/*
 *  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 java.security.MessageDigest;
import java.util.Arrays;

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;


/**
 * A Kerberos symmetric encryption key, which includes metadata support for
 * the associated key type and key version number.
 * 
 * The ASN.1 description for this structure is :
 * <pre>
 * EncryptionKey   ::= SEQUENCE {
 *       keytype         [0] Int32 -- actually encryption type --,
 *       keyvalue        [1] OCTET STRING
 * }
 * </pre>
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 */
public class EncryptionKey implements Asn1Object
{
    /** The logger */
    private static final Logger log = LoggerFactory.getLogger( EncryptionKey.class );

    /** Speedup for logs */
    private static final boolean IS_DEBUG = log.isDebugEnabled();

    /** The encryption type */
    private EncryptionType keyType;

    /** The encrypted value */
    private byte[] keyValue;

    /** The key version */
    private int keyVersion;

    // Storage for computed lengths
    private int keyTypeLength;
    private int keyValueLength;
    private int encryptionKeyLength;


    /**
     * Creates a new instance of EncryptionKey.
     */
    public EncryptionKey()
    {
    }


    /**
     * Creates a new instance of EncryptionKey.
     *
     * @param keyType The encryptionType 
     * @param keyValue The value
     */
    public EncryptionKey( EncryptionType keyType, byte[] keyValue )
    {
        this.keyType = keyType;
        this.keyValue = keyValue;
    }


    /**
     * Creates a new instance of EncryptionKey.
     *
     * @param keyType The encryptionType 
     * @param keyValue The value
     * @param keyVersion ???
     */
    public EncryptionKey( EncryptionType keyType, byte[] keyValue, int keyVersion )
    {
        this.keyType = keyType;
        this.keyValue = keyValue;
        this.keyVersion = keyVersion;
    }


    /**
     * Destroys this key by overwriting the symmetric key material with zeros.
     */
    public synchronized void destroy()
    {
        if ( keyValue != null )
        {
            Arrays.fill( keyValue, ( byte ) 0x00 );
        }
    }


    /**
     * Returns the key type.
     *
     * @return The key type.
     */
    public EncryptionType getKeyType()
    {
        return keyType;
    }


    /**
     * Set the encryption type
     * @param keyType The encryption type
     */
    public void setKeyType( EncryptionType keyType )
    {
        this.keyType = keyType;
    }


    /**
     * Returns the key value.
     *
     * @return The key value.
     */
    public byte[] getKeyValue()
    {
        return keyValue;
    }


    /**
     * Returns the key version.
     *
     * @return The key version.
     */
    public int getKeyVersion()
    {
        return keyVersion;
    }


    /**
     * Set the key value
     * @param keyVersion The key version
     */
    public void setKeyVersion( int keyVersion )
    {
        this.keyVersion = keyVersion;
    }


    /**
     * Set the key value
     * @param keyValue The key value
     */
    public void setKeyValue( byte[] keyValue )
    {
        this.keyValue = keyValue;
    }


    /**
     * {@inheritDoc}
     */
    @Override
    public int hashCode()
    {
        int hash = 37;
        hash = hash * 17 + keyType.hashCode();
        hash = hash * 17 + Arrays.hashCode( keyValue );

        return hash;
    }


    /**
     * @see Object#equals(Object)
     */
    @Override
    public boolean equals( Object o )
    {
        if ( this == o )
        {
            return true;
        }

        if ( !( o instanceof EncryptionKey ) )
        {
            return false;
        }

        EncryptionKey that = ( EncryptionKey ) o;
        return ( this.keyType == that.keyType ) && ( MessageDigest.isEqual( this.keyValue, that.keyValue ) );
    }


    /**
     * Compute the EncryptionKey length
     * <pre>
     * EncryptionKey :
     * 
     * 0x30 L1 EncryptionKey
     *  |
     *  +--&gt; 0xA0 L2 keyType tag
     *  |     |
     *  |     +--&gt; 0x02 L2-1 keyType (int)
     *  |
     *  +--&gt; 0xA1 L3 keyValue tag
     *        |
     *        +--&gt; 0x04 L3-1 keyValue (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 keyType. The Length will always be cobntained in 1 byte
        keyTypeLength = 1 + 1 + BerValue.getNbBytes( keyType.getValue() );
        encryptionKeyLength = 1 + TLV.getNbBytes( keyTypeLength ) + keyTypeLength;

        // Compute the keyValue
        if ( keyValue == null )
        {
            keyValueLength = 1 + 1;
        }
        else
        {
            keyValueLength = 1 + TLV.getNbBytes( keyValue.length ) + keyValue.length;
        }

        encryptionKeyLength += 1 + TLV.getNbBytes( keyValueLength ) + keyValueLength;

        // Compute the whole sequence length
        return 1 + BerValue.getNbBytes( encryptionKeyLength ) + encryptionKeyLength;
    }


    /**
     * Encode the EncryptionKey message to a PDU. 
     * <pre>
     * EncryptionKey :
     * 
     * 0x30 LL
     *   0xA0 LL 
     *     0x02 0x01 keyType
     *   0xA1 LL 
     *     0x04 LL keyValue
     * </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 EncryptionKey SEQ Tag
            buffer.put( UniversalTag.SEQUENCE.getValue() );
            buffer.put( TLV.getBytes( encryptionKeyLength ) );

            // The keyType, first the tag, then the value
            buffer.put( ( byte ) KerberosConstants.ENCRYPTION_KEY_TYPE_TAG );
            buffer.put( TLV.getBytes( keyTypeLength ) );
            BerValue.encode( buffer, keyType.getValue() );

            // The keyValue, first the tag, then the value
            buffer.put( ( byte ) KerberosConstants.ENCRYPTION_KEY_VALUE_TAG );
            buffer.put( TLV.getBytes( keyValueLength ) );
            BerValue.encode( buffer, keyValue );
        }
        catch ( BufferOverflowException boe )
        {
            log.error( I18n.err( I18n.ERR_142, 1 + TLV.getNbBytes( encryptionKeyLength )
                + encryptionKeyLength, buffer.capacity() ) );
            throw new EncoderException( I18n.err( I18n.ERR_138 ), boe );
        }

        if ( IS_DEBUG )
        {
            log.debug( "EncryptionKey encoding : {}", Strings.dumpBytes( buffer.array() ) );
            log.debug( "EncryptionKey initial value : {}", this );
        }

        return buffer;
    }


    /**
     * @see Object#toString()
     */
    public String toString()
    {
        return keyType.toString() + " (" + keyType.getValue() + ")";
    }
}