/*
 * Created on 12-Mar-2005
 * Created by Paul Gardner
 * Copyright (C) 2004, 2005, 2006 Aelitis, 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.
 * 
 * AELITIS, SAS au capital de 46,603.30 euros
 * 8 Allee Lenotre, La Grille Royale, 78600 Le Mesnil le Roi, France.
 *
 */

package com.aelitis.azureus.plugins.dht.impl;

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.Signature;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.RSAPublicKeySpec;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.gudy.azureus2.core3.util.*;

import com.aelitis.azureus.core.dht.DHT;
import com.aelitis.azureus.core.dht.DHTLogger;
import com.aelitis.azureus.core.dht.DHTStorageAdapter;
import com.aelitis.azureus.core.dht.DHTStorageBlock;
import com.aelitis.azureus.core.dht.DHTStorageKey;
import com.aelitis.azureus.core.dht.DHTStorageKeyStats;
import com.aelitis.azureus.core.dht.impl.DHTLog;
import com.aelitis.azureus.core.dht.transport.DHTTransportContact;
import com.aelitis.azureus.core.dht.transport.DHTTransportValue;
import com.aelitis.azureus.core.util.bloom.BloomFilter;
import com.aelitis.azureus.core.util.bloom.BloomFilterFactory;

/**
 * @author parg
 *
 */

public class 
DHTPluginStorageManager 
	implements DHTStorageAdapter
{
	private static final String	pub_exp = "10001";
	private static final String	modulus	= "b8a440c76405b2175a24c86d70f2c71929673a31045791d8bd84220a48729998900d227b560e88357074fa534ccccc6944729bfdda5413622f068e7926176a8afc8b75d4ba6cde760096624415b544f73677e8093ddba46723cb973b4d55f61c2003b73f52582894c018e141e8d010bb615cdbbfaeb97a7af6ce1a5a20a62994da81bde6487e8a39e66c8df0cfd9d763c2da4729cbf54278ea4912169edb0a33";
	
	private static final long		ADDRESS_EXPIRY			= 7*24*60*60*1000L; 
	private static final int		DIV_WIDTH				= 10;
	private static final int		DIV_FRAG_GET_SIZE		= 2;
	private static final long		DIV_EXPIRY_MIN			= 2*24*60*60*1000L;
	private static final long		DIV_EXPIRY_RAND			= 1*24*60*60*1000L;
	private static final long		KEY_BLOCK_TIMEOUT_SECS	= 7*24*60*60;
	
	public static final int			LOCAL_DIVERSIFICATION_SIZE_LIMIT			= 4096;
	public static final int			LOCAL_DIVERSIFICATION_ENTRIES_LIMIT			= 512;
	public static final int			LOCAL_DIVERSIFICATION_READS_PER_MIN_SAMPLES	= 3;
	public static final int			LOCAL_DIVERSIFICATION_READS_PER_MIN			= 30;
	
	public static final int			MAX_STORAGE_KEYS	= 65536;
	
	private int				network;
	private DHTLogger		log;
	private File			data_dir;
	
	private AEMonitor	address_mon	= new AEMonitor( "DHTPluginStorageManager:address" );
	private AEMonitor	contact_mon	= new AEMonitor( "DHTPluginStorageManager:contact" );
	private AEMonitor	storage_mon	= new AEMonitor( "DHTPluginStorageManager:storage" );
	private AEMonitor	version_mon	= new AEMonitor( "DHTPluginStorageManager:version" );
	private AEMonitor	key_block_mon	= new AEMonitor( "DHTPluginStorageManager:block" );
	
	private Map					version_map			= new HashMap();
	private Map					recent_addresses	= new HashMap();
	
	private Map					remote_diversifications	= new HashMap();
	private Map					local_storage_keys		= new HashMap();
	
	private volatile ByteArrayHashMap	key_block_map_cow		= new ByteArrayHashMap();
	private volatile DHTStorageBlock[]	key_blocks_direct_cow	= new DHTStorageBlock[0];
	private BloomFilter					kb_verify_fail_bloom;
	private long						kb_verify_fail_bloom_create_time;
	
	private static RSAPublicKey key_block_public_key;
	
	static{
		try{
			KeyFactory key_factory = KeyFactory.getInstance("RSA");
			
			RSAPublicKeySpec 	public_key_spec = 
				new RSAPublicKeySpec( new BigInteger(modulus,16), new BigInteger(pub_exp,16));
	
			key_block_public_key 	= (RSAPublicKey)key_factory.generatePublic( public_key_spec );

		}catch( Throwable e ){
			
			Debug.printStackTrace(e);
		}
	}
	
	public
	DHTPluginStorageManager(
		int					_network,
		DHTLogger			_log,
		File				_data_dir )
	{	
		network		= _network;
		log			= _log;
		data_dir	= _data_dir;
		
		FileUtil.mkdirs(data_dir);
		
		readRecentAddresses();
		
		readDiversifications();
		
		readVersionData();
		
		readKeyBlocks();
	}
	
	protected void
	importContacts(
		DHT		dht )
	{
		try{
			contact_mon.enter();
						
			File	target = new File( data_dir, "contacts.dat" );

			if ( !target.exists()){
				
				target	= new File( data_dir, "contacts.saving" );
			}

			if ( target.exists()){
				
				DataInputStream	dis =  new DataInputStream( new FileInputStream( target ));
				
				try{
					
					dht.importState( dis );
					
				}finally{
											
					dis.close();
				}
			}
		}catch( Throwable e ){
			
			Debug.printStackTrace( e );
			
		}finally{
			
			contact_mon.exit();
		}
	}
	
	protected void
	exportContacts(
		DHT		dht )
	{
		try{
			contact_mon.enter();
						
			File	saving = new File( data_dir, "contacts.saving" );
			File	target = new File( data_dir, "contacts.dat" );

			saving.delete();
			
			DataOutputStream	dos	= null;
			
			boolean	ok = false;
			
			try{
				FileOutputStream fos = new FileOutputStream( saving );
					
				dos = new DataOutputStream(fos);
					
				dht.exportState( dos, 32 );
					
				dos.flush();
					
				fos.getFD().sync();
			
				ok	= true;
				
			}finally{
				
				if ( dos != null ){
					
					dos.close();
					
					if ( ok ){
						
						target.delete();
						
						saving.renameTo( target );
					}
				}
			}
		}catch( Throwable e ){
			
			Debug.printStackTrace( e );
			
		}finally{
			
			contact_mon.exit();
		}
		
			// this is a good point to save diversifications - useful when they've expired
			// as writing isn't triggered at expiry time 
		
		writeDiversifications();
	}
	
	protected void
	readRecentAddresses()
	{
		try{
			address_mon.enter();
			
			recent_addresses = readMapFromFile( "addresses" );
	
		}finally{
			
			address_mon.exit();
		}
	}
	
	protected void
	writeRecentAddresses()
	{
		try{
			address_mon.enter();
			
				// remove any old crud
			
			Iterator	it = recent_addresses.keySet().iterator();
			
			while( it.hasNext()){
				
				String	key = (String)it.next();
				
				if ( !key.equals( "most_recent" )){
					
					Long	time = (Long)recent_addresses.get(key);
					
					if ( SystemTime.getCurrentTime() - time.longValue() > ADDRESS_EXPIRY ){
						
						it.remove();
					}
				}
			}
			
			writeMapToFile( recent_addresses, "addresses" );
			
		}catch( Throwable e ){
			
			Debug.printStackTrace(e);
	
		}finally{
			
			address_mon.exit();
		}
	}
	
	protected void
	recordCurrentAddress(
		String		address )
	{
		try{
			address_mon.enter();
			
			recent_addresses.put( address, new Long( SystemTime.getCurrentTime()));
		
			recent_addresses.put( "most_recent", address.getBytes());
			
			writeRecentAddresses();
			
		}finally{
			
			address_mon.exit();
		}
	}
	
	protected String
	getMostRecentAddress()
	{
		byte[]	addr = (byte[])recent_addresses.get( "most_recent" );
		
		if ( addr == null ){
			
			return( null );
		}
		
		return( new String( addr ));
	}
	
	protected boolean
	isRecentAddress(
		String		address )
	{
		try{
			address_mon.enter();

			if ( recent_addresses.containsKey( address )){
				
				return( true );
			}
					
			String	most_recent = getMostRecentAddress();
			
			return( most_recent != null && most_recent.equals( address ));
			
		}finally{
			
			address_mon.exit();
		}
	}
	
	protected void
	localContactChanged(
		DHTTransportContact	contact )
	{
		purgeDirectKeyBlocks();
	}
			
	
	protected Map
	readMapFromFile(
		String		file_prefix )
	{
		try{
			File target = new File( data_dir, file_prefix + ".dat" );
			
			if ( !target.exists()){
				
				target	= new File( data_dir, file_prefix + ".saving" );
			}
			
			if ( target.exists()){
				
				BufferedInputStream	is = new BufferedInputStream( new FileInputStream( target ));
				
				try{
					return( BDecoder.decode( is ));
					
				}finally{
					
					is.close();
				}
			}
		}catch( Throwable e ){
			
			Debug.printStackTrace( e );	
		}		
		
		return( new HashMap());
	}
	
	protected void
	writeMapToFile(
		Map			map,
		String		file_prefix )
	{
		try{
			File	saving = new File( data_dir, file_prefix + ".saving" );
			File	target = new File( data_dir, file_prefix + ".dat" );

			saving.delete();
			
			if ( map.size() == 0 ){
				
				target.delete();
				
			}else{
				
				FileOutputStream os = null;
				
				boolean	ok = false;
				
				try{
					byte[]	data = BEncoder.encode( map );
					
					os = new FileOutputStream( saving );
						
					os.write( data );
				
					os.flush();
				
					os.getFD().sync();
				
					os.close();
				
					ok	= true;
					
				}finally{
					
					if ( os != null ){
						
						os.close();
						
						if ( ok ){
							
							target.delete();
							
							saving.renameTo( target );
						}
					}
				}
			}
		}catch( Throwable e ){
			
			Debug.printStackTrace(e);
		}
	}
	
	protected void
	readVersionData()
	{
		try{
			version_mon.enter();
			
			version_map = readMapFromFile( "version" );
	
		}finally{
			
			version_mon.exit();
		}
	}
	
	protected void
	writeVersionData()
	{
		try{
			version_mon.enter();
			
			writeMapToFile( version_map, "version" );
	
		}finally{
			
			version_mon.exit();
		}
	}
	public int
	getNextValueVersions(
		int		num )
	{
		try{
			version_mon.enter();

			Long	l_next = (Long)version_map.get( "next" );
			
			int	now = (int)(SystemTime.getCurrentTime()/1000);

			int	next;
			
			if ( l_next == null ){

				next = now;
				
			}else{
				
				next = l_next.intValue();
				
					// if "next" is in the future then we live with it to try and ensure increasing
					// values (system clock must have changed)
				
				if ( next < now ){
					
					next = now;
				}
			}
			
			version_map.put( "next", new Long( next+num ));
			
			writeVersionData();
			
			return( next );
			
		}finally{
			
			version_mon.exit();
		}
	}
	
		// key storage
	
	public DHTStorageKey
	keyCreated(
		HashWrapper		key,
		boolean			local )
	{
		//System.out.println( "DHT key created");
		
		try{
			storage_mon.enter();
		
			return(	getStorageKey( key ));
			
		}finally{
			
			storage_mon.exit();
		}
	}
	
	public void
	keyDeleted(
		DHTStorageKey		key )
	{
		//System.out.println( "DHT key deleted" );
		
		try{
			storage_mon.enter();
		
			deleteStorageKey((storageKey)key );
			
		}finally{
			
			storage_mon.exit();
		}
	}
	
	public void
	keyRead(
		DHTStorageKey			key,
		DHTTransportContact		contact )
	{
		//System.out.println( "DHT value read" );
		
		try{
			storage_mon.enter();
		
			((storageKey)key).read( contact );
			
		}finally{
			
			storage_mon.exit();
		}
	}
	
	public void
	serialiseStats(
		storageKey			key,
		DataOutputStream	dos )
	
		throws IOException
	{
		dos.writeByte( (byte)0 );	// version
		dos.writeInt( key.getEntryCount());
		dos.writeInt( key.getSize());
		dos.writeInt( key.getReadsPerMinute());
		dos.writeByte( key.getDiversificationType());
	}
	
	public DHTStorageKeyStats
	deserialiseStats(
		DataInputStream			is )
	
		throws IOException
	{
		
		byte	version 	= is.readByte();
		
		final int	entry_count = is.readInt();
		final int	size		= is.readInt();
		final int	reads		= is.readInt();
		final byte	div			= is.readByte();

		return( 
			new DHTStorageKeyStats()
			{
				public int
				getEntryCount()
				{
					return( entry_count );
				}
				
				public int
				getSize()
				{
					return( size );
				}
				
				public int
				getReadsPerMinute()
				{
					return( reads );
				}
				
				public byte
				getDiversification()
				{
					return( div );
				}
			});
	}
	
	public void
	valueAdded(
		DHTStorageKey		key,
		DHTTransportValue	value )
	{
		// System.out.println( network + ": DHT value added: "  + DHTLog.getString2( ((storageKey)key).getKey().getBytes()) + " -> " + value.getString());
		
		try{
			storage_mon.enter();
		
			((storageKey)key).valueChanged( 1, value.getValue().length);
			
		}finally{
			
			storage_mon.exit();
		}
	}
	
	public void
	valueUpdated(
		DHTStorageKey		key,
		DHTTransportValue	old_value,
		DHTTransportValue	new_value )
	{
		//System.out.println( "DHT value updated" );
		
		try{
			storage_mon.enter();
			
			((storageKey)key).valueChanged( 0, new_value.getValue().length - old_value.getValue().length);
			
		}finally{
			
			storage_mon.exit();
		}
	}
	
	public void
	valueDeleted(
		DHTStorageKey		key,
		DHTTransportValue	value )
	{
		//System.out.println( "DHT value deleted" );
		
		try{
			storage_mon.enter();
		
			((storageKey)key).valueChanged( -1, -value.getValue().length);
			
		}finally{
			
			storage_mon.exit();
		}
	}
	
	public boolean
	isDiversified(
		byte[]		key )
	{
		HashWrapper	wrapper = new HashWrapper( key );
		
		try{
			storage_mon.enter();
		
			return( lookupDiversification( wrapper ) != null );
			
		}finally{
			
			storage_mon.exit();
		}
	}
	
		// get diversifications for put operations must deterministically return the same end points
		// but gets for gets should be randomised to load balance
	
	public byte[][]
	getExistingDiversification(
		byte[]			key,
		boolean			put_operation,
		boolean			exhaustive )
	{
		//System.out.println( "DHT get existing diversification: put = " + put_operation  );
		
		HashWrapper	wrapper = new HashWrapper( key );
		
			// must always return a value - original if no diversification exists
		
		try{
			storage_mon.enter();
		
			byte[][]	res = followDivChain( wrapper, put_operation, exhaustive );
			
			if ( !Arrays.equals( res[0], key )){
				
				String	trace = "";
				
				for (int i=0;i<res.length;i++){
					trace += (i==0?"":",") + DHTLog.getString2( res[i] );
				}
				
				log.log( "SM: get div: " + DHTLog.getString2(key) + ", put = " + put_operation + ", exh = " + exhaustive + " -> " + trace );
			}
			
			return( res );
			
		}finally{
			
			storage_mon.exit();
		}
	}
	
	public byte[][]
	createNewDiversification(
		DHTTransportContact	cause,
		byte[]				key,
		boolean				put_operation,
		byte				diversification_type,
		boolean				exhaustive )
	{
		//System.out.println( "DHT create new diversification: put = " + put_operation +", type = " + diversification_type );
		
		HashWrapper	wrapper = new HashWrapper( key );
		
		try{
			storage_mon.enter();
		
			diversification	div = lookupDiversification( wrapper );
		
			boolean	created = false;
			
			if ( div == null ){
				
				div = createDiversification( wrapper, diversification_type );
				
				created	= true;			
			}
		
			byte[][] res = followDivChain( wrapper, put_operation, exhaustive );
		
			String	trace = "";
			
			for (int i=0;i<res.length;i++){
				
				trace += (i==0?"":",") + DHTLog.getString2( res[i] );
			}
			
			log.log( "SM: create div: " + DHTLog.getString2(key) + 
						", new = " + created + ", put = " + put_operation + 
						", exh = " + exhaustive + 
						", type = " + DHT.DT_STRINGS[diversification_type] + " -> " + trace +
						", cause = " + (cause==null?"<unknown>":cause.getString()));
			

			return( res );
			
		}finally{
			
			storage_mon.exit();
		}
	} 
	
	protected byte[][]
	followDivChain(
		HashWrapper	wrapper,
		boolean		put_operation,
		boolean		exhaustive )
	{
		List	list = new ArrayList();
		
		list.add( wrapper );
		
		list	= followDivChain( list, put_operation, 0, exhaustive, new ArrayList());
		
		byte[][]	res = new byte[list.size()][];
		
		for (int i=0;i<list.size();i++){
			
			res[i] = ((HashWrapper)list.get(i)).getBytes();
		}
		
		return( res );
	}
	
	protected List
	followDivChain(
		List		list_in,
		boolean		put_operation,
		int			depth,
		boolean		exhaustive,
		List		keys_done )
	{
		List	list_out = new ArrayList();
	
		/*
		String	indent = "";
		for(int i=0;i<depth;i++){
			indent+= "  ";
		}
		System.out.println( indent + "->" );
		*/
		
			// for each entry, if there are no diversifications then we just return the value
			// for those with divs we replace their entry with the diversified set (which can
			// include the entry itself under some circumstances )
		
		for (int i=0;i<list_in.size();i++){
			
			HashWrapper	wrapper = (HashWrapper)list_in.get(i);
		
			diversification	div = lookupDiversification( wrapper );

			if ( div == null ){
				
				if ( !list_out.contains( wrapper )){
					
					list_out.add(wrapper);
				}
				
			}else{
				
				if ( keys_done.contains( wrapper )){
					
						// we've recursed on the key, this means that a prior diversification wanted
						// the key included, so include it now
					
					if ( !list_out.contains( wrapper )){
						
						list_out.add(wrapper);
					}
					
					continue;
				}
				
				keys_done.add( wrapper );
				
					// replace this entry with the diversified keys 
				
				List	new_list = followDivChain( div.getKeys( put_operation, exhaustive ), put_operation, depth+1, exhaustive, keys_done );
				
				for (int j=0;j<new_list.size();j++){
					
					Object	entry =  new_list.get(j);
					
					if ( !list_out.contains( entry )){
						
						list_out.add(entry);
					}
				}
			}
		}
		// System.out.println( indent + "<-" );

		return( list_out );
	}
	
	protected storageKey
	getStorageKey(
		HashWrapper		key )
	{
		storageKey	res = (storageKey)local_storage_keys.get( key );
		
		if ( res == null ){
			
				// someout could be spamming us with crap, prevent things from getting
				// out of control
			
			if ( local_storage_keys.size() >= MAX_STORAGE_KEYS ){
				
				res = new storageKey( this, DHT.DT_SIZE, key ); 

				Debug.out( "DHTStorageManager: max key limit exceeded" );
				
				log.log( "SM: max storage key limit exceeded - " + DHTLog.getString2( key.getBytes()));
				
			}else{

				res = new storageKey( this, DHT.DT_NONE, key ); 
			
				local_storage_keys.put( key, res );
			}
		}
		
		return( res );
	}
	
	protected void
	deleteStorageKey(
		storageKey		key )
	{
		if ( local_storage_keys.remove( key ) != null ){
		
			if ( key.getDiversificationType() != DHT.DT_NONE ){
				
				writeDiversifications();
			}
		}
	}
	
	protected void
	readDiversifications()
	{
		try{
			storage_mon.enter();
			
			Map	map = readMapFromFile( "diverse" );
	
			List	keys = (List)map.get("local");
			
			if ( keys != null ){
				
				long	now = SystemTime.getCurrentTime();
				
				for (int i=0;i<keys.size();i++){
					
					storageKey d = storageKey.deserialise(this, (Map)keys.get(i));
						
					long	time_left = d.getExpiry() - now;
					
					if ( time_left > 0 ){
					
						local_storage_keys.put( d.getKey(), d );
						
					}else{
						
						log.log( "SM: serialised sk: " + DHTLog.getString2( d.getKey().getBytes()) + " expired" );
					}
				}
			}
			List	divs = (List)map.get("remote");
			
			if ( divs != null ){
				
				long	now = SystemTime.getCurrentTime();
				
				for (int i=0;i<divs.size();i++){
					
					diversification d = diversification.deserialise( this, (Map)divs.get(i));
						
					long	time_left = d.getExpiry() - now;

					if ( time_left > 0 ){
					
						remote_diversifications.put( d.getKey(), d );
						
					}else{
						
						log.log( "SM: serialised div: " + DHTLog.getString2( d.getKey().getBytes()) + " expired" );
					}
				}
			}
			
		}finally{
			
			storage_mon.exit();
		}
	}
	
	protected void
	writeDiversifications()
	{
		try{
			storage_mon.enter();
	
			Map	map = new HashMap();
			
			List	keys = new ArrayList();
			
			map.put( "local", keys );
			
			Iterator	it = local_storage_keys.values().iterator();
			
			while( it.hasNext()){
			
				storageKey	key = (storageKey)it.next();
				
				if ( key.getDiversificationType() != DHT.DT_NONE ){
					
					keys.add(key.serialise());
				}
			}
			
			List	divs = new ArrayList();
			
			map.put( "remote", divs );
			
			it = remote_diversifications.values().iterator();
			
			while( it.hasNext()){
			
				divs.add(((diversification)it.next()).serialise());
			}
			
			writeMapToFile( map, "diverse" );
			
		}catch( Throwable e ){
			
			Debug.printStackTrace(e);
	
		}finally{
			
			storage_mon.exit();
		}
	}
	
	protected diversification
	lookupDiversification(
		HashWrapper	wrapper )
	{
		diversification	div = (diversification)remote_diversifications.get(wrapper);
		
		if ( div != null ){
			
			if ( div.getExpiry() < SystemTime.getCurrentTime()){
				
				log.log( "SM: div: " + DHTLog.getString2( div.getKey().getBytes()) + " expired" );

				remote_diversifications.remove( wrapper );
				
				div = null;
			}
		}
		
		return( div );
	}
	
	protected diversification
	createDiversification(
		HashWrapper			wrapper,
		byte				type )
	{
		diversification	div = new diversification( this, wrapper, type );
			
		remote_diversifications.put( wrapper, div );
		
		writeDiversifications();
		
		return( div );
	}
	
	protected static String
	formatExpiry(
		long	l )
	{
		long	diff = l - SystemTime.getCurrentTime();
		
		return( (diff<0?"-":"") + DisplayFormatters.formatTime(Math.abs(diff)));
	}
	
	
		// key blocks
	
	protected void
	readKeyBlocks()
	{
		try{
			key_block_mon.enter();
			
			Map	map = readMapFromFile( "block" );
	
			List	entries = (List)map.get( "entries" );
			
			int	now_secs = (int)(SystemTime.getCurrentTime()/1000);
			
			ByteArrayHashMap	new_map = new ByteArrayHashMap();
			
			if ( entries != null ){
			
				for (int i=0;i<entries.size();i++){
					
					try{
						Map	m = (Map)entries.get(i);
						
						byte[]	request = (byte[])m.get( "req" );
						byte[]	cert	= (byte[])m.get( "cert" );
						int		recv	= ((Long)m.get( "received" )).intValue();
						boolean	direct	= ((Long)m.get( "direct" )).longValue()==1;
						
						if ( recv > now_secs ){
							
							recv	= now_secs;
						}

						keyBlock	kb = new keyBlock( request, cert, recv, direct );

							// direct "add" values never timeout, however direct "removals" do, as do 
							// indirect values
						
						if ( ( direct && kb.isAdd()) || now_secs - recv < KEY_BLOCK_TIMEOUT_SECS ){
						
							if ( verifyKeyBlock( request, cert )){
								
								log.log( "KB: deserialised " + DHTLog.getString2( kb.getKey()) + ",add=" + kb.isAdd() + ",dir=" + kb.isDirect());
						
								new_map.put( kb.getKey(), kb );
							}
						}
						
					}catch( Throwable e ){
						
						Debug.printStackTrace(e);
					}
				}
			}
			
			key_block_map_cow		= new_map;
			key_blocks_direct_cow	= buildKeyBlockDetails( new_map );
			
		}finally{
			
			key_block_mon.exit();
		}
	}
	
	protected DHTStorageBlock[]
	buildKeyBlockDetails(
		ByteArrayHashMap		map )
	{
		List	kbs = map.values();
		
		Iterator	it = kbs.iterator();
		
		while( it.hasNext()){
			
			keyBlock	kb = (keyBlock)it.next();
			
			if ( !kb.isDirect()){
				
				it.remove();
			}
		}
		
		DHTStorageBlock[]	new_blocks = new DHTStorageBlock[kbs.size()];
		
		kbs.toArray( new_blocks );
		
		return( new_blocks );
	}
	
	protected void
	writeKeyBlocks()
	{
		try{
			key_block_mon.enter();
	
			Map	map = new HashMap();
			
			List	entries = new ArrayList();
			
			map.put( "entries", entries );
			
			List	kbs = key_block_map_cow.values();
			
			for (int i=0;i<kbs.size();i++){
								
				keyBlock	kb = (keyBlock)kbs.get(i);
									
				Map	m = new HashMap();
				
				m.put( "req", kb.getRequest());
				m.put( "cert", kb.getCertificate());
				m.put( "received", new Long(kb.getReceived()));
				m.put( "direct", new Long(kb.isDirect()?1:0));
				
				entries.add( m );
			}
			
			writeMapToFile( map, "block" );
			
		}catch( Throwable e ){
			
			Debug.printStackTrace(e);
	
		}finally{
			
			key_block_mon.exit();
		}
	}
	
	
	public DHTStorageBlock
	keyBlockRequest(
		DHTTransportContact		originating_contact,
		byte[]					request,
		byte[]					signature )
	{
			// request is 4 bytes flags, 4 byte time, K byte key
			// flag: MSB 00 -> unblock, 01 ->block
		
		if ( request.length <= 8 ){
			
			return( null );
		}
				
		keyBlock	kb = 
			new keyBlock(request, signature, (int)(SystemTime.getCurrentTime()/1000), originating_contact != null );
		
		try{
			key_block_mon.enter();

			boolean	add_it	= false;
			
			try{
				keyBlock	old = (keyBlock)key_block_map_cow.get( kb.getKey());
								
				if ( old != null ){
				
						// never override a direct value with an indirect one as direct = first hand knowledge
						// whereas indirect is hearsay

					if ( old.isDirect() && !kb.isDirect()){
					
						return( null );
					}
					 
						// don't let older instructions override newer ones
					
					if ( old.getCreated() > kb.getCreated()){
						
						return( null );
					}
				}
				
				if ( kb.isAdd()){
					
					if ( old == null || !old.isAdd()){
						
						if ( !verifyKeyBlock( kb, originating_contact )){
							
							return( null );
						}
					
						add_it	= true;
					}
					
					return( kb );
					
				}else{
					
						// only direct operations can "remove" blocks
					
					if ( kb.isDirect() && ( old == null || old.isAdd())){
					
						if ( !verifyKeyBlock( kb, originating_contact )){
							
							return( null );
						}
						
						add_it	= true;
					}
					
					return( null );
				}
			}finally{
				
				if ( add_it ){
					
					ByteArrayHashMap new_map = key_block_map_cow.duplicate();
					
					new_map.put( kb.getKey(), kb );
					
						// seeing as we've received this from someone there's no point in replicating it
						// back to them later - mark them to prevent this
					
					if ( originating_contact != null ){
						
						kb.sentTo( originating_contact );
					}
					
					key_block_map_cow		= new_map;
					key_blocks_direct_cow	= buildKeyBlockDetails( key_block_map_cow );
					
					writeKeyBlocks();
				}
			}
		}finally{
			
			key_block_mon.exit();
		}
	}
	
	protected boolean
	verifyKeyBlock(
		keyBlock				kb,
		DHTTransportContact		originator )
	{
		byte[]	id = originator==null?new byte[20]:originator.getID();
		
		BloomFilter	filter = kb_verify_fail_bloom;
		
		long	now = SystemTime.getCurrentTime();
		
		if ( 	filter == null || 
				kb_verify_fail_bloom_create_time > now ||
				now - kb_verify_fail_bloom_create_time > 30*60*1000 ){
			
			kb_verify_fail_bloom_create_time	= now;
			
			filter = BloomFilterFactory.createAddOnly(4000);
			
			kb_verify_fail_bloom	= filter;
		}
		
		if ( filter.contains( id )){
			
			log.log( "KB: request verify denied" );
			
			return( false );
		}
		
		try{
			Signature	verifier = Signature.getInstance("MD5withRSA" );
			
			verifier.initVerify( key_block_public_key );
			
			verifier.update( kb.getRequest() );

			if ( !verifier.verify( kb.getCertificate())){
			
				log.log( "KB: request verify failed for " + DHTLog.getString2( kb.getKey()));

				filter.add( id );
				
				return( false );
			}
			
			log.log( "KB: request verify ok " + DHTLog.getString2( kb.getKey()) + ", add = " + kb.isAdd() + ", direct = " + kb.isDirect());

			return( true );
			
		}catch( Throwable e ){
			
			return( false );
		}
	}
	
	public static boolean
	verifyKeyBlock(
		byte[]		request,
		byte[]		signature )
	{
		try{
			Signature	verifier = Signature.getInstance("MD5withRSA" );
			
			verifier.initVerify( key_block_public_key );
			
			verifier.update( request );

			if ( !verifier.verify( signature )){
			
				return( false );
			}
			
			return( true );
			
		}catch( Throwable e ){
			
			return( false );
		}
	}
	
	public DHTStorageBlock
	getKeyBlockDetails(
		byte[]		key )
	{
		keyBlock	kb = (keyBlock)key_block_map_cow.get( key );
		
		if ( kb == null || !kb.isAdd()){
			
			return( null );
		}
		
		if ( !kb.getLogged()){
			
			kb.setLogged();
			
			log.log( "KB: Access to key '" + DHTLog.getFullString( kb.getKey()) + "' denied as it is blocked" );
		}
		
		return( kb );
	}
	
	public DHTStorageBlock[]
	getDirectKeyBlocks()
	{
		return( key_blocks_direct_cow );
	}
	
	public byte[]
	getKeyForKeyBlock(
		byte[]	request )
	{
		if ( request.length <= 8 ){
			
			return( new byte[0] );
		}
		
		byte[]	key = new byte[ request.length - 8 ];
		
		System.arraycopy( request, 8, key, 0, key.length );
		
		return( key );
	}
	
	protected void
	purgeDirectKeyBlocks()
	{
		try{
			key_block_mon.enter();
		
			ByteArrayHashMap new_map = new ByteArrayHashMap();
			
			Iterator	it = key_block_map_cow.values().iterator();
			
			boolean	changed = false;
			
			while( it.hasNext()){
				
				keyBlock	kb = (keyBlock)it.next();
				
				if ( kb.isDirect()){
					
					changed	= true;
					
				}else{
					
					new_map.put( kb.getKey(), kb );
				}
			}
			
			if ( changed ){
				
				log.log( "KB: Purged direct entries on ID change" );
				
				key_block_map_cow		= new_map;
				key_blocks_direct_cow	= buildKeyBlockDetails( key_block_map_cow );
				
				writeKeyBlocks();
			}
		}finally{
			
			key_block_mon.exit();
		}
	}
	
	public void
	setStorageForKey(
		String	key,
		byte[]	data )
	{
		try{
			storage_mon.enter();
			
			Map	map = readMapFromFile( "general" );
			
			map.put( key, data );
			
			writeMapToFile( map, "general" );
			
		}finally{
			
			storage_mon.exit();
		}
	}
	
	public byte[]
	getStorageForKey(
		String	key )
	{
		try{
			storage_mon.enter();
			
			Map	map = readMapFromFile( "general" );
			
			return((byte[])map.get( key ));
			
		}finally{
			
			storage_mon.exit();
		}
	}
	
	protected static class
	keyBlock
		implements DHTStorageBlock
	{
		private byte[]		request;
		private byte[]		cert;
		private int			received;
		private boolean		direct;
		
		private BloomFilter	sent_to_bloom;
		private boolean		logged;
		
		protected
		keyBlock(
			byte[]		_request,
			byte[]		_cert,
			int			_received,
			boolean		_direct )
		{
			request		= _request;
			cert		= _cert;
			received	= _received;
			direct		= _direct;
		}
		
		public byte[]
		getRequest()
		{
			return( request );
		}
		
		public byte[]
		getCertificate()
		{
			return( cert );
		}
		    		
		public byte[]
		getKey()
		{
			byte[]	key = new byte[ request.length - 8 ];
		
			System.arraycopy( request, 8, key, 0, key.length );
			
			return( key );
		}
		
		protected boolean
		isAdd()
		{
			return( request[0] == 0x01 );
		}
		
		protected boolean
		getLogged()
		{
			return( logged );
		}
		
		protected void
		setLogged()
		{
			logged	= true;
		}
		
		protected int
		getCreated()
		{
			int	created = 
					(request[4]<<24)&0xff000000 | 
					(request[5]<<16)&0x00ff0000 | 
					(request[6]<< 8)&0x0000ff00 | 
					 request[7]     &0x000000ff;
						
			return( created );
		}
		
		protected int
		getReceived()
		{
			return( received );
		}
		
		protected boolean
		isDirect()
		{
			return( direct );
		}
		
		public boolean
		hasBeenSentTo(
			DHTTransportContact	contact )
		{
			BloomFilter	filter = sent_to_bloom;
			
			if ( filter == null ){
				
				return( false );
			}
			
			return( filter.contains( contact.getID()));
		}
		
		public void
		sentTo(
			DHTTransportContact	contact )
		{
			BloomFilter	filter = sent_to_bloom;
			
			if ( filter == null || filter.getEntryCount() > 100 ){
				
				filter = BloomFilterFactory.createAddOnly(500);
				
				sent_to_bloom	= filter;
			}
		
			filter.add( contact.getID());
		}
	}
	
	protected static class
	diversification
	{
		private DHTPluginStorageManager	manager;	

		private HashWrapper			key;
		private byte				type;
		
		private long				expiry;
		
		private int[]				fixed_put_offsets;
		
		protected
		diversification(
			DHTPluginStorageManager	_manager,
			HashWrapper				_key,
			byte					_type )
		
		{
			manager	= _manager;
			key		= _key;
			type	= _type;
			
			expiry	= SystemTime.getCurrentTime() + DIV_EXPIRY_MIN + (long)(Math.random() * DIV_EXPIRY_RAND );
			
			fixed_put_offsets	= new int[DIV_FRAG_GET_SIZE];
			
			int	pos = 0;
			
			while( pos < DIV_FRAG_GET_SIZE ){
				
				int i = (int)(Math.random()*DIV_WIDTH);
				
				boolean	found = false;
				
				for (int j=0;j<pos;j++){
					
					if( i == fixed_put_offsets[j] ){
						
						found	= true;
						
						break;
					}
				}
				
				if ( !found ){
					
					fixed_put_offsets[pos++] = i;
				}
			}
		}
		
		protected
		diversification(
			DHTPluginStorageManager	_manager,
			HashWrapper				_key,
			byte					_type,
			long					_expiry,
			int[]					_fixed_put_offsets )
		{
			manager				= _manager;
			key					= _key;
			type				= _type;
			expiry				= _expiry;
			fixed_put_offsets	= _fixed_put_offsets;
		}
		
		protected Map
		serialise()
		{
			Map	map = new HashMap();
			
			map.put( "key", key.getBytes());
			map.put( "type", new Long(type));
			map.put( "exp", new Long(expiry));
			
			List	offsets = new ArrayList();
			
			for (int i=0;i<fixed_put_offsets.length;i++){
				
				offsets.add( new Long( fixed_put_offsets[i]));
			}
			
			map.put( "fpo", offsets );
			
			manager.log.log( "SM: serialised div: " + DHTLog.getString2( key.getBytes()) + ", " + DHT.DT_STRINGS[type] + ", " + formatExpiry(expiry));

			return( map );
		}
		
		protected static diversification
		deserialise(
			DHTPluginStorageManager	_manager,
			Map						_map )
		{
			HashWrapper	key 	= new HashWrapper((byte[])_map.get("key"));
			int			type 	= ((Long)_map.get("type")).intValue(); 
			long		exp 	= ((Long)_map.get("exp")).longValue();
			
			List	offsets = (List)_map.get("fpo");
			
			int[]	fops = new int[offsets.size()];
			
			for (int i=0;i<fops.length;i++){
				
				fops[i] = ((Long)offsets.get(i)).intValue();
			}
			
			_manager.log.log( "SM: deserialised div: " + DHTLog.getString2( key.getBytes()) + ", " + DHT.DT_STRINGS[type] + ", " + formatExpiry(exp));

			return( new diversification( _manager, key, (byte)type, exp, fops ));
		}
		
		protected HashWrapper
		getKey()
		{
			return( key );
		}
		
		protected long
		getExpiry()
		{
			return( expiry );
		}
		
		protected List
		getKeys(
			boolean		put,
			boolean		exhaustive )
		{
			List	keys = new ArrayList();
			
			if ( put ){
				
				if ( type == DHT.DT_FREQUENCY ){
					
						// put to all keys
										
					for (int i=0;i<DIV_WIDTH;i++){
						
						keys.add( diversifyKey( key, i ));
					}
					
					if ( exhaustive ){
						
							// include original key
						
						// System.out.println( "followDivs:put:freq adding original" );
						
						keys.add( key );
					}				
				}else{
					
						// put to a fixed subset. has to be fixed else over time we'll put to
						// all the fragmented locations and nullify the point of this. gets are
						// randomised to we don't loose out by fixing the puts
															
					for (int i=0;i<fixed_put_offsets.length;i++){
						
						keys.add( diversifyKey( key, fixed_put_offsets[i]));
					}	
					
					if ( exhaustive ){
						
							// include original key
						
						// System.out.println( "followDivs:put:size adding original" );

						keys.add( key );
					}
				}
			}else{
				
					// get always returns a randomised selection
				
				if ( type == DHT.DT_FREQUENCY ){
					
						// diversification has lead to caching at all 'n' places
					
					keys.add( diversifyKey( key,(int)(Math.random()*DIV_WIDTH)));
					
				}else{
					
						// diversification has fragmented across 'n' places
						// select 2 to search or all if exhaustive
					
					if ( exhaustive ){
						
						for (int i=0;i<DIV_WIDTH;i++){
							
							keys.add( diversifyKey( key, i ));
						}

						// System.out.println( "followDivs:get:size adding all" );

					}else{
						
						List	randoms = new ArrayList();
						
						while( randoms.size() < DIV_FRAG_GET_SIZE ){
							
							Integer	i = new Integer((int)(Math.random()*DIV_WIDTH));
							
							if ( !randoms.contains(i)){
								
								randoms.add( i );
							}
						}
											
						for (int i=0;i<DIV_FRAG_GET_SIZE;i++){
							
							keys.add( diversifyKey( key, ((Integer) randoms.get(i)).intValue()));
						}
					}
				}
			}
			
			return( keys );
		}
	
		protected HashWrapper
		diversifyKey(
			HashWrapper		key_in,
			int				offset )
		{
			byte[]	old_bytes	= key_in.getBytes();
			
			byte[]	bytes = new byte[old_bytes.length+1];
			
			System.arraycopy( old_bytes, 0, bytes, 0, old_bytes.length );
			
			bytes[old_bytes.length] = (byte)offset;
			
			return( new HashWrapper( new SHA1Simple().calculateHash( bytes )));
		}
	}
	
	protected static class
	storageKey
		implements DHTStorageKey
	{
		private DHTPluginStorageManager	manager;
		
		private HashWrapper				key;	
		private byte					type;
		
		private int				size;
		private int				entries;
		
		private long			expiry;
		
		private long			read_count_start;
		private short			reads_per_min;
		
		private BloomFilter		ip_bloom_filter;
		
		protected
		storageKey(
			DHTPluginStorageManager	_manager,
			byte					_type,
			HashWrapper				_key )
		{
			manager		= _manager;
			type		= _type;
			key			= _key;
			
			expiry	= SystemTime.getCurrentTime() + DIV_EXPIRY_MIN + (long)(Math.random() * DIV_EXPIRY_RAND );
		}
		
		protected
		storageKey(
			DHTPluginStorageManager	_manager,
			byte					_type,
			HashWrapper				_key,
			long					_expiry )
		{
			manager		= _manager;
			type		= _type;
			key			= _key;
			expiry		= _expiry;
		}
		
		protected Map
		serialise()
		{
			Map	map = new HashMap();
			
			map.put( "key", key.getBytes());
			map.put( "type", new Long(type));
			map.put( "exp", new Long(expiry));
			
			manager.log.log( "SM: serialised sk: " + DHTLog.getString2( key.getBytes()) + ", " + DHT.DT_STRINGS[type] + ", " + formatExpiry(expiry) );
			
			return( map );
		}
		
		protected static storageKey
		deserialise(
			DHTPluginStorageManager	_manager,
			Map						map )
		{
			HashWrapper	key 	= new HashWrapper((byte[])map.get("key"));
			int			type 	= ((Long)map.get("type")).intValue(); 
			long		exp 	= ((Long)map.get("exp")).longValue();
			
			_manager.log.log( "SM: deserialised sk: " + DHTLog.getString2( key.getBytes()) + ", " + DHT.DT_STRINGS[type] + ", " + formatExpiry(exp));

			return( new storageKey( _manager, (byte)type, key, exp ));
		}
	
		public void
		serialiseStats(
			DataOutputStream	dos )
		
			throws IOException
		{
			manager.serialiseStats( this, dos );
		}
		
		protected HashWrapper
		getKey()
		{
			return( key );
		}
		
		protected long
		getExpiry()
		{
			return( expiry );
		}
		
		public byte
		getDiversificationType()
		{
			if ( type != DHT.DT_NONE ){
				
					// trigger timeouts here
				
				if ( expiry < SystemTime.getCurrentTime()){

					type	= DHT.DT_NONE;
					
					manager.log.log( "SM: sk: " + DHTLog.getString2( getKey().getBytes()) + " expired" );

					manager.writeDiversifications();
				}
			}
			
			return( type );
		}
		
		public int
		getReadsPerMinute()
		{
			return( reads_per_min );
		}
		
		public int
		getSize()
		{
			return( size );
		}
		
		public int
		getEntryCount()
		{
			return( entries );
		}
		
		protected void
		read(
			DHTTransportContact	contact )
		{
			// System.out.println( "read: " + DHTLog.getString2( key.getBytes()));
						
			if ( type == DHT.DT_NONE ){				

				long	now = SystemTime.getCurrentTime();
				
				long	diff = now - read_count_start;

				if ( diff > LOCAL_DIVERSIFICATION_READS_PER_MIN_SAMPLES*60*1000 ){

					if ( ip_bloom_filter != null ){
						
						int	ip_entries = ip_bloom_filter.getEntryCount();
						
						reads_per_min = (short)( ip_entries / LOCAL_DIVERSIFICATION_READS_PER_MIN_SAMPLES );
						
						if ( reads_per_min == 0 && ip_entries > 0 ){
						
								// show at least some activity!
							
							reads_per_min	= 1;
						}
						
						if ( ip_entries > LOCAL_DIVERSIFICATION_READS_PER_MIN * LOCAL_DIVERSIFICATION_READS_PER_MIN_SAMPLES ){
						
							type = DHT.DT_FREQUENCY;
							
							manager.log.log( "SM: sk freq created (" + ip_entries + "reads ) - " + DHTLog.getString2( key.getBytes()));
							
							manager.writeDiversifications();
						}
					}
										
					read_count_start	= now;

					ip_bloom_filter	= null;	// just null it and drop this read, doesn't matter
											// and means that we don't bother creating a filter for
											// infrequently accessed data
					
				}else{
					
					if ( ip_bloom_filter == null ){
						
							// we want to hold enough IPs to detect a hit rate of reads_per_min*min
							// with a reasonable accuracy (sized to 10/3 to save space - this gives
							// an average of 100 adds required to detect 90 unique)
						
						ip_bloom_filter = BloomFilterFactory.createAddOnly(
								( LOCAL_DIVERSIFICATION_READS_PER_MIN * LOCAL_DIVERSIFICATION_READS_PER_MIN_SAMPLES *10 ) / 3 );
					}
					
					byte[]	address_bytes = contact.getAddress().getAddress().getAddress();
					
					ip_bloom_filter.add( address_bytes );
				}
			}
		}
		
		protected void
		valueChanged(
			int		entries_diff,
			int		size_diff )
		{
			entries += entries_diff;
			size	+= size_diff;
			
			if ( entries < 0 ){
				Debug.out( "entries negative" );
				entries	= 0;
			}
			
			if ( size < 0 ){
				Debug.out( "size negative" );
				size	= 0;
			}
			
			if ( type == DHT.DT_NONE ){
				
				if ( size > LOCAL_DIVERSIFICATION_SIZE_LIMIT ){
				
					type	= DHT.DT_SIZE;
					
					manager.log.log( "SM: sk size total created (size " + size + ") - " + DHTLog.getString2( key.getBytes()));

					manager.writeDiversifications();
					
				}else if ( entries > LOCAL_DIVERSIFICATION_ENTRIES_LIMIT ){
					
					type 	= DHT.DT_SIZE;
					
					manager.log.log( "SM: sk size entries created (" + entries + " entries) - " + DHTLog.getString2( key.getBytes()));

					manager.writeDiversifications();
				}
			}
			
			// System.out.println( "value changed: entries = " + entries + "(" + entries_diff + "), size = " +	size +  "(" + size_diff + ")");
		}
	}
}
