/*
 * Copyright 2006 SitePoint Pty. Ltd, www.sitepoint.com
 *
 * 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.
*/

function Ajax() 
   {
      this.req = null;
      this.url = null;
      this.status = null;
      this.statusText = '';
      this.method = 'GET';
      this.async = true;
      this.dataPayload = null;
      this.readyState = null;
      this.responseText = null;
      this.responseXML = null;
      this.handleResp = null;
      this.responseFormat = 'text', // 'text', 'xml', 'object'
      this.mimeType = null;
      this.headers = [];

      this.init = function() 
         {
            var i = 0;
            var reqTry = 
               [ 
                  function() { return new XMLHttpRequest(); },
                  function() { return new ActiveXObject('Msxml2.XMLHTTP') },
                  function() { return new ActiveXObject('Microsoft.XMLHTTP' )} 
               ];

            while (!this.req && (i < reqTry.length)) 
               {
                  try 
                     { 
                        this.req = reqTry[i++]();
                     } 
                  catch(e) {}
               }
            return true;
         };

      this.doGet = function(url, hand, format) 
         {
            this.url = url;
            this.handleResp = hand;
            this.responseFormat = format || 'text';
            this.doReq();
         };

      this.doPost = function(url, dataPayload, hand, format) 
         {
            this.url = url;
            this.dataPayload = dataPayload;
            this.handleResp = hand;
            this.responseFormat = format || 'text';
            this.method = 'POST';
            this.doReq();
         };

      this.doReq = function() 
         {
            var self = null;
            var req = null;
            var headArr = [];

            if (!this.init()) 
               {
                  alert('Could not create XMLHttpRequest object.');
                  return;
               }

            req = this.req;
            req.open(this.method, this.url, this.async);

            if (this.method == "POST") 
               {
                  this.req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
               }

            if (this.method == 'POST') 
               {
                  req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
               }

            self = this;

            req.onreadystatechange = function() 
               {
                  var resp = null;
                  self.readyState = req.readyState;

                  if (req.readyState == 4) 
                     {        
                        self.status = req.status;
                        self.statusText = req.statusText;
                        self.responseText = req.responseText;
                        self.responseXML = req.responseXML;        

                        switch(self.responseFormat) 
                           {
                              case 'text':
                                 resp = self.responseText;
                                 break;
                              case 'xml':
                                 resp = self.responseXML;
                                 break;
                              case 'object':
                                 resp = req;
                                 break;
                           }

                        if (self.status > 199 && self.status < 300) 
                           {
                              if (!self.handleResp) 
                                 {
                                    alert('No response handler defined for this XMLHttpRequest object.');
                                    return;
                                 }
                              else 
                                 {
                                    self.handleResp(resp);
                                 }
                           }

                        else 
                           {
                              self.handleErr(resp);
                           }
                     }
               }

            req.send(this.dataPayload);
         };

      this.abort = function() 
         {
            if (this.req) 
               {
                  this.req.onreadystatechange = function() { };
                  this.req.abort();
                  this.req = null;
               }
         };

      this.handleErr = function() 
         {
            var errorWin;
            // Create new window and display error
            try 
               {
                  errorWin = window.open('', 'errorWin');
                  errorWin.document.body.innerHTML = this.responseText;
               }
            // If pop-up gets blocked, inform user
            catch(e) 
               {
                  alert('An error occurred, but the error message cannot be' +
                  ' displayed because of your browser\'s pop-up blocker.\n' +
                  'Please allow pop-ups from this Web site.');
               }
         };

      this.setMimeType = function(mimeType) 
         {
            this.mimeType = mimeType;
         };

      this.setHandlerResp = function(funcRef) 
         {
            this.handleResp = funcRef;
         };

      this.setHandlerErr = function(funcRef) 
         {
            this.handleErr = funcRef; 
         };

      this.setHandlerBoth = function(funcRef) 
         {
            this.handleResp = funcRef;
            this.handleErr = funcRef;
         };

      this.setRequestHeader = function(headerName, headerValue) 
         {
            this.headers.push(headerName + ': ' + headerValue);
         };

   }