/*
 * aTunes 2.1.0-SNAPSHOT
 * Copyright (C) 2006-2011 Alex Aranda, Sylvain Gaudard and contributors
 *
 * See http://www.atunes.org/wiki/index.php?title=Contributing for information about contributors
 *
 * http://www.atunes.org
 * http://sourceforge.net/projects/atunes
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

package net.sourceforge.atunes.utils;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.security.GeneralSecurityException;
import java.security.Key;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.spec.SecretKeySpec;

/**
 * <p>
 * Utility methods for encrypting and decrypting
 * </p>
 * <p>
 * <b> NOTE: This class does not not produce really secret encryptions (the
 * secret key is public)!</b>
 * </p>
 */
public final class CryptoUtils {

    /* Length: 8 Bytes for DES */
    private static final String SECRET_KEY = "5Gjd9T0b";

    private CryptoUtils() {
    }

    /**
     * Decrypts a byte array.
     * 
     * @param bytes
     *            The byte array to decrypt
     * 
     * @return The decrypted byte array
     * 
     * @throws GeneralSecurityException
     *             the general security exception
     * @throws IOException
     *             Signals that an I/O exception has occurred.
     */
    public static byte[] decrypt(byte[] bytes) throws GeneralSecurityException, IOException {
        if (bytes == null || bytes.length == 0) {
            return new byte[0];
        }

        Cipher c = Cipher.getInstance("DES");
        Key k = new SecretKeySpec(SECRET_KEY.getBytes(), "DES");
        c.init(Cipher.DECRYPT_MODE, k);

        ByteArrayInputStream input = new ByteArrayInputStream(bytes);
        CipherInputStream cis = new CipherInputStream(input, c);
        BufferedReader reader = new BufferedReader(new InputStreamReader(cis));
        String string = reader.readLine();
        reader.close();
        return string != null ? string.getBytes() : new byte[0];
    }

    /**
     * Encrypts a byte array.
     * 
     * @param bytes
     *            The byte array to encrypt
     * 
     * @return The encrypted byte array
     * 
     * @throws GeneralSecurityException
     *             the general security exception
     * @throws IOException
     *             Signals that an I/O exception has occurred.
     */
    public static byte[] encrypt(byte[] bytes) throws GeneralSecurityException, IOException {
        if (bytes == null || bytes.length == 0) {
            return new byte[0];
        }

        Cipher c = Cipher.getInstance("DES");
        Key k = new SecretKeySpec(SECRET_KEY.getBytes(), "DES");
        c.init(Cipher.ENCRYPT_MODE, k);

        ByteArrayOutputStream output = new ByteArrayOutputStream();
        CipherOutputStream cos = new CipherOutputStream(output, c);
        cos.write(bytes);
        cos.close();
        return output.toByteArray();
    }

}
