/*

     dsh-evolve  Framework for evolutionary algorithms.

     Copyright (c) 2005-2012 held jointly by the individual authors.

     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 3 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; with out 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA.

     > http://www.fsf.org/licensing/licenses/lgpl.html

     > http://www.opensource.org/licenses/lgpl-license.php

 */

 package org.dishevelled.evolve.select;

 import java.util.List;

 import java.util.Random;

 import java.util.ArrayList;

 import java.util.Collection;

 import org.dishevelled.weighted.WeightedMap;

 import org.dishevelled.evolve.Selection;

 /**

  * Random selection function.

  *

  * @param <I> individual type

  * @author  Michael Heuer

  * @version $Revision: 1059 $ $Date: 2012-01-03 14:03:02 -0600 (Tue, 03 Jan 2012) $

  */

 public final class RandomSelection<I>

     implements Selection<I>

 {

     /** Source of randomness. */

     private final Random random;

     /**

      * Create a new random selection function with the default

      * source of randomness.

      */

     public RandomSelection()

     {

         random = new Random();

     }

     /**

      * Create a new random selection function with the specified

      * source of randomness.

      *

      * @param random source of randomness, must not be null

      */

     public RandomSelection(final Random random)

     {

         if (random == null)

         {

             throw new IllegalArgumentException("random must not be null");

         }

         this.random = random;

     }

     /**

      * Return the source of randomness for this random selection function.

      * The source of randomness will not be null.

      *

      * @return the source of randomness for this random selection function

      */

     public Random getRandom()

     {

         return random;

     }

     /** {@inheritDoc} */

     public Collection<I> select(final Collection<I> population,

                                 final WeightedMap<I> scores)

     {

         if (scores.totalWeight() == 0.0d)

         {

             throw new IllegalStateException("scores total weight must be greater than zero");

         }

         int size = population.size();

         List<I> populationAsList = new ArrayList<I>(population);

         List<I> selected = new ArrayList<I>(size);

         for (int i = 0; i < size; i++)

         {

             I individual = populationAsList.get(random.nextInt(size));

             selected.add(individual);

         }

         populationAsList = null;

         return selected;

     }

 }