var Cards = new makeArray(5);
Cards[0] = new ddlCardType("MASTERCARD", "51,52,53,54,55", "16");
var MASTERCARD = Cards[0];
Cards[1] = new ddlCardType("VISA", "4", "13,16");
var VISA = Cards[1];
Cards[2] = new ddlCardType("AMEX", "34,37", "15");
var AMEX = Cards[2];
Cards[3] = new ddlCardType("DINERS", "30,36,38", "14");
var DINERS = Cards[3];
var LuhnCheckSum = Cards[4] = new ddlCardType();

/*************************************************************************\
ChecktxtCCNumber(form)
function called when users click the "check" button.
\*************************************************************************/
function ChecktxtCCNumber(form, o) {
	var tmpyear;
	o.bResult = true;
	if (form.txtCCNumber.value.length == 0) {
		//enter a Card Number
		_displayError('',o,'txtCCNumber-error');
		o.bResult = false;
	}

	if (form.ddlExpiryYear.value > 96){
		tmpyear = "19" + form.ddlExpiryYear.value;
	} else if (form.ddlExpiryYear.value < 21){
		tmpyear = "20" + form.ddlExpiryYear.value;
	} else {
		_displayError('',o,'ddlExpiryDate-error');
		o.bResult = false;
	}
	
	tmpmonth = form.ddlExpiryMonth.options[form.ddlExpiryMonth.selectedIndex].value;

	if (!(new ddlCardType()).isExpiryDate(tmpyear, tmpmonth)) {
		// card has already expired
		_displayError('',o,'ddlExpiryDate-error');
		o.bResult = false;
	}
	card = form.ddlCardType.options[form.ddlCardType.selectedIndex].value;
	var retval = eval(card + ".checktxtCCNumber(\"" + form.txtCCNumber.value + "\", " + tmpyear + ", " + tmpmonth + ");");
	cardname = "";

	if (retval){
		// card number appears to be valid
		o.bResult = true;
	} else {
		// The txtCCNumber has the valid luhn checksum, but we want to know which
		// ddlCardType it belongs to.
		for (var n = 0; n < Cards.size; n++) {
			if (Cards[n].checktxtCCNumber(form.txtCCNumber.value, tmpyear, tmpmonth)) {
				cardname = Cards[n].getddlCardType();
				break;
			}
		}
		if (cardname.length > 0) {
			// card number is not valid - check card type
			_displayError('',o,'txtCCValid-error');
			o.bResult = false;
		} else {
			//card number is not valid
			_displayError('',o,'txtCCValid-error');
			o.bResult = false;
		}
	}
	return o;
}
/*************************************************************************\
Object ddlCardType([String ddlCardType, String rules, String len, int year,
                                        int month])
ddlCardType    : type of card, eg: MASTERCARD, Visa, etc.
rules       : rules of the txtCCNumber, eg: "4", "6011", "34,37".
len         : valid length of txtCCNumber, eg: "16,19", "13,16".
year        : year of expiry date.
month       : month of expiry date.
eg:
var VISA = new ddlCardType("Visa", "4", "16");
var AMEX = new ddlCardType("AmEx", "34,37", "15");
\*************************************************************************/
function ddlCardType() {
var n;
var argv = ddlCardType.arguments;
var argc = ddlCardType.arguments.length;

this.objname = "object ddlCardType";

var tmpddlCardType = (argc > 0) ? argv[0] : "CardObject";
var tmprules = (argc > 1) ? argv[1] : "0,1,2,3,4,5,6,7,8,9";
var tmplen = (argc > 2) ? argv[2] : "13,14,15,16,19";

this.settxtCCNumber = settxtCCNumber;  // set txtCCNumber method.
this.setddlCardType = setddlCardType;  // setddlCardType method.
this.setLen = setLen;  // setLen method.
this.setRules = setRules;  // setRules method.
this.setExpiryDate = setExpiryDate;  // setExpiryDate method.

this.setddlCardType(tmpddlCardType);
this.setLen(tmplen);
this.setRules(tmprules);
if (argc > 4)
this.setExpiryDate(argv[3], argv[4]);

this.checktxtCCNumber = checktxtCCNumber;  // checktxtCCNumber method.
this.getExpiryDate = getExpiryDate;  // getExpiryDate method.
this.getddlCardType = getddlCardType;  // getddlCardType method.
this.istxtCCNumber = istxtCCNumber;  // istxtCCNumber method.
this.isExpiryDate = isExpiryDate;  // isExpiryDate method.
this.luhnCheck = luhnCheck;// luhnCheck method.
return this;
}

/*************************************************************************\
boolean checktxtCCNumber([String txtCCNumber, int year, int month])
return true if txtCCNumber pass the luhncheck and the expiry date is
valid, else return false.
\*************************************************************************/
function checktxtCCNumber() {
var argv = checktxtCCNumber.arguments;
var argc = checktxtCCNumber.arguments.length;
var txtCCNumber = (argc > 0) ? argv[0] : this.txtCCNumber;
var year = (argc > 1) ? argv[1] : this.year;
var month = (argc > 2) ? argv[2] : this.month;

this.settxtCCNumber(txtCCNumber);
this.setExpiryDate(year, month);

if (!this.istxtCCNumber())
return false;
if (!this.isExpiryDate())
return false;

return true;
}
/*************************************************************************\
String getddlCardType()
return the ddlCardType.
\*************************************************************************/
function getddlCardType() {
return this.ddlCardType;
}
/*************************************************************************\
String getExpiryDate()
return the expiry date.
\*************************************************************************/
function getExpiryDate() {
return this.month + "/" + this.year;
}
/*************************************************************************\
boolean istxtCCNumber([String txtCCNumber])
return true if txtCCNumber pass the luhncheck and the rules, else return
false.
\*************************************************************************/
function istxtCCNumber() {
var argv = istxtCCNumber.arguments;
var argc = istxtCCNumber.arguments.length;
var txtCCNumber = (argc > 0) ? argv[0] : this.txtCCNumber;
if (!this.luhnCheck())
return false;

for (var n = 0; n < this.len.size; n++)
	if (txtCCNumber.toString().length == this.len[n]) {
		for (var m = 0; m < this.rules.size; m++) {
		var headdigit = txtCCNumber.substring(0, this.rules[m].toString().length);
		if (headdigit == this.rules[m])
			return true;
		}
		return false;
	}
	return false;
}

/*************************************************************************\
boolean isExpiryDate([int year, int month])
return true if the date is a valid expiry date,
else return false.
\*************************************************************************/
function isExpiryDate() {
	var argv = isExpiryDate.arguments;
	var argc = isExpiryDate.arguments.length;

	year = argc > 0 ? argv[0] : this.year;
	month = argc > 1 ? argv[1] : this.month;

	if (!isNum(year+""))
	return false;
	if (!isNum(month+""))
	return false;
	today = new Date();
	expiry = new Date(year, month);
	if (today.getTime() > expiry.getTime())
	return false;
	else
	return true;
}

/*************************************************************************\
boolean isNum(String argvalue)
return true if argvalue contains only numeric characters,
else return false.
\*************************************************************************/
function isNum(argvalue) {
argvalue = argvalue.toString();

if (argvalue.length == 0)
return false;

for (var n = 0; n < argvalue.length; n++)
if (argvalue.substring(n, n+1) < "0" || argvalue.substring(n, n+1) > "9")
return false;

return true;
}

/*************************************************************************\
boolean luhnCheck([String txtCCNumber])
return true if txtCCNumber pass the luhn check else return false.
Reference: http://www.ling.nwu.edu/~sburke/pub/luhn_lib.pl
\*************************************************************************/
function luhnCheck() {
var argv = luhnCheck.arguments;
var argc = luhnCheck.arguments.length;

var txtCCNumber = argc > 0 ? argv[0] : this.txtCCNumber;

if (! isNum(txtCCNumber)) {
return false;
  }

var no_digit = txtCCNumber.length;
var oddoeven = no_digit & 1;
var sum = 0;

for (var count = 0; count < no_digit; count++) {
var digit = parseInt(txtCCNumber.charAt(count));
if (!((count & 1) ^ oddoeven)) {
digit *= 2;
if (digit > 9)
digit -= 9;
}
sum += digit;
}
if (sum % 10 == 0)
return true;
else
return false;
}

/*************************************************************************\
ArrayObject makeArray(int size)
return the array object in the size specified.
\*************************************************************************/
function makeArray(size) {
this.size = size;
return this;
}

/*************************************************************************\
ddlCardType settxtCCNumber(txtCCNumber)
return the ddlCardType object.
\*************************************************************************/
function settxtCCNumber(txtCCNumber) {
this.txtCCNumber = txtCCNumber;
return this;
}

/*************************************************************************\
ddlCardType setddlCardType(ddlCardType)
return the ddlCardType object.
\*************************************************************************/
function setddlCardType(ddlCardType) {
this.ddlCardType = ddlCardType;
return this;
}

/*************************************************************************\
ddlCardType setExpiryDate(year, month)
return the ddlCardType object.
\*************************************************************************/
function setExpiryDate(year, month) {
this.year = year;
this.month = month;
return this;
}

/*************************************************************************\
ddlCardType setLen(len)
return the ddlCardType object.
\*************************************************************************/
function setLen(len) {
// Create the len array.
if (len.length == 0 || len == null)
len = "13,14,15,16,19";

var tmplen = len;
n = 1;
while (tmplen.indexOf(",") != -1) {
tmplen = tmplen.substring(tmplen.indexOf(",") + 1, tmplen.length);
n++;
}
this.len = new makeArray(n);
n = 0;
while (len.indexOf(",") != -1) {
var tmpstr = len.substring(0, len.indexOf(","));
this.len[n] = tmpstr;
len = len.substring(len.indexOf(",") + 1, len.length);
n++;
}
this.len[n] = len;
return this;
}

/*************************************************************************\
ddlCardType setRules()
return the ddlCardType object.
\*************************************************************************/
function setRules(rules) {
// Create the rules array.
if (rules.length == 0 || rules == null)
rules = "0,1,2,3,4,5,6,7,8,9";

var tmprules = rules;
n = 1;
while (tmprules.indexOf(",") != -1) {
tmprules = tmprules.substring(tmprules.indexOf(",") + 1, tmprules.length);
n++;
}
this.rules = new makeArray(n);
n = 0;
while (rules.indexOf(",") != -1) {
var tmpstr = rules.substring(0, rules.indexOf(","));
this.rules[n] = tmpstr;
rules = rules.substring(rules.indexOf(",") + 1, rules.length);
n++;
}
this.rules[n] = rules;
return this;
}