/*
    *  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.shared.kerberos.components;
  
  
  import java.nio.BufferOverflowException;
  import java.nio.ByteBuffer;
  
  import org.apache.directory.api.asn1.Asn1Object;
  import org.apache.directory.api.asn1.EncoderException;
  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.util.Strings;
  import org.apache.directory.server.i18n.I18n;
  import org.apache.directory.shared.kerberos.KerberosConstants;
  import org.apache.directory.shared.kerberos.codec.types.EncryptionType;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * Provides encryption info information sent to the client.
   * 
   * The ASN.1 grammar for this structure is :
   * <pre>
   * ETYPE-INFO-ENTRY        ::= SEQUENCE {
   *            etype           [0] Int32,
   *            salt            [1] OCTET STRING OPTIONAL
   *    }
   * </pre>
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class ETypeInfoEntry implements Asn1Object
  {
      /** The logger */
      private static final Logger LOG = LoggerFactory.getLogger( ETypeInfoEntry.class );
  
      /** Speedup for logs */
      private static final boolean IS_DEBUG = LOG.isDebugEnabled();
  
      /** The encryption type */
      private EncryptionType etype;
  
      /** The salt */
      private byte[] salt;
  
      // Storage for computed lengths
      private int etypeTagLength;
      private int saltTagLength;
      private int etypeInfoEntrySeqLength;
  
  
      /**
       * Creates a new instance of ETypeInfoEntry.
       * 
       * @param etype the Encryption type
       * @param salt the salt
       */
      public ETypeInfoEntry( EncryptionType etype, byte[] salt )
      {
          this.etype = etype;
          this.salt = salt;
      }
  
  
      /**
       * Creates a new instance of ETypeInfoEntry.
       */
      public ETypeInfoEntry()
      {
      }
  
  
      /**
       * Returns the salt.
       *
       * @return The salt.
       */
      public byte[] getSalt()
      {
          return salt;
     }
 
 
     /**
      * @param salt the salt to set
      */
     public void setSalt( byte[] salt )
     {
         this.salt = salt;
     }
 
 
     /**
      * Returns the {@link EncryptionType}.
      *
      * @return The {@link EncryptionType}.
      */
     public EncryptionType getEType()
     {
         return etype;
     }
 
 
     /**
      * @param etype the encryptionType to set
      */
     public void setEType( EncryptionType etype )
     {
         this.etype = etype;
     }
 
 
     /**
      * Compute the ETYPE-INFO-ENTRY length
      * <pre>
      * ETYPE-INFO-ENTRY :
      * 
      * 0x30 L1 ETYPE-INFO-ENTRY sequence
      *  |
      *  +--&gt; 0xA0 L2 etype tag
      *  |     |
      *  |     +--&gt; 0x02 L2-1etype (int)
      *  |
      *  +--&gt; 0xA1 L3 salt tag
      *        |
      *        +--&gt; 0x04 L3-1 salt (OCTET STRING)
      *        
      *  where L1 = L2 + lenght(0xA0) + length(L2) +
      *             L3 + lenght(0xA1) + length(L3) 
      *  and
      *  L2 = L2-1 + length(0x02) + length( L2-1) 
      *  L3 = L3-1 + length(0x04) + length( L3-1) 
      *  </pre>
      */
     public int computeLength()
     {
         // Compute the etype. The Length will always be contained in 1 byte
         int etypeLength = BerValue.getNbBytes( etype.getValue() );
         etypeTagLength = 1 + TLV.getNbBytes( etypeLength ) + etypeLength;
         etypeInfoEntrySeqLength = 1 + TLV.getNbBytes( etypeTagLength ) + etypeTagLength;
 
         // Compute the salt
         if ( salt != null )
         {
             saltTagLength = 1 + TLV.getNbBytes( salt.length ) + salt.length;
             etypeInfoEntrySeqLength += 1 + TLV.getNbBytes( saltTagLength ) + saltTagLength;
         }
 
         return 1 + TLV.getNbBytes( etypeInfoEntrySeqLength ) + etypeInfoEntrySeqLength;
     }
 
 
     /**
      * Encode the ETYPE-INFO-ENTRY message to a PDU. 
      * <pre>
      * ETYPE-INFO-ENTRY :
      * 
      * 0x30 LL
      *   0xA1 LL 
      *     0x02 0x01 etype
      *   0xA2 LL 
      *     0x04 LL salt
      * </pre>
      * @param buffer The buffer where to put the PDU. It should have been allocated
      * before, with the right size.
      * @return The constructed PDU.
      */
     public ByteBuffer encode( ByteBuffer buffer ) throws EncoderException
     {
         if ( buffer == null )
         {
             throw new EncoderException( I18n.err( I18n.ERR_148 ) );
         }
 
         try
         {
             // The ETYPE-INFO-ENTRY SEQ Tag
             buffer.put( UniversalTag.SEQUENCE.getValue() );
             buffer.put( TLV.getBytes( etypeInfoEntrySeqLength ) );
 
             // The etype, first the tag, then the value
             buffer.put( ( byte ) KerberosConstants.ETYPE_INFO_ENTRY_ETYPE_TAG );
             buffer.put( TLV.getBytes( etypeTagLength ) );
             BerValue.encode( buffer, etype.getValue() );
 
             // The salt, first the tag, then the value, if salt is not null
             if ( salt != null )
             {
                 buffer.put( ( byte ) KerberosConstants.ETYPE_INFO_ENTRY_SALT_TAG );
                 buffer.put( TLV.getBytes( saltTagLength ) );
                 BerValue.encode( buffer, salt );
             }
         }
         catch ( BufferOverflowException boe )
         {
             LOG.error( I18n.err( I18n.ERR_145, 1 + TLV.getNbBytes( etypeInfoEntrySeqLength )
                 + etypeInfoEntrySeqLength, buffer.capacity() ) );
             throw new EncoderException( I18n.err( I18n.ERR_138 ), boe );
         }
 
         if ( IS_DEBUG )
         {
             LOG.debug( "ETYPE-INFO-ENTRY encoding : {}", Strings.dumpBytes( buffer.array() ) );
             LOG.debug( "ETYPE-INFO-ENTRY initial value : {}", this );
         }
 
         return buffer;
     }
 
 
     /**
      * @see Object#toString()
      */
     public String toString()
     {
         StringBuilder sb = new StringBuilder();
 
         sb.append( "ETYPE-INFO-ENTRY : {\n" );
         sb.append( "    etype: " ).append( etype ).append( '\n' );
 
         if ( salt != null )
         {
             sb.append( "    salt: " ).append( Strings.dumpBytes( salt ) ).append( '\n' );
         }
 
         sb.append( "}\n" );
 
         return sb.toString();
     }
 }