function swapPairs(s){
  var res = "";
  for (var i=0; i<s.length; i++){
	var ch = s.charCodeAt(i) ;
	res += String.fromCharCode(
		   ( ch & 0xF0 ) +
		   ((ch & 0x0C)>>2) +
		   ((ch & 0x03)<<2)
		   );
	}
  return res;
   }
function toggleLayer(whichLayer) {
	if (document.getElementById) {
		// this is the way the standards work
		var style2 = document.getElementById(whichLayer).style;
		style2.display = style2.display=="block"?"none":"block";
	} else if (document.all) {
		// this is the way old msie versions work
		var style2 = document.all[whichLayer].style;
		style2.display = style2.display=="block"?"none":"block";
	} else if (document.layers) {
		// this is the way nn4 works
		var style2 = document.layers[whichLayer].style;
		style2.display = style2.display=="block"?"none":"block";
	}
}
function getLayer(whichLayer) {
	if (document.getElementById) {
		// this is the way the standards work
		return document.getElementById(whichLayer);
	} else if (document.all) {
		// this is the way old msie versions work
		return document.all[whichLayer];
	} else if (document.layers) {
		// this is the way nn4 works
		return document.layers[whichLayer];
	}
}

function hideLayer(whichLayer) {
	var style2 = document.getElementById(whichLayer).style;
	style2.display = "none";
}
function showLayer(whichLayer) {
	var style2 = document.getElementById(whichLayer).style;
	style2.display = "block";
}

function GetRadioValue(rArray)
{
	for (var i=0;i<rArray.length;i++)
	{
		if (rArray[i].checked)
			return rArray[i].value;
	}

	return null;
}


function allDigits(str)
{
	return inValidCharSet(str,"0123456789");
}

function inValidCharSet(str,charset)
{
	var result = true;

	for (var i=0;i<str.length;i++)
		if (charset.indexOf(str.substr(i,1))<0)
		{
			result = false;
			break;
		}

	return result;
}

function isValidExpDate(formField,fieldLabel,required)
{
	var result = true;
	var formValue = formField.value;

	if (required && !validRequired(formField,fieldLabel))
		result = false;

 	if (result && (formField.value.length>0))
 	{
 		var elems = formValue.split("/");

 		result = (elems.length == 2); // should be two components
 		var expired = false;

 		if (result)
 		{
 			var month = parseInt(elems[0],10);
 			var year = parseInt(elems[1],10);

 			if (elems[1].length == 2)
 				year += 2000;

 			var now = new Date();

 			var nowMonth = now.getMonth() + 1;
 			var nowYear = now.getFullYear();

 			expired = (nowYear > year) || ((nowYear == year ) && (nowMonth > month));

			result = allDigits(elems[0]) && (month > 0) && (month < 13) &&
					 allDigits(elems[1]) && ((elems[1].length == 2) || (elems[1].length == 4));
 		}

  		if (!result)
 		{
 			alert('Please enter a date in the format MM/YY for the "' + fieldLabel +'" field.');
			formField.focus();
		}
		else if (expired)
		{
 			result = false;
 			alert('The date for "' + fieldLabel +'" has expired.');
			formField.focus();
		}
	}

	return result;
}

function isValidCreditCardNumber(formField,ccType,fieldLabel,required)
{
	var result = true;
 	var ccNum = formField.value;

  	if (result && (formField.value.length>0))
 	{
 		if (!allDigits(ccNum))
 		{
			result = false;
		}

		if (result)
 		{
 			if (!LuhnCheck(ccNum) || !validateCCNum(ccType,ccNum))
 			{
				result = false;
			}
		}

	}

	return result;
}

function LuhnCheck(str)
{
  var result = true;

  var sum = 0;
  var mul = 1;
  var strLen = str.length;

  for (i = 0; i < strLen; i++)
  {
    var digit = str.substring(strLen-i-1,strLen-i);
    var tproduct = parseInt(digit ,10)*mul;
    if (tproduct >= 10)
      sum += (tproduct % 10) + 1;
    else
      sum += tproduct;
    if (mul == 1)
      mul++;
    else
      mul--;
  }
  if ((sum % 10) != 0)
    result = false;

  return result;
}

function validateCCNum(cardType,cardNum)
{
	var result = false;
	cardType = cardType.toUpperCase();

	var cardLen = cardNum.length;
	var firstdig = cardNum.substring(0,1);
	var seconddig = cardNum.substring(1,2);
	var first4digs = cardNum.substring(0,4);

	switch (cardType)
	{
		case "VISA":
			result = ((cardLen == 16) || (cardLen == 13)) && (firstdig == "4");
			break;
		case "AMEX":
		case "AMERICAN EXPRESS":
			var validNums = "47";
			result = (cardLen == 15) && (firstdig == "3") && (validNums.indexOf(seconddig)>=0);
			break;
		case "MASTERCARD":
			var validNums = "12345";
			result = (cardLen == 16) && (firstdig == "5") && (validNums.indexOf(seconddig)>=0);
			break;
		case "DISCOVER":
			result = (cardLen == 16) && (first4digs == "6011");
			break;
		case "DINERS":
			var validNums = "068";
			result = (cardLen == 14) && (firstdig == "3") && (validNums.indexOf(seconddig)>=0);
			break;
	}
	return result;
}