function nahledy(gid, pid, posun)
{
  if (!send_xmlhttprequest(nahledyObsluha, 'GET', 'ajax/nahledy.php?gid=' + gid + '&pid=' + pid + '&posun=' + posun))
  {
    return false; 
  }

  return true;
}

function nahledyObsluha(xmlhttp)
{
  if (xmlhttp.readyState == 4) 
  { 
    var url = xmlhttp.responseXML.getElementsByTagName('url');
    var alt = xmlhttp.responseXML.getElementsByTagName('alt');
    var pid = xmlhttp.responseXML.getElementsByTagName('pid');
    
    document.getElementById('imgNahled').src = url[0].firstChild.data;
    document.getElementById('pid').value = pid[0].firstChild.data;
    document.getElementById('imgNahled').alt = alt[0].firstChild.data;
  }
}

function send_xmlhttprequest(obsluha, method, url, content, headers) 
{
  var xmlhttp = (window.XMLHttpRequest ? new XMLHttpRequest : (window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : false)); 
  if (!xmlhttp) 
  { 
    return false; 
  } 
  xmlhttp.open(method, url); 
  xmlhttp.onreadystatechange = function() { obsluha(xmlhttp); }; 
  if (headers) 
  { 
    for (var key in headers) 
    { 
      xmlhttp.setRequestHeader(key, headers[key]); 
    } 
  } 
  xmlhttp.send(content); 
  return true; 
}

function checkData(formField){
    var str = formField.email.value; // načtena hodnota (value) z políčka s name=email
    if( str.indexOf("@") = -1) // zavináč se nevyskytuje
        return false
    else return true;
}

function kontrola(formular) {
	var status = 0;
	var globStatus = 0;

	for (t=1; t < kontrola.arguments.length; t++) {
		status = 0;
		// osetreni checkboxu
		if (eval('formular.' + kontrola.arguments[t] + '.type') == 'checkbox') {
			if (!eval('formular.' + kontrola.arguments[t] + '.checked')) {
				status = 1;
			}
		}
		else {
			// zbyle elementy (text, textarea, password)
			var hodnota = eval('formular.' + kontrola.arguments[t] + '.value');

			switch (eval('formular.' + kontrola.arguments[t] + '.type')) {
				case 'text':
				if (isBlank(hodnota)) {
					status = 2;
				}
				else {
					switch(kontrola.arguments[t]) {
						case 'email':
							if(!isEmail(hodnota))
								status = 21;								
							break;
						case 'phone':
							break;
					}
				}			
				
				break;
				case 'textarea':
				if (isBlank(hodnota)) {
					status = 3;
				}
				break;
				case 'password':
				if (isBlank(hodnota)) {
					status = 4;
				}
				break;
			}
		}
		if (status) {
			eval('formular.'+ kontrola.arguments[t] + '.style').border = '1px solid red';
			globStatus = 1;
		}
	}

	if (globStatus) {
		alert('Formulář je chybně vyplněný!');
		return false;
	}

	return true;
}

function isBlank(val) {
	if(val==null){
		return true;
	}
	for(var i=0;i<val.length;i++) {
		if ((val.charAt(i) != ' ') && (val.charAt(i) != "\t") && (val.charAt(i) != "\n") && (val.charAt(i) != "\r")){return false;}
	}
	return true;
}

function isEmail(argvalue) {
	var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
	return filter.test(argvalue);
}