/**
 * Check for valid EGN
 */
function isValidEgn(egn) {

	var year, mon, day;

	if (egn.length != 10)
		return 0;

	for (i=0; i<egn.length; i++) {
		if (isNaN(egn.charAt(i)))
			return 0;
	}

	year  = egn.substr(0, 2);
	mon   = egn.substr(2, 2);
	day   = egn.substr(4, 2);

	if (!checkDate(mon, day, year))
		return 0;

	checksum = egn.charAt(9);

	res = (2*(parseInt(egn.charAt(0))) + 4*(parseInt(egn.charAt(1))) +  8*(parseInt(egn.charAt(2))) + 5*(parseInt(egn.charAt(3))) + 10*(parseInt(egn.charAt(4))) + 9*(parseInt(egn.charAt(5))) + 7*(parseInt(egn.charAt(6))) + 3*(parseInt(egn.charAt(7))) + 6*(parseInt(egn.charAt(8)))) % 11 % 10;

	if (res == (parseInt(checksum)))
		return 1;
	else
		return 0;
}


/**
 * Check for valid date
 */
function checkDate(month, day, year) {
	
	var errorCode = 0;

	if (isNaN(day)) errorCode = 1;
	
	if (isNaN(month)) errorCode = 1;
	
	if (isNaN(year)) errorCode = 1;
	
	if ((day < 1) || (day > 31)) errorCode = 2;
	
	if ((month < 1) || (month > 12)) errorCode = 4;
	
	if ((month == 4) || (month == 6) || (month == 9) || (month == 11)) {
		if (day == 31) errorCode = 7
	}

	if (month == 2) {
		var g = parseInt(year/4);
		if (isNaN(g)) errorCode=8;
		if (day > 29) errorCode = 9;
		if ((day == 29) && ((year/4) != parseInt(year/4))) errorCode=10;
	}

	if (errorCode > 0) {
		return false;
	} else {
		return true;
	}
}

/**
 * Open popup window and write the html code there
 */
function openPopup(html, name, width, height) {

    left_param = (screen.width) ? (screen.width - width) / 2 : 0;

    top_param = (screen.height) ? (screen.height - height) / 2 : 0;        

    params = 'top=' + top_param + ', left=' + left_param + ',width=' + width + ',height=' + height
    		+ 'resizable=yes,scrollbars=yes,toolbar=no,titlebar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no';             

    popup = window.open('', name, params);    

    popup.focus();

    popup.document.write(html);
	
    popup.document.close();        

    return false;	
}


/**
 * Open some url in popup window
 */
function openPopupPage(url, name, width, height) {

    left_param = (screen.width) ? (screen.width - width) / 2 : 0;

    top_param = (screen.height) ? (screen.height - height) / 2 : 0;        

    params = 'top=' + top_param + ', left=' + left_param + ',width=' + width + ',height=' + height
    		+ 'resizable=yes,scrollbars=yes,toolbar=no,titlebar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no';             

    popup = window.open(url, name, params);    
	
    popup.focus();     

    return false;	
}