/*
    *  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.xdbm.search.cursor;
  
  
  import java.io.IOException;
  
  import org.apache.directory.api.ldap.model.constants.Loggers;
  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.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.i18n.I18n;
  import org.apache.directory.server.xdbm.AbstractIndexCursor;
  import org.apache.directory.server.xdbm.IndexEntry;
  import org.apache.directory.server.xdbm.Store;
  import org.apache.directory.server.xdbm.search.Evaluator;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * A Cursor returning candidates satisfying a logical negation expression.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class NotCursor<V> extends AbstractIndexCursor<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 static final String UNSUPPORTED_MSG = I18n.err( I18n.ERR_718 );
      private final AllEntriesCursor uuidCursor;
      private final Evaluator<? extends ExprNode> childEvaluator;
  
  
      /**
       * Creates a new instance of an NotCursor
       * 
       * @param partitionTxn The transaction to use
       * @param store The store
       * @param childEvaluator The inner evaluator
       * @throws LdapException If the creation failed
       */
      public NotCursor( PartitionTxn partitionTxn, Store store, Evaluator<? extends ExprNode> childEvaluator ) 
              throws LdapException
      {
          if ( IS_DEBUG )
          {
              LOG_CURSOR.debug( "Creating NotCursor {}", this );
          }
  
          this.childEvaluator = childEvaluator;
          this.partitionTxn = partitionTxn;
          this.uuidCursor = new AllEntriesCursor( partitionTxn, store );
  
      }
  
  
      /**
       * {@inheritDoc}
       */
      protected String getUnsupportedMessage()
      {
          return UNSUPPORTED_MSG;
      }
  
  
      /**
       * {@inheritDoc}
       */
      public void beforeFirst() throws LdapException, CursorException
      {
          checkNotClosed();
          uuidCursor.beforeFirst();
          setAvailable( false );
      }
  
 
     /**
      * {@inheritDoc}
      */
     public void afterLast() throws LdapException, CursorException
     {
         checkNotClosed();
         uuidCursor.afterLast();
         setAvailable( false );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean first() throws LdapException, CursorException
     {
         beforeFirst();
 
         return next();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean last() throws LdapException, CursorException
     {
         afterLast();
 
         return previous();
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean previous() throws LdapException, CursorException
     {
         while ( uuidCursor.previous() )
         {
             checkNotClosed();
             IndexEntry<?, String> candidate = uuidCursor.get();
 
             if ( !childEvaluator.evaluate( partitionTxn, candidate ) )
             {
                 return setAvailable( true );
             }
         }
 
         return setAvailable( false );
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean next() throws LdapException, CursorException
     {
         while ( uuidCursor.next() )
         {
             checkNotClosed();
             IndexEntry<?, String> candidate = uuidCursor.get();
 
             if ( !childEvaluator.evaluate( partitionTxn, candidate ) )
             {
                 return setAvailable( true );
             }
         }
 
         return setAvailable( false );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public IndexEntry<V, String> get() throws CursorException
     {
         checkNotClosed();
 
         if ( available() )
         {
             return ( IndexEntry<V, String> ) uuidCursor.get();
         }
 
         throw new InvalidCursorPositionException( I18n.err( I18n.ERR_708 ) );
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close() throws IOException
     {
         if ( IS_DEBUG )
         {
             LOG_CURSOR.debug( "Closing NotCursor {}", this );
         }
 
         super.close();
         uuidCursor.close();
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close( Exception cause ) throws IOException
     {
         if ( IS_DEBUG )
         {
             LOG_CURSOR.debug( "Closing NotCursor {}", this );
         }
 
         super.close( cause );
         uuidCursor.close( cause );
     }
 
 
     /**
      * @see Object#toString()
      */
     @Override
     public String toString( String tabs )
     {
         StringBuilder sb = new StringBuilder();
 
         sb.append( tabs ).append( "NotCursor (" );
 
         if ( available() )
         {
             sb.append( "available)" );
         }
         else
         {
             sb.append( "absent)" );
         }
 
         sb.append( tabs + "  >>" ).append( childEvaluator ).append( '\n' );
 
         sb.append( uuidCursor.toString( tabs + "    " ) );
 
         return sb.toString();
     }
 
 
     /**
      * @see Object#toString()
      */
     public String toString()
     {
         return "";
     }
 }