/*
 *  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.ntp.io;


import java.nio.ByteBuffer;

import org.apache.directory.server.ntp.messages.LeapIndicatorType;
import org.apache.directory.server.ntp.messages.ModeType;
import org.apache.directory.server.ntp.messages.NtpMessage;
import org.apache.directory.server.ntp.messages.ReferenceIdentifier;


/**
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 * @version $Rev$, $Date$
 */
public class NtpMessageEncoder
{
    /**
     * Encodes the {@link NtpMessage} into the {@link ByteBuffer}.
     *
     * @param byteBuffer
     * @param message
     */
    public void encode( ByteBuffer byteBuffer, NtpMessage message )
    {
        byte header = 0x00;
        header = encodeLeapIndicator( message.getLeapIndicator(), header );
        header = encodeVersionNumber( message.getVersionNumber(), header );
        header = encodeMode( message.getMode(), header );
        byteBuffer.put( header );

        byteBuffer.put( ( byte ) ( message.getStratum().getOrdinal() & 0xFF ) );
        byteBuffer.put( ( byte ) ( message.getPollInterval() & 0xFF ) );
        byteBuffer.put( ( byte ) ( message.getPrecision() & 0xFF ) );

        byteBuffer.putInt( message.getRootDelay() );
        byteBuffer.putInt( message.getRootDispersion() );

        encodeReferenceIdentifier( message.getReferenceIdentifier(), byteBuffer );

        message.getReferenceTimestamp().writeTo( byteBuffer );
        message.getOriginateTimestamp().writeTo( byteBuffer );
        message.getReceiveTimestamp().writeTo( byteBuffer );
        message.getTransmitTimestamp().writeTo( byteBuffer );
    }


    private byte encodeLeapIndicator( LeapIndicatorType leapIndicator, byte header )
    {
        byte twoBits = ( byte ) ( leapIndicator.getOrdinal() & 0x03 );
        return ( byte ) ( ( twoBits << 6 ) | header );
    }


    private byte encodeVersionNumber( int versionNumber, byte header )
    {
        byte threeBits = ( byte ) ( versionNumber & 0x07 );
        return ( byte ) ( ( threeBits << 3 ) | header );
    }


    private byte encodeMode( ModeType mode, byte header )
    {
        byte threeBits = ( byte ) ( mode.getOrdinal() & 0x07 );
        return ( byte ) ( threeBits | header );
    }


    private void encodeReferenceIdentifier( ReferenceIdentifier identifier, ByteBuffer byteBuffer )
    {
        char[] characters = identifier.getCode().toCharArray();

        for ( int ii = 0; ii < characters.length; ii++ )
        {
            byteBuffer.put( ( byte ) characters[ii] );
        }
    }
}
