package be.bastard.mtracker.external;
   
   import java.net.InetAddress;
   import java.util.Enumeration;
   import java.util.Locale;
   import java.util.Properties;
   import java.util.Random;
   
   /***
   * PlatformIndependentGuidGen.
   * This file does not belong explicitely to the Media Tracker project.
   * It is a id generator that was written by Todd Clark in 2004.
   * Below is the original license information of the class.
   * <pre>
   * --------------------------------------------------------------------------------------
   *  Just a stand alone class that I posted to a forum
   *
   *  Copyright (C) 2004 Todd Clark quirkware0@yahoo.com
   *
   *  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 FITfNESS 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 program; if not, write to the Free Software
   *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
   *
   *  If you make changes or improvements to the this class I ask that you you 
   *  post them to a forum thread and email the improvements to quirkware0@yahoo.com 
   *  and that you leave my name intact in the header comments.
   *
   *  If you use this code in an application that you distribute. I require that you
   *  include my name in the credits of your application.
   * --------------------------------------------------------------------------------------
   * </pre>
   */
  public class PlatformIndependentGuidGen {
  	private static PlatformIndependentGuidGen _TheInstance = null;
  
  	private Random _RandomForSpace = null;
  
  	private Random _RandomForTime = null;
  
  	/***
  	 * Note: the first time you call this function it is very expensive
  	 * 
  	 * @return PlatformIndependentGuidGen the instace of the Guid generator
  	 */
  	public static synchronized PlatformIndependentGuidGen getInstance() {
  		if (_TheInstance == null)
  			_TheInstance = new PlatformIndependentGuidGen();
  
  		return _TheInstance;
  	}
  
  	/***
  	 * 
  	 * @return String a new Guid
  	 */
  	public String genNewGuid() {
  		long uniqueInSpace = _RandomForSpace.nextLong();
  		long uniqueInTime = _RandomForTime.nextLong();
  
  		return Long.toHexString(uniqueInSpace) + "-"
  				+ Long.toHexString(uniqueInTime);
  	}
  
  	private PlatformIndependentGuidGen() {
  		long uniqueSpaceSeed = createUniqueSpaceSeed();
  		long uniqueTimeSeed = System.currentTimeMillis();
  
  		_RandomForSpace = new Random(uniqueSpaceSeed);
  		_RandomForTime = new Random(uniqueTimeSeed);
  	}
  
  	/***
  	 * Does the best job it can to produce a number that is dependent on the
  	 * machine on which this code is running
  	 * 
  	 * @return long
  	 */
  	private long createUniqueSpaceSeed() {
  		String hashingString = ""; // Contains the conglomeration of as much
  									// machine or
  		// or config dependant stuff as I could come up with
  
  		Properties systemProps = System.getProperties();
  		Enumeration systemPropKeys = systemProps.keys();
  		String systemPropKey = null;
  		Locale[] locales = Locale.getAvailableLocales();
  		int iCounter = 0;
  		Runtime runtime = Runtime.getRuntime();
  		InetAddress myAddress = null;
 
 		// Loop through all the system properties and add them to the
 		// hashingString
 		while (systemPropKeys.hasMoreElements()) {
 			systemPropKey = (String) systemPropKeys.nextElement();
 
 			// Append the system prop to the hashing string
 			hashingString = hashingString + " " + systemPropKey + " = "
 					+ systemProps.getProperty(systemPropKey) + "\n";
 
 		}
 
 		// Do a hardware dependent test and add the result to the hashingString
 		hashingString = hashingString + "Cycle Test = " + cpuCycleTest() + "\n";
 
 		// Loop through all the locales that are installed and add them to the
 		// hashingString
 		for (iCounter = 0; iCounter < locales.length; iCounter++) {
 			hashingString = hashingString + locales[iCounter].getCountry()
 					+ " " + locales[iCounter].getDisplayCountry() + " "
 					+ locales[iCounter].getDisplayName() + "\n";
 		}
 
 		// Get as much machine dependent stuff out of the runtime as
 		// you can and add them to the hashingString
 		hashingString = hashingString + "Available proc = "
 				+ runtime.availableProcessors() + "\n";
 
 		hashingString = hashingString + "free memory = " + runtime.freeMemory()
 				+ "\n";
 
 		hashingString = hashingString + "max memory = " + runtime.maxMemory()
 				+ "\n";
 
 		hashingString = hashingString + "total memory = "
 				+ runtime.totalMemory() + "\n";
 
 		// try to get my IP address and add to the hashingString
 		try {
 			myAddress = InetAddress.getLocalHost();
 			hashingString = hashingString + "my IP address = "
 					+ myAddress.toString();
 		} catch (Exception e) {
 			// Do nothing
 		}
 
 		// System.out.println(hashingString);
 
 		return hashingString.hashCode();
 	}
 
 	/***
 	 * how high can we count in 10 msec
 	 * 
 	 * @return long
 	 */
 	private long cpuCycleTest() {
 		long returnValue = 0;
 		long startTime = System.currentTimeMillis();
 		long rightNow = System.currentTimeMillis();
 
 		// Do this for thirty millisec
 		while ((rightNow - startTime) < 10
 				&& returnValue < (Long.MAX_VALUE - 10)) {
 			returnValue++;
 			rightNow = System.currentTimeMillis();
 		}
 
 		return returnValue;
 	}
 }