/*
    *  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.Cursor;
  import org.apache.directory.api.ldap.model.cursor.CursorException;
  import org.apache.directory.api.ldap.model.exception.LdapException;
  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.ParentIdAndRdn;
  import org.apache.directory.server.xdbm.Store;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * A Cursor over entries satisfying one level scope constraints with alias
   * dereferencing considerations when enabled during search.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class ChildrenCursor extends AbstractIndexCursor<String>
  {
      /** 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();
  
      /** Error message for unsupported operations */
      private static final String UNSUPPORTED_MSG = I18n.err( I18n.ERR_719 );
  
      /** A Cursor over the entries in the scope of the search base */
      private final Cursor<IndexEntry<ParentIdAndRdn, String>> cursor;
  
      /** The Parent ID */
      private String parentId;
  
      /** The prefetched element */
      private IndexEntry<String, String> prefetched;
  
  
      /**
       * Creates a Cursor over entries satisfying one level scope criteria.
       *
       * @param partitionTxn The transaction to use
       * @param db the entry store
       * @param parentId The parent ID
       * @param cursor The wrapped cursor
       */
      public ChildrenCursor( PartitionTxn partitionTxn, Store db, String parentId, 
              Cursor<IndexEntry<ParentIdAndRdn, String>> cursor )
      {
          this.parentId = parentId;
          this.cursor = cursor;
          this.partitionTxn = partitionTxn;
  
          if ( IS_DEBUG )
          {
              LOG_CURSOR.debug( "Creating ChildrenCursor {}", this );
          }
      }
  
  
      /**
       * {@inheritDoc}
       */
      protected String getUnsupportedMessage()
      {
          return UNSUPPORTED_MSG;
      }
  
  
      /**
       * {@inheritDoc}
       */
     public void beforeFirst() throws LdapException, CursorException
     {
         checkNotClosed();
         setAvailable( false );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void afterLast() throws LdapException, CursorException
     {
         throw new UnsupportedOperationException( getUnsupportedMessage() );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean first() throws LdapException, CursorException
     {
         beforeFirst();
 
         return next();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean last() throws LdapException, CursorException
     {
         throw new UnsupportedOperationException( getUnsupportedMessage() );
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean previous() throws LdapException, CursorException
     {
         checkNotClosed();
 
         boolean hasPrevious = cursor.previous();
 
         if ( hasPrevious )
         {
             IndexEntry entry = cursor.get();
 
             if ( ( ( ParentIdAndRdn ) entry.getTuple().getKey() ).getParentId().equals( parentId ) )
             {
                 prefetched = entry;
                 return true;
             }
         }
 
         return false;
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean next() throws LdapException, CursorException
     {
         checkNotClosed();
 
         boolean hasNext = cursor.next();
 
         if ( hasNext )
         {
             IndexEntry cursorEntry = cursor.get();
             IndexEntry<String, String> entry = new IndexEntry();
             entry.setId( ( String ) cursorEntry.getId() );
             entry.setKey( ( ( ParentIdAndRdn ) cursorEntry.getTuple().getKey() ).getParentId() );
 
             if ( entry.getKey().equals( parentId ) )
             {
                 prefetched = entry;
                 return true;
             }
         }
 
         return false;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public IndexEntry<String, String> get() throws CursorException
     {
         checkNotClosed();
 
         return prefetched;
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close() throws IOException
     {
         if ( IS_DEBUG )
         {
             LOG_CURSOR.debug( "Closing ChildrenCursor {}", this );
         }
 
         cursor.close();
 
         super.close();
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close( Exception cause ) throws IOException
     {
         if ( IS_DEBUG )
         {
             LOG_CURSOR.debug( "Closing ChildrenCursor {}", this );
         }
 
         cursor.close( cause );
 
         super.close( cause );
     }
 
 
     /**
      * @see Object#toString()
      */
     @Override
     public String toString( String tabs )
     {
         StringBuilder sb = new StringBuilder();
 
         sb.append( tabs ).append( "ChildrenCursor (" );
 
         if ( available() )
         {
             sb.append( "available)" );
         }
         else
         {
             sb.append( "absent)" );
         }
 
         sb.append( "#parent<" ).append( parentId ).append( "> :\n" );
 
         sb.append( cursor.toString( tabs + "  " ) );
 
         return sb.toString();
     }
 
 
     /**
      * @see Object#toString()
      */
     public String toString()
     {
         return toString( "" );
     }
 }