/*******************************************************************************
 * Copyright 2014 Federal Chancellery Austria
 * MOA-ID has been developed in a cooperation between BRZ, the Federal
 * Chancellery Austria - ICT staff unit, and Graz University of Technology.
 * 
 * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * http://www.osor.eu/eupl/
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 * 
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 ******************************************************************************/
/*
 * Copyright 2003 Federal Chancellery Austria
 * MOA-ID has been developed in a cooperation between BRZ, the Federal
 * Chancellery Austria - ICT staff unit, and Graz University of Technology.
 *
 * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * http://www.osor.eu/eupl/
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 */


package at.gv.egiz.eaaf.core.impl.utils;


import java.nio.ByteBuffer;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

import org.apache.commons.codec.binary.Hex;
import org.apache.commons.lang3.ArrayUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * Random number generator used to generate ID's
 * @author Paul Ivancsics
 * @version $Id$
 */
public class Random {
	private static final Logger log = LoggerFactory.getLogger(Random.class);
	
	private final static char[] allowedPreFix = 
		{'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
		 'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
	private static final DateFormat dateFormater = new SimpleDateFormat("yyyyddMM");
	
  /** random number generator used */
	private static SecureRandom random;
	//private static SeedGenerator seedgenerator;	
		
	static {
		try {
			random = SecureRandom.getInstance("SHA256PRNG-FIPS186");
			
		} catch (NoSuchAlgorithmException e) {
			log.warn("Can NOT initialize SecureRandom with: 'SHA256PRNG-FIPS186'. Use 'StrongSecureRandom' as backup");

			try {
				random = SecureRandom.getInstanceStrong();
				
			} catch (NoSuchAlgorithmException e1) {
				log.error("Can NOT initialize SecureRandom. StartUp process FAILED!");
				throw new RuntimeException("Can NOT initialize SecureRandom. StartUp process FAILED!", e);
				
			}
			
		}
		
		
		//random = iaik.security.random.SHA256FIPS186Random.getDefault();		
	}
	
	/**
	 * Generate a unique process reference-value [160bit], which always starts with a letter
	 * <br>
	 * This unique ID consists of single letter, a 64bit date String[yyyyddMM],
	 *  and a 88bit random value.  
	 * 
	 * @return 160bit ID, which is hex encoded
	 */
	public static String nextProcessReferenceValue() {		
		//pre-process all three parts of a unique reference value
		String now = dateFormater.format(new Date()); //8 bytes = 64bit
		byte[] randValue = nextByteRandom(11);
		char preFix = allowedPreFix[Math.abs(random.nextInt() % allowedPreFix.length)];
	 
		//generate ID
		String returnValue = preFix + new String(Hex.encodeHex(ArrayUtils.addAll(now.getBytes(), randValue))); // 20 bytes = 160 bits
		if (returnValue.length() > 40)
			return returnValue.substring(0, 40);
		else
			return returnValue;
			
	}
	
	
	
	/**
	 * Creates a new random number [256bit], and encode it as hex value.
	 * 
	 * @return random hex encoded value [256bit]
	 */
	public static String nextHexRandom32() {
		return new String(Hex.encodeHex(nextByteRandom(32))); // 32 bytes = 256 bits
		
	}
	
	/**
	 * Creates a new random number [128bit], and encode it as hex value.
	 * 
	 * @return random hex encoded value [128bit]
	 */
	public static String nextHexRandom16() {
		return new String(Hex.encodeHex(nextByteRandom(16))); // 16 bytes = 128 bits
		
	}
	
	  /**
	   * Creates a new random number [64bit], to be used as an ID.
	   * 
	   * @return random long as a String [64bit]
	   */
	public static String nextLongRandom() {	  
		return "".concat(String.valueOf(Math.abs(generateLongRandom(32)))); // 32 bytes = 256 bits	
			
	  }
		
  /**
   * Creates a new random number, to be used as an ID.
   * 
   * @return random long as a String [64bit]
   */
	@Deprecated
  public static String nextRandom() {	  
	long l = ByteBuffer.wrap(nextByteRandom(32)).getLong(); // 32 bytes = 256 bits
	return "" + Math.abs(l);
		
  }
  
/**
 * Creates a new random byte[]
 * 	
 * @param size Size of random number in byte
 * @return
 */
public static byte[] nextBytes(int size) {
	return  nextByteRandom(size);
	
}
  
  public static void seedRandom() {
	  //TODO: implement reflection on IAIK Seed generator	  
//      seedgenerator = iaik.security.random.AutoSeedGenerator.getDefault();  
//	  if (seedgenerator.seedAvailable())
//		  random.setSeed(seedgenerator.getSeed());
	  
	  random.setSeed(System.nanoTime());
  }
  
	private static long generateLongRandom(int size) {
		return ByteBuffer.wrap(nextByteRandom(size)).getLong(); 	
	}
  
  /**
   * Generate a new random number
   * 
   * @param size Size of random number in byte
   * @return
   */
  private static synchronized byte[] nextByteRandom(int size) {
	  byte[] b = new byte[size];
	  random.nextBytes(b);			 
	  return b;
	  
  }
}