package org.djutils.immutablecollections;
   
   import java.util.HashSet;
   import java.util.Map;
   import java.util.Set;
   
   import org.djutils.exceptions.Throw;
   
   /**
   * An abstract base class for an immutable wrapper for a Map.
   * <p>
   * Copyright (c) 2016-2019 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See
   * for project information <a href="https://djutils.org" target="_blank"> https://djutils.org</a>. The DJUTILS project is
   * distributed under a three-clause BSD-style license, which can be found at
   * <a href="https://djutils.org/docs/license.html" target="_blank"> https://djutils.org/docs/license.html</a>.
   * </p>
   * @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://www.tudelft.nl/staff/p.knoppers/">Peter Knoppers</a>
   * @author <a href="https://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   * @param <K> the key type of content of this Map
   * @param <V> the value type of content of this Map
   */
  public abstract class ImmutableAbstractMap<K, V> implements ImmutableMap<K, V>
  {
      /** */
      private static final long serialVersionUID = 20160507L;
  
      /** the map that is wrapped, without giving access to methods that can change it. */
      private final Map<K, V> map;
  
      /** COPY stores a safe, internal copy of the collection; WRAP stores a pointer to the original collection. */
      protected final Immutable copyOrWrap;
  
      /** the cached values. */
      protected ImmutableCollection<V> cachedValues = null;
  
      /**
       * Construct an abstract immutable map. Make sure that the argument is a safe copy of the map of the right type! Copying
       * does not take place in the Abstract class!
       * @param map Map&lt;K,V&gt;; a safe copy of the map to use for the immutable map
       * @param copyOrWrap Immutable; indicate whether the immutable is a copy or a wrap
       */
      protected ImmutableAbstractMap(final Map<K, V> map, final Immutable copyOrWrap)
      {
          Throw.whenNull(copyOrWrap, "the copyOrWrap argument should be Immutable.COPY or Immutable.WRAP");
          this.copyOrWrap = copyOrWrap;
          Throw.whenNull(map, "the map argument cannot be null");
          this.map = map;
      }
  
      /**
       * Prepare the map of the right type for use a subclass. Implement e.g. as follows:
       * 
       * <pre>
       * {@literal @}Override
       * protected HashMap&lt;E&gt; getMap()
       * {
       *     return (HashMap&lt;E&gt;) super.getMap();
       * }
       * </pre>
       * 
       * @return the map of the right type for use a subclass
       */
      @SuppressWarnings("checkstyle:designforextension")
      protected Map<K, V> getMap()
      {
          return this.map;
      }
  
      /** {@inheritDoc} */
      @Override
      public final int size()
      {
          return this.map.size();
      }
  
      /** {@inheritDoc} */
      @Override
      public final boolean isEmpty()
      {
          return this.map.isEmpty();
      }
  
      /** {@inheritDoc} */
      @Override
      public final boolean containsKey(final Object key)
      {
          return this.map.containsKey(key);
      }
  
      /** {@inheritDoc} */
      @Override
      public final boolean containsValue(final Object value)
      {
          return this.map.containsValue(value);
      }
  
      /** {@inheritDoc} */
      @Override
     public final V get(final Object key)
     {
         return this.map.get(key);
     }
 
     /** {@inheritDoc} */
     @Override
     public ImmutableCollection<V> values()
     {
         if (this.cachedValues == null)
         {
             Set<V> immutableValues = new HashSet<>(getMap().values());
             this.cachedValues = new ImmutableHashSet<>(immutableValues, Immutable.WRAP);
         }
         return this.cachedValues;
     }
 
     /** {@inheritDoc} */
     @Override
     public final boolean isWrap()
     {
         return this.copyOrWrap.isWrap();
     }
 
     /** {@inheritDoc} */
     @Override
     @SuppressWarnings("checkstyle:designforextension")
     public int hashCode()
     {
         final int prime = 31;
         int result = 1;
         result = prime * result + ((this.map == null) ? 0 : this.map.hashCode());
         return result;
     }
 
     /** {@inheritDoc} */
     @Override
     @SuppressWarnings({"checkstyle:designforextension", "checkstyle:needbraces"})
     public boolean equals(final Object obj)
     {
         if (this == obj)
             return true;
         if (obj == null)
             return false;
         if (getClass() != obj.getClass())
             return false;
         ImmutableAbstractMap<?, ?> other = (ImmutableAbstractMap<?, ?>) obj;
         if (this.map == null)
         {
             if (other.map != null)
                 return false;
         }
         else if (!this.map.equals(other.map))
             return false;
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     @SuppressWarnings("checkstyle:designforextension")
     public String toString()
     {
         return "Immutable[" + this.map.toString() + "]";
     }
 }