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/*
 * Copyright 2017 Futeh Kao
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package net.e6tech.elements.security.hsm;

import net.e6tech.elements.common.util.StringUtil;
import net.e6tech.elements.security.Hex;

/**
 * Created by futeh.
 */
public class AnsiPinBlock {
    byte[] encoding;
    String pin;

    public AnsiPinBlock(String partialPan, String pin) {
        if (partialPan.length() != 12) throw new IllegalArgumentException("invalid partial pan length, must be 12");
        if (pin == null) throw new IllegalArgumentException("null pin");
        if (pin.length() < 4 || pin.length() > 12) throw new IllegalArgumentException("invalid pin length.");
        int pinLen = pin.length();
        String pinBlock = "0" + Hex.toNumeric(pinLen) + pin;
        pinBlock = StringUtil.padRight(pinBlock, 16, 'F');
        byte[] pinBytes = Hex.toBytes(pinBlock);
        byte[] panBytes = Hex.toBytes("0000" + partialPan);
        byte[] xor = new byte[8];
        for (int i = 0; i < 8; i++) xor[i] = (byte)(pinBytes[i] ^ panBytes[i]);
        encoding = xor;
        this.pin = pin;
    }

    public AnsiPinBlock(byte[] encoding, String partialPan) {
        if (partialPan.length() != 12) throw new IllegalArgumentException("invalid partial pan length, must be 12");
        this.encoding = encoding;
        byte[] panBytes = Hex.toBytes("0000" + partialPan);
        byte[] pinBytes = new byte[8];
        for (int i = 0; i < 8; i++) pinBytes[i] = (byte)(encoding[i] ^ panBytes[i]);
        String pinStr = Hex.toString(pinBytes);
        int pinLen = Integer.parseInt(pinStr.substring(1, 2));
        pin = pinStr.substring(2, pinLen + 2);
    }

    public String getPIN() {
        return pin;
    }

    public byte[] getEncoding() {
        return encoding;
    }

    public static void main(String ... args) throws Exception {
        AnsiPinBlock ansi = new AnsiPinBlock("999789012345", "1234");
        System.out.println(Hex.toString(ansi.encoding)); // should be 0412AD6876FEDCBA
        ansi = new AnsiPinBlock(ansi.encoding, "999789012345");
        System.out.println(ansi.pin); // should be 1234
    }
}