/*
lance (at) forensickb.com
June 2, 2008

*/


class MyDialog: DialogClass {
  String ccNum, Desc;
  ButtonClass        _Help;
  StringEditClass _ccNum;


  MyDialog():
  Desc(     "LUHN Credit Card Number Validation v1.0\n"
            "This EnScript uses the LUHN algorithm to test the entered credit card\n"
            " number and then tries to identify the credit card type by the first few digits.\n\n"
            "lance (at) forensickb.com\n"
            "June 02, 2008"
          );

    DialogClass(null, "LUHN credit card number validation"),
    _Help(this, "Info", START, START, DEFAULT, DEFAULT, 0),
    _ccNum(this, "Credit card number:", START, NEXT, 200, 10, 0, ccNum, 20, WindowClass::REQUIRED)

  {
  }

   virtual void ChildEvent(const EventClass &event) {
    if (_Help.Matches(event))
      SystemClass::Message(SystemClass::MBOK, "Info", Desc);
    DialogClass::ChildEvent(event);
  }

  virtual bool CanClose() {
    return true;
  }
}

class MainClass {

  String digits, type;

  void Main() {
    MyDialog dialogbox();
    if (dialogbox.Execute() == SystemClass::OK){
      bool luhn =isValidNumber(dialogbox.ccNum);

      if (dialogbox.ccNum.GetLength() < 13 || dialogbox.ccNum.GetLength() > 19){
        Console.WriteLine("The credit card number is either too short or too long. (<13 or >19)");
        SystemClass::Message(0, "Notice", "The credit card number is either too short or too long. (<13 or >19)");
      }

      else if (type.Contains("Unknown")){
        Console.WriteLine("The credit card number passes the LUHN validation test, but the number sequence does not belong to a known vendor");
        SystemClass::Message(0, "Notice", "The credit card passes the LUHN validation test, but the number sequence does not belong to a known vendor");
      }
      else if (luhn) {
        Console.WriteLine ("The credit card number entered passes the LUHN validation test and is identified as belonging to " + type);
        SystemClass::Message(0, "Notice", "The credit card number entered passes the LUHN validation test and is identified as belonging to " + type);
      }
      else{
        Console.WriteLine ("The credit card number entered is *not* valid");
        SystemClass::Message(0, "Notice", "The credit card number entered is *not* valid");
      }
    }
  }


  bool isValidNumber(String &number) {

    int len = number.GetLength();

    if (len == 16){
      String begining1 = number.SubString(0, 1);
      String begining2 = number.SubString(0, 2);
      String begining4 = number.SubString(0, 4);
      if (begining1 == "4")
        type = "VISA";
      else if (begining2 == "51" || begining2 == "52" || begining2 == "53" || begining2 == "54" || begining2 == "55")
        type = "MASTERCARD";
      else if (begining4 == "6011")
        type = "DISCOVER";
      else if (begining2 == "35")
        type = "JCB";
      else {
        type = "Unknown Type-16";
      }
    }
    else if (len == 15){
      String begining2 = number.SubString(0, 2);
      String begining4 = number.SubString(0, 4);
      if (begining2 == "34" || begining2 == "37")
        type = "AMEX";
      else if (begining4 == "1800" || begining4 == "2131")
        type = "JCB";
      else {
        type = "Unknown Type-15";
      }
    }
    else if (len ==14) {
      String begining2 = number.SubString(0, 2);
      String begining3 = number.SubString(0, 3);
      if (begining2 == "36" || begining2 == "38" || begining3 == "300" || begining3 == "301" || begining3 == "302" || begining3 == "303" || begining3 == "304" || begining3 == "305")
        type = "DINERS";
      else {
        type = "Unknown Type-14";

      }
    }
    else if (len == 13){
      String begining1 = number.SubString(0, 1);
      if (begining1 == "4")
        type = "VISA";
      else {
        type == "Unknown Type-13";

      }
    }

    int sum;
    bool alternate = false;
    int n;
    for (int i = number.GetLength() - 1; i >= 0; i--) {
      n = int::Convert(number[i], int::DECIMAL);

      if (alternate) {
        n *= 2;
        if (n > 9) {
          n = (n % 10) + 1;
        }
      }

      sum += n;
      alternate = !alternate;
  }
  return (sum % 10 == 0);
  }
}