

    if (this.iframe.attachEvent) {
      iframe.onreadystatechange = function () {
        if (self.iframe.readyState == 'complete') {
          complete();
        }
      };
    } else {
      this.iframe.onload = complete;
    }

    this.socket.setBuffer(true);
  };
  
  /**
   * Creates a new JSONP poll that can be used to listen
   * for messages from the Socket.IO server.
   *
   * @api private
   */

  JSONPPolling.prototype.get = function () {
    var self = this
      , script = document.createElement('script')
      , query = io.util.query(
             this.socket.options.query
          , 't='+ (+new Date) + '&i=' + this.index
        );

    if (this.script) {
      this.script.parentNode.removeChild(this.script);
      this.script = null;
    }

    script.async = true;
    script.src = this.prepareUrl() + query;
    script.onerror = function () {
      self.onClose();
    };

    var insertAt = document.getElementsByTagName('script')[0]
    insertAt.parentNode.insertBefore(script, insertAt);
    this.script = script;

    if (indicator) {
      setTimeout(function () {
        var iframe = document.createElement('iframe');
        document.body.appendChild(iframe);
        document.body.removeChild(iframe);
      }, 100);
    }
  };

  /**
   * Callback function for the incoming message stream from the Socket.IO server.
   *
   * @param {String} data The message
   * @api private
   */

  JSONPPolling.prototype._ = function (msg) {
    this.onData(msg);
    if (this.open) {
      this.get();
    }
    return this;
  };

  /**
   * The indicator hack only works after onload
   *
   * @param {Socket} socket The socket instance that needs a transport
   * @param {Function} fn The callback
   * @api private
   */

  JSONPPolling.prototype.ready = function (socket, fn) {
    var self = this;
    if (!indicator) return fn.call(this);

    io.util.load(function () {
      fn.call(self);
    });
  };

  /**
   * Checks if browser supports this transport.
   *
   * @return {Boolean}
   * @api public
   */

  JSONPPolling.check = function () {
    return 'document' in global;
  };

  /**
   * Check if cross domain requests are supported
   *
   * @returns {Boolean}
   * @api public
   */

  JSONPPolling.xdomainCheck = function () {
    return true;
  };

  /**
   * Add the transport to your public io.transports array.
   *
   * @api private
   */

  io.transports.push('jsonp-polling');

})(
    'undefined' != typeof io ? io.Transport : module.exports
  , 'undefined' != typeof io ? io : module.parent.exports
  , this
);