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package cz.monetplus.mnsp.tools.misc;

import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Hex;
import org.apache.commons.lang.StringUtils;

/**
 * Tools for encoding a decoding pinblock
 * 
 * @author Tomas Jacko <tomas.jacko [at] monetplus.cz>
 *
 */
public class PinblockTool {

	/**
	 * Decode pinblock format 0 (ISO 9564)
	 * @param pin pin 
	 * @param pan primary account number (PAN/CLN/CardNumber)
	 * @return pinblock in HEX format
	 */
	public static String format0Encode(String pin, String pan) {
		try {
			final String pinLenHead = StringUtils.leftPad(Integer.toString(pin.length()), 2, '0')+pin;
			final String pinData = StringUtils.rightPad(pinLenHead, 16,'F');
			final byte[] bPin = Hex.decodeHex(pinData.toCharArray());
			final String panPart = extractPanAccountNumberPart(pan);
			final String panData = StringUtils.leftPad(panPart, 16, '0');
			final byte[] bPan = Hex.decodeHex(panData.toCharArray());

			final byte[] pinblock = new byte[8];
			for (int i = 0; i < 8; i++)
				pinblock[i] = (byte) (bPin[i] ^ bPan[i]);

			return Hex.encodeHexString(pinblock).toUpperCase();
		} catch (DecoderException e) {
			throw new RuntimeException("Hex decoder failed!",e);
		}
	}
	
	/**
	 * @param accountNumber PAN - primary account number
	 * @return extract right-most 12 digits of the primary account number (PAN)
	 */
	public static String extractPanAccountNumberPart(String accountNumber) {
		String accountNumberPart = null;
		if (accountNumber.length() > 12)
			accountNumberPart = accountNumber.substring(accountNumber.length() - 13, accountNumber.length() - 1);
		else
			accountNumberPart = accountNumber;
		return accountNumberPart;
	}
	
	/**
	 * decode pinblock format 0 - ISO 9564
	 * @param pinblock pinblock in format 0 - ISO 9564 in HEX format 
	 * @param pan primary account number (PAN/CLN/CardNumber)
	 * @return clean PIN
	 */
	public static String format0decode(String pinblock, String pan) {
		try {
			final String panPart = extractPanAccountNumberPart(pan);
			final String panData = StringUtils.leftPad(panPart, 16, '0');
			final byte[] bPan = Hex.decodeHex(panData.toCharArray());
			
			final byte[] bPinBlock = Hex.decodeHex(pinblock.toCharArray());
			
			final byte[] bPin  = new byte[8];
			for (int i = 0; i < 8; i++)
				bPin[i] = (byte) (bPinBlock[i] ^ bPan[i]);
			
			final String pinData = Hex.encodeHexString(bPin);
			final int pinLen = Integer.parseInt(pinData.substring(0, 2));
			return pinData.substring(2,2+pinLen);
		} catch (NumberFormatException e) {
			throw new RuntimeException("Invalid pinblock format!");
		} catch (DecoderException e) {
			throw new RuntimeException("Hex decoder failed!",e);
		}
	}
}