function isCreditCard(st) 
{
  if (st.length > 19 || st.length == 0) return (false);
/*
  var sum = 0; 
  var mul = 1; 
  var l = st.length;
  
  for (i = 0; i < l; i++) {
	digit = st.substring(l-i-1,l-i);
    tproduct = parseInt(digit ,10)*mul;
    if (tproduct >= 10) {
		sum += (tproduct % 10) + 1;
    } else {
		sum += tproduct;
	}
    if (mul == 1) {
		mul++;
    } else {
		mul--;
	}
  }
*/

// Uncomment the following line to help create credit card numbers
// 1. Create a dummy number with a 0 as the last digit
// 2. Examine the sum written out
// 3. Replace the last digit with the difference between the sum and
//    the next multiple of 10.

/*  if ((sum % 10) == 0) */
		return (true);
/*
    else
		return (false);
*/
} 

/*  ================================================================
    FUNCTION:  isVisa()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid VISA number.
		    
	      false, otherwise

    Sample number: 4111 1111 1111 1111 (16 digits)
    ================================================================ */

function isVisa(cc)
{
	firstdig = cc.substring(0,1);
/*	if (((cc.length == 16) || (cc.length == 13)) && (cc.substring(0,1) == 4)) */
    if ((cc.length == 16) && (firstdig == 4))
		return isCreditCard(cc);
	return false;
} 

/*  ================================================================
    FUNCTION:  isMasterCard()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid MasterCard
		    number.
		    
	      false, otherwise

    Sample number: 5500 0000 0000 0004 (16 digits)
    ================================================================ */

function isMasterCard(cc)
{
	firstdig = cc.substring(0,1);
/*	seconddig = cc.substring(1,2);
	if ((cc.length == 16) && (firstdig == 5) && ((seconddig >= 1) && (seconddig <= 5))) */
    if ((cc.length == 16) && (firstdig == 5))
		return isCreditCard(cc);
	return false;
} 

/*  ================================================================
    FUNCTION:  isAmericanExpress()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid American
		    Express number.
		    
	      false, otherwise

    Sample number: 340000000000009 (15 digits)
    ================================================================ */

function isAmericanExpress(cc)
{
	firstdig = cc.substring(0,1);
/*	seconddig = cc.substring(1,2);
	if ((cc.length == 15) && (firstdig == 3) && ((seconddig == 4) || (seconddig == 7))) */
    if ((cc.length == 15) && (firstdig == 3))
		return isCreditCard(cc);
	return false;
} 

/*  ================================================================
    FUNCTION:  isDinersClub()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid Diner's
		    Club number.
		    
	      false, otherwise

    Sample number: 30000000000004 (14 digits)
    ================================================================ */

function isDinersClub(cc)
{
	firstdig = cc.substring(0,1);
	seconddig = cc.substring(1,2);
	if ((cc.length == 14) && (firstdig == 3) && ((seconddig == 0) || (seconddig == 6) || (seconddig == 8)))
		return isCreditCard(cc);
	return false;
}

/*  ================================================================
    FUNCTION:  isCarteBlanche()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid Carte
		    Blanche number.
		    
	      false, otherwise
    ================================================================ */

function isCarteBlanche(cc)
{
	return isDinersClub(cc);
}

/*  ================================================================
    FUNCTION:  isDiscover()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid Discover
		    card number.
		    
	      false, otherwise

    Sample number: 6011000000000004 (16 digits)
    ================================================================ */

function isDiscover(cc)
{
	/*first4digs = cc.substring(0,4);*/
	firstdig = cc.substring(0,1);	
	/*if ((cc.length == 16) && (first4digs == "6011"))*/
	if ((cc.length == 16) && (firstdig == 6))
		return isCreditCard(cc);
	return false;
} 

/*  ================================================================
    FUNCTION:  isEnRoute()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid enRoute
		    card number.
		    
	      false, otherwise

    Sample number: 201400000000009 (15 digits)
    ================================================================ */

function isEnRoute(cc)
{
	first4digs = cc.substring(0,4);
	if ((cc.length == 15) && ((first4digs == "2014") || (first4digs == "2149")))
		return isCreditCard(cc);
	return false;
}

/*  ================================================================
    FUNCTION:  isJCB()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid JCB
		    card number.
		    
	      false, otherwise
    ================================================================ */

function isJCB(cc)
{
	first4digs = cc.substring(0,4);
	if ((cc.length == 16) &&
      ((first4digs == "3088") ||
       (first4digs == "3096") ||
       (first4digs == "3112") ||
       (first4digs == "3158") ||
       (first4digs == "3337") ||
       (first4digs == "3528")))
    return isCreditCard(cc);
  return false;
} 

/*  ================================================================
    FUNCTION:  isAnyCard()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is any valid credit
		    card number for any of the accepted card types.
		    
	      false, otherwise
    ================================================================ */

function isAnyCard(cc)
{
	if (!isCreditCard(cc)) return false;
	if (!isMasterCard(cc) && !isVisa(cc) && !isAmericanExpress(cc) && !isDinersClub(cc) &&
      !isDiscover(cc) && !isEnRoute(cc) && !isJCB(cc)) {
		return false;
	}
	return true;
} 

/*  ================================================================
    FUNCTION:  isCardMatch()
 
    INPUT:    cardType - a string representing the credit card type
	      cardNumber - a string representing a credit card number

    RETURNS:  true, if the credit card number is valid for the particular
	      credit card type given in "cardType".
		    
	      false, otherwise
    ================================================================ */

function isCardMatch (cardType, cardNumber)
{

	cardType = cardType.toUpperCase();
	var doesMatch = true;

	if ((cardType == "VISA") && (!isVisa(cardNumber)))	
		doesMatch = false;
	if ((cardType == "MASTERCARD") && (!isMasterCard(cardNumber)))	
		doesMatch = false;
	if ( ( (cardType == "AMERICANEXPRESS") || (cardType == "AMEX") )
                && (!isAmericanExpress(cardNumber))) 
        doesMatch = false;
	if ((cardType == "DISCOVER") && (!isDiscover(cardNumber)))
		doesMatch = false;
	if ((cardType == "JCB") && (!isJCB(cardNumber)))
		doesMatch = false;
	if ((cardType == "DINERS") && (!isDinersClub(cardNumber)))
		doesMatch = false;
	if ((cardType == "CARTEBLANCHE") && (!isCarteBlanche(cardNumber)))
		doesMatch = false;
	if ((cardType == "ENROUTE") && (!isEnRoute(cardNumber)))
		doesMatch = false;
	return doesMatch;

}  

/*  ================================================================
    The below stub functions are retained for backward compatibility
    with the original LivePayment code so that it should be possible
    in principle to swap in this new module as a replacement for the  
    older module without breaking existing code.  (There are no
    guarantees, of course, but it should work.)

    When writing new code, do not use these stub functions; use the
    functions defined above.
    ================================================================ */

function IsCC (st) 
{
    return isCreditCard(st);
}

function IsVisa (cc)  
{
	return isVisa(cc);
}

function IsVISA (cc)  
{
	return isVisa(cc);
}

function IsMasterCard (cc)  
{
	return isMasterCard(cc);
}

function IsMastercard (cc)  
{
	return isMasterCard(cc);
}

function IsMC (cc)  
{
	return isMasterCard(cc);
}

function IsAmericanExpress (cc)  
{
	return isAmericanExpress(cc);
}

function IsAmEx (cc)  
{
	return isAmericanExpress(cc);
}

function IsDinersClub (cc)  
{
	return isDinersClub(cc);
}

function IsDC (cc)  
{
	return isDinersClub(cc);
}

function IsDiners (cc)  
{
	return isDinersClub(cc);
}

function IsCarteBlanche (cc)  
{
	return isCarteBlanche(cc);
}

function IsCB (cc)  
{
	return isCarteBlanche(cc);
}

function IsDiscover (cc)  
{
	return isDiscover(cc);
}

function IsEnRoute (cc)  
{
	return isEnRoute(cc);
}

function IsenRoute (cc)  
{
	return isEnRoute(cc);
}

function IsJCB (cc)  
{
	return isJCB(cc);
}

function IsAnyCard(cc)  
{
	return isAnyCard(cc);
}

function IsCardMatch (cardType, cardNumber)  
{
	return isCardMatch (cardType, cardNumber);
}