/*

  * Copyright 2005-2008 The Kuali Foundation

  * 

  * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php

  * 

  * 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 org.kuali.rice.kns.util;

 import java.security.MessageDigest;

 import java.security.NoSuchAlgorithmException;

 import org.apache.ojb.broker.util.GUID;

 /**

  * 

  * This class wraps an OJB Guid so that it conforms to the format (and using the algorithm) described in

  * RFC 4122 entitled " A Universally Unique IDentifier (UUID) URN Namespace" 

  */

 public class Guid {

     private final static char HYPHEN='-';

     private final static String DIGITS="0123456789ABCDEF";

     private String stringValue=null;

     private GUID guid;

     public Guid() {

         guid = new GUID(); // This OJB class is deprecated; remove this line when we upgrade OJB

         String guidString=guid.toString();

         // this is roughly the prefered way with the new OJB GUIDFactory:

         // String guidString=org.apache.ojb.broker.util.GUIDFactory.next(); 

         MessageDigest sha;

         try {

             sha = MessageDigest.getInstance("SHA-1");

         }

         catch (NoSuchAlgorithmException e) {

             throw new RuntimeException(e);

         }

         sha.update(guidString.getBytes());

         byte[] hash=sha.digest();

         StringBuffer result=new StringBuffer();

         for (int i=0; i<hash.length; i++) {

             result.append(toHex(hash[i]));

         }

         // hyphenate

         for (int i=20; i>4; i-=4) {

             result.insert(i,HYPHEN);

         }

         // truncate

         result.delete(32,40);

         stringValue=result.toString();

     }    

     public static String toHex(byte b) {

         int ub=b<0?b+256:b;

         StringBuffer result=new StringBuffer(2);

         result.append(DIGITS.charAt(ub/16));

         result.append(DIGITS.charAt(ub%16));

         return result.toString();

     }

     @Override

     public String toString() {

         return stringValue;

     }

 }