/*
    *   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.partition.impl.btree.mavibot;
  
  
  import java.io.IOException;
  
  import org.apache.directory.api.ldap.model.cursor.AbstractCursor;
  import org.apache.directory.api.ldap.model.cursor.CursorException;
  import org.apache.directory.api.ldap.model.exception.LdapException;
  import org.apache.directory.mavibot.btree.ValueCursor;
  import org.apache.directory.server.i18n.I18n;
  
  
  /**
   * TODO ValueTreeCursor.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class ValueTreeCursor<V> extends AbstractCursor<V>
  {
  
      private ValueCursor<V> wrapped;
  
      private V available;
  
      // marker to detect the availability (cause Mavibot supports null values also)
      private V notAvailable = ( V ) new Object();
  
  
      public ValueTreeCursor( ValueCursor<V> cursor )
      {
          this.wrapped = cursor;
      }
  
  
      @Override
      public boolean available()
      {
          return ( available != notAvailable );
      }
  
  
      @Override
      public void before( V element ) throws LdapException, CursorException
      {
          throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
      }
  
  
      @Override
      public void after( V element ) throws LdapException, CursorException
      {
          throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
      }
  
  
      @Override
      public void beforeFirst() throws LdapException, CursorException
      {
      }
  
  
      @Override
      public void afterLast() throws LdapException, CursorException
      {
          throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
      }
  
  
      @Override
      public boolean first() throws LdapException, CursorException
      {
          throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
      }
  
  
      @Override
      public boolean last() throws LdapException, CursorException
      {
          throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
     }
 
 
     @Override
     public boolean previous() throws LdapException, CursorException
     {
         try
         {
             if ( wrapped.hasPrev() )
             {
                 available = wrapped.prev();
                 return true;
             }
             else
             {
                 available = notAvailable;
                 return false;
             }
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
     }
 
 
     @Override
     public boolean next() throws LdapException, CursorException
     {
         try
         {
             if ( wrapped.hasNext() )
             {
                 available = wrapped.next();
                 return true;
             }
             else
             {
                 available = notAvailable;
                 return false;
             }
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
     }
 
 
     @Override
     public V get() throws CursorException
     {
         return available;
     }
 
 }