/*
    *  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.jdbm;
  
  
  import java.io.IOException;
  
  import jdbm.btree.BTree;
  import jdbm.helper.TupleBrowser;
  
  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;
  
  
  /**
   * A cursor for browsing tables with duplicates which returns the container
   * for values rather than just the value.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   * @param K The Key
   * @param V The associated value
   */
  public class DupsContainerCursor<K, V> extends AbstractCursor<Tuple<K, DupsContainer<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();
  
      /** The JDBM table we are building a cursor over */
      private final JdbmTable<K, V> table;
  
      /** A container to pass to the underlying JDBM to get back a tuple */
      private jdbm.helper.Tuple<K, V> jdbmTuple = new jdbm.helper.Tuple<>();
  
      private Tuple<K, DupsContainer<V>> returnedTuple = new Tuple<>();
  
      /** A browser over the JDBM Table */
      private TupleBrowser<K, V> browser;
  
      /** Tells if we have a tuple to return */
      private boolean valueAvailable;
  
      /** TODO : do we need this flag ??? */
      private Boolean forwardDirection;
  
  
      /**
       * Creates a Cursor over the tuples of a JDBM table.
       *
       * @param table the JDBM Table to build a Cursor over
       */
      public DupsContainerCursor( JdbmTable<K, V> table )
      {
          if ( IS_DEBUG )
          {
              LOG_CURSOR.debug( "Creating DupsContainerCursor {}", this );
          }
  
          if ( !table.isDupsEnabled() )
          {
              throw new IllegalStateException( I18n.err( I18n.ERR_572 ) );
          }
  
          this.table = table;
      }
  
  
      /**
       * Clean the tuples we use to store the returned resut.
       */
      private void clearValue()
      {
          returnedTuple.setKey( null );
         returnedTuple.setValue( null );
         jdbmTuple.setKey( null );
         jdbmTuple.setValue( null );
         valueAvailable = false;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean available()
     {
         return valueAvailable;
     }
 
 
     /**
      * {@inheritDoc}
      */
     @SuppressWarnings("unchecked")
     public void beforeKey( K key ) throws CursorException
     {
         checkNotClosed();
         try
         {
             browser = ( ( BTree<K, V> ) table.getBTree() ).browse( key );
             forwardDirection = null;
             clearValue();
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     @SuppressWarnings("unchecked")
     public void afterKey( K key ) throws CursorException
     {
         checkNotClosed();
 
         try
         {
             browser = ( ( BTree<K, V> ) table.getBTree() ).browse( key );
             forwardDirection = null;
 
             /*
              * While the next value is less than or equal to the element keep
              * advancing forward to the next item.  If we cannot advance any
              * further then stop and return.  If we find a value greater than
              * the element then we stop, backup, and return so subsequent calls
              * to getNext() will return a value greater than the element.
              */
             while ( browser.getNext( jdbmTuple ) )
             {
                 checkNotClosed();
                 K next = jdbmTuple.getKey();
 
                 int nextCompared = table.getKeyComparator().compare( next, key );
 
                 if ( nextCompared > 0 )
                 {
                     browser.getPrevious( jdbmTuple );
 
                     // switch in direction bug workaround: when a JDBM browser
                     // switches direction with next then previous as is occurring
                     // here then two previous moves are needed.
                     browser.getPrevious( jdbmTuple );
                     forwardDirection = false;
                     clearValue();
 
                     return;
                 }
             }
 
             clearValue();
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void beforeValue( K key, DupsContainer<V> value ) throws Exception
     {
         throw new UnsupportedOperationException( I18n.err( I18n.ERR_573 ) );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void afterValue( K key, DupsContainer<V> value ) throws Exception
     {
         throw new UnsupportedOperationException( I18n.err( I18n.ERR_573 ) );
     }
 
 
     /**
      * Positions this Cursor before the key of the supplied tuple.
      *
      * @param element the tuple who's key is used to position this Cursor
      * @throws LdapException if there are failures to position the Cursor
      * @throws CursorException if there are failures to position the Cursor
      */
     public void before( Tuple<K, DupsContainer<V>> element ) throws LdapException, CursorException
     {
         beforeKey( element.getKey() );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void after( Tuple<K, DupsContainer<V>> element ) throws CursorException
     {
         afterKey( element.getKey() );
     }
 
 
     /**
      * {@inheritDoc}
      */
     @SuppressWarnings("unchecked")
     public void beforeFirst() throws LdapException, CursorException
     {
         checkNotClosed();
         try
         {
             browser = table.getBTree().browse();
             forwardDirection = null;
             clearValue();
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     @SuppressWarnings("unchecked")
     public void afterLast() throws LdapException, CursorException
     {
         checkNotClosed();
         try
         {
             browser = table.getBTree().browse( null );
             forwardDirection = null;
             clearValue();
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
     }
 
 
     /**
      * {@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 ( browser == null )
         {
             afterLast();
         }
 
         try
         {
             boolean advanceSuccess = browser.getPrevious( jdbmTuple );
 
             // only want to set this if the advance is a success which means we
             // are not at front
             if ( forwardDirection == null )
             {
                 if ( advanceSuccess )
                 {
                     forwardDirection = false;
                 }
                 else
                 {
                     clearValue();
 
                     return false;
                 }
             }
             else if ( forwardDirection )
             {
                 advanceSuccess = browser.getPrevious( jdbmTuple );
                 forwardDirection = false;
             }
 
             valueAvailable = advanceSuccess;
 
             if ( valueAvailable )
             {
                 returnedTuple.setKey( jdbmTuple.getKey() );
                 returnedTuple.setValue( table.getDupsContainer( ( byte[] ) jdbmTuple.getValue() ) );
             }
             else
             {
                 clearValue();
             }
 
             return valueAvailable;
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean next() throws LdapException, CursorException
     {
         checkNotClosed();
 
         if ( browser == null )
         {
             // The tuple browser is not initialized : set it to the beginning of the cursor
             beforeFirst();
         }
 
         try
         {
             // Check if we can move forward and grab a tuple
             boolean advanceSuccess = browser.getNext( jdbmTuple );
 
             // only want to set this if the advance is a success which means
             // we are not at end
             if ( forwardDirection == null )
             {
                 if ( advanceSuccess )
                 {
                     forwardDirection = true;
                 }
                 else
                 {
                     clearValue();
 
                     // No value available
                     return false;
                 }
             }
 
             if ( !forwardDirection )
             {
                 advanceSuccess = browser.getNext( jdbmTuple );
                 forwardDirection = true;
             }
 
             valueAvailable = advanceSuccess;
 
             if ( valueAvailable )
             {
                 // create the fetched tuple containing the key and the deserialized value
                 returnedTuple.setKey( jdbmTuple.getKey() );
                 returnedTuple.setValue( table.getDupsContainer( ( byte[] ) jdbmTuple.getValue() ) );
             }
             else
             {
                 clearValue();
             }
 
             return valueAvailable;
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     public Tuple<K, DupsContainer<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 DupsContainerCursor {}", this );
         }
 
         super.close();
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close( Exception cause ) throws IOException
     {
         if ( IS_DEBUG )
         {
             LOG_CURSOR.debug( "Closing DupsContainerCursor {}", this );
         }
 
         super.close( cause );
     }
 }