var ajax_call = {

  myConn:      false, // the XMLHttpRequest
  body:        false, // the body element
  form:        false, // the form element
  target:      false, // the target container
  loader:      false, // the loader

  init:        function(controlId, targetId){

    // test for methods & elements
    if(!document.getElementById ||
       !document.getElementsByTagName ||
       !document.getElementById(controlId) ||
       !document.getElementById(targetId)) {

       return;
    }
   
    // set and test XHConn, quitting silently if it fails
    ajax_call.myConn = new XHConn();
    if(!ajax_call.myConn) return;
    
    // get the body
    ajax_call.body = document.getElementsByTagName('body')[0];
    // get the form
    ajax_call.form = document.getElementsByTagName('form')[0];
    
    // get the controller
    ajax_call.control = document.getElementById(controlId);

    // get the target
    ajax_call.target = document.getElementById(targetId);
    
    ajax_call.part2 = document.getElementById('part2');
    
    
    if (semid = ajax_call.checkCondition()) {
    	ajax_call.getConn(semid);
    }

    // add the onchange event to the controller,
    ajax_call.addEvent(ajax_call.control,
                         'change',
                         function(){  
                           ajax_call.part2.style.display = 'none';                      
                           if ( semid = ajax_call.checkCondition() ){
                           	                         
                             ajax_call.getConn(semid);
                             
                           } else {                              
                             ajax_call.target.innerHTML = '<p><b>Fehler:</b> Sie haben eine Kategorie ausgew&auml;lt.</p><p>Bitte wählen Sie ein Seminar aus!</p>';                             
                           }
                         });
                         

  },

  
  checkCondition: function() {
  	index = ajax_call.form.seminar_select.selectedIndex;
	if (ajax_call.form.seminar_select.options[index].value != 0) {
		return ajax_call.form.seminar_select.options[index].value;
	}	
	return false;
  },
  
  terminSelect: function(){                        
    
    obj = document.getElementById('termin_select');
    val = obj.options[obj.selectedIndex].value;

    //alert(ajax_call.part2.style.display);

	if (val != 0) {
		ajax_call.part2.style.display = 'block';
	} else {
		ajax_call.part2.style.display = 'none';
	}

  }, 

  
  getConn:  function(semid, termin_id){ // the Ajax call
    // let's let the user know something is happening (see below)
    ajax_call.buildLoader();
    /* this is the function that is run
       once the Ajax call completes */
    var fnWhenDone = function(oXML) {
      // get rid of the loader
      ajax_call.killLoader();
      // insert the returned address information into the target
      ajax_call.target.innerHTML = oXML.responseText;
    };
    // use XHConn's connect method

	if (termin_id != 'undefined' && termin_id > 0) {
		ajax_call.part2.style.display = 'block';
	}
    ajax_call.myConn.connect('seminaranmeldung_ajax.php', 'POST',
                               'semid='+semid+'&termin_id='+termin_id, fnWhenDone);
  },
  
  
  buildLoader: function(){     // builds a loader
    // create a new div
    ajax_call.loader = document.createElement('div');
    // give it some style
    ajax_call.loader.style.position   = 'absolute';
    ajax_call.loader.style.top        = '0';
    ajax_call.loader.style.left       = '0';
    ajax_call.loader.style.width      = '100px';
    ajax_call.loader.style.lineHeight = '20px';
    ajax_call.loader.style.margin     = '0';
    ajax_call.loader.style.textAlign  = 'center';
    ajax_call.loader.style.border     = '1px solid #870108';
    ajax_call.loader.style.background = '#990033';
    ajax_call.loader.style.color      = '#FFFFFF';
    ajax_call.loader.style.fontFamily = 'Arial, Helvetica, sans-serif';
    ajax_call.loader.style.fontWeight = 'bold';
    // give it some text
    ajax_call.loader.appendChild( document.createTextNode( 'Lade\u2026'));
    // append it to the body
    ajax_call.body.appendChild(ajax_call.loader);
  },
  
  
  killLoader:  function(){     // kills the loader
    // remove the loader form the body
    ajax_call.body.removeChild(ajax_call.loader);
  },
  
  
  addEvent: function(obj, type, fn){  // the add event function
    if (obj.addEventListener) obj.addEventListener(type, fn, false);
    else if (obj.attachEvent) {
      obj["e"+type+fn] = fn;
      obj[type+fn] = function() {
        obj["e"+type+fn](window.event);
      };
      obj.attachEvent("on"+type, obj[type+fn]);
    }
  }
};


/* run the init() method on page load, passing it
   the required arguments */
ajax_call.addEvent(window, 'load',
                 function() {
                 
                   ajax_call.init('seminar_select',
                                'termin_select_div');
                 });