/* generate top menu */
pageImages = new Array(
	'img/essay_nav1on.gif',
	'img/essay_nav2on.gif',
	'img/essay_nav3on.gif',
	'img/essay_nav4on.gif',
	'img/essay_nav5on.gif',
	'img/essay_nav6on.gif'
);

function turning(imageName, imageSrc) {
	var img = document.getElementById(imageName);
	img.src = imageSrc;
}

/* check user values in html-forms */
function trim(val) { 
	while (val.charAt(0) == " ") {	val = val.substring(1, val.length);	}
	while (val.charAt(val.length-1) == " ") { val = val.substring(0,val.length-1); }
	return val;
}

var validInteger = /^\d+$/;
var validAlphabetic = /^[a-zA-Z\s\.]+$/;
var validAlphanumeric = /^[a-zA-Z0-9\s\.]+$/;
var validEmail = /^.+\@.+\..+$/;

function checkOrderForm() {
	var myForm=document.order;
	var err='';
	var illegal='';
	var blank='';
	
	if (trim(myForm.pages.value) && !validInteger.test(myForm.pages.value))
		illegal += '\n - Number of pages';
	if (trim(myForm.email.value) && !validEmail.test(myForm.email.value))
		illegal += '\n - Your e-mail';

	if (!trim(myForm.topic.value))
		blank += '\n - Topic';
	if (!trim(myForm.pages.value))
		blank += '\n - Number of pages';
	if (!trim(myForm.ins.value))
		blank += '\n - Description and instructions';
	if (!trim(myForm.name.value))
		blank += '\n - Your name';
	if (!trim(myForm.email.value))
		blank += '\n - Your e-mail';
	
	if (illegal)
		err += 'Error! Illegal values of fields:' + illegal;
	if (blank)
		err += '\nPlease fill in the folowing fields:' + blank;
	if (err)
		alert(err);
	else {
		var dat = new Date(); 
		var tz=dat.getTimezoneOffset(); 
		tz = tz/60*(-1);
		myForm.tz.value = tz;
		myForm.submit();
	}
}