/*
    *  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.messages;
  
  
  import java.nio.ByteBuffer;
  import java.text.SimpleDateFormat;
  import java.util.Date;
  import java.util.Locale;
  import java.util.TimeZone;
  
  
  /**
   * NTP timestamps are represented as a 64-bit unsigned fixed-point number,
   * in seconds relative to 0h on 1 January 1900. The integer part is in the
   * first 32 bits and the fraction part in the last 32 bits. In the fraction
   * part, the non-significant low order can be set to 0.
   * 
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class NtpTimeStamp
  {
      /**
       * The number of milliseconds difference between the Java epoch and
       * the NTP epoch ( January 1, 1900, 00:00:00 GMT ).
       */
      private static final long NTP_EPOCH_DIFFERENCE = -2208988800000L;
  
      private static final SimpleDateFormat DATE_FORMAT = new SimpleDateFormat( "yyyy-MM-dd HH:mm:ss.SSS z", Locale.ROOT );
  
      private static final TimeZone UTC_TIME_ZONE = TimeZone.getTimeZone( "UTC" );
      
      static
      {
          DATE_FORMAT.setTimeZone( UTC_TIME_ZONE );
      }
  
      private long seconds = 0;
      private long fraction = 0;
  
  
      /**
       * Creates a new instance of NtpTimeStamp that represents the time "right now."
       */
      public NtpTimeStamp()
      {
          this( new Date() );
      }
  
  
      /**
       * Creates a new instance of NtpTimeStamp that represents the given {@link Date}.
       *
       * @param date
       */
      public NtpTimeStamp( Date date )
      {
          long msSinceStartOfNtpEpoch = date.getTime() - NTP_EPOCH_DIFFERENCE;
  
          seconds = msSinceStartOfNtpEpoch / 1000;
          fraction = ( ( msSinceStartOfNtpEpoch % 1000 ) * 0x100000000L ) / 1000;
      }
  
  
      /**
       * Creates a new instance of NtpTimeStamp from encoded data in a {@link ByteBuffer}.
       *
       * @param data
       */
      public NtpTimeStamp( ByteBuffer data )
      {
          for ( int ii = 0; ii < 4; ii++ )
          {
              seconds = 256 * seconds + makePositive( data.get() );
          }
  
          for ( int ii = 4; ii < 8; ii++ )
          {
              fraction = 256 * fraction + makePositive( data.get() );
          }
      }
 
 
     /**
      * Writes this {@link NtpTimeStamp} to the given {@link ByteBuffer}.
      *
      * @param buffer
      */
     public void writeTo( ByteBuffer buffer )
     {
         byte[] bytes = new byte[8];
 
         long temp = seconds;
         for ( int ii = 3; ii >= 0; ii-- )
         {
             bytes[ii] = ( byte ) ( temp % 256 );
             temp = temp / 256;
         }
 
         temp = fraction;
         for ( int ii = 7; ii >= 4; ii-- )
         {
             bytes[ii] = ( byte ) ( temp % 256 );
             temp = temp / 256;
         }
 
         buffer.put( bytes );
     }
 
 
     public String toString()
     {
         long msSinceStartOfNtpEpoch = seconds * 1000 + ( fraction * 1000 ) / 0x100000000L;
         Date date = new Date( msSinceStartOfNtpEpoch + NTP_EPOCH_DIFFERENCE );
 
         synchronized ( DATE_FORMAT )
         {
             return "org.apache.ntp.message.NtpTimeStamp[ date = " + DATE_FORMAT.format( date ) + " ]";
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public int hashCode()
     {
         int hash = 37;
         hash = hash * 17 + Long.valueOf( seconds ).hashCode();
         hash = hash * 17 + Long.valueOf( fraction ).hashCode();
 
         return hash;
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean equals( Object o )
     {
         if ( this == o )
         {
             return true;
         }
 
         if ( !( o instanceof NtpTimeStamp ) )
         {
             return false;
         }
 
         NtpTimeStamp/../../../../org/apache/directory/server/ntp/messages/NtpTimeStamp.html#NtpTimeStamp">NtpTimeStamp that = ( NtpTimeStamp ) o;
         return ( this.seconds == that.seconds ) && ( this.fraction == that.fraction );
     }
 
 
     private int makePositive( byte b )
     {
         int byteAsInt = b;
         return ( byteAsInt < 0 ) ? 256 + byteAsInt : byteAsInt;
     }
 }