/*
    *   Licensed to the Apache Software Foundation (ASF) under one
    *   or more contributor license agreements.  See the NOTICE file
    *   distributed with this work for additional information
    *   regarding copyright ownership.  The ASF licenses this file
    *   to you under the Apache License, Version 2.0 (the
    *   "License"); you may not use this file except in compliance
    *   with the License.  You may obtain a copy of the License at
    *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   *   Unless required by applicable law or agreed to in writing,
   *   software distributed under the License is distributed on an
   *   "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   *   KIND, either express or implied.  See the License for the
   *   specific language governing permissions and limitations
   *   under the License.
   *
   */
  package org.apache.directory.server.core.avltree;
  
  
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.List;
  
  import org.apache.directory.server.i18n.I18n;
  
  
  /**
   * An immutable AvlTree wrapping a singleton.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class AvlTreeSingleton<K> implements AvlTree<K>
  {
      private final LinkedAvlNode<K> singleton;
      private final Comparator<K> comparator;
  
  
      public AvlTreeSingleton( K key, Comparator<K> comparator )
      {
          this.singleton = new LinkedAvlNode<>( key );
          this.comparator = comparator;
      }
  
  
      /**
       * {@inheritDoc}
       */
      public LinkedAvlNode<K> find( K key )
      {
          if ( key != null && comparator.compare( key, singleton.key ) == 0 )
          {
              return singleton;
          }
  
          return null;
      }
  
  
      /**
       * {@inheritDoc}
       */
      public LinkedAvlNode<K> findGreater( K key )
      {
          if ( key != null && comparator.compare( key, singleton.key ) < 0 )
          {
              return singleton;
          }
  
          return null;
      }
  
  
      /**
       * {@inheritDoc}
       */
      public LinkedAvlNode<K> findGreaterOrEqual( K key )
      {
          if ( key != null && comparator.compare( key, singleton.key ) <= 0 )
          {
              return singleton;
          }
  
          return null;
      }
  
  
      /**
       * {@inheritDoc}
       */
      public LinkedAvlNode<K> findLess( K key )
      {
          if ( key != null && comparator.compare( key, singleton.key ) > 0 )
          {
              return singleton;
          }
  
         return null;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public LinkedAvlNode<K> findLessOrEqual( K key )
     {
         if ( key != null && comparator.compare( key, singleton.key ) >= 0 )
         {
             return singleton;
         }
 
         return null;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public Comparator<K> getComparator()
     {
         return comparator;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public LinkedAvlNode<K> getFirst()
     {
         return singleton;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public List<K> getKeys()
     {
         return Collections.singletonList( singleton.getKey() );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public LinkedAvlNode<K> getLast()
     {
         return singleton;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public LinkedAvlNode<K> getRoot()
     {
         return singleton;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public int getSize()
     {
         return 1;
     }
 
 
     public K insert( K key )
     {
         throw new UnsupportedOperationException( I18n.err( I18n.ERR_444 ) );
     }
 
 
     public boolean isEmpty()
     {
         return false;
     }
 
 
     public void printTree()
     {
         System.out.println( "[ " + singleton + " ]" );
     }
 
 
     public K remove( K key )
     {
         throw new UnsupportedOperationException( I18n.err( I18n.ERR_444 ) );
     }
 }