/*
 * Created on 21-Jan-2005
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package com.aelitis.azureus.core.dht.transport.udp.impl;

import java.io.*;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.TreeSet;

import org.gudy.azureus2.core3.util.BEncoder;
import org.gudy.azureus2.core3.util.Constants;
import org.gudy.azureus2.core3.util.Debug;
import org.gudy.azureus2.core3.util.RandomUtils;
import org.gudy.azureus2.core3.util.SHA1Simple;
import org.gudy.azureus2.core3.util.SystemTime;

import com.aelitis.azureus.core.dht.DHT;
import com.aelitis.azureus.core.dht.impl.DHTLog;
import com.aelitis.azureus.core.dht.netcoords.DHTNetworkPosition;
import com.aelitis.azureus.core.dht.netcoords.DHTNetworkPositionManager;
import com.aelitis.azureus.core.dht.netcoords.vivaldi.ver1.VivaldiPositionFactory;
import com.aelitis.azureus.core.dht.transport.DHTTransportAlternativeContact;
import com.aelitis.azureus.core.dht.transport.DHTTransportAlternativeNetwork;
import com.aelitis.azureus.core.dht.transport.DHTTransportContact;
import com.aelitis.azureus.core.dht.transport.DHTTransportException;
import com.aelitis.azureus.core.dht.transport.DHTTransportFullStats;
import com.aelitis.azureus.core.dht.transport.DHTTransportValue;
import com.aelitis.azureus.core.dht.transport.udp.DHTTransportUDP;

/**
 * @author parg
 *
 */

public class 
DHTUDPUtils 
{
	public static final IOException INVALID_PROTOCOL_VERSION_EXCEPTION = new IOException( "Invalid DHT protocol version, please update Azureus" );
	
	protected static final int	CT_UDP		= 1;
			
	private static Map<String,byte[]>	node_id_history = 
		new LinkedHashMap<String,byte[]>(128,0.75f,true)
		{
			protected boolean 
			removeEldestEntry(
		   		Map.Entry<String,byte[]> eldest) 
			{
				return size() > 128;
			}
		};
		
	private static SHA1Simple	hasher = new SHA1Simple();
	
	protected static byte[]
	getNodeID(
		InetSocketAddress	address,
		byte				protocol_version )
	
		throws DHTTransportException
	{		
		final String	key;

		InetAddress ia = address.getAddress();
		
		if ( ia == null ){
			
			if ( address.getHostName().equals( Constants.DHT_SEED_ADDRESS_V6 )){
				
				key = "IPv6SeedHack";
				
			}else{
				// Debug.out( "Address '" + address + "' is unresolved" );
				
				throw( new DHTTransportException( "Address '" + address + "' is unresolved" ));
			}
		}else{
			
			
			if ( protocol_version >= DHTTransportUDP.PROTOCOL_VERSION_RESTRICT_ID3 ){
				
				byte[] bytes = ia.getAddress();
				
				if ( bytes.length == 4 ){
					
					//final long K0	= Long.MAX_VALUE;	
					//final long K1	= Long.MAX_VALUE;	
					
						// restrictions suggested by UoW researchers as effective at reducing Sybil opportunity but 
						// not so restrictive as to impact DHT performance
					
					final long K2	= 2500;
					final long K3	= 50;
					final long K4	= 5;

					long	result = address.getPort() % K4;
					
					result = ((((long)bytes[3] << 8 ) &0x000000ff00L ) | result ) % K3;
					result = ((((long)bytes[2] << 16 )&0x0000ff0000L ) | result ) % K2;
					result = ((((long)bytes[1] << 24 )&0x00ff000000L ) | result ); // % K1;
					result = ((((long)bytes[0] << 32 )&0xff00000000L ) | result ); // % K0;

					key = String.valueOf( result );
										
				}else{

						// stick with existing approach for IPv6 at the moment
					
					key = ia.getHostAddress() + ":" + ( address.getPort() % 8 );
				}
			}else if ( protocol_version >= DHTTransportUDP.PROTOCOL_VERSION_RESTRICT_ID_PORTS2 ){

					// more draconian limit, analysis shows that of 500,000 node addresses only
					// 0.01% had >= 8 ports active. ( 1% had 2 ports, 0.1% 3)
					// Having > 1 node with the same ID doesn't actually cause too much grief
		
				key = ia.getHostAddress() + ":" + ( address.getPort() % 8 );
				
			}else if ( protocol_version >= DHTTransportUDP.PROTOCOL_VERSION_RESTRICT_ID_PORTS ){

					// limit range to around 2000 (1999 is prime)

				key = ia.getHostAddress() + ":" + ( address.getPort() % 1999 );
				
			}else{
			
				key = ia.getHostAddress() + ":" + address.getPort();
			}
		}
		
		synchronized( node_id_history ){
			
			byte[]	res = node_id_history.get( key );
			
			if ( res == null ){
								
				res = hasher.calculateHash( key.getBytes());
		
				node_id_history.put( key, res );
			}
			
			// System.out.println( "NodeID: " + address + " -> " + DHTLog.getString( res ));
		
			return( res );
		}
	}
	
	protected static byte[]
	getBogusNodeID()
	{
		byte[]	id = new byte[20];
		
		RandomUtils.nextBytes( id );
		
		return( id );
	}
	
	protected static void
	serialiseLength(
		DataOutputStream	os,
		int					len,
		int					max_length )
	
		throws IOException
	{
		if ( len > max_length ){
			
			throw( new IOException( "Invalid DHT data length: max=" + max_length + ",actual=" + len ));
		}
		
		if ( max_length < 256 ){
			
			os.writeByte( len );
			
		}else if ( max_length < 65536 ){
			
			os.writeShort( len );
			
		}else{
			
			os.writeInt( len );
		}
	}
	
	protected static int
	deserialiseLength(
		DataInputStream	is,
		int				max_length )
	
		throws IOException
	{
		int		len;
		
		if ( max_length < 256 ){
			
			len = is.readByte()&0xff;
			
		}else if ( max_length < 65536 ){
			
			len = is.readShort()&0xffff;
			
		}else{
			
			len = is.readInt();
		}
		
		if ( len > max_length ){
			
			throw( new IOException( "Invalid DHT data length: max=" + max_length + ",actual=" + len ));
		}
		
		return( len );
	}
	
	protected static byte[]
	deserialiseByteArray(
		DataInputStream	is,
		int				max_length )
	
		throws IOException
	{
		int	len = deserialiseLength( is, max_length );
		
		byte[] data	= new byte[len];
		
		is.read(data);
		
		return( data );
	}
	
	protected static void
	serialiseByteArray(
		DataOutputStream	os,
		byte[]				data,
		int					max_length )
	
		throws IOException
	{
		serialiseByteArray( os, data, 0, data.length, max_length );
	}
	
	protected static void
	serialiseByteArray(
		DataOutputStream	os,
		byte[]				data,
		int					start,
		int					length,
		int					max_length )
	
		throws IOException
	{
		serialiseLength( os, length, max_length );
		
		os.write( data, start, length );
	}
	
	protected static void
	serialiseByteArrayArray(
		DataOutputStream		os,
		byte[][]				data,
		int						max_length )
	
		throws IOException
	{
		serialiseLength(os,data.length,max_length);
		
		for (int i=0;i<data.length;i++){
			
			serialiseByteArray( os, data[i], max_length );
		}
	}
	
	protected static byte[][]
	deserialiseByteArrayArray(
		DataInputStream	is,
		int				max_length )
	
		throws IOException
	{
		int	len = deserialiseLength( is, max_length );
		
		byte[][] data	= new byte[len][];
		
		for (int i=0;i<data.length;i++){
			
			data[i] = deserialiseByteArray( is, max_length );
		}
		
		return( data );
	}
	
	public static final int INETSOCKETADDRESS_IPV4_SIZE	= 7;
	public static final int INETSOCKETADDRESS_IPV6_SIZE	= 19;
	
	protected static void
	serialiseAddress(
		DataOutputStream	os,
		InetSocketAddress	address )
	
		throws IOException, DHTTransportException
	{
		InetAddress	ia = address.getAddress();
		
		if ( ia == null ){
			
				// could be an unresolved dht6 seed, stick in a fake value as we are committed to serialising
				// something here
			
			serialiseByteArray( os, new byte[4], 16 );
			
			os.writeShort( 0 );
			
		}else{
		
			serialiseByteArray( os, ia.getAddress(), 16);	// 16 (Pv6) + 1 length
			
			os.writeShort( address.getPort());	//19
		}
	}
	
	protected static InetSocketAddress
	deserialiseAddress(
		DataInputStream		is )
	
		throws IOException
	{
		byte[]	bytes = deserialiseByteArray( is, 16 );
				
		int	port = is.readShort()&0xffff;
		
		return( new InetSocketAddress( InetAddress.getByAddress( bytes ), port ));
	}
	
	protected static DHTTransportValue[][]
	deserialiseTransportValuesArray(
		DHTUDPPacket			packet,
		DataInputStream			is,
		long					skew,
		int						max_length )
	
		throws IOException
	{
		int	len = deserialiseLength( is, max_length );
		
		DHTTransportValue[][] data	= new DHTTransportValue[len][];
		
		for (int i=0;i<data.length;i++){
			
			data[i] = deserialiseTransportValues( packet, is, skew );
		}
		
		return( data );	
	}
	
	protected static void
	serialiseTransportValuesArray(
		DHTUDPPacket			packet,
		DataOutputStream		os,
		DHTTransportValue[][]	values,
		long					skew,
		int						max_length )
	
		throws IOException, DHTTransportException
	{
		serialiseLength(os,values.length,max_length);
		
		for (int i=0;i<values.length;i++){
			
			serialiseTransportValues( packet, os, values[i], skew );
		}	
	}
	
	public static final int	DHTTRANSPORTCONTACT_SIZE	= 2 + INETSOCKETADDRESS_IPV4_SIZE;
	
	protected static void
	serialiseContact(
		DataOutputStream		os,
		DHTTransportContact		contact )
	
		throws IOException, DHTTransportException
	{
		if ( contact.getTransport() instanceof DHTTransportUDP ){
			
			os.writeByte( CT_UDP );		// 1
			
			os.writeByte( contact.getProtocolVersion());	// 2
											
			serialiseAddress( os, contact.getExternalAddress() );	// 2 + address
			
		}else{
			
			throw( new IOException( "Unsupported contact type:" + contact.getClass().getName()));
		}
	}
	
	protected static DHTTransportUDPContactImpl
	deserialiseContact(
		DHTTransportUDPImpl		transport,
		DataInputStream			is )
	
		throws IOException, DHTTransportException
	{
		byte	ct = is.readByte();
		
		if ( ct != CT_UDP ){
			
			throw( new IOException( "Unsupported contact type:" + ct ));
		}
			
		byte	version = is.readByte();
		
			// we don't transport instance ids around via this route as they are just
			// cached versions and not useful
				
		InetSocketAddress	external_address = deserialiseAddress( is );
		
		return( new DHTTransportUDPContactImpl( false, transport, external_address, external_address, version, 0, 0, (byte)0 ));
	}
	
	protected static void
	serialiseAltContact(
		DataOutputStream					os,
		DHTTransportAlternativeContact		contact )
	
		throws IOException, DHTTransportException
	{
		os.write((byte)contact.getNetworkType());
		
		os.write((byte)contact.getVersion());
		
		os.writeShort( contact.getAge());
	
		byte[] encoded = BEncoder.encode( contact.getProperties());
		
		serialiseByteArray( os, encoded, 65535 );
	}
	
	protected static DHTTransportAlternativeContactImpl
	deserialiseAltContact(
		DataInputStream			is )
	
		throws IOException, DHTTransportException
	{
		byte	network_type 	= is.readByte();
		byte	version		 	= is.readByte();
		short	age				= is.readShort();
		
		byte[]	encoded = deserialiseByteArray( is, 65535 );
		
		return( new DHTTransportAlternativeContactImpl( network_type, version, age, encoded ));
	}

	protected static DHTTransportValue[]
	deserialiseTransportValues(
		DHTUDPPacket			packet,
		DataInputStream			is,
		long					skew )
	
		throws IOException
	{
		int	len = deserialiseLength( is, 65535 );
		
		List	l = new ArrayList( len );
		
		for (int i=0;i<len;i++){
			
			try{
				
				l.add( deserialiseTransportValue( packet, is, skew ));
				
			}catch( DHTTransportException e ){
				
				Debug.printStackTrace(e);
			}
		}
				
		DHTTransportValue[]	res = new DHTTransportValue[l.size()];
		
		l.toArray( res );
		
		return( res );
	}

	protected static void
	serialiseTransportValues(
		DHTUDPPacket			packet,
		DataOutputStream		os,
		DHTTransportValue[]		values,
		long					skew )
	
		throws IOException, DHTTransportException
	{
		serialiseLength( os, values.length, 65535 );
	
		for (int i=0;i<values.length;i++){
			
			serialiseTransportValue( packet, os, values[i], skew );
		}
	}
	
	protected static DHTTransportValue
	deserialiseTransportValue(
		DHTUDPPacket		packet,
		DataInputStream		is, 
		long				skew )
	
		throws IOException, DHTTransportException
	{
		final int	version;
		
		if ( packet.getProtocolVersion() >= DHTTransportUDP.PROTOCOL_VERSION_REMOVE_DIST_ADD_VER ){
			
			version = is.readInt();
			
			//System.out.println( "read: version = " + version );
			
		}else{
			
			version	= -1;
			
			// int distance = is.readInt();
			
			//System.out.println( "read:" + distance );
		}
		
		final long 	created		= is.readLong() + skew;
		
		// System.out.println( "    Adjusted creation time by " + skew );
		
		final byte[]	value_bytes = deserialiseByteArray( is, DHT.MAX_VALUE_SIZE );
		
		final DHTTransportContact	originator		= deserialiseContact( packet.getTransport(), is );
		
		final int flags	= is.readByte()&0xff;
		
		final int life_hours;
		
		if ( packet.getProtocolVersion() >= DHTTransportUDP.PROTOCOL_VERSION_LONGER_LIFE ){

			life_hours = is.readByte()&0xff;
			
		}else{
			
			life_hours = 0;
		}
		
		final byte rep_control;
		
		if ( packet.getProtocolVersion() >= DHTTransportUDP.PROTOCOL_VERSION_REPLICATION_CONTROL ){

			rep_control = is.readByte();
			
		}else{
			
			rep_control = DHT.REP_FACT_DEFAULT;
		}
		
		DHTTransportValue value = 
			new DHTTransportValue()
			{
				public boolean
				isLocal()
				{
					return( false );
				}
				
				public long
				getCreationTime()
				{
					return( created );
				}
				
				public byte[]
				getValue()
				{
					return( value_bytes );
				}
				
				public int
				getVersion()
				{
					return( version );
				}
				
				public DHTTransportContact
				getOriginator()
				{
					return( originator );
				}
				
				public int
				getFlags()
				{
					return( flags );
				}
				
				public int
				getLifeTimeHours()
				{
					return( life_hours );
				}
				
				public byte
				getReplicationControl()
				{
					return( rep_control );
				}
				
				public byte 
				getReplicationFactor() 
				{
					return( rep_control == DHT.REP_FACT_DEFAULT?DHT.REP_FACT_DEFAULT:(byte)(rep_control&0x0f));
				}
				
				public byte 
				getReplicationFrequencyHours() 
				{
					return( rep_control == DHT.REP_FACT_DEFAULT?DHT.REP_FACT_DEFAULT:(byte)(rep_control>>4));
				}
				
				public String
				getString()
				{
					long	now = SystemTime.getCurrentTime();
					
					return( DHTLog.getString( value_bytes ) + " - " + new String(value_bytes) + "{v=" + version + ",f=" + 
							Integer.toHexString(flags) + ",l=" + life_hours + ",r=" + Integer.toHexString(getReplicationControl()) + ",ca=" + (now - created ) + ",or=" + originator.getString() +"}" );
				}
			};
			
		return( value );
	}
	
	public static final int DHTTRANSPORTVALUE_SIZE_WITHOUT_VALUE	= 17 + DHTTRANSPORTCONTACT_SIZE;
		
	protected static void
	serialiseTransportValue(
		DHTUDPPacket		packet,
		DataOutputStream	os,
		DHTTransportValue	value,
		long				skew )
	
		throws IOException, DHTTransportException
	{		
		if ( packet.getProtocolVersion() >= DHTTransportUDP.PROTOCOL_VERSION_REMOVE_DIST_ADD_VER ){
			
			int	version = value.getVersion();
			
			//System.out.println( "write: version = " + version );

			os.writeInt( version );
		}else{
			
			//System.out.println( "write: 0" );

			os.writeInt( 0 );
		}
		
			// Don't forget to change the CONSTANT above if you change the size of this!
				
		os.writeLong( value.getCreationTime() + skew );	// 12
		
		serialiseByteArray( os, value.getValue(), DHT.MAX_VALUE_SIZE );	// 12+2+X
		
		serialiseContact( os, value.getOriginator());	// 12 + 2+X + contact
		
		os.writeByte( value.getFlags());	// 13 + 2+ X + contact
		
		if ( packet.getProtocolVersion() >= DHTTransportUDP.PROTOCOL_VERSION_LONGER_LIFE ){

			os.writeByte( value.getLifeTimeHours()); // 14 + 2+ X + contact
		}
		
		if ( packet.getProtocolVersion() >= DHTTransportUDP.PROTOCOL_VERSION_REPLICATION_CONTROL ){
			
			os.writeByte( value.getReplicationControl()); // 15 + 2+ X + contact
		}
	}
	
	protected static void
	serialiseContacts(
		DataOutputStream		os,
		DHTTransportContact[]	contacts )
	
		throws IOException
	{
		serialiseLength( os, contacts.length, 65535 );
		
		for (int i=0;i<contacts.length;i++){
			
			try{
				serialiseContact( os, contacts[i] );
				
			}catch( DHTTransportException e ){
				
				Debug.printStackTrace(e);
				
					// not much we can do here to recover - shouldn't fail anyways
				
				throw( new IOException(e.getMessage()));
			}
		}
	}

	protected static DHTTransportContact[]
	deserialiseContacts(
		DHTTransportUDPImpl		transport,
		DataInputStream			is )
	
		throws IOException
	{
		int	len = deserialiseLength( is, 65535 );
		
		List<DHTTransportContact>	l = new ArrayList<DHTTransportContact>( len );
		
		for (int i=0;i<len;i++){
			
			try{
				
				DHTTransportContact contact = deserialiseContact( transport, is );
				
				if ( contact.getAddress().getPort() > 0 ){
				
					l.add( contact );
				}
				
			}catch( DHTTransportException e ){
				
				Debug.printStackTrace(e);
			}
		}
				
		DHTTransportContact[]	res = new DHTTransportContact[l.size()];
		
		l.toArray( res );
		
		return( res );
	}
		
	protected static void
	serialiseAltContacts(
		DataOutputStream					os,
		DHTTransportAlternativeContact[]	contacts )
	
		throws IOException
	{
		if ( contacts == null ){
			
			contacts = new DHTTransportAlternativeContact[0];
		}
		
		serialiseLength( os, contacts.length, 64 );
		
		for (int i=0;i<contacts.length;i++){
			
			try{
				serialiseAltContact( os, contacts[i] );
				
			}catch( DHTTransportException e ){
				
				Debug.printStackTrace(e);
				
					// not much we can do here to recover - shouldn't fail anyways
				
				throw( new IOException(e.getMessage()));
			}
		}
	}

	protected static DHTTransportAlternativeContact[]
	deserialiseAltContacts(
		DataInputStream			is )
	
		throws IOException
	{
		int	len = deserialiseLength( is, 64 );
		
		List<DHTTransportAlternativeContact>	l = new ArrayList<DHTTransportAlternativeContact>( len );
		
		for (int i=0;i<len;i++){
			
			try{
				
				DHTTransportAlternativeContact contact = deserialiseAltContact( is );
								
				l.add( contact );
				
			}catch( DHTTransportException e ){
				
				Debug.printStackTrace(e);
			}
		}
				
		DHTTransportAlternativeContact[]	res = new DHTTransportAlternativeContact[l.size()];
		
		l.toArray( res );
		
		return( res );
	}
	
	protected static void
	serialiseAltContactRequest(
		DHTUDPPacketRequestPing		ping,
		DataOutputStream			os )
		
		throws IOException
	{
		int[]	nets 	= ping.getAltNetworks();
		int[]	counts	= ping.getAltNetworkCounts();
		
		int len = nets==null||counts==null?0:nets.length;
		
		serialiseLength( os, len, 16 );
		
		for ( int i=0;i<len;i++ ){
			
			os.write( nets[i] );
			os.write( counts[i] );
		}
	}
	
	protected static void
	deserialiseAltContactRequest(
		DHTUDPPacketRequestPing		ping,
		DataInputStream				is )
		
		throws IOException
	{
		int	len = deserialiseLength( is, 16 );

		int[]	nets 	= new int[len];
		int[]	counts	= new int[len];
		
		for ( int i=0;i<len;i++){
			
			nets[i] 	= is.read();
			counts[i]	= is.read();
			
			if ( nets[i] == -1 || counts[i] == -1 ){
				
				throw( new EOFException());
			}
		}
		
		ping.setAltContactRequest( nets, counts );
	}
	
	protected static void
	serialiseVivaldi(
		DHTUDPPacketReply	reply, 
		DataOutputStream	os )
	
		throws IOException
	{
		DHTNetworkPosition[]	nps = reply.getNetworkPositions();

		if ( reply.getProtocolVersion() >= DHTTransportUDP.PROTOCOL_VERSION_GENERIC_NETPOS ){
			
			boolean	v1_found = false;
			
			for (int i=0;i<nps.length;i++){
					
				DHTNetworkPosition	np = nps[i];
				
				if ( np.getPositionType() == DHTNetworkPosition.POSITION_TYPE_VIVALDI_V1 ){
					
					v1_found	= true;
					
					break;
				}
			}
			
			if ( !v1_found ){
				
				if ( reply.getProtocolVersion() < DHTTransportUDP.PROTOCOL_VERSION_VIVALDI_OPTIONAL ){
					
						// need to add one in for backward compatability
					
					DHTNetworkPosition np = VivaldiPositionFactory.createPosition( Float.NaN );
					
					DHTNetworkPosition[] new_nps = new DHTNetworkPosition[nps.length+1];
					
					System.arraycopy( nps, 0, new_nps, 0, nps.length );
					
					new_nps[ nps.length ] = np;
					
					nps = new_nps;
				}
			}
			
			os.writeByte((byte)nps.length);
						
			for (int i=0;i<nps.length;i++){
					
				DHTNetworkPosition	np = nps[i];
				
				os.writeByte( np.getPositionType());
				os.writeByte( np.getSerialisedSize());
				
				np.serialise( os );
			}
		}else{
			
				// dead code these days 
			
			for (int i=0;i<nps.length;i++){
				
				if ( nps[i].getPositionType() == DHTNetworkPosition.POSITION_TYPE_VIVALDI_V1 ){
										
					nps[i].serialise( os );
					
					return;
				}
			}

			Debug.out( "Vivaldi V1 missing" );
			
			throw( new IOException( "Vivaldi V1 missing" ));
		}
	}
	
	protected static void
	deserialiseVivaldi(
		DHTUDPPacketReply	reply,
		DataInputStream		is )
	
		throws IOException
	{
		DHTNetworkPosition[]	nps;
		
		if ( reply.getProtocolVersion() >= DHTTransportUDP.PROTOCOL_VERSION_GENERIC_NETPOS ){
			
			int	entries = is.readByte()&0xff;
			
			nps	= new DHTNetworkPosition[ entries ];
			
			int	skipped = 0;
			
			for (int i=0;i<entries;i++){
				
				byte	type = is.readByte();
				byte	size = is.readByte();
				
				DHTNetworkPosition	np = DHTNetworkPositionManager.deserialise( reply.getAddress().getAddress(), type, is );
				
				if ( np == null ){
					
					skipped++;
					
					for (int j=0;j<size;j++){
						
						is.readByte();
					}
				}else{
					
					nps[i] = np;
				}
			}
			
			if ( skipped > 0 ){
				
				DHTNetworkPosition[] x	= new DHTNetworkPosition[ entries - skipped ];
				
				int	pos = 0;
				
				for (int i=0;i<nps.length;i++){
					
					if ( nps[i] != null ){
						
						x[pos++] = nps[i];
					}
				}
				
				nps	= x;
			}
		}else{
			
				// dead code these days 
			
			nps = new DHTNetworkPosition[]{ DHTNetworkPositionManager.deserialise( reply.getAddress().getAddress(), DHTNetworkPosition.POSITION_TYPE_VIVALDI_V1, is )};	
		}
				
		reply.setNetworkPositions( nps );
	}
	
	protected static void
	serialiseStats(
		int						version,
		DataOutputStream		os,
		DHTTransportFullStats	stats )
	
		throws IOException
	{
		os.writeLong( stats.getDBValuesStored());
		
		os.writeLong( stats.getRouterNodes());
		os.writeLong( stats.getRouterLeaves());
		os.writeLong( stats.getRouterContacts());
		
		os.writeLong( stats.getTotalBytesReceived());
		os.writeLong( stats.getTotalBytesSent());
		os.writeLong( stats.getTotalPacketsReceived());
		os.writeLong( stats.getTotalPacketsSent());
		os.writeLong( stats.getTotalPingsReceived());
		os.writeLong( stats.getTotalFindNodesReceived());
		os.writeLong( stats.getTotalFindValuesReceived());
		os.writeLong( stats.getTotalStoresReceived());
		os.writeLong( stats.getAverageBytesReceived());
		os.writeLong( stats.getAverageBytesSent());
		os.writeLong( stats.getAveragePacketsReceived());
		os.writeLong( stats.getAveragePacketsSent());
		
		os.writeLong( stats.getIncomingRequests());
		
		String	azversion = stats.getVersion() + "["+version+"]";
		
		serialiseByteArray( os, azversion.getBytes(), 64);
					
		os.writeLong( stats.getRouterUptime());
		os.writeInt( stats.getRouterCount());
		
		if ( version >= DHTTransportUDP.PROTOCOL_VERSION_BLOCK_KEYS ){
			
			os.writeLong( stats.getDBKeysBlocked());
			os.writeLong( stats.getTotalKeyBlocksReceived());
		}
		
		if ( version >= DHTTransportUDP.PROTOCOL_VERSION_MORE_STATS ){
			
			os.writeLong( stats.getDBKeyCount());
			os.writeLong( stats.getDBValueCount());
			os.writeLong( stats.getDBStoreSize());
			os.writeLong( stats.getDBKeyDivFreqCount());
			os.writeLong( stats.getDBKeyDivSizeCount());
		}
	}
	
	protected static DHTTransportFullStats
	deserialiseStats(
		int					version,
		DataInputStream		is )
	
		throws IOException
	{
		final long db_values_stored				= is.readLong();
		
		final long router_nodes					= is.readLong();
		final long router_leaves				= is.readLong();
		final long router_contacts 				= is.readLong();
		
		final long total_bytes_received			= is.readLong();
		final long total_bytes_sent				= is.readLong();
		final long total_packets_received		= is.readLong();
		final long total_packets_sent			= is.readLong();
		final long total_pings_received			= is.readLong();
		final long total_find_nodes_received	= is.readLong();
		final long total_find_values_received	= is.readLong();
		final long total_stores_received		= is.readLong();
		final long average_bytes_received		= is.readLong();
		final long average_bytes_sent			= is.readLong();
		final long average_packets_received		= is.readLong();
		final long average_packets_sent			= is.readLong();
		
		final long incoming_requests			= is.readLong();
		
		final String	az_version = new String( deserialiseByteArray( is, 64 ));
		
		final long	router_uptime	= is.readLong();
		final int	router_count	= is.readInt();
			
		final long db_keys_blocked;
		final long total_key_blocks_received;
		
		if ( version >= DHTTransportUDP.PROTOCOL_VERSION_BLOCK_KEYS ){
			
			db_keys_blocked				= is.readLong();
			total_key_blocks_received	= is.readLong();
		}else{
			db_keys_blocked				= -1;
			total_key_blocks_received	= -1;
		}
		
		final long db_key_count;
		final long db_value_count;
		final long db_store_size;
		final long db_freq_divs;
		final long db_size_divs;
		
		if ( version >= DHTTransportUDP.PROTOCOL_VERSION_MORE_STATS ){
			
			db_key_count 	= is.readLong();
			db_value_count	= is.readLong();
			db_store_size	= is.readLong();
			db_freq_divs	= is.readLong();
			db_size_divs	= is.readLong();
			
		}else{
			
			db_key_count 	= -1;
			db_value_count	= -1;
			db_store_size	= -1;
			db_freq_divs	= -1;
			db_size_divs	= -1;
		}
		
		DHTTransportFullStats	res = 
			new DHTTransportFullStats()
			{
				public long
				getDBValuesStored()
				{
					return( db_values_stored );
				}
				
				public long
				getDBKeysBlocked()
				{
					return( db_keys_blocked );
				}
				
				public long
				getDBValueCount()
				{
					return( db_value_count );
				}
				
				public long
				getDBKeyCount()
				{
					return( db_key_count );
				}
								
				public long
				getDBKeyDivSizeCount()
				{
					return( db_size_divs );
				}
				
				public long
				getDBKeyDivFreqCount()
				{
					return( db_freq_divs );
				}

				public long
				getDBStoreSize()
				{
					return( db_store_size );
				}
				
					// Router
				
				public long
				getRouterNodes()
				{
					return( router_nodes );
				}
				
				public long
				getRouterLeaves()
				{
					return( router_leaves );
				}
				
				public long
				getRouterContacts()
				{
					return( router_contacts );
				}
			
				public long
				getRouterUptime()
				{
					return( router_uptime );
				}
				
				public int
				getRouterCount()
				{
					return( router_count );
				}
				public long
				getTotalBytesReceived()
				{
					return( total_bytes_received );
				}
				
				public long
				getTotalBytesSent()
				{
					return( total_bytes_sent );
				}
				
				public long
				getTotalPacketsReceived()
				{
					return( total_packets_received );
				}
				
				public long
				getTotalPacketsSent()
				{
					return( total_packets_sent );
				}
				
				public long
				getTotalPingsReceived()
				{
					return( total_pings_received );
				}
				
				public long
				getTotalFindNodesReceived()
				{
					return( total_find_nodes_received );
				}
				
				public long
				getTotalFindValuesReceived()
				{
					return( total_find_values_received );
				}
				
				public long
				getTotalStoresReceived()
				{
					return( total_stores_received );
				}
				
				public long
				getTotalKeyBlocksReceived()
				{
					return( total_key_blocks_received );
				}

					// averages
				
				public long
				getAverageBytesReceived()
				{
					return( average_bytes_received );
				}
				
				public long
				getAverageBytesSent()
				{
					return( average_bytes_sent );
				}
				
				public long
				getAveragePacketsReceived()
				{
					return( average_packets_received );
				}
				
				public long
				getAveragePacketsSent()
				{
					return( average_packets_sent );
				}
				
				public long
				getIncomingRequests()
				{
					return( incoming_requests );
				}
				
				public String
				getVersion()
				{
					return( az_version );
				}
				
				public String
				getString()
				{
					return(	"transport:" + 
							getTotalBytesReceived() + "," +
							getTotalBytesSent() + "," +
							getTotalPacketsReceived() + "," +
							getTotalPacketsSent() + "," +
							getTotalPingsReceived() + "," +
							getTotalFindNodesReceived() + "," +
							getTotalFindValuesReceived() + "," +
							getTotalStoresReceived() + "," +
							getTotalKeyBlocksReceived() + "," +
							getAverageBytesReceived() + "," +
							getAverageBytesSent() + "," +
							getAveragePacketsReceived() + "," +
							getAveragePacketsSent() + "," +
							getIncomingRequests() + 
							",router:" +
							getRouterNodes() + "," +
							getRouterLeaves() + "," +
							getRouterContacts() + 
							",database:" +
							getDBKeyCount() + ","+
							getDBValueCount() + ","+
							getDBValuesStored() + ","+
							getDBStoreSize() + ","+
							getDBKeyDivFreqCount() + ","+
							getDBKeyDivSizeCount() + ","+
							getDBKeysBlocked()+ 
							",version:" + getVersion()+","+
							getRouterUptime() + ","+
							getRouterCount());
					}
			};
	
		
		return( res );
	}
	
	private static List<DHTTransportUDPImpl>			transports 		= new ArrayList<DHTTransportUDPImpl>();
	private static List<DHTTransportAlternativeNetwork>	alt_networks 	= new ArrayList<DHTTransportAlternativeNetwork>();
	
	protected static void
	registerTransport(
		DHTTransportUDPImpl		transport )
	{
		synchronized( transports ){
			
			transports.add( transport );
			
			for ( DHTTransportAlternativeNetwork net: alt_networks ){
				
				transport.registerAlternativeNetwork( net );
			}
		}
	}
	
	public static void
	registerAlternativeNetwork(
		DHTTransportAlternativeNetwork	net )
	{
		synchronized( transports ){
			
			alt_networks.add( net );
			
			for ( DHTTransportUDPImpl transport: transports ){
				
				transport.registerAlternativeNetwork( net );
			}
		}
	}
	
	public static void
	unregisterAlternativeNetwork(
		DHTTransportAlternativeNetwork	net )
	{
		synchronized( transports ){
			
			alt_networks.remove( net );
			
			for ( DHTTransportUDPImpl transport: transports ){
				
				transport.unregisterAlternativeNetwork( net );
			}
		}
	}
	
	public static List<DHTTransportAlternativeContact>
	getAlternativeContacts(
		int			network,
		int			max )
	{
		List<DHTTransportAlternativeContact>	result_list = new ArrayList<DHTTransportAlternativeContact>(max);
		
		if ( max > 0 ){
			
			TreeSet<DHTTransportAlternativeContact> result_set =
				new TreeSet<DHTTransportAlternativeContact>(
					new Comparator<DHTTransportAlternativeContact>() 
					{
						public int 
						compare(
							DHTTransportAlternativeContact o1,
							DHTTransportAlternativeContact o2 ) 
						{
							int res = o1.getAge() - o2.getAge();
							
							if ( res == 0 ){
								
								res = o1.getID() - o2.getID();
							}
							
							return( res );
						}
					});
			
			synchronized( transports ){

					// if we have a local provider then grab stuff from here
				
				for ( DHTTransportAlternativeNetwork net: alt_networks ){
					
					if ( net.getNetworkType() == network ){
						
						List<DHTTransportAlternativeContact> temp = net.getContacts( max );
						
						if ( temp != null ){
							
							result_set.addAll( temp );
						}
					}
				}
								
					// merge in any remote contacts and then take the best ones
				
				for ( DHTTransportUDPImpl transport: transports ){
										
					DHTTransportAlternativeNetwork alt = transport.getAlternativeNetwork( network );
					
					if ( alt != null ){
						
						List<DHTTransportAlternativeContact> temp = alt.getContacts( max );
						
						if ( temp != null ){
							
							result_set.addAll( temp );
						}
					}
				}
			}
	
			Iterator<DHTTransportAlternativeContact> it = result_set.iterator();
			
			while( it.hasNext() && result_list.size() < max ){
				
				result_list.add( it.next());
			}
		}
		
		return( result_list );
	}
}
