/**
 * @author Tomasz Lubinski
 * www.algorym.org
 * (c) 2005
 *
 * Class for REGON validating
 */
public class REGONValidator {
	
	private byte REGON[] = new byte[14];
	private int REGONLength;
	private boolean valid = false;
	
	public REGONValidator(String REGONNumber) {
		if ((REGONNumber.length() != 9) && (REGONNumber.length() != 14)) {
			valid = false;
		}
		else {
			REGONLength = REGONNumber.length();
			for (int i = 0; i < REGONLength; i++){
				REGON[i] = Byte.parseByte(REGONNumber.substring(i, i+1));
			}
			if (checkSum()) {
				valid = true;
			}
			else {
				valid = false;	
			}
		}
	}
	
	public boolean isValid() {
		return valid;
	}
	
	//for 9 digit REGON
	private boolean checkSum9() {
		int sum = 8 * REGON[0] + 
		          9 * REGON[1] +
				  2 * REGON[2] +
				  3 * REGON[3] +
				  4 * REGON[4] +
				  5 * REGON[5] +
				  6 * REGON[6] +
				  7 * REGON[7];
		sum %= 11;
		if (sum == 10) {
			sum = 0;
		}
		if (sum == REGON[8]) {
			return true;
		}
		else {
			return false;
		}
	}

	//for 14 digit REGON
	private boolean checkSum14() {
		int sum = 2 * REGON[0] + 
		          4 * REGON[1] +
				  8 * REGON[2] +
				  5 * REGON[3] +
				  0 * REGON[4] +
				  9 * REGON[5] +
				  7 * REGON[6] +
				  3 * REGON[7] +
				  6 * REGON[8] +
				  1 * REGON[9] +
				  2 * REGON[10] +
				  4 * REGON[11] +
				  8 * REGON[12];
		sum %= 11;
		if (sum == 10) {
			sum = 0;
		}
		if (sum == REGON[13]) {
			return true;
		}
		else {
			return false;
		}
	}
	
	private boolean checkSum() {
		if (REGONLength == 9) {
			return checkSum9();
		}
		else {
			return (checkSum9() && checkSum14());
		}
	}
}