package org.opentrafficsim.core.perception.collections;
   
   import java.util.Collections;
   import java.util.Iterator;
   import java.util.NavigableSet;
   
   import org.opentrafficsim.core.perception.HistoryManager;
   
   /**
   * NavigableSet-valued historical state. The current navigable set is always maintained, and past states of the navigable set
   * are obtained by applying the events between now and the requested time in reverse.<br>
   * <br>
   * The {@code Iterator} returned by this class does not support the {@code remove()} method. Any returned subset is
   * unmodifiable.
   * <p>
   * Copyright (c) 2013-2019 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="http://opentrafficsim.org/node/13">OpenTrafficSim License</a>.
   * <p>
   * @version $Revision$, $LastChangedDate$, by $Author$, initial version 2 feb. 2018 <br>
   * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   * @param <E> element type
   * @param <S> navigable set type
   */
  public abstract class AbstractHistoricalNavigableSet<E, S extends NavigableSet<E>> extends AbstractHistoricalSortedSet<E, S>
          implements HistoricalNavigableSet<E>
  {
  
      /**
       * Constructor.
       * @param historyManager HistoryManager; history manager
       * @param set S; initial set
       */
      protected AbstractHistoricalNavigableSet(final HistoryManager historyManager, final S set)
      {
          super(historyManager, set);
      }
  
      /** {@inheritDoc} */
      @Override
      public String toString()
      {
          return "HistoricalNavigableSet [current=" + getCollection() + "]";
      }
  
      // Altering NavigableSet methods
  
      /** {@inheritDoc} */
      @Override
      public E pollFirst()
      {
          if (getCollection().isEmpty())
          {
              return null;
          }
          E element = getCollection().first();
          remove(element);
          return element;
      }
  
      /** {@inheritDoc} */
      @Override
      public E pollLast()
      {
          if (getCollection().isEmpty())
          {
              return null;
          }
          E element = getCollection().last();
          remove(element);
          return element;
      }
  
      // Non-altering NavigableSet methods
  
      /** {@inheritDoc} */
      @Override
      public E lower(final E e)
      {
          return getCollection().lower(e);
      }
  
      /** {@inheritDoc} */
      @Override
      public E floor(final E e)
      {
          return getCollection().floor(e);
      }
  
      /** {@inheritDoc} */
      @Override
      public E ceiling(final E e)
      {
          return getCollection().ceiling(e);
      }
  
      /** {@inheritDoc} */
      @Override
     public E higher(final E e)
     {
         return getCollection().higher(e);
     }
 
     /** {@inheritDoc} */
     @Override
     public NavigableSet<E> descendingSet()
     {
         return Collections.unmodifiableNavigableSet(getCollection().descendingSet());
     }
 
     /** {@inheritDoc} */
     @Override
     public Iterator<E> descendingIterator()
     {
         return Collections.unmodifiableNavigableSet(getCollection()).descendingIterator();
     }
 
     /** {@inheritDoc} */
     @Override
     public NavigableSet<E> subSet(final E fromElement, final boolean fromInclusive, final E toElement,
             final boolean toInclusive)
     {
         return Collections.unmodifiableNavigableSet(getCollection().subSet(fromElement, fromInclusive, toElement, toInclusive));
     }
 
     /** {@inheritDoc} */
     @Override
     public NavigableSet<E> headSet(final E toElement, final boolean inclusive)
     {
         return Collections.unmodifiableNavigableSet(getCollection().headSet(toElement, inclusive));
     }
 
     /** {@inheritDoc} */
     @Override
     public NavigableSet<E> tailSet(final E fromElement, final boolean inclusive)
     {
         return Collections.unmodifiableNavigableSet(getCollection().tailSet(fromElement, inclusive));
     }
 
 }