// Form Field Validation Functions:
//
// isValidExpDate(formField,fieldLabel,required)
//   -- checks for date in the format MM/YY or MM/YYYY against the current date
// isValidCreditCardNumber(formField,ccType,fieldLabel,required)
//   -- checks for valid credit card format using the Luhn check and known digits about various cards
//

function validRequired(formField,fieldLabel)
{
	var result = true;
	
	if (formField.value == "")
	{
		alert('Please enter a value for the "' + fieldLabel +'" field.');
		formField.focus();
		result = false;
	}
	
	return result;
}


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

	if (required && !validRequired(formField,fieldLabel))
		result = false;
 
  	if (result && (formField.value.length>0))
 	{ 
 		if (!allDigits(ccNum))
 		{
 			alert('Please enter only numbers (no dashes or spaces) for the "' + fieldLabel +'" field.');
			formField.focus();
			result = false;
		}	

		if (result)
 		{ 
 			if (!LuhnCheck(ccNum) || !validateCCNum(ccType,ccNum))
 			{
 				alert('Please enter a valid card number for the "' + fieldLabel +'" field.');
				formField.focus();
				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 GetRadioValue(rArray)
{
	for (var i=0;i<rArray.length;i++)
	{
		if (rArray[i].checked)
			return rArray[i].value;
	}
	
	return null;
}


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":
			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;
}

function CheckCardNumber(form)
{
  if (form.CardType.options[form.CardType.selectedIndex].value == 0) {
    alert("Please Select Card Type.");
    form.CardType.focus();
    return false;
  }
  if (form.credit_card_number.value.length == 0) {
    alert("Please key in Card Number.");
    form.credit_card_number.focus();
    return false;
  }
  if (form.cardholder.value.length == 0) {
    alert("Please key in Name On Credit Card.");
    form.cardholder.focus();
    return false;
  }
  if (form.expiry_date.value.length == 0) {
    alert("Please key in Expiry Date On Credit Card.");
    form.CreditCardNameOnCard.focus();
    return false;
  }
	var result = isValidCreditCardNumber(form.credit_card_number,form.CardType.options[form.CardType.selectedIndex].value ,"Credit Card Number",true);
	return result;
}