/*
    * 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.io.IOException;
  
  import org.apache.directory.api.ldap.model.constants.Loggers;
  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.cursor.InvalidCursorPositionException;
  import org.apache.directory.api.ldap.model.cursor.Tuple;
  import org.apache.directory.api.ldap.model.exception.LdapException;
  import org.apache.directory.server.i18n.I18n;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * Cursor over a set of values for the same key which are store in an in
   * memory AvlTree.  This Cursor is limited to the same key and it's tuples
   * will always return the same key.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class KeyTupleAvlCursor<K, V> extends AbstractCursor<Tuple<K, V>>
  {
      /** A dedicated log for cursors */
      private static final Logger LOG_CURSOR = LoggerFactory.getLogger( Loggers.CURSOR_LOG.getName() );
  
      /** Speedup for logs */
      private static final boolean IS_DEBUG = LOG_CURSOR.isDebugEnabled();
  
      private final AvlTreeCursor<V> wrapped;
      private final K key;
  
      private Tuple<K, V> returnedTuple = new Tuple<>();
      private boolean valueAvailable;
  
  
      /**
       * Creates a Cursor over the tuples of an AvlTree.
       *
       * @param avlTree the AvlTree to build a Tuple returning Cursor over
       * @param key the constant key for which values are returned
       */
      public KeyTupleAvlCursor( AvlTree<V> avlTree, K key )
      {
          if ( IS_DEBUG )
          {
              LOG_CURSOR.debug( "Creating KeyTupleAvlCursor {}", this );
          }
  
          this.key = key;
          this.wrapped = new AvlTreeCursor<>( avlTree );
      }
  
  
      private void clearValue()
      {
          returnedTuple.setKey( key );
          returnedTuple.setValue( null );
          valueAvailable = false;
      }
  
  
      public boolean available()
      {
          return valueAvailable;
      }
  
  
      public void beforeKey( K key ) throws Exception
      {
          throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
      }
  
  
      public void afterKey( K key ) throws Exception
      {
          throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
      }
  
 
     public void beforeValue( K key, V value ) throws Exception
     {
         checkNotClosed();
         if ( key != null && !key.equals( this.key ) )
         {
             throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
         }
 
         wrapped.before( value );
         clearValue();
     }
 
 
     public void afterValue( K key, V value ) throws Exception
     {
         checkNotClosed();
         if ( key != null && !key.equals( this.key ) )
         {
             throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
         }
 
         wrapped.after( value );
         clearValue();
     }
 
 
     /**
      * Positions this Cursor over the same keys before the value of the
      * supplied element Tuple.  The supplied element Tuple's key is not
      * considered at all.
      *
      * @param element the valueTuple who's value is used to position this Cursor
      * @throws CursorException if there are failures to position the Cursor
      * @throws LdapException if there are failures to position the Cursor
      */
     public void before( Tuple<K, V> element ) throws CursorException, LdapException
     {
         checkNotClosed();
         wrapped.before( element.getValue() );
         clearValue();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void after( Tuple<K, V> element ) throws LdapException, CursorException
     {
         checkNotClosed();
         wrapped.after( element.getValue() );
         clearValue();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void beforeFirst() throws LdapException, CursorException
     {
         checkNotClosed();
         wrapped.beforeFirst();
         clearValue();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void afterLast() throws LdapException, CursorException
     {
         checkNotClosed();
         wrapped.afterLast();
         clearValue();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean first() throws LdapException, CursorException
     {
         beforeFirst();
         return next();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean last() throws LdapException, CursorException
     {
         afterLast();
         return previous();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean previous() throws LdapException, CursorException
     {
         checkNotClosed();
         if ( wrapped.previous() )
         {
             returnedTuple.setKey( key );
             returnedTuple.setValue( wrapped.get() );
             valueAvailable = true;
             return true;
         }
         else
         {
             clearValue();
             return false;
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean next() throws LdapException, CursorException
     {
         checkNotClosed();
 
         if ( wrapped.next() )
         {
             returnedTuple.setKey( key );
             returnedTuple.setValue( wrapped.get() );
             valueAvailable = true;
             return true;
         }
         else
         {
             clearValue();
             return false;
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     public Tuple<K, V> get() throws CursorException
     {
         checkNotClosed();
         if ( valueAvailable )
         {
             return returnedTuple;
         }
 
         throw new InvalidCursorPositionException();
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close() throws IOException
     {
         if ( IS_DEBUG )
         {
             LOG_CURSOR.debug( "Closing KeyTupleAvlCursor {}", this );
         }
 
         super.close();
 
         if ( wrapped != null )
         {
             wrapped.close();
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close( Exception cause ) throws IOException
     {
         if ( IS_DEBUG )
         {
             LOG_CURSOR.debug( "Closing KeyTupleAvlCursor {}", this );
         }
 
         super.close( cause );
 
         if ( wrapped != null )
         {
             wrapped.close( cause );
         }
     }
 }