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

/**
 * @private This is a hack to make the context be this window
 */
DWREngine._eval = function(script) {
  return eval(script);
}

/**
 * @private Called as a result of a request timeout
 */ 
DWREngine._abortRequest = function(batch) {
  if (batch && batch.metadata != null && !batch.completed) {
    DWREngine._clearUp(batch);
    if (batch.req) batch.req.abort();
    // Call all the timeout errorHandlers
    var handlers;
    var id;
    for (var i = 0; i < batch.ids.length; i++) {
      id = batch.ids[i];
      handlers = DWREngine._handlersMap[id];
      DWREngine._handleMetaDataError(handlers, "Timeout");
    }
  }
};

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

  // Irame tidyup
  if (batch.div) batch.div.parentNode.removeChild(batch.div);
  if (batch.iframe) {
    // If this is a poll frame then stop comet polling
    if (batch.iframe == DWREngine._pollFrame) DWREngine._pollFrame = null;
    batch.iframe.parentNode.removeChild(batch.iframe);
  }
  if (batch.form) batch.form.parentNode.removeChild(batch.form);

  // XHR tidyup: avoid IE handles increase
  if (batch.req) {
    // If this is a poll frame then stop comet polling
    if (batch.req == DWREngine._pollReq) DWREngine._pollReq = null;
    delete batch.req;
  }

  for (var i = 0; i < batch.postHooks.length; i++) {
    batch.postHooks[i]();
  }
  batch.postHooks = null;

  // 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;
};

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

/**
 * @private Generic error handling routing to save having null checks everywhere.
 */
DWREngine._handleWarning = function(reason, ex) {
  if (DWREngine._warningHandler) {
    DWREngine._warningHandler(reason, ex);
  }
};

/**
 * @private Generic error handling routing to save having null checks everywhere.
 */
DWREngine._handleMetaDataError = function(handlers, reason, ex) {
  if (handlers && typeof handlers.errorHandler == "function") {
    handlers.errorHandler(reason, ex);
  }
  else {
    DWREngine._handleError(reason, ex);
  }
};

/**
 * @private 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
 */
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 instanceof String) {
      batch.map[name] = "String:" + encodeURIComponent(data);
    }
    else if (data instanceof Boolean) {
      batch.map[name] = "Boolean:" + data;
    }
    else if (data instanceof Number) {
      batch.map[name] = "Number:" + data;
    }
    else if (data instanceof Date) {
      batch.map[name] = "Date:" + data.getTime();
    }
    else if (data instanceof Array) {
      batch.map[name] = DWREngine._serializeArray(batch, referto, data, name);
    }
    else {
      batch.map[name] = DWREngine._serializeObject(batch, referto, data, name);
    }
    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;
  }
};

/** @private Have we already converted this object? */
DWREngine._lookup = function(referto, data, name) {
  var lookup;
  // Can't use a map: http://getahead.ltd.uk/ajax/javascript-gotchas
  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;
};

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

  // This check for an HTML is not complete, but is there a better way.
  // Maybe we should add: data.hasChildNodes typeof "function" == true
  if (data.nodeName && data.nodeType) {
    return DWREngine._serializeXml(batch, referto, data, name);
  }

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

/** @private Marshall an object */
DWREngine._serializeXml = function(batch, referto, data, name) {
  var ref = DWREngine._lookup(referto, data, 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);
};

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

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

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

  return reply;
};

/** @private Convert an XML string into a DOM object. */
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 {
    var div = document.createElement('div');
    div.innerHTML = xml;
    return div;
  }
};

/**
 * @private Helper to find an ActiveX object that works.
 * @param axarray An array of strings to attempt to create ActiveX objects from
 */
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;
};

/** @private To make up for the lack of encodeURIComponent() on IE5.0 */
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;
  }
}

/** @private To make up for the lack of Array.splice() on IE5.0 */
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;
  }
}

/** @private To make up for the lack of Array.shift() on IE5.0 */
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;
  }
}

/** @private To make up for the lack of Array.unshift() on IE5.0 */
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];
    }
  }
}

/** @private To make up for the lack of Array.push() on IE5.0 */
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++;
    }
  }
}

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