package fr.xephi.authme.security.pbkdf2;

/*
 * Free auxiliary functions. Copyright 2007, 2014, Matthias Gärtner
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

/**
 * Free auxiliary functions
 *
 * @author Matthias Gärtner
 */
public class BinTools {
    public static final String hex = "0123456789ABCDEF";

    /**
     * Simple binary-to-hexadecimal conversion.
     *
     * @param b
     *            Input bytes. May be <code>null</code>.
     * @return Hexadecimal representation of b. Uppercase A-F, two characters
     *         per byte. Empty string on <code>null</code> input.
     */
    public static String bin2hex(final byte[] b) {
        if (b == null) {
            return "";
        }
        StringBuffer sb = new StringBuffer(2 * b.length);
        for (int i = 0; i < b.length; i++) {
            int v = (256 + b[i]) % 256;
            sb.append(hex.charAt((v / 16) & 15));
            sb.append(hex.charAt((v % 16) & 15));
        }
        return sb.toString();
    }

    /**
     * Convert hex string to array of bytes.
     *
     * @param s
     *            String containing hexadecimal digits. May be <code>null</code>
     *            . On odd length leading zero will be assumed.
     * @return Array on bytes, non-<code>null</code>.
     * @throws IllegalArgumentException
     *             when string contains non-hex character
     */
    public static byte[] hex2bin(final String s) {
        String m = s;
        if (s == null) {
            // Allow empty input string.
            m = "";
        } else if (s.length() % 2 != 0) {
            // Assume leading zero for odd string length
            m = "0" + s;
        }
        byte r[] = new byte[m.length() / 2];
        for (int i = 0, n = 0; i < m.length(); n++) {
            char h = m.charAt(i++);
            char l = m.charAt(i++);
            r[n] = (byte) (hex2bin(h) * 16 + hex2bin(l));
        }
        return r;
    }

    /**
     * Convert hex digit to numerical value.
     *
     * @param c
     *            0-9, a-f, A-F allowd.
     * @return 0-15
     * @throws IllegalArgumentException
     *             on non-hex character
     */
    public static int hex2bin(char c) {
        if (c >= '0' && c <= '9') {
            return (c - '0');
        }
        if (c >= 'A' && c <= 'F') {
            return (c - 'A' + 10);
        }
        if (c >= 'a' && c <= 'f') {
            return (c - 'a' + 10);
        }
        throw new IllegalArgumentException("Input string may only contain hex digits, but found '" + c + "'");
    }

    public static void main(String[] args) {
        byte b[] = new byte[256];
        byte bb = 0;
        for (int i = 0; i < 256; i++) {
            b[i] = bb++;
        }
        String s = bin2hex(b);
        byte c[] = hex2bin(s);
        String t = bin2hex(c);
        if (!s.equals(t)) {
            throw new AssertionError("Mismatch");
        }
    }
}