/* AJASON
 * Bringing AJAX and JSON together
 *
 * This file is part of AJASON.
 *
 * AJASON is a PHP 5 library and JavaScript client for the upcoming
 * Web technology called AJAX. AJAX permits data to be fetched
 * asynchronously without the need for reloading the Web page and
 * thus allows the development of interactive GUI-like Web applications.
 * JSON is a lightweight data interchange format which is used by AJASON
 * to exchange data between server and client.
 *
 * AJASON is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * AJASON is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Foobar; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * AJASON has been developed by Sven Jacobs <sven.jacobs@web.de>.
 * For more details visit sven-jacobs.de/wiki/AJASON
 *
 * Some parts of this project are contributed by other projects, namely
 * JSON (json.org) and JSON-PHP (mike.teczno.com/json.html) which are
 * copyrighted by their respective authors.
 */

/**
 * Ajax JavaScript class
 *
 * Contains methods to create the XMLHttpRequest object and to call remote
 * functions and object methods.
 *
 * @author Sven Jacobs <sven.jacobs@web.de>
**/
function Ajax( mtd, handler, debug, displayErrors )
{
   var _method        = mtd;
   var _handler       = handler;
   var _debug         = debug;
   var _displayErrors = displayErrors;
   var _clientVersion = "0.9";
   var _async = true;

   this.setAsync = function(val){
     _async = val;
   }
   /*** Private methods ***/

   /**
    * Return instance of XMLHttpRequest class
    *
    * @return Object of XMLHttpRequest
   **/
   function getXmlHttpRequestObject()
   {
      var xmlHttpRequest = false;

      if ( window.XMLHttpRequest )
      {
         try
         {
            xmlHttpRequest = new XMLHttpRequest();
         }
         catch (e)
         {
            xmlHttpRequest = false;
         }
      }
      else if ( window.ActiveXObject )
      {
         try
         {
            xmlHttpRequest = new ActiveXObject( "Msxml2.XMLHTTP" );
         }
         catch (e)
         {
            try
            {
               xmlHttpRequest = new ActiveXObject( "Microsoft.XMLHTTP" );
            }
            catch (e)
            {
               xmlHttpRequest = false;
            }
         }
      }

      // Override mime type if browser supports it (like Mozilla)
      if ( xmlHttpRequest.overrideMimeType )
      {
         xmlHttpRequest.overrideMimeType( "text/xml" );
      }
      TZR.xmlHttpRequest=xmlHttpRequest;
      return xmlHttpRequest;
   }

   /**
    * Prepare XMLHttpRequest object
    *
    * @param[in] xmlHttpRequest XMLHttpRequest object
    * @param[in] params Parameters of function or method which has been called
    * @param[in] data Data which will be send
    * @return Final data which will be send
   **/
   function prepareXmlHttpRequest( xmlHttpRequest, params, data )
   {
      var callbackFunction = getCallbackFunction( params );
      var handler;
      var finalData;

      if ( _method == "GET" )
      {
         handler   = _handler + "?" + data;
         finalData = null;
      }
      else
      {
         handler   = _handler;
         finalData = data;
      }

      xmlHttpRequest.onreadystatechange = function()
      {
         if ( xmlHttpRequest.readyState == 4 )
         {
            try
            {
               var response = JSON.parse( xmlHttpRequest.responseText );
            }
            catch (e)
            {
               alert( "AJAX error:\nUnknown response from server!\n\n" + xmlHttpRequest.responseText );
               return;
            }

            if ( response.errorCode == 0 && callbackFunction != null )
            {
               if ( _debug )
               {
                  // Show client/server versions and whole server response before executing callback function
                  alert( "AJAX debug info:\n\nServer version: " + response.serverVersion + "\nClient version: " + _clientVersion + "\nServer response: " + xmlHttpRequest.responseText );
               }
               callbackFunction( response.response );
            }
            else if ( response.errorCode != 0 && _displayErrors )
            {
               alert( "AJAX error:\n" + response.errorMessage );
            }
         }
      }

      xmlHttpRequest.open( _method, handler, _async );

      if ( _method == "POST" )
      {
         xmlHttpRequest.setRequestHeader( "Method",        "POST " + _handler + " HTTP/1.1" );
         xmlHttpRequest.setRequestHeader( "Content-Type",  "application/x-www-form-urlencoded" );
         xmlHttpRequest.setRequestHeader( "Content-Length", finalData.length );
      }

      return finalData;
   }

   /**
    * Do params include callback function?
    *
    * @param[in] params Parameters of function or method which has been called
    * @return Returns true if params contain callback function
   **/
   function paramsHaveCallbackFunction( params )
   {
      if ( typeof( params ) == "object" && params.length > 0 )
      {
         return ( typeof( params[ params.length - 1 ] ) == "function" );
      }
      else
      {
         return false;
      }
   }

   /**
    * Return callback function from params
    *
    * @param[in] params Parameters of function or method which has been called
    * @return Callback function
   **/
   function getCallbackFunction( params )
   {
      if ( paramsHaveCallbackFunction( params ) )
      {
         return params[ params.length - 1 ];
      }
      else
      {
         return null;
      }
   }

   /**
    * Prepare parameters
    *
    * @param[in] params Parameters of function or method which has been called
    * @return Prepared parameters
   **/
   function prepareParams( params )
   {
      var preparedParams = new Array();

      if ( typeof( params ) == "object" && params.length > 0 )
      {
         var end;

         if ( paramsHaveCallbackFunction( params ) )
         {
            end = 1;
         }
         else
         {
            end = 0;
         }

         for( var i = 0; i < params.length - end ; i++ )
         {
            preparedParams.push( params[ i ] );
         }
      }

      return preparedParams;
   }

   /**
    * Prepare data
    *
    * @param[in] cls Class name or null
    * @param[in] funcOrMtd Function name (if cls == null) or method name
    * @param[in] params Parameters of function or method which has been called
    * @return Prepared data
   **/
   function prepareData( cls, funcOrMtd, params )
   {
      var data = new Object();

      data[ "clientVersion" ] = _clientVersion;
      data[ "params" ]        = prepareParams( params );

      if ( cls != null )
      {
         data[ "cls" ] = cls;
         data[ "mtd" ] = funcOrMtd;
      }
      else
      {
         data[ "func" ] = funcOrMtd;
      }

      return "ajax=" + escape( JSON.stringify( data ) );
   }

   /**
    * Finally send request
    *
    * @param[in] params Parameters of function or method which has been called
    * @param[in] data Data to be send
   **/
   function call( params, data )
   {
      var xmlHttpRequest = getXmlHttpRequestObject();
      var finalData      = prepareXmlHttpRequest( xmlHttpRequest, params, data );
      xmlHttpRequest.send( finalData );
   }

   /*** Public methods ***/

   /**
    * Call remote method
    *
    * @param[in] cls Name of remote class
    * @param[in] mtd Name of remote method
    * @param[in] params Parameters of local method which has been called
   **/
   this.callMethod = function( cls, mtd, params )
   {
      var data = prepareData( cls, mtd, params );
      call( params, data );
   }

   /**
    * Call remote function
    *
    * @param[in] func Name of remote function
    * @param[in] params Parameters of local function which has been called
   **/
   this.callFunction = function( func, params )
   {
      var data = prepareData( null, func, params );
      call( params, data );
   }
}