function quiz_plein(obj) {
	return obj.id.substring(0, obj.id.indexOf('_'));
}

function quiz_vraag(obj) {
	var str = obj.id;
	var qStart = str.indexOf('antwoord_') + 9;
	var qEnd = qStart+str.substring(qStart).indexOf('_');
	return (1 * (str.substring(qStart, qEnd)));
}

function quiz_antwoord(obj) {
	var str = obj.id;
	var qStart = str.indexOf('antwoord_') + 9;
	str = str.substring(qStart);
	qStart = str.indexOf('_') + 1;
	return (1 * (str.substring(qStart)));
}

function quiz_status(obj) {
	if (obj.src.indexOf('up.gif') >= 0 || obj.src.indexOf('over.gif') >= 0) {
		return false;
	} else {
		return true;
	}
} 

function quiz_groupOff(obj) {
	var b1 = document.getElementById(quiz_plein(obj) + '_antwoord_' + quiz_vraag(obj) + '_1');
	var b2 = document.getElementById(quiz_plein(obj) + '_antwoord_' + quiz_vraag(obj) + '_2');
	var b3 = document.getElementById(quiz_plein(obj) + '_antwoord_' + quiz_vraag(obj) + '_3');
	b1.src="artwork/up.gif";
	b2.src="artwork/up.gif";
	b3.src="artwork/up.gif";
}

function quiz_over(obj)  {	
	if (!quiz_status(obj)) {	
		obj.src="artwork/over.gif";
	}
	return false;
}

function quiz_out(obj) {
	if (!quiz_status(obj)) {		
		obj.src="artwork/up.gif";
	}
	return false;
}


function quiz_click(obj) {
	quiz_groupOff(obj);
	obj.src="artwork/down.gif";
	quiz_ajax_on(obj);
	return false;
}

function quiz_ajax_on(obj) {
	var url='ajax.php?quiz=' + quiz_plein(obj) + '&vraag=' + quiz_vraag(obj) + '&status=' + quiz_antwoord(obj);
	ajaxFunction(url);
}

function checkForm(frm) {
	// tel het aantal down images, dit moet gelijk zijn aan het aantal vragen gedeeld door 3!
	var total_cnt = 0;
	var down_cnt = 0;
	for(i=0; i < document.images.length; i++) {
		if (document.images[i].id.indexOf(frm.plein.value + '_antwoord_') != -1) {
			total_cnt++;
			if (document.images[i].src.indexOf('down.gif') != -1) {
				down_cnt++;
			}
		}
	}
	if (total_cnt / 3 != down_cnt) {
		alert('Je moet eerst op alle vragen een antwoord geven!');
		return false;
	}
	
	return true;
}


function ajaxFunction(url) {  
	var xmlHttp;
	try {    // Firefox, Opera 8.0+, Safari    
		xmlHttp=new XMLHttpRequest();    
	}
	catch (e) {    // Internet Explorer   
		try {      
				xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");      
		} catch (e) {     
			try {
					xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");        
			} catch (e) { 
				alert("Your browser does not support AJAX!");        
				return false;        
			}      
		}    
	}
	xmlHttp.onreadystatechange=function() {
		if(xmlHttp.readyState==4) {
			//document.myForm.time.value=xmlHttp.responseText;
		}
	}
	//alert(url);
	xmlHttp.open("GET", url, true);
	xmlHttp.send(null);  
}