function mod10( cardNumber ) { // LUHN Formula for validation of credit card numbers.
	var ar = new Array( cardNumber.length );
	var i = 0,sum = 0;


    	for( i = 0; i < cardNumber.length; ++i ) {
    		ar[i] = parseInt(cardNumber.charAt(i));
    	}
    	for( i = ar.length -2; i >= 0; i-=2 ) { // you have to start from the right, and work back.
    		ar[i] *= 2;							 // every second digit starting with the right most (check digit)
    		if( ar[i] > 9 ) ar[i]-=9;			 // will be doubled, and summed with the skipped digits.
    	}										 // if the double digit is > 9, add those individual digits together 


        	for( i = 0; i < ar.length; ++i ) {
        		sum += ar[i];						 // if the sum is divisible by 10 mod10 succeeds
        	}
        	return (((sum%10)==0)?true:false);	 	
    }


        function expired( month, year ) {
        	var now = new Date();							// this function is designed to be Y2K compliant.
        	var expiresIn = new Date(year,month,0,0,0);		// create an expired on date object with valid thru expiration date
        	expiresIn.setMonth(expiresIn.getMonth()+1);		// adjust the month, to first day, hour, minute & second of expired month
        	if( now.getTime() < expiresIn.getTime() ) return false;
        	return true;									// then we get the miliseconds, and do a long integer comparison
    		}
    		
    		function isExpired(month,year) {
    			return expired(month,year);
    		}


        function isValidCardNumber(cardNumber) {
        	
		if( cardNumber.length == 0 ) {						//most of these checks are self explanitory
			//alert("Please enter a valid card number.");
			return false;				
		}
		for( var i = 0; i < cardNumber.length; ++i ) {		// make sure the number is all digits.. (by design)
			var c = cardNumber.charAt(i);

			if( c < '0' || c > '9' ) {
				//alert("Please enter a valid card number. Use only digits. Do not use spaces or hyphens.");
				return false;
			} // if
	  	} // for

		if( !mod10( cardNumber ) ) { 		// run the check digit algorithm
			//alert("Sorry! This is not a valid credit card number.");
			return false;
		}                                                	
		return true; // at this point card has not been proven to be invalid
	} // validateCard
				
				

/*				
function CheckValidCard(sCardNo, sCardType)
{

	alert(sCardNo);
	alert(sCardType);

   sCardNo = sCardNo.replace(/[^\d]/g, '');
	
   if(sCardType == "Switch")
   {
   	  if (sCardNo.length != 16) {
	  	return false;
	  }
      return true;
   }

   if(sCardType == "VIS")
   {
       var iRangeStart = 4000;
       var iRangeEnd = 4999;
       var iLength = 16;
       var iLength2 = 13;
   }
   if(sCardType == "MSC")
   {
       var iRangeStart = 5100;
       var iRangeEnd = 5599;
       var iLength = 16;
   }
   if(sCardType == "VIS")
   {
       var iRangeStart = 3400;
       var iRangeEnd = 3499;
       var iRangeStart2 = 3700;
       var iRangeEnd2 = 3799;
       var iLength = 15;
   }

   // Check Length of Number

   if(sCardNo.length != iLength)
   {
      if(iLength2)
      {
         if(sCardNo.length != iLength2)
         {
         
            return false;
         }
      }
      return false;
   }

   // Check First 4 digits

   if((sCardNo.substr(0, 4) < iRangeStart) || (sCardNo.substr(0, 4) > iRangeEnd))
   {
   
   	alert('first 4');
      return false;
   }

   if(iRangeStart2)
   {
      if((sCardNo.substr(0, 4) < iRangeStart2) || (sCardNo.substr(0, 4) > iRangeEnd2))
      {
         alert('rtange2');
         return false;
      }
   }
   // Mod 10 check

   iDigit = 0;
   iChecksum = 0;

   for(i = 1 - (sCardNo.length % 2); i < sCardNo.length; i += 2)
   {
       iChecksum += sCardNo.substr(i, 1) - 0;
   }
   for(i = (sCardNo.length % 2);i < sCardNo.length; i += 2)
   {
       iDigit = (sCardNo.substr(i, 1) - 0) * 2;
       if(iDigit < 10)
       {
          iChecksum += iDigit;
       }
       else
       {
          iChecksum += iDigit - 9;
       }
   }
   if(iChecksum % 10 == 0)
   {
       return true;
   }

   return false;
}
*/




function checkCreditCard (cardnumber, cardname) {

  // Array to hold the permitted card characteristics
  
  if (bSupervisor && cardnumber=='0000') {
  	return true;
  }
  
  var cards = new Array();

  // Define the cards we support. You may add addtional card types.
  
  //  Name:      As in the selection box of the form - must be same as user's
  //  Length:    List of possible valid lengths of the card number for the card
  //  prefixes:  List of possible prefixes for the card
  //  checkdigit Boolean to say whether there is a check digit
  
  cards [0] = {name: "VIS", 
               length: "13,16", 
               prefixes: "4",
               checkdigit: true};
  cards [1] = {name: "MSC", 
               length: "16", 
               prefixes: "51,52,53,54,55",
               checkdigit: true};
  cards [2] = {name: "DIN", 
               length: "14,16", 
               prefixes: "300,301,302,303,304,305,36,38,55",
               checkdigit: true};
  cards [3] = {name: "CarteBlanche", 
               length: "14", 
               prefixes: "300,301,302,303,304,305,36,38",
               checkdigit: true};
  cards [4] = {name: "AMX", 
               length: "15", 
               prefixes: "34,37",
               checkdigit: true};
  cards [5] = {name: "Discover", 
               length: "16", 
               prefixes: "6011,650",
               checkdigit: true};
  cards [6] = {name: "JCB", 
               length: "15,16", 
               prefixes: "3,1800,2131",
               checkdigit: true};
  cards [7] = {name: "enRoute", 
               length: "15", 
               prefixes: "2014,2149",
               checkdigit: true};
  cards [8] = {name: "Solo", 
               length: "16,18,19", 
               prefixes: "6334, 6767",
               checkdigit: true};
  cards [9] = {name: "SWI", 
               length: "16,18,19", 
               prefixes: "4903,4905,4911,4936,564182,633110,6333,6759",
               checkdigit: true};
  cards [10] = {name: "Maestro", 
               length: "16", 
               prefixes: "5020,6",
               checkdigit: true};
  cards [11] = {name: "VisaElectron", 
               length: "16", 
               prefixes: "417500,4917,4913",
               checkdigit: true};
               
  // Establish card type
  var cardType = -1;
  for (var i=0; i<cards.length; i++) {

    // See if it is this card (ignoring the case of the string)
    if (cardname.toLowerCase () == cards[i].name.toLowerCase()) {
      cardType = i;
      break;
    }
  }

  
  // If card type not found, report an error
  if (cardType == -1) {
     ccErrorNo = 0;
     return false; 
  }
   
  // Ensure that the user has provided a credit card number
  if (cardnumber.length == 0)  {
     ccErrorNo = 1;
     return false; 
  }
    
  // Now remove any spaces from the credit card number
  cardnumber = cardnumber.replace (/\s/g, "");
  
  // Check that the number is numeric
  var cardNo = cardnumber
  var cardexp = /^[0-9]{13,19}$/;
  if (!cardexp.exec(cardNo))  {
     ccErrorNo = 2;
     return false; 
  }
       
  // Now check the modulus 10 check digit - if required
  if (cards[cardType].checkdigit) {
    var checksum = 0;                                  // running checksum total
    var mychar = "";                                   // next char to process
    var j = 1;                                         // takes value of 1 or 2
  
    // Process each digit one by one starting at the right
    var calc;
    for (i = cardNo.length - 1; i >= 0; i--) {
    
      // Extract the next digit and multiply by 1 or 2 on alternative digits.
      calc = Number(cardNo.charAt(i)) * j;
    
      // If the result is in two digits add 1 to the checksum total
      if (calc > 9) {
        checksum = checksum + 1;
        calc = calc - 10;
      }
    
      // Add the units element to the checksum total
      checksum = checksum + calc;
    
      // Switch the value of j
      if (j ==1) {j = 2} else {j = 1};
    } 
  
    // All done - if checksum is divisible by 10, it is a valid modulus 10.
    // If not, report an error.
    if (checksum % 10 != 0)  {
     ccErrorNo = 3;
     alert ('error 3');
     return false; 
    }
  }  

  // The following are the card-specific checks we undertake.
  var LengthValid = false;
  var PrefixValid = false; 
  var undefined; 

  // We use these for holding the valid lengths and prefixes of a card type
  var prefix = new Array ();
  var lengths = new Array ();
    
  // Load an array with the valid prefixes for this card
  prefix = cards[cardType].prefixes.split(",");
      
  // Now see if any of them match what we have in the card number
  for (i=0; i<prefix.length; i++) {
    var exp = new RegExp ("^" + prefix[i]);
    if (exp.test (cardNo)) PrefixValid = true;
  }
      
  // If it isn't a valid prefix there's no point at looking at the length
  if (!PrefixValid) {
     ccErrorNo = 3;
     return false; 
  }
    
  // See if the length is valid for this card
  lengths = cards[cardType].length.split(",");
  for (j=0; j<lengths.length; j++) {
    if (cardNo.length == lengths[j]) LengthValid = true;
  }
  
  // See if all is OK by seeing if the length was valid. We only check the 
  // length if all else was hunky dory.
  if (!LengthValid) {
     ccErrorNo = 4;
     return false; 
  };   
  
  // The credit card is in the required format.
  return true;
}