/*
 * Copyright 2011 by Graz University of Technology, Austria
 * MOCCA has been developed by the E-Government Innovation Center EGIZ, a joint
 * initiative of the Federal Chancellery Austria 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.bku.binding;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Creates or converts Ids for BindingProcessors.
 * @author wbauer
 *
 */
public class IdFactory {

  private final Logger log = LoggerFactory.getLogger(IdFactory.class);

  public static int DEFAULT_NUMBER_OF_BITS = 168;

  private static IdFactory instance = new IdFactory();

  private SecureRandom random;
  private int numberOfBits = DEFAULT_NUMBER_OF_BITS;

  private IdFactory() {
    try {
      random = SecureRandom.getInstance("SHA1PRNG");
    } catch (NoSuchAlgorithmException e) {
      log.error("Cannot instantiate secure random.", e);
    }
  }

  public static IdFactory getInstance() {
    return instance;
  }


  /**
   * set the secure random number generator to create secure ids.
   * 
   * @param random
   *          must not be null
   */
  public void setSecureRandom(SecureRandom random) {
    if (random == null) {
      throw new NullPointerException("Cannot set secure random to null");
    }
    this.random = random;
  }

  /**
   * Don't use this method unless you know exactly what you do !
   * Be sure to use a sufficient large entropy 
   * @param numberOfBits >=1 (although this small entropy does not make sense)
   */
  public void setNumberOfBits(int numberOfBits) {
    if (numberOfBits <1) {
      throw new IllegalArgumentException("Cannot set number of bits < 1");
    }
    this.numberOfBits = numberOfBits;
  }

  public int getNumberOfBits() {
    return numberOfBits;
  }
  
  /**
   * Creates a new Id object with the factory's secure RNG and the set number of
   * bits.
   * 
   * @return
   */
  public Id createId() {
    return new IdImpl(numberOfBits, random);
  }

  /**
   * Creates an Id object for the provided String
   * 
   * @param idString
   *          may be null in this case the method call creates a new Id.
   * @return
   */
  public Id createId(String idString) {
    if (idString == null) {
      return createId();
    }
    return new IdImpl(idString);
  }
}