/*
 * Based on http://www.cs.ru.nl/~erikpoll/hw/samples/ChipknipTerminal.java, 
 * Freed from JCOP libraries by porting it to javax.smartcardio.* ;-)
 */

import javax.smartcardio.*;
import java.util.List;


public class ChipknipTerminal {
	private static CommandAPDU GET_BALANCE_APDU = new CommandAPDU((byte) 0xE1,
			(byte) 0xB4, (byte) 0x00, (byte) 0x01, null, 5);


	public ChipknipTerminal() {
	    try {
		TerminalFactory tf = TerminalFactory.getDefault();
		CardTerminals ct = tf.terminals();
		List<CardTerminal> cs = ct.list(CardTerminals.State.CARD_PRESENT);
		if (cs.isEmpty()) {
			System.err.println("No terminals with a card found.");
			return;
		}
		for(CardTerminal c : cs) {
			if (c.isCardPresent()) {
				try {
					Card card = c.connect("*");

					try {
						CardChannel ch = card.getBasicChannel();
						System.out.println("Chipknip balance: "
								+ amountString(getBalance(ch
										.transmit(GET_BALANCE_APDU))));
					} catch (Exception e) {
						System.err.println("Card is not a Chipknip?!");
					}
					card.disconnect(false);

				} catch (CardException e) {
					System.err.println("Couldn't connect to card!");
				}
				return;

			} else {
				System.err.println("No card present!");
			}
		}
    	    } catch (CardException e) {
		System.err.println("Card status problem!");
	    }
	}

	public static int getBalance(ResponseAPDU ra) {
		byte[] data = ra.getBytes();
		return ((data[0] & 0x000000FF) << 16) | ((data[1] & 0x000000FF) << 8)
				| (data[2] & 0x000000FF);
	}

	private static String amountString(int value) {
		return (value / 100) + "." + (((value % 100) < 10) ? "0" : "")
				+ (value % 100);
	}

	public static void main(String[] arg) {
		new ChipknipTerminal();
	}
}