/////////////////////////////////////////////////
// This  Function Checks whether the given input String is null or ""
// returns boolean
// @param s is a String
// @return is boolean
//
function isEmpty(s)
{
	return ((s == null) || (s.length == 0));
}

/////////////////////////////////////////////////
// This  Function eliminates leading zero's (0)
// in a string. Use this before converting a string
// to a date, because leading 0's in parseInt()
// will signal this function to use octal mode
//
function eliminateLeading0s (str)
{
	if (str == null)
		return null;
	
	var idx = 0;
	for (idx = 0; (idx < str.length) && (str.charAt(idx)=='0'); idx++) {}
	if (idx >= str.length)
		return "0";
	else
		return str.substr(idx);	
}

// checkDate checks whether a input date variable is in
// choosen format or not
// @param dataStr input variable of type text for Date Field
// @return is message or true
//
function checkDate(field)
{
	var dateStr = field.value;
	if (isEmpty(dateStr))
	{
		return true;
	}

	var dayStr   = null;
	var monthStr = null;
	var yearStr  = null;
	
	var matchArray = null;
	
	// format dd/mm/yyyy
	if (matchArray == null)
	{
		matchArray = dateStr.match(/^(\d{1,2})\/(\d{1,2})\/((\d{4})|(\d{2}))$/);
		if (matchArray != null)
		{
			dayStr   = matchArray[1];
			monthStr = matchArray[2];
			yearStr  = matchArray[3];
		}
	}
	
	// format dd.mm.yyyy
	if (matchArray == null)
	{
		matchArray = dateStr.match(/^(\d{1,2})\.(\d{1,2})\.((\d{4})|(\d{2}))$/);
		if (matchArray != null)
		{
			dayStr   = matchArray[1];
			monthStr = matchArray[2];
			yearStr  = matchArray[3];
		}
	}
	
	// format ddmmyyyy
	if (matchArray == null)
	{
		matchArray = dateStr.match(/^(\d{2})(\d{2})((\d{4})|(\d{2}))$/);
		if (matchArray != null)
		{	// format dd/mm/yyyy
			dayStr   = matchArray[1];
			monthStr = matchArray[2];
			yearStr  = matchArray[3];
		}
	}

	// check for error
	if (matchArray == null)
	{
		alert("Date is not in a valid format.\nPlease use dd/mm/yyyy.");
		return false;
	}

	// eliminate leading 0's because they will
	// force the conversion to be execetued in octal mode!
	dayStr    = eliminateLeading0s (dayStr);
	monthStr  = eliminateLeading0s (monthStr);
	yearStr   = eliminateLeading0s (yearStr);
	var day   = parseInt(dayStr);
	var month = parseInt(monthStr);
	var year  = parseInt(yearStr);
	
	// window technique for 2 digit years
	if (year < 100)
		if (year < 20)
			year += 2000;
		else
			year += 1900;
		
	if (month < 1 || month > 12)
	{ // check month range
		alert(" Month must be between 1 and 12.");
		return false;
	}
	
	if (month==4 || month==6 || month==9 || month==11)
	{
		if (day < 1 || day > 30)
		{
			alert(" Day must be between 1 and 30.");
			return false;
		}
	}
	
	if (day < 1 || day > 31)
	{
		alert(" Day must be between 1 and 31.");
		return false;
	}
	
	if (month == 2)
	{ // check for february 29th
		var isleap = (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0));
		if (day >29 || (day==29 && !isleap))
		{
			alert("February " + year + " doesn't have " + day + " days.");
			return false;
		}
	}

	field.value  = (day<10) ? ("0"+day) : day;
	field.value += "/";
	field.value += (month<10)? "0"+month: month;
	field.value += "/";
	field.value += year;
	return true;
}

/////////////////////////////////////////////////
// This  Function Checks whether the given input field is
// a valid Date or not
// @param  field  The field, usually provided as
//                onblur="isValidDateField(this)"
// @return boolean
//	   true   Valid Date
//	   false  Not a valid Format
function isValidDateField(field)
{
	if (!checkDate(field))
	{
		if (!field.disabled)
		{
			field.focus();
			field.select();
		}
		return false;
	}
	return true;
}

/////////////////////////////////////////////////
// This  Function Checks whether the given input field is
// a number or empty string
// @param  field  The field, usually provided as
//                onblur="isValidNumber(this)"
// @return boolean
//	   true   Valid Number
//	   false  Not a valid Number
function isValidNumber(field)
{
	var num = Number (field.value);
	var val = num.toString();
	if (val == "NaN") {
		alert ('Number invalid!');
		if (!field.disabled)
		{
			field.focus();
			field.select();
		}
		return false;
	}
	return true;
}