/*
	This function is called when
	the 'Sign Guestbook' button is pressed
	Output : true if all input are correct, false otherwise
*/
function checkForm()
{
	// the variables below are assigned to each
	// form input 
	var gname, gemail, gurl, gmessage;
	with(window.document.guestform)
	{
		gname    = name;
		gemail   = email;
		gmessage = comment;
	}
	
	// if name is empty alert the visitor
	if(trim(gname.value) == '')
	{
		alert('Ievadiet savu vārdu');
		gname.focus();
		return false;
	}
	// alert the visitor if email is empty or the format is not correct 
	else if(trim(gemail.value) != '' && !isEmail(trim(gemail.value)))
	{
		alert('Ievadiet derīgu e-pasta adresi vai atstājiet tukšu');
		gemail.focus();
		return false;
	}
	// alert the visitor if message is empty
	else if(trim(gmessage.value) == '')
	{
		alert('Lūdzu, ierakstiet kaut ko');
		gmessage.focus();
		return false;
	}
	else
	{
		// when all input are correct 
		// return true so the form will submit		
		return true;
	}
}

/*
Strip whitespace from the beginning and end of a string
Input  : a string
Output : the trimmed string
*/
function trim(str)
{
	return str.replace(/^\s+|\s+$/g,'');
}

/*
Check if a string is in valid email format. 
Input  : the string to check
Output : true if the string is a valid email address, false otherwise.
*/
function isEmail(str)
{
	var regex = /^[-_.a-z0-9]+@(([-a-z0-9]+\.)+(ad|ae|aero|af|ag|ai|al|am|an|ao|aq|ar|arpa|as|at|au|aw|az|ba|bb|bd|be|bf|bg|bh|bi|biz|bj|bm|bn|bo|br|bs|bt|bv|bw|by|bz|ca|cc|cd|cf|cg|ch|ci|ck|cl|cm|cn|co|com|coop|cr|cs|cu|cv|cx|cy|cz|de|dj|dk|dm|do|dz|ec|edu|ee|eg|eh|er|es|et|eu|fi|fj|fk|fm|fo|fr|ga|gb|gd|ge|gf|gh|gi|gl|gm|gn|gov|gp|gq|gr|gs|gt|gu|gw|gy|hk|hm|hn|hr|ht|hu|id|ie|il|in|info|int|io|iq|ir|is|it|jm|jo|jp|ke|kg|kh|ki|km|kn|kp|kr|kw|ky|kz|la|lb|lc|li|lk|lr|ls|lt|lu|lv|ly|ma|mc|md|mg|mh|mil|mk|ml|mm|mn|mo|mp|mq|mr|ms|mt|mu|museum|mv|mw|mx|my|mz|na|name|nc|ne|net|nf|ng|ni|nl|no|np|nr|nt|nu|nz|om|org|pa|pe|pf|pg|ph|pk|pl|pm|pn|pr|pro|ps|pt|pw|py|qa|re|ro|ru|rw|sa|sb|sc|sd|se|sg|sh|si|sj|sk|sl|sm|sn|so|sr|st|su|sv|sy|sz|tc|td|tf|tg|th|tj|tk|tm|tn|to|tp|tr|tt|tv|tw|tz|ua|ug|uk|um|us|uy|uz|va|vc|ve|vg|vi|vn|vu|wf|ws|ye|yt|yu|za|zm|zw)|(([0-9][0-9]?|[0-1][0-9][0-9]|[2][0-4][0-9]|[2][5][0-5])\.){3}([0-9][0-9]?|[0-1][0-9][0-9]|[2][0-4][0-9]|[2][5][0-5]))$/i;
	return regex.test(str);
}