/* Copyright (2007) Schibsted Søk AS

  * This file is part of SESAT.

  *

  *   SESAT is free software: you can redistribute it and/or modify

  *   it under the terms of the GNU Affero General Public License as published by

  *   the Free Software Foundation, either version 3 of the License, or

  *   (at your option) any later version.

  *

  *   SESAT 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 Affero General Public License for more details.

  *

  *   You should have received a copy of the GNU Affero General Public License

  *   along with SESAT.  If not, see <http://www.gnu.org/licenses/>.

  */

 package no.sesat.search.security;

 import org.apache.commons.codec.binary.Hex;

 import java.security.MessageDigest;

 import java.security.NoSuchAlgorithmException;

 /**

  *

  * @version <tt>$Revision: 6596 $</tt>

  */

 public final class MD5Generator {

     private static final byte[] EMPTY_STRING = new byte[0];

     private final String secret;

     public MD5Generator(final String secret) {

         this.secret = secret;

     }

     public String generateMD5(final String s) {

         final MessageDigest digest  = getDigest("MD5");

         digest.update(null != s ? s.getBytes() : EMPTY_STRING);

         digest.update(secret.getBytes());

         return String.valueOf(Hex.encodeHex(digest.digest()));

     }

     public boolean validate(final String s, final String hash) {

         return generateMD5(s).equals(hash);

     }

     /**

      * Returns a MessageDigest for the given <code>algorithm</code>.

      *

      * @param algorithm The MessageDigest algorithm name.

      * @return An digest instance.

      * @throws RuntimeException when a {@link java.security.NoSuchAlgorithmException} is caught,

      */

     static MessageDigest getDigest(String algorithm) {

         try {

             return MessageDigest.getInstance(algorithm);

         } catch (NoSuchAlgorithmException e) {

             throw new RuntimeException(e.getMessage());

         }

     }

 }