/*
    * Copyright (C) 2003-2012 David E. Berry
    *
    * This library 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 library 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 library; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
   *
   * A copy of the GNU Lesser General Public License may also be found at
   * http://www.gnu.org/licenses/lgpl.txt
   */
  package org.synchronoss.cpo;
  
  import org.slf4j.*;
  
  import java.math.BigInteger;
  import java.net.InetAddress;
  import java.security.SecureRandom;
  
  public class GUID {
  
    private static GUID guid_ = new GUID();
    private SecureRandom seeder;
    SecureRandom sr;
    String guidMidValue;
    private static final Logger logger = LoggerFactory.getLogger(GUID.class);
  
    private GUID() {
      initGuid();
    }
  
    private void initGuid() {
      try {
        seeder = SecureRandom.getInstance("SHA1PRNG");
        seeder.generateSeed(20);
        sr = SecureRandom.getInstance("SHA1PRNG");
        byte[] newSeed = new byte[20];
        seeder.nextBytes(newSeed);
        sr.setSeed(newSeed);
  
        StringBuilder tmpBuffer = new StringBuilder();
        // get the inet address
        InetAddress inet = InetAddress.getLocalHost();
        byte[] bytes = inet.getAddress();
        String hexInetAddress = hexFormat(new BigInteger(bytes).intValue());
  
        // get the hashcode
        String thisHashCode = hexFormat(this.hashCode());
  
        /*
         * set up a cached midValue as this is the same per method / call as is object specific and is the /
         * ...-xxxx-xxxx-xxxx-xxxx.. mid part of the sequence
         */
        tmpBuffer.append("-");
        tmpBuffer.append(hexInetAddress.substring(0, 4));
        tmpBuffer.append("-");
        tmpBuffer.append(hexInetAddress.substring(4));
        tmpBuffer.append("-");
        tmpBuffer.append(thisHashCode.substring(0, 4));
        tmpBuffer.append("-");
        tmpBuffer.append(thisHashCode.substring(4));
        guidMidValue = tmpBuffer.toString();
      } catch (Exception e) {
        logger.debug("initGuid: " + e.getMessage());
      }
    }
  
    static GUID getInstance() {
      return guid_;
    }
  
    public static String getGUID() {
      GUID guid = GUID.getInstance();
      long timeNow = System.currentTimeMillis();
      int timeLow = (int) timeNow & 0xFFFFFFFF;
      int node = guid.sr.nextInt();
      String retVal = (hexFormat(timeLow) + guid.guidMidValue + hexFormat(node));
      logger.debug("getGUID(): " + retVal);
      return retVal;
    }
  
    /**
     * Returns an 8 character hexidecimal representation of trgt. If the result is not equal to eight characters leading
     * zeros are prefixed.
     *
     * @return 8 character hex representation of trgt
     */
    private static String hexFormat(int trgt) {
      String s = Integer.toHexString(trgt);
      int sz = s.length();
 
     if (sz == 8) {
       return s;
     }
     int fill = 8 - sz;
     StringBuilder buf = new StringBuilder();
 
     for (int i = 0; i < fill; ++i) {
       // add leading zeros
       buf.append('0');
     }
     buf.append(s);
     return buf.toString();
   }
 }