/*
    *  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.api.ldap.codec.controls.search.entryChange;
  
  
  import java.nio.ByteBuffer;
  
  import org.apache.directory.api.asn1.Asn1Object;
  import org.apache.directory.api.asn1.DecoderException;
  import org.apache.directory.api.asn1.EncoderException;
  import org.apache.directory.api.asn1.ber.Asn1Decoder;
  import org.apache.directory.api.asn1.ber.tlv.BerValue;
  import org.apache.directory.api.asn1.ber.tlv.TLV;
  import org.apache.directory.api.asn1.ber.tlv.UniversalTag;
  import org.apache.directory.api.i18n.I18n;
  import org.apache.directory.api.ldap.codec.api.ControlDecorator;
  import org.apache.directory.api.ldap.codec.api.LdapApiService;
  import org.apache.directory.api.ldap.model.message.controls.ChangeType;
  import org.apache.directory.api.ldap.model.message.controls.EntryChange;
  import org.apache.directory.api.ldap.model.message.controls.EntryChangeImpl;
  import org.apache.directory.api.ldap.model.name.Dn;
  import org.apache.directory.api.util.Strings;
  
  
  /**
   * An EntryChange implementation, that wraps and decorates the Control with codec
   * specific functionality.
   *
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class EntryChangeDecorator extends ControlDecorator<EntryChange> implements EntryChange
  {
  
      public static final int UNDEFINED_CHANGE_NUMBER = -1;
  
      /** A temporary storage for the previous Dn */
      private byte[] previousDnBytes = null;
  
      /** The entry change global length */
      private int eccSeqLength;
  
      /** An instance of this decoder */
      private static final Asn1Decoder decoder = new Asn1Decoder();
  
  
      /**
       * Creates a new instance of EntryChangeDecoder wrapping a newly created
       * EntryChange Control object.
       */
      public EntryChangeDecorator( LdapApiService codec )
      {
          super( codec, new EntryChangeImpl() );
      }
  
  
      /**
       * Creates a new instance of EntryChangeDecorator wrapping the supplied
       * EntryChange Control.
       *
       * @param control The EntryChange Control to be decorated.
       */
      public EntryChangeDecorator( LdapApiService codec, EntryChange control )
      {
          super( codec, control );
      }
  
  
      /**
       * Internally used to not have to cast the decorated Control.
       *
       * @return the decorated Control.
       */
      private EntryChange getEntryChange()
      {
          return ( EntryChange ) getDecorated();
      }
  
  
      /**
       * Compute the EntryChangeControl length 
       * 
      * 0x30 L1 
      *   | 
      *   +--> 0x0A 0x0(1-4) [1|2|4|8] (changeType) 
      *  [+--> 0x04 L2 previousDN] 
      *  [+--> 0x02 0x0(1-4) [0..2^63-1] (changeNumber)]
      */
     public int computeLength()
     {
         int changeTypesLength = 1 + 1 + 1;
 
         int previousDnLength = 0;
         int changeNumberLength = 0;
 
         if ( getPreviousDn() != null )
         {
             previousDnBytes = Strings.getBytesUtf8( getPreviousDn().getName() );
             previousDnLength = 1 + TLV.getNbBytes( previousDnBytes.length ) + previousDnBytes.length;
         }
 
         if ( getChangeNumber() != UNDEFINED_CHANGE_NUMBER )
         {
             changeNumberLength = 1 + 1 + BerValue.getNbBytes( getChangeNumber() );
         }
 
         eccSeqLength = changeTypesLength + previousDnLength + changeNumberLength;
         valueLength = 1 + TLV.getNbBytes( eccSeqLength ) + eccSeqLength;
 
         return valueLength;
     }
 
 
     /**
      * Encodes the entry change control.
      * 
      * @param buffer The encoded sink
      * @return A ByteBuffer that contains the encoded PDU
      * @throws EncoderException If anything goes wrong.
      */
     public ByteBuffer encode( ByteBuffer buffer ) throws EncoderException
     {
         if ( buffer == null )
         {
             throw new EncoderException( I18n.err( I18n.ERR_04023 ) );
         }
 
         buffer.put( UniversalTag.SEQUENCE.getValue() );
         buffer.put( TLV.getBytes( eccSeqLength ) );
 
         buffer.put( UniversalTag.ENUMERATED.getValue() );
         buffer.put( ( byte ) 1 );
         buffer.put( BerValue.getBytes( getChangeType().getValue() ) );
 
         if ( getPreviousDn() != null )
         {
             BerValue.encode( buffer, previousDnBytes );
         }
 
         if ( getChangeNumber() != UNDEFINED_CHANGE_NUMBER )
         {
             BerValue.encode( buffer, getChangeNumber() );
         }
 
         return buffer;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public byte[] getValue()
     {
         if ( value == null )
         {
             try
             {
                 computeLength();
                 ByteBuffer buffer = ByteBuffer.allocate( valueLength );
 
                 buffer.put( UniversalTag.SEQUENCE.getValue() );
                 buffer.put( TLV.getBytes( eccSeqLength ) );
 
                 buffer.put( UniversalTag.ENUMERATED.getValue() );
                 buffer.put( ( byte ) 1 );
                 buffer.put( BerValue.getBytes( getChangeType().getValue() ) );
 
                 if ( getPreviousDn() != null )
                 {
                     BerValue.encode( buffer, previousDnBytes );
                 }
 
                 if ( getChangeNumber() != UNDEFINED_CHANGE_NUMBER )
                 {
                     BerValue.encode( buffer, getChangeNumber() );
                 }
 
                 value = buffer.array();
             }
             catch ( Exception e )
             {
                 return null;
             }
         }
 
         return value;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public ChangeType getChangeType()
     {
         return getEntryChange().getChangeType();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void setChangeType( ChangeType changeType )
     {
         getEntryChange().setChangeType( changeType );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public Dn getPreviousDn()
     {
         return getEntryChange().getPreviousDn();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void setPreviousDn( Dn previousDn )
     {
         getEntryChange().setPreviousDn( previousDn );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public long getChangeNumber()
     {
         return getEntryChange().getChangeNumber();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void setChangeNumber( long changeNumber )
     {
         getEntryChange().setChangeNumber( changeNumber );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public Asn1Object decode( byte[] controlBytes ) throws DecoderException
     {
         ByteBuffer bb = ByteBuffer.wrap( controlBytes );
         EntryChangeContainer container = new EntryChangeContainer( getCodecService(), this );
         decoder.decode( bb, container );
         return this;
     }
 }