/*
 * Copyright 2005 Joe Walker
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


/*
TODO: put this documentation somewhere better

         global   batch
timeout      Y    Y
errorHandler     Y    Y
preHook      Y    Y
postHook       Y    Y
method       Y    Y
verb         Y    Y
asynchronous     Y    Y
ordered      Y    -
warningHandler   Y    -

skipBatch      Y(1)   X
onBackButton     X    X
onForwardButton  X    X

(1) There is no setSkipBatch() method - batching is controlled via beginBatch() and endBatch()
*/


/**
 * Declare a constructor function to which we can add real functions.
 * @constructor
 */
function DWREngine() {
}

/**
 * Constants to pick the XMLHttpRequest remoting method.
 * For example:
 * <code>DWREngine.setMethod(DWREngine.XMLHttpRequest);</code>
 * @see DWREngine.setMethod()
 * @see DWREngine.IFrame
 */
DWREngine.XMLHttpRequest = 1;

/**
 * Constants to pick the iframe remoting method.
 * For example:
 * <code>DWREngine.setMethod(DWREngine.IFrame);</code>
 * @see DWREngine.setMethod()
 * @see DWREngine.XMLHttpRequest
 */
DWREngine.IFrame = 2;

/**
 * The default error handler displays an alert box, but that is not correct
 * for all applications, so this method allows you to set an alternative
 * error handler.
 * By default there is no error handler set.
 * @param handler A function to call with single an error parameter on failure
 * @see DWREngine.defaultMessageHandler()
 */
DWREngine.setErrorHandler = function(handler) {
  DWREngine._errorHandler = handler;
};

/**
 * The default warning handler displays an alert box, but that is not correct
 * for all applications, so this method allows you to set an alternative
 * warning handler.
 * By default there is no error handler set.
 * @param handler A function to call with single an warning parameter on failure
 * @see DWREngine.defaultMessageHandler()
 */
DWREngine.setWarningHandler = function(handler) {
  DWREngine._warningHandler = handler;
};

/**
 * Set a default timeout value for all DWR calls. A value of 0 (the default)
 * turns call timeouts off.
 * @param newTimeout The new default timeout to be set on all calls
 */
DWREngine.setTimeout = function(newTimeout) {
  DWREngine._timeout = newTimeout;
};

/**
 * The Pre-Hook is called before any DWR remoting is done.
 * Pre hooks can be useful for displaying "please wait" messages.
 * @param handler A function to call with no params before remoting
 * @see DWREngine.setPostHook()
 */
DWREngine.setPreHook = function(handler) {
  DWREngine._preHook = handler;
};

/**
 * The Post-Hook is called after any DWR remoting is done.
 * Pre hooks can be useful for removing "please wait" messages.
 * @param handler A function to call with no params after remoting
 * @see DWREngine.setPreHook()
 */
DWREngine.setPostHook = function(handler) {
  DWREngine._postHook = handler;
};

/**
 * Set the preferred remoting method.
 * setMethod does not guarantee that the selected method will be used, just that
 * we will try that method first.
 * @param newmethod One of DWREngine.XMLHttpRequest or DWREngine.IFrame
 */
DWREngine.setMethod = function(newmethod) {
  if (newmethod != DWREngine.XMLHttpRequest && newmethod != DWREngine.IFrame) {
    DWREngine._handleError("Remoting method must be one of DWREngine.XMLHttpRequest or DWREngine.IFrame");
    return;
  }
  DWREngine._method = newmethod;
};

/**
 * Which HTTP verb do we use so send results?
 * Must be one of "GET" or "POST".
 * @param verb the new HTTP verb.
 */
DWREngine.setVerb = function(verb) {
  if (verb != "GET" && verb != "POST") {
    DWREngine._handleError("Remoting verb must be one of GET or POST");
    return;
  }
  DWREngine._verb = verb;
};

/**
 * Do we attempt to ensure that remote calls happen in the order in which they
 * were sent? (Default: false)
 * Warning: Setting this to true will slow down your application, and could
 * leave users with an unresponsive browser if a message gets lost.
 * Sometimes there are better solutions where you make your application use the
 * asynchronous model properly. Please think before you use this method.
 * @param ordered true or false
 */
DWREngine.setOrdered = function(ordered) {
  DWREngine._ordered = ordered;
};

/**
 * Do we ask the XHR object to be asynchronous? (Default: true)
 * Warning: This option will be ignored if you are using iframes and is often
 * generally a bad idea to change it to false because it can make your browser
 * slow to respond and prone to hangs. If you do need this option then consider
 * setting a timeout too.
 * @param asynchronous true or false
 */
DWREngine.setAsynchronous = function(asynchronous) {
  DWREngine._asynchronous = asynchronous;
};

/**
 * The default message handler.
 * Useful in calls to setErrorHandler() or setWarningHandler() to allow you to
 * get the default back.
 * @param message The message to display to the user somehow
 */
DWREngine.defaultMessageHandler = function(message) {
  if (typeof message == "object" && message.name == "Error" && message.description) {
    alert("Error: " + message.description);
  }
  else {
    alert(message);
  }
};

/**
 * You can group several remote calls together using a batch.
 * This saves on round trips to the server so there is much less latency involved.
 * @see DWREngine.endBatch()
 */
DWREngine.beginBatch = function() {
  if (DWREngine._batch) {
    DWREngine._handleError("Batch already started.");
    return;
  }
  // Setup a batch
  DWREngine._batch = {};
  DWREngine._batch.map = {};
  DWREngine._batch.paramCount = 0;
  DWREngine._batch.map.callCount = 0;
  DWREngine._batch.metadata = {};
};

/**
 * We are finished grouping a set of remote calls together, now go and execute
 * them all.
 */
DWREngine.endBatch = function() {
  var batch = DWREngine._batch;
  if (batch == null) {
    DWREngine._handleError("No batch in progress.");
    return;
  }
  // Merge the global batch level properties into the batch meta data
  if (!batch.preHook) batch.preHook = DWREngine._preHook;
  if (!batch.postHook) batch.postHook = DWREngine._postHook;
  if (!batch.method) batch.method = DWREngine._method;
  if (!batch.verb) batch.verb = DWREngine._verb;
  if (!batch.asynchronous) batch.asynchronous = DWREngine._asynchronous;

  // If we are in ordered mode, then we don't send unless the list of sent
  // items is empty
  if (!DWREngine._ordered) {
    DWREngine._sendData(batch);
    DWREngine._batches[DWREngine._batches.length] = batch;
  }
  else {
    if (DWREngine._batches.length == 0) {
      // We aren't waiting for anything, go now.
      DWREngine._sendData(batch);
      DWREngine._batches[DWREngine._batches.length] = batch;
    }
    else {
      // Push the batch onto the waiting queue
      DWREngine._batchQueue[DWREngine._batchQueue.length] = batch;
    }
  }

  DWREngine._batch = null;
};

//==============================================================================
// Only private stuff below here
//==============================================================================

/**
 * A function to call if something fails.
 * @private
 */
DWREngine._errorHandler = DWREngine.defaultMessageHandler;

/**
 * A function to call to alert the user to some breakage.
 * @private
 */
DWREngine._warningHandler = DWREngine.defaultMessageHandler;

/**
 * A function to be called before requests are marshalled. Can be null.
 * @private
 */
DWREngine._preHook = null;

/**
 * A function to be called after replies are received. Can be null.
 * @private
 */
DWREngine._postHook = null;

/**
 * An array of the batches that we have sent and are awaiting a reply on.
 * @private
 */
DWREngine._batches = [];

/**
 * An array of batches that we'd like to send, but because we are in ordered
 * mode we won't until the current batch has been returned.
 * @private
 */
DWREngine._batchQueue = [];

/**
 * A map of all the known current call metadata objects
 * @private
 */
DWREngine._callData = {};

/**
 * What is the default remoting method
 * @private
 */
DWREngine._method = DWREngine.XMLHttpRequest;

/**
 * What is the default remoting verb (ie GET or POST)
 * @private
 */
DWREngine._verb = "POST";

/**
 * Do we attempt to ensure that remote calls happen in the order in which they
 * were sent?
 * @private
 */
DWREngine._ordered = false;

/**
 * Do we make the calls asynchronous?
 * @private
 */
DWREngine._asynchronous = true;

/**
 * The current batch (if we are in batch mode)
 * @private
 */
DWREngine._batch = null;

/**
 * The global timeout
 * @private
 */
DWREngine._timeout = 0;

/**
 * The ActiveX objects to use when we want to convert an xml string into a DOM
 * object.
 * @private
 */
DWREngine._DOMDocument = ["Msxml2.DOMDocument.5.0", "Msxml2.DOMDocument.4.0", "Msxml2.DOMDocument.3.0", "MSXML2.DOMDocument", "MSXML.DOMDocument", "Microsoft.XMLDOM"];

/**
 * The ActiveX objects to use when we want to do an XMLHttpRequest call.
 * @private
 */
DWREngine._XMLHTTP = ["Msxml2.XMLHTTP.5.0", "Msxml2.XMLHTTP.4.0", "MSXML2.XMLHTTP.3.0", "MSXML2.XMLHTTP", "Microsoft.XMLHTTP"];

/**
 * Send a request to the server
 * This method is called by Javascript that is emitted by server
 * @param path The part of the URL after the host and before the exec bit
 *       without leading or trailing /s
 * @param scriptName The class to execute
 * @param methodName The method on said class to execute
 * @param func The callback function to which any returned data should be passed
 *       if this is null, any returned data will be ignored
 * @param vararg_params The parameters to pass to the above class
 * @private
 */
DWREngine._execute = function(path, scriptName, methodName, vararg_params) {
  var singleShot = false;
  if (DWREngine._batch == null) {
    DWREngine.beginBatch();
    singleShot = true;
  }
  // To make them easy to manipulate we copy the arguments into an args array
  var args = [];
  for (var i = 0; i < arguments.length - 3; i++) {
    args[i] = arguments[i + 3];
  }
  // All the paths MUST be to the same servlet
  if (DWREngine._batch.path == null) {
    DWREngine._batch.path = path;
  }
  else {
    if (DWREngine._batch.path != path) {
      DWREngine._handleError("Can't batch requests to multiple DWR Servlets.");
      return;
    }
  }
  // From the other params, work out which is the function (or object with
  // call meta-data) and which is the call parameters
  var params;
  var callData;
  var firstArg = args[0];
  var lastArg = args[args.length - 1];

  if (typeof firstArg == "function") {
    callData = { callback:args.shift() };
    params = args;
  }
  else if (typeof lastArg == "function") {
    callData = { callback:args.pop() };
    params = args;
  }
  else if (firstArg == null) {
    // This could be a null callback function, but if the last arg is also
    // null then we can't tell which is the function unless there are only
    // 2 args, in which case we don't care!
    if (lastArg == null && args.length > 2) {
      if (DWREngine._warningHandler) {
        DWREngine._warningHandler("Ambiguous nulls at start and end of parameter list. Which is the callback function?");
      }
    }
    callData = { callback:args.shift() };
    params = args;
  }
  else if (lastArg == null) {
    callData = { callback:args.pop() };
    params = args;
  }
  else if (typeof lastArg == "object" && lastArg.callback != null && typeof lastArg.callback == "function") {
    callData = args.pop();
    params = args;
  }
  else {
    if (DWREngine._warningHandler) {
      DWREngine._warningHandler("Missing callback function or metadata object.");
    }
    return;
  }

  // Get a unique ID for this call
  var random = Math.floor(Math.random() * 10001);
  var id = (random + "_" + new Date().getTime()).toString();
  DWREngine._callData[id] = callData;
  var prefix = "c" + DWREngine._batch.map.callCount + "-";

  if (!callData.errorHandler) callData.errorHandler = DWREngine._errorHandler;
  if (!callData.warningHandler) callData.warningHandler = DWREngine._warningHandler;
  if (!callData.timeout) callData.timeout = DWREngine._timeout;

  // merge the metadata from this call into the batch
  if (callData != null)  {
    for (var prop in callData) {
      DWREngine._batch.metadata[prop] = callData[prop];
    }
  }
  DWREngine._batch.map[prefix + "scriptName"] = scriptName;
  DWREngine._batch.map[prefix + "methodName"] = methodName;
  DWREngine._batch.map[prefix + "id"] = id;

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

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

/**
 * Actually send the block of data in the batch object.
 * @param batch Block of data about the calls we are making on the server
 * @private
 */
DWREngine._sendData = function(batch) {
  // If the batch is empty, don't send anything
  if (batch.map.callCount == 0) return;
  // Call any pre-hooks
  if (batch.preHook) batch.preHook();
  // Set a timeout
  if (batch.metadata && batch.metadata.timeout && batch.metadata.timeout != 0) {
    var funcReq = function() { DWREngine._abortRequest(batch); };
    setTimeout(funcReq, batch.metadata.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"];
  }
  else {
    statsInfo = "Multiple." + batch.map.callCount;
  }

  // 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;
  if (batch.req) {
    batch.map.xml = "true";
    // Proceed using XMLHttpRequest
    batch.req.onreadystatechange = function() { DWREngine._stateChange(batch); };
    // Force Mac people to use GET because Safari is broken.
    if (batch.verb == "GET" || navigator.userAgent.indexOf('Safari') >= 0) {
      // 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 = query.substring(0, query.length - 1);

      try {
        batch.req.open("GET", batch.path + "/exec/" + statsInfo + "?" + query, batch.asynchronous);
        batch.req.send(null);
      }
      catch (ex) {
        DWREngine._handleMetaDataError(batch.metadata, 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 + "/exec/" + statsInfo, batch.asynchronous);
        batch.req.send(query);
      }
      catch (ex) {
        DWREngine._handleMetaDataError(batch.metadata, ex);
      }
    }
  }
  else {
    batch.map.xml = "false";
    var idname = "dwr-if-" + batch.map["c0-id"];
    // Proceed using iframe
    batch.div = document.createElement('div');
    batch.div.innerHTML = "<iframe 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;');

    if (batch.verb == "GET") {
      for (prop in batch.map) {
        query += encodeURIComponent(prop) + "=" + encodeURIComponent(batch.map[prop]) + "&";
      }
      query = query.substring(0, query.length - 1);

      batch.iframe.setAttribute('src', batch.path + "/exec/" + statsInfo + "?" + query);
      document.body.appendChild(batch.iframe);
    }
    else {
      batch.form = document.createElement('form');
      batch.form.setAttribute('id', 'dwr-form');
      batch.form.setAttribute('action', batch.path + "/exec" + statsInfo);
      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();
    }
  }
};

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

      // We're done. Clear up
      DWREngine._clearUp(batch);

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

      // This should get us out of 404s etc.
      if (reply.search("DWREngine._handle") == -1) {
        DWREngine._handleMetaDataError(batch.metadata, "Invalid reply from server");
        return;
      }

      if (status != 200) {
        if (reply == null) reply = "Unknown error occured";
        DWREngine._handleMetaDataError(batch.metadata, reply);
        return;
      }

      eval(reply);
    }
    catch (ex) {
      if (ex == null) ex = "Unknown error occured";
      DWREngine._handleMetaDataError(batch.metadata, 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;
      }
    }
  }
};

/**
 * Called when the replies are received.
 * This method is called by Javascript that is emitted by server
 * @param id The identifier of the call that we are handling a response for
 * @param reply The data to pass to the callback function
 * @private
 */
DWREngine._handleResponse = function(id, reply) {
  // Clear this callback out of the list - we don't need it any more
  var callData = DWREngine._callData[id];
  DWREngine._callData[id] = null;
  if (callData) {
    // Error handlers inside here indicate an error that is nothing to do
    // with DWR so we handle them differently.
    try {
      if (callData.callback) callData.callback(reply);
    }
    catch (ex) {
      DWREngine._handleMetaDataError(callData, ex);
    }
  }
};

/**
 * This method is called by Javascript that is emitted by server
 * @private
 */
DWREngine._handleServerError = function(id, error) {
  // Clear this callback out of the list - we don't need it any more
  var callData = DWREngine._callData[id];
  DWREngine._callData[id] = null;
  if (error.message) {
    DWREngine._handleMetaDataError(callData, error.message, error);
  }
  else {
    DWREngine._handleMetaDataError(callData, error);
  }
};

/**
 * Called as a result of a request timeout or an http reply status != 200
 * @param batch Block of data about the calls we are making on the server
 * @private
 */ 
DWREngine._abortRequest = function(batch) {
  if (batch && batch.metadata && !batch.completed) {
    DWREngine._clearUp();
    if (batch.req) batch.req.abort();
  }
};

/**
 * A call has finished by whatever means and we need to shut it all down.
 * @private
 */
DWREngine._clearUp = function(batch) {
  if (batch.completed) {
    alert("double complete");
    return;
  }

  if (batch.div) batch.div.parentNode.removeChild(batch.div);
  if (batch.iframe) batch.iframe.parentNode.removeChild(batch.iframe);
  if (batch.form) batch.form.parentNode.removeChild(batch.form);
  // Avoid IE handles increase
  delete batch.req;

  if (batch.postHook) batch.postHook();
  // TODO: There must be a better way???
  for (var i = 0; i < DWREngine._batches.length; i++) {
    if (DWREngine._batches[i] == batch) {
      DWREngine._batches.splice(i, 1);
      break;
    }
  }

  batch.completed = true;
};

/**
 * Generic error handling routing to save having null checks everywhere.
 * @private
 */
DWREngine._handleError = function(reason, ex) {
  if (DWREngine._errorHandler) {
    DWREngine._errorHandler(reason, ex);
  }
  else { alert("HE"+reason);}
};

/**
 * Generic error handling routing to save having null checks everywhere.
 * @private
 */
DWREngine._handleMetaDataError = function(metadata, reason, ex) {
  if (metadata.errorHandler) {
    metadata.errorHandler(reason, ex);
  }
  else { alert("HMDE"+reason);}
};

/**
 * Hack a polymorphic dwrSerialize() function on all basic types. Yeulch
 * @see DWREngine._addSerializeFunctions
 * @private
 */
DWREngine._addSerializeFunctions = function() {
  Object.prototype.dwrSerialize = DWREngine._serializeObject;
  Array.prototype.dwrSerialize = DWREngine._serializeArray;
  Boolean.prototype.dwrSerialize = DWREngine._serializeBoolean;
  Number.prototype.dwrSerialize = DWREngine._serializeNumber;
  String.prototype.dwrSerialize = DWREngine._serializeString;
  Date.prototype.dwrSerialize = DWREngine._serializeDate;
};

/**
 * Remove the hacked polymorphic dwrSerialize() function on all basic types.
 * @see DWREngine._removeSerializeFunctions
 * @private
 */
DWREngine._removeSerializeFunctions = function() {
  delete Object.prototype.dwrSerialize;
  delete Array.prototype.dwrSerialize;
  delete Boolean.prototype.dwrSerialize;
  delete Number.prototype.dwrSerialize;
  delete String.prototype.dwrSerialize;
  delete Date.prototype.dwrSerialize;
};

/**
 * Marshall a data item
 * @param batch A map of variables to how they have been marshalled
 * @param referto An array of already marshalled variables to prevent recurrsion
 * @param data The data to be marshalled
 * @param name The name of the data being marshalled
 * @private
 */
DWREngine._serializeAll = function(batch, referto, data, name) {
  if (data == null) {
    batch.map[name] = "null:null";
    return;
  }

  switch (typeof data) {
  case "boolean":
    batch.map[name] = "boolean:" + data;
    break;

  case "number":
    batch.map[name] = "number:" + data;
    break;

  case "string":
    batch.map[name] = "string:" + encodeURIComponent(data);
    break;

  case "object":
    if (data.dwrSerialize) {
      batch.map[name] = data.dwrSerialize(batch, referto, data, name);
    }
    else if (data.nodeName) {
      batch.map[name] = DWREngine._serializeXml(batch, referto, data, name);
    }
    else {
      if (DWREngine._warningHandler) {
        DWREngine._warningHandler("Object without dwrSerialize: " + typeof data + ", attempting default converter.");
      }
      batch.map[name] = "default:" + data;
    }
    break;

  case "function":
    // We just ignore functions.
    break;

  default:
    if (DWREngine._warningHandler) {
      DWREngine._warningHandler("Unexpected type: " + typeof data + ", attempting default converter.");
    }
    batch.map[name] = "default:" + data;
    break;
  }
};

/**
 * This is for the types that can recurse so we need to check that we've not
 * marshalled this object before.
 * We'd like to do:
 *   var lookup = referto[data];
 * However hashmaps in Javascript appear to use the hash values of the *string*
 * versions of the objects used as keys so all objects count as the same thing.
 * So we need to have referto as an array and go through it sequentially
 * checking for equality with data
 * @private
 */
DWREngine._lookup = function(referto, data, name) {
  var lookup;
  for (var i = 0; i < referto.length; i++) {
    if (referto[i].data == data) {
      lookup = referto[i];
      break;
    }
  }
  if (lookup) {
    return "reference:" + lookup.name;
  }
  referto.push({ data:data, name:name });
  return null;
};

/**
 * Marshall an object
 * @private
 * @see DWREngine._serializeAll()
 */
DWREngine._serializeObject = function(batch, referto, data, name) {
  var ref = DWREngine._lookup(referto, this, name);
  if (ref) return ref;

  if (data.nodeName) {
    return DWREngine._serializeXml(batch, referto, data, name);
  }

  // treat objects as an associative arrays
  var reply = "Object:{";
  var element;
  for (element in this)  {
    if (element != "dwrSerialize") {
      batch.paramCount++;
      var childName = "c" + DWREngine._batch.map.callCount + "-e" + batch.paramCount;
      DWREngine._serializeAll(batch, referto, this[element], childName);

      reply += encodeURIComponent(element);
      reply += ":reference:";
      reply += childName;
      reply += ", ";
    }
  }

  if (reply.substring(reply.length - 2) == ", ") {
    reply = reply.substring(0, reply.length - 2);
  }
  reply += "}";

  return reply;
};

/**
 * Marshall an object
 * @private
 * @see DWREngine._serializeAll()
 */
DWREngine._serializeXml = function(batch, referto, data, name) {
  var ref = DWREngine._lookup(referto, this, name);
  if (ref) {
    return ref;
  }
  var output;
  if (window.XMLSerializer) {
    var serializer = new XMLSerializer();
    output = serializer.serializeToString(data);
  }
  else {
    output = data.toXml;
  }
  return "XML:" + encodeURIComponent(output);
};

/**
 * Marshall an array
 * @private
 * @see DWREngine._serializeAll()
 */
DWREngine._serializeArray = function(batch, referto, data, name) {
  var ref = DWREngine._lookup(referto, this, name);
  if (ref) return ref;

  var reply = "Array:[";
  for (var i = 0; i < this.length; i++) {
    if (i != 0) {
      reply += ",";
    }

    batch.paramCount++;
    var childName = "c" + DWREngine._batch.map.callCount + "-e" + batch.paramCount;
    DWREngine._serializeAll(batch, referto, this[i], childName);
    reply += "reference:";
    reply += childName;
  }
  reply += "]";

  return reply;
};

/**
 * Marshall a Boolean
 * @private
 * @see DWREngine._serializeAll()
 */
DWREngine._serializeBoolean = function(batch, referto, data, name) {
  return "Boolean:" + this;
};

/**
 * Marshall a Number
 * @private
 * @see DWREngine._serializeAll()
 */
DWREngine._serializeNumber = function(batch, referto, data, name) {
  return "Number:" + this;
};

/**
 * Marshall a String
 * @private
 * @see DWREngine._serializeAll()
 */
DWREngine._serializeString = function(batch, referto, data, name) {
  return "String:" + encodeURIComponent(this);
};

/**
 * Marshall a Date
 * @private
 * @see DWREngine._serializeAll()
 */
DWREngine._serializeDate = function(batch, referto, data, name) {
  return "Date:" + this.getTime();
};

/**
 * Convert an XML string into a DOC object.
 * @param xml The xml string
 * @return a DOM version of the xml string
 * @private
 */
DWREngine._unserializeDocument = function(xml) {
  var dom;
  if (window.DOMParser) {
    var parser = new DOMParser();
    dom = parser.parseFromString(xml, "text/xml");
    if (!dom.documentElement || dom.documentElement.tagName == "parsererror") {
      var message = dom.documentElement.firstChild.data;
      message += "\n" + dom.documentElement.firstChild.nextSibling.firstChild.data;
      throw message;
    }
    return dom;
  }
  else if (window.ActiveXObject) {
    dom = DWREngine._newActiveXObject(DWREngine._DOMDocument);
    dom.loadXML(xml);
    // What happens on parse fail with IE?
    return dom;
  }
  //else if (window.XMLHttpRequest) {
  //  // Hack with XHR to get at Safari's parser
  //  var req = new XMLHttpRequest;
  //  var url = "data:application/xml;charset=utf-8," + encodeURIComponent(xml);
  //  req.open("GET", url, false);
  //  req.send(null);
  //  return req.responseXML;
  //}
  else {
    var div = document.createElement('div');
    div.innerHTML = xml;
    return div;
  }
};

/**
 * Helper to find an ActiveX object that works.
 * @param axarray An array of strings to attempt to create ActiveX objects from
 * @return An ActiveX object from the first string in the array not to die
 * @private
 */
DWREngine._newActiveXObject = function(axarray) {
  var returnValue;  
  for (var i = 0; i < axarray.length; i++) {
    try {
      returnValue = new ActiveXObject(axarray[i]);
      break;
    }
    catch (ex) {
    }
  }
  return returnValue;
};

/**
 * To make up for the lack of encodeURIComponent() on IE5.0
 * @private
 */
if (typeof window.encodeURIComponent === 'undefined') {
  DWREngine._utf8 = function(wide) {
    wide = "" + wide; // Make sure it is a string
    var c;
    var s;
    var enc = "";
    var i = 0;
    while (i < wide.length) {
      c = wide.charCodeAt(i++);
      // handle UTF-16 surrogates
      if (c >= 0xDC00 && c < 0xE000) continue;
      if (c >= 0xD800 && c < 0xDC00) {
        if (i >= wide.length) continue;
        s = wide.charCodeAt(i++);
        if (s < 0xDC00 || c >= 0xDE00) continue;
        c = ((c - 0xD800) << 10) + (s - 0xDC00) + 0x10000;
      }
      // output value
      if (c < 0x80) {
        enc += String.fromCharCode(c);
      }
      else if (c < 0x800) {
        enc += String.fromCharCode(0xC0 + (c >> 6), 0x80 + (c & 0x3F));
      }
      else if (c < 0x10000) {
        enc += String.fromCharCode(0xE0 + (c >> 12), 0x80 + (c >> 6 & 0x3F), 0x80 + (c & 0x3F));
      }
      else {
        enc += String.fromCharCode(0xF0 + (c >> 18), 0x80 + (c >> 12 & 0x3F), 0x80 + (c >> 6 & 0x3F), 0x80 + (c & 0x3F));
      }
    }
    return enc;
  }

  DWREngine._hexchars = "0123456789ABCDEF";

  DWREngine._toHex = function(n) {
    return DWREngine._hexchars.charAt(n >> 4) + DWREngine._hexchars.charAt(n & 0xF);
  }

  DWREngine._okURIchars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_-";

  window.encodeURIComponent = function(s)  {
    s = DWREngine._utf8(s);
    var c;
    var enc = "";
    for (var i= 0; i<s.length; i++) {
      if (DWREngine._okURIchars.indexOf(s.charAt(i)) == -1) {
        enc += "%" + DWREngine._toHex(s.charCodeAt(i));
      }
      else {
        enc += s.charAt(i);
      }
    }
    return enc;
  }
}

/**
 * To make up for the lack of Array.splice() on IE5.0
 * @private
 */
if (typeof Array.prototype.splice === 'undefined') {
  Array.prototype.splice = function(ind, cnt)
  {
    if (arguments.length == 0) {
      return ind;
    }
    if (typeof ind != "number") {
      ind = 0;
    }
    if (ind < 0) {
      ind = Math.max(0,this.length + ind);
    }
    if (ind > this.length) {
      if (arguments.length > 2) {
        ind = this.length;
      }
      else {
        return [];
      }
    }
    if (arguments.length < 2) {
      cnt = this.length-ind;
    }

    cnt = (typeof cnt == "number") ? Math.max(0, cnt) : 0;
    removeArray = this.slice(ind, ind + cnt);
    endArray = this.slice(ind + cnt);
    this.length = ind;

    for (var i = 2; i < arguments.length; i++) {
      this[this.length] = arguments[i];
    }
    for (i = 0; i < endArray.length; i++) {
      this[this.length] = endArray[i];
    }

    return removeArray;
  }
}

/**
 * To make up for the lack of Array.shift() on IE5.0
 * @private
 */
if (typeof Array.prototype.shift === 'undefined') {
  Array.prototype.shift = function(str) {
    var val = this[0];
    for (var i = 1; i < this.length; ++i) {
      this[i - 1] = this[i];
    }
    this.length--;
    return val;
  }
}

/**
 * To make up for the lack of Array.unshift() on IE5.0
 * @private
 */
if (typeof Array.prototype.unshift === 'undefined') {
  Array.prototype.unshift = function() {
    var i = unshift.arguments.length;
    for (var j = this.length - 1; j >= 0; --j) {
      this[j + i] = this[j];
    }
    for (j = 0; j < i; ++j) {
      this[j] = unshift.arguments[j];
    }
  }
}

/**
 * To make up for the lack of Array.push() on IE5.0
 * @private
 */
if (typeof Array.prototype.push === 'undefined') {
  Array.prototype.push = function() {
    var sub = this.length;
    for (var i = 0; i < push.arguments.length; ++i) {
      this[sub] = push.arguments[i];
      sub++;
    }
  }
}

/**
 * To make up for the lack of Array.pop() on IE5.0
 * @private
 */
if (typeof Array.prototype.pop === 'undefined') {
  Array.prototype.pop = function() {
    var lastElement = this[this.length - 1];
    this.length--;
    return lastElement;
  }
}