if (callData.errorHandler == null) callData.errorHandler = DWREngine._errorHandler;
  if (callData.warningHandler == null) callData.warningHandler = DWREngine._warningHandler;

  // Save the callMetaData
  DWREngine._handlersMap[id] = callData;

  // Copy extra callData into the map
  var data, prop;
  for (prop in callData) {
    data = callData[prop];
    if (typeof data != "function") {
      DWREngine._batch.map[prop] = "" + data;
    }
  }

  // Add in the page and session ids
  DWREngine._batch.map.httpSessionId = DWREngine._httpSessionId;
  DWREngine._batch.map.scriptSessionId = DWREngine._scriptSessionId;
  DWREngine._batch.map.page = window.location.pathname;

  DWREngine._batch.map[prefix + "scriptName"] = scriptName;
  DWREngine._batch.map[prefix + "methodName"] = methodName;
  DWREngine._batch.map[prefix + "id"] = id;

  // Serialize the parameters into batch.map
  for (i = 0; i < params.length; i++) {
    DWREngine._serializeAll(DWREngine._batch, [], params[i], prefix + "param" + i);
  }

  // Now we have finished remembering the call, we incr the call count
  DWREngine._batch.map.callCount++;
  if (singleShot) {
    DWREngine.endBatch();
  }
};

/**
 * @private Poll the server to see if there is any data waiting
 */
DWREngine._poll = function(overridePath) {
  if (!DWREngine._reverseAjax) {
    return;
  }
  // Get a unique ID for this call
  var random = Math.floor(Math.random() * 10001);
  var id = (random + "_" + new Date().getTime()).toString();
  // Create a batch object that describes how we are to call the server
  var batch = {
    completed:false,
    map:{
      callCount:1,
      'c0-scriptName':'DWRSystem',
      'c0-methodName':'poll',
      'c0-id':id,
      httpSessionId:DWREngine._httpSessionId,
      scriptSessionId:DWREngine._scriptSessionId,
      page:window.location.pathname
    },
    method:DWREngine._pollMethod,
    isPoll:true,
    verb:"POST",
    async:true,
    paramCount:0,
    ids:[ id ],
    path:(overridePath) ? overridePath : DWREngine._defaultPath,
    preHooks:(DWREngine._preHook) ? [ DWREngine._preHook ] : [],
    postHooks:(DWREngine._postHook) ? [ DWREngine._postHook ] : [],
    timeout:0
  };
  // IE can't handle XHR polling, so we must back off to iframe
  if (!window.XMLHttpRequest && DWREngine._pollMethod == DWREngine.XMLHttpRequest) {
    batch.method = DWREngine.IFrame;
  }
  // Create an entry in the handlers map for what happens when the reply arrives
  DWREngine._handlersMap[id] = {
    errorHandler:DWREngine._errorHandler,
    warningHandler:DWREngine._warningHandler,
    callback:DWREngine._triggerNextPoll
  };
  // Send the data
  DWREngine._sendData(batch);
  DWREngine._batches[DWREngine._batches.length] = batch;
  DWREngine._checkCometPoll();
};

/**
 * Setup an interval to kick off the next poll
 */
DWREngine._triggerNextPoll = function(pause) {
  setTimeout("DWREngine._poll()", pause);
}

/**
 * @private Check for reverse Ajax activity
 */
DWREngine._checkCometPoll = function() {
  if (DWREngine._pollComet) {
    if (DWREngine._pollFrame) {
      setTimeout("DWREngine._checkCometPoll()", DWREngine._pollCometInterval);
      var text = DWREngine._getTextFromCometIFrame();
      DWREngine._processCometResponse(text);
    }
    else if (DWREngine._pollReq) {
      setTimeout("DWREngine._checkCometPoll()", DWREngine._pollCometInterval);
      try {
        var xhrtext = DWREngine._pollReq.responseText;
        DWREngine._processCometResponse(xhrtext);
      }
      catch (ex) {
        // IE complains for no good reason. Ignore
      }
    }
  }
}

/**
 * @private Extract the whole (executed an all) text from the current iframe
 */
DWREngine._getTextFromCometIFrame = function() {
  var frameDocument;
  if (DWREngine._pollFrame.contentDocument) {
    frameDocument = DWREngine._pollFrame.contentDocument.defaultView.document;
  }
  else if (DWREngine._pollFrame.contentWindow) {
    frameDocument = DWREngine._pollFrame.contentWindow.document
  }
  else {
    return "";
  }
  var bodyNodes = frameDocument.getElementsByTagName("body");
  if (bodyNodes == null || bodyNodes.length == 0) return "";
  if (bodyNodes[0] == null) return "";
  var text = bodyNodes[0].innerHTML.toString();
  // IE plays silly-pants and adds <PRE>...</PRE> for some unknown reason
  if (text.indexOf("<PRE>") == 0) text = text.substring(5, text.length - 7);
  return text;
}

/**
 * @private Some more text might have come in, test and execute the new stuff
 */
DWREngine._processCometResponse = function(response) {
  if (DWREngine._pollCometSize != response.length) {
    var firstStartTag = response.indexOf("//@DWR-START@", DWREngine._pollCometSize);
    if (firstStartTag == -1) {
      // There is no start tag so we ignore the rest
      // DWRUtil.debug("Missing //@DWR-START@ Skipping: " + response.substring(DWREngine._pollCometSize));
      DWREngine._pollCometSize = response.length;
    }
    else {
      // if (firstStartTag != DWREngine._pollCometSize) {
      //   DWRUtil.debug("//@DWR-START@ not at start skipping: " + response.substring(DWREngine._pollCometSize, firstStartTag));
      // }
      var lastEndTag = response.lastIndexOf("//@DWR-END@");
      if (lastEndTag != -1) {
        var executeString = response.substring(firstStartTag + 13, lastEndTag);
        // DWRUtil.debug(executeString);
        eval(executeString);
        // Skip the end tag too for next time
        DWREngine._pollCometSize = lastEndTag + 11;
      }
      // else {
      //   DWRUtil.debug("Missing //@DWR-END@ Postponing: " + executeString);
      // }
    }
  }
}

/**
 * @private Actually send the block of data in the batch object.
 */
DWREngine._sendData = function(batch) {
  // If the batch is empty, don't send anything
  if (batch.map.callCount == 0) return;
  // Call any pre-hooks
  for (var i = 0; i < batch.preHooks.length; i++) {
    batch.preHooks[i]();
  }
  batch.preHooks = null;
  // Set a timeout
  if (batch.timeout && batch.timeout != 0) {
    batch.interval = setInterval(function() {
      clearInterval(batch.interval);
      DWREngine._abortRequest(batch);
    }, batch.timeout);
  }
  // A quick string to help people that use web log analysers
  var statsInfo;
  if (batch.map.callCount == 1) {
    statsInfo = batch.map["c0-scriptName"] + "." + batch.map["c0-methodName"] + ".dwr";
  }
  else {
    statsInfo = "Multiple." + batch.map.callCount + ".dwr";
  }

  // Get setup for XMLHttpRequest if possible
  if (batch.method == DWREngine.XMLHttpRequest) {
    if (window.XMLHttpRequest) {
      batch.req = new XMLHttpRequest();
    }
    // IE5 for the mac claims to support window.ActiveXObject, but throws an error when it's used
    else if (window.ActiveXObject && !(navigator.userAgent.indexOf('Mac') >= 0 && navigator.userAgent.indexOf("MSIE") >= 0)) {
      batch.req = DWREngine._newActiveXObject(DWREngine._XMLHTTP);
    }
  }

  var query = "";
  var prop;

  // This equates to (batch.method = XHR && browser supports XHR)
  if (batch.req) {
    // Proceed using XMLHttpRequest
    if (batch.async) {
      batch.req.onreadystatechange = function() {
        DWREngine._stateChange(batch);
      };
    }
    // If we're polling, record this for monitoring
    if (batch.isPoll) DWREngine._pollReq = batch.req;
    // Workaround for Safari 1.x POST bug
    var indexSafari = navigator.userAgent.indexOf('Safari/');
    if (indexSafari >= 0) {
      // So this is Safari, are we on 1.x? POST is broken
      var version = navigator.userAgent.substring(indexSafari + 7);
      var verNum = parseInt(version, 10);
      if (verNum < 400) {
        batch.verb == "GET";
      }
    }
    if (batch.verb == "GET") {
      // Some browsers (Opera/Safari2) seem to fail to convert the value
      // of batch.map.callCount to a string in the loop below so we do it
      // manually here.
      batch.map.callCount = "" + batch.map.callCount;

      for (prop in batch.map) {
        var qkey = encodeURIComponent(prop);
        var qval = encodeURIComponent(batch.map[prop]);
        if (qval == "") {
          if (DWREngine._warningHandler) {
            DWREngine._warningHandler("Found empty qval for qkey=" + qkey);
          }
        }
        query += qkey + "=" + qval + "&";
      }
      query += "jsessionid=" + DWREngine._httpSessionId;

      try {
        batch.req.open("GET", batch.path + "/plainjs/" + statsInfo + "?" + query, batch.async);
        batch.req.send(null);
        if (!batch.async) {
          DWREngine._stateChange(batch);
        }
      }
      catch (ex) {
        DWREngine._handleMetaDataError(null, ex);
      }
    }
    else {
      for (prop in batch.map) {
        if (typeof batch.map[prop] != "function") {
          query += prop + "=" + batch.map[prop] + "\n";
        }
      }

      try {
        // This might include Safari too, but it shouldn't do any harm
        //   if (navigator.userAgent.indexOf('Gecko') >= 0) {
        //     batch.req.setRequestHeader('Connection', 'close');
        //   }
        batch.req.open("POST", batch.path + "/plainjs/" + statsInfo, batch.async);
        batch.req.setRequestHeader('Content-Type', 'text/plain');
        batch.req.send(query);
        if (!batch.async) {
          DWREngine._stateChange(batch);
        }
      }
      catch (ex) {
        DWREngine._handleMetaDataError(null, ex);
      }
    }
  }
  else if (batch.method != DWREngine.ScriptTag) {
    var idname = "dwr-if-" + batch.map["c0-id"];
    // Proceed using iframe
    batch.div = document.createElement('div');
    batch.div.innerHTML = "<iframe src='javascript:void(0)' frameborder='0' width='0' height='0' id='" + idname + "' name='" + idname + "'></iframe>";
    document.body.appendChild(batch.div);
    batch.iframe = document.getElementById(idname);
    batch.iframe.setAttribute('style', 'width:0px; height:0px; border:0px;');
    // Settings that vary if we are polling
    var baseUrl;
    if (batch.isPoll) {
      DWREngine._pollFrame = batch.iframe;
      DWREngine._pollCometSize = 0;
      baseUrl = batch.path + "/plainjs/" + statsInfo;
    }
    else {
      baseUrl = batch.path + "/htmljs/" + statsInfo;
    }
    if (batch.verb == "GET") {
      for (prop in batch.map) {
        if (typeof batch.map[prop] != "function") {
          query += encodeURIComponent(prop) + "=" + encodeURIComponent(batch.map[prop]) + "&";
        }
      }
      query = query.substring(0, query.length - 1);

      batch.iframe.setAttribute('src', baseUrl + "?" + query);
      document.body.appendChild(batch.iframe);
    }
    else {
      batch.form = document.createElement('form');
      batch.form.setAttribute('id', 'dwr-form');
      batch.form.setAttribute('action', baseUrl);
      batch.form.setAttribute('target', idname);
      batch.form.target = idname;
      batch.form.setAttribute('method', 'post');
      for (prop in batch.map) {
        var formInput = document.createElement('input');
        formInput.setAttribute('type', 'hidden');
        formInput.setAttribute('name', prop);
        formInput.setAttribute('value', batch.map[prop]);
        batch.form.appendChild(formInput);
      }
      document.body.appendChild(batch.form);
      batch.form.submit();
	}
  }
  else {
    if (!batch.scriptTagBase) {
      DWREngine._handleError("Please specify the scriptTagBase property within the call data.");
      return;
    }
    for (prop in batch.map) {
      if (typeof batch.map[prop] != "function") {
        query += encodeURIComponent(prop) + "=" + encodeURIComponent(batch.map[prop]) + "&";
      }
    }
    query = query.substring(0, query.length - 1);
    batch.script = document.createElement('script');
    batch.script.id = "dwr-st-" + batch.map["c0-id"];
    batch.script.src = batch.scriptTagBase + batch.path + "/plainjs/" + statsInfo + "?" + query;
    document.body.appendChild(batch.script);
  }
};

/**
 * @private Called by XMLHttpRequest to indicate that something has happened
 */
DWREngine._stateChange = function(batch) {
  if (!batch.completed && batch.req.readyState == 4) {
    try {
      var reply = batch.req.responseText;
      var status = batch.req.status;

      if (reply == null || reply == "") {
        DWREngine._handleMetaDataError(null, "No data received from server");
        return;
      }

// DWR doesn't use response codes for failure conditions, so we should be able
// to delete this. If no one complains, we will.
//      if (status != 200) {
//        if (reply == null) reply = "Unknown error occured";
//        DWREngine._handleMetaDataError(null, reply);
//        return;
//      }

      var contentType = batch.req.getResponseHeader('Content-Type');
      if (DWREngine._textHtmlHandler && contentType.match(/^text\/html/)) {
        DWREngine._textHtmlHandler();
        return;
      }

      // Comet replies might have already partially executed
      if (batch.req == DWREngine._pollReq) {
        DWREngine._processCometResponse(reply);
      }
      else {
        // This should get us out of 404s etc.
        if (reply.search("DWREngine._handle") == -1) {
          DWREngine._handleMetaDataError(null, "Invalid reply from server");
          return;
        }
        eval(reply);
      }

      // We're done. Clear up
      DWREngine._clearUp(batch);
    }
    catch (ex) {
      if (ex == null) ex = "Unknown error occured";
      DWREngine._handleMetaDataError(null, ex);
    }
    finally {
      // If there is anything on the queue waiting to go out, then send it.
      // We don't need to check for ordered mode, here because when ordered mode
      // gets turned off, we still process *waiting* batches in an ordered way.
      if (DWREngine._batchQueue.length != 0) {
        var sendbatch = DWREngine._batchQueue.shift();
        DWREngine._sendData(sendbatch);
        DWREngine._batches[DWREngine._batches.length] = sendbatch;
      }
    }
  }
};

/**
 * @private Called by reply scripts generated as a result of remote requests
 * @param id The identifier of the call that we are handling a response for
 * @param reply The data to pass to the callback function
 */
DWREngine._handleResponse = function(id, reply) {
  // Clear this callback out of the list - we don't need it any more
  var handlers = DWREngine._handlersMap[id];
  DWREngine._handlersMap[id] = null;
  // TODO: How can we do this - delete DWREngine._handlersMap.id
  if (handlers) {
    // Error handlers inside here indicate an error that is nothing to do
    // with DWR so we handle them differently.
    try {
      if (handlers.callback) handlers.callback(reply);
    }
    catch (ex) {
      DWREngine._handleMetaDataError(handlers, ex);
    }
  }

  // Finalize the call for IFrame transport 
  var responseBatch = DWREngine._batches[DWREngine._batches.length-1];
  if (responseBatch.method == DWREngine.IFrame) {
    // Only finalize after the last call has been handled
    if (responseBatch.map["c"+(responseBatch.map.callCount-1)+"-id"] == id) {
      DWREngine._clearUp(responseBatch);
    }
  }
};