/*
    *   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;
  
  
  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.ClosureMonitor;
  import org.apache.directory.api.ldap.model.cursor.Cursor;
  import org.apache.directory.api.ldap.model.cursor.CursorException;
  import org.apache.directory.api.ldap.model.entry.Entry;
  import org.apache.directory.api.ldap.model.exception.LdapException;
  import org.apache.directory.api.ldap.model.filter.ExprNode;
  import org.apache.directory.server.core.api.partition.PartitionTxn;
  import org.apache.directory.server.xdbm.IndexEntry;
  import org.apache.directory.server.xdbm.search.Evaluator;
  import org.apache.directory.server.xdbm.search.PartitionSearchResult;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * Adapts index cursors to return just Entry objects.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class EntryCursorAdaptor extends AbstractCursor<Entry>
  {
      /** 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();
      
      /** The transaction in use */
      private PartitionTxn partitionTxn;
  
      private final Cursor<IndexEntry<String, String>> indexCursor;
      private final Evaluator<? extends ExprNode> evaluator;
  
  
      public EntryCursorAdaptor( PartitionTxn partitionTxn, AbstractBTreePartition db, PartitionSearchResult searchResult )
      {
          if ( IS_DEBUG )
          {
              LOG_CURSOR.debug( "Creating EntryCursorAdaptor {}", this );
          }
  
          indexCursor = searchResult.getResultSet();
          evaluator = searchResult.getEvaluator();
          this.partitionTxn = partitionTxn;
      }
  
  
      /**
       * {@inheritDoc}
       */
      public void after( Entry element ) throws LdapException, CursorException
      {
          throw new UnsupportedOperationException();
      }
  
  
      /**
       * {@inheritDoc}
       */
      public void afterLast() throws LdapException, CursorException
      {
          this.indexCursor.afterLast();
      }
  
  
      /**
       * {@inheritDoc}
       */
      public boolean available()
      {
          return indexCursor.available();
      }
  
 
     /**
      * {@inheritDoc}
      */
     public void before( Entry element ) throws LdapException, CursorException
     {
         throw new UnsupportedOperationException();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void beforeFirst() throws LdapException, CursorException
     {
         indexCursor.beforeFirst();
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public final void setClosureMonitor( ClosureMonitor monitor )
     {
         indexCursor.setClosureMonitor( monitor );
     }
 
 
     /**
      * {@inheritDoc}}
      */
     @Override
     public void close() throws IOException
     {
         if ( IS_DEBUG )
         {
             LOG_CURSOR.debug( "Closing EntryCursorAdaptor {}", this );
         }
 
         indexCursor.close();
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close( Exception cause ) throws IOException
     {
         if ( IS_DEBUG )
         {
             LOG_CURSOR.debug( "Closing EntryCursorAdaptor {}", this );
         }
 
         indexCursor.close( cause );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean first() throws LdapException, CursorException
     {
         return indexCursor.first();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public Entry get() throws CursorException
     {
         IndexEntry<String, String> indexEntry = indexCursor.get();
 
         try
         {
             if ( evaluator.evaluate( partitionTxn, indexEntry ) )
             {
                 Entry entry = indexEntry.getEntry();
                 indexEntry.setEntry( null );
 
                 return entry;
             }
             else
             {
                 indexEntry.setEntry( null );
             }
 
             return null;
         }
         catch ( Exception e )
         {
             throw new CursorException( e.getMessage(), e );
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean isClosed()
     {
         return indexCursor.isClosed();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean last() throws LdapException, CursorException
     {
         return indexCursor.last();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean next() throws LdapException, CursorException
     {
         return indexCursor.next();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean previous() throws LdapException, CursorException
     {
         return indexCursor.previous();
     }
 
 
     /**
      * @see Object#toString()
      */
     @Override
     public String toString( String tabs )
     {
         StringBuilder sb = new StringBuilder();
 
         sb.append( tabs ).append( "EntryCursorAdaptor\n" );
 
         if ( indexCursor != null )
         {
             sb.append( tabs ).append( "    " ).append( "IndexCursor : \n" );
             sb.append( indexCursor.toString( tabs + "        " ) );
         }
 
         if ( evaluator != null )
         {
             sb.append( tabs ).append( "    " ).append( "Evaluator : \n" );
             sb.append( evaluator.toString( tabs + "        " ) );
         }
 
         return sb.toString();
     }
 
 
     /**
      * @see Object#toString()
      */
     public String toString()
     {
         return toString( "" );
     }
 }