package com.n2bb.util;

import java.security.MessageDigest;

public final class DigestUtil {

  static class HexUtils {
    /**
     * Convert a byte array into a printable format containing a
     * String of hexadecimal digit characters (two per byte).
     *
     * @param bytes Byte array representation
     */
    public static String convert(byte bytes[]) {

        StringBuffer sb = new StringBuffer(bytes.length * 2);
        for (int i = 0; i < bytes.length; i++) {
            sb.append(convertDigit((int) (bytes[i] >> 4)));
            sb.append(convertDigit((int) (bytes[i] & 0x0f)));
        }
        return (sb.toString());

    }


        /**
     * [Private] Convert the specified value (0 .. 15) to the corresponding
     * hexadecimal digit.
     *
     * @param value Value to be converted
     */
    private static char convertDigit(int value) {

        value &= 0x0f;
        if (value >= 10)
            return ((char) (value - 10 + 'a'));
        else
            return ((char) (value + '0'));

    }

  }

    /**
     * Digest password using the algorithm especificied and
     * convert the result to a corresponding hex string.
     * If exception, the plain credentials string is returned
     *
     * @param credentials Password or other credentials to use in
     *  authenticating this username
     * @param algorithm Algorithm used to do th digest
     */
    public final static String Digest(String credentials, String algorithm) {

        try {
            // Obtain a new message digest with "digest" encryption
            MessageDigest md =
                (MessageDigest) MessageDigest.getInstance(algorithm).clone();
            // encode the credentials
            md.update(credentials.getBytes());
            // Digest the credentials and return as hexadecimal
            return (HexUtils.convert(md.digest()));
        } catch(Exception ex) {
            ex.printStackTrace();
            return credentials;
        }

    }
    
}