package org.opentrafficsim.core.perception.collections;
   
   import java.util.Collection;
   import java.util.Collections;
   import java.util.HashSet;
   import java.util.Map;
   import java.util.Objects;
   import java.util.Set;
   
  import org.djunits.value.vdouble.scalar.Time;
  import org.djutils.exceptions.Throw;
  import org.opentrafficsim.core.perception.AbstractHistorical;
  import org.opentrafficsim.core.perception.HistoryManager;
  import org.opentrafficsim.core.perception.collections.AbstractHistoricalMap.EventMap;
  
  /**
   * Map-valued historical state. The current map is always maintained, and past states of the map are obtained by applying the
   * events between now and the requested time in reverse.<br>
   * <br>
   * The set views returned by this class are 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 1 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 <K> key type
   * @param <V> value type
   * @param <M> map type
   */
  public abstract class AbstractHistoricalMap<K, V, M extends Map<K, V>> extends AbstractHistorical<K, EventMap<K, V, M>>
          implements HistoricalMap<K, V>
  {
  
      /** Current map. */
      private final M current;
  
      /**
       * Constructor.
       * @param historyManager HistoryManager; history manager
       * @param map M; initial map
       */
      protected AbstractHistoricalMap(final HistoryManager historyManager, final M map)
      {
          super(historyManager);
          Throw.when(!map.isEmpty(), IllegalArgumentException.class, "The initial map should be empty.");
          this.current = map;
      }
  
      /**
       * Returns the internal map.
       * @return M; internal map
       */
      protected M getMap()
      {
          return this.current;
      }
  
      /**
       * Fill map with the current map.
       * @param map M; map to fill
       * @return M; input map filled
       */
      protected M fill(final M map)
      {
          map.putAll(this.current);
          return map;
      }
  
      /**
       * Fill map with the map at the given simulation time.
       * @param time Time; time
       * @param map M; map to fill
       * @return M; input map filled
       */
      protected M fill(final Time time, final M map)
      {
          // copy all current elements and decrement per event
          map.putAll(this.current);
          for (EventMap<K, V, M> event : getEvents(time))
          {
              event.restore(map);
          }
          return map;
      }
  
      // Altering Map methods
  
      /** {@inheritDoc} */
      @Override
      public void clear()
      {
          new HashSet<>(this.current.keySet()).forEach(this::remove);
      }
  
      /** {@inheritDoc} */
      @Override
     public V put(final K key, final V value)
     {
         boolean contained = this.current.containsKey(key);
         V previousValue = contained ? this.current.get(key) : null;
         if (!contained || !Objects.equals(previousValue, value))
         {
             addEvent(new EventMap<>(now().si, key, contained, previousValue));
             return this.current.put(key, value);
         }
         return previousValue;
     }
 
     /** {@inheritDoc} */
     @Override
     public void putAll(final Map<? extends K, ? extends V> m)
     {
         m.forEach(this::put);
     }
 
     /** {@inheritDoc} */
     @Override
     @SuppressWarnings("unchecked")
     public V remove(final Object key)
     {
         boolean contained = this.current.containsKey(key);
         if (contained)
         {
             V previousValue = this.current.get(key);
             addEvent(new EventMap<>(now().si, (K) key, contained, previousValue)); // contains, so safe cast
             return this.current.remove(key);
         }
         return null;
     }
 
     // Non-altering Map methods
 
     /** {@inheritDoc} */
     @Override
     public int size()
     {
         return this.current.size();
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean isEmpty()
     {
         return this.current.isEmpty();
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean containsKey(final Object key)
     {
         return this.current.containsKey(key);
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean containsValue(final Object value)
     {
         return this.current.containsValue(value);
     }
 
     /** {@inheritDoc} */
     @Override
     public V get(final Object key)
     {
         return this.current.get(key);
     }
 
     /** {@inheritDoc} */
     @Override
     public Set<K> keySet()
     {
         return Collections.unmodifiableSet(this.current.keySet());
     }
 
     /** {@inheritDoc} */
     @Override
     public Collection<V> values()
     {
         return Collections.unmodifiableCollection(this.current.values());
     }
 
     /** {@inheritDoc} */
     @Override
     public Set<Entry<K, V>> entrySet()
     {
         // need to ensure that the Entries themselves allow no alterations
         return Collections.unmodifiableMap(this.current).entrySet();
     }
 
     // Events
 
     /**
      * Abstract super class for events that add or remove a value from the map.
      * <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 1 jan. 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 <K> key type
      * @param <V> value type
      * @param <M> map type
      */
     public static class EventMap<K, V, M extends Map<K, V>> extends AbstractHistorical.EventValue<K>
     {
 
         /** Whether the map contained the key prior to the event. */
         private final boolean contained;
 
         /** Previous value in the map. */
         private final V previousValue;
 
         /**
          * Constructor.
          * @param time double; time of event
          * @param key K; key of event
          * @param contained boolean; whether the map contained the key prior to the event
          * @param previousValue V; previous value in the map
          */
         public EventMap(final double time, final K key, final boolean contained, final V previousValue)
         {
             super(time, key);
             this.contained = contained;
             this.previousValue = previousValue;
         }
 
         /**
          * Restores the map to the state of before the event.
          * @param map M; map to restore
          */
         public void restore(final M map)
         {
             if (this.contained)
             {
                 map.put(getValue(), this.previousValue); // event value = map key
             }
             else
             {
                 map.remove(getValue()); // event value = map key
             }
         }
 
         /** {@inheritDoc} */
         @Override
         public String toString()
         {
             return "EventMap [contained=" + this.contained + ", previousValue=" + this.previousValue + "]";
         }
 
     }
 
 }