/*
 * Created on 03-Mar-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 org.gudy.azureus2.pluginsimpl.local.ddb;


import java.util.*;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

import org.gudy.azureus2.core3.download.DownloadManager;
import org.gudy.azureus2.core3.logging.LogAlert;
import org.gudy.azureus2.core3.logging.Logger;
import org.gudy.azureus2.core3.peer.PEPeerSource;
import org.gudy.azureus2.core3.util.*;
import org.gudy.azureus2.plugins.PluginInterface;
import org.gudy.azureus2.plugins.ddb.*;
import org.gudy.azureus2.plugins.download.Download;
import org.gudy.azureus2.plugins.torrent.Torrent;
import org.gudy.azureus2.plugins.torrent.TorrentAttribute;
import org.gudy.azureus2.pluginsimpl.local.PluginCoreUtils;
import org.gudy.azureus2.pluginsimpl.local.PluginInitializer;

import com.aelitis.azureus.plugins.dht.DHTPluginProgressListener;

/**
 * @author parg
 *
 */

public class 
DDBaseTTTorrent
	implements DistributedDatabaseTransferType, DistributedDatabaseTransferHandler
{
	private static final boolean	TRACE			= false;
	
	private static final byte	CRYPTO_VERSION	= 1;
	
	static{
		if ( TRACE ){
			System.out.println( "**** Torrent xfer tracing on ****" );
		}
	}
	
	private DDBaseImpl		ddb;
		
	private TorrentAttribute	ta_sha1;
	
	private boolean				crypto_tested;
	private boolean				crypto_available;
	
	private List				external_downloads;
	
	private Map	data_cache = 
		new LinkedHashMap(5,0.75f,true)
		{
			protected boolean 
			removeEldestEntry(
		   		Map.Entry eldest) 
			{
				return size() > 5;
			}
		};
		
	protected
	DDBaseTTTorrent(
		DDBaseImpl		_ddb )
	{
		ddb					= _ddb;
	}
	
	public void
	addDownload(
		Download		download )
	{
		synchronized( this ){
			
			if ( external_downloads == null ){
				
				external_downloads = new ArrayList();
			}
			
			external_downloads.add( download );
		}
	}
	
	public void
	removeDownload(
		Download		download )
	{
		synchronized( this ){
			
			if ( external_downloads != null ){
				
				external_downloads.remove( download );
			
				if ( external_downloads.size() == 0 ){
				
					external_downloads = null;
				}
			}
		}
	}
	
		// server side read
	
	public DistributedDatabaseValue
	read(
		DistributedDatabaseContact			contact,
		DistributedDatabaseTransferType		type,
		DistributedDatabaseKey				key )
	
		throws DistributedDatabaseException
	{
			// We use sha1(hash) as the key for torrent downloads
			// and encrypt the torrent content using the hash as the basis for a key. This
			// prevents someone without the hash from downloading the torrent
		
		try{
			byte[]	search_key = ((DDBaseKeyImpl)key).getBytes();
			
			Download 	download = null;
				
			PluginInterface pi = PluginInitializer.getDefaultInterface();
									
			String	search_sha1 = pi.getUtilities().getFormatters().encodeBytesToString( search_key );
			
			if ( ta_sha1 == null ){
				
				ta_sha1 = pi.getTorrentManager().getPluginAttribute( "DDBaseTTTorrent::sha1");
			}
				
				// gotta look for the sha1(hash)
			
			Download[]	downloads = pi.getDownloadManager().getDownloads();
			
			for (int i=0;i<downloads.length;i++){
				
				Download	dl = downloads[i];
				
				if ( dl.getTorrent() == null ){
					
					continue;
				}
				
				String	sha1 = dl.getAttribute( ta_sha1 );
				
				if ( sha1 == null ){
					
					sha1 = pi.getUtilities().getFormatters().encodeBytesToString( 
								new SHA1Simple().calculateHash( dl.getTorrent().getHash()));
					
					dl.setAttribute( ta_sha1, sha1 );
				}
				
				if ( sha1.equals( search_sha1 )){
					
					download	= dl;
										
					break;
				}
			}
				
			if ( download == null ){
				
				synchronized( this ){
					
					if ( external_downloads != null ){
						
						for (int i=0;i<external_downloads.size();i++){
							
							Download	dl = (Download)external_downloads.get(i);
							
							if ( dl.getTorrent() == null ){
								
								continue;
							}
							
							String	sha1 = dl.getAttribute( ta_sha1 );
							
							if ( sha1 == null ){
								
								sha1 = pi.getUtilities().getFormatters().encodeBytesToString( 
											new SHA1Simple().calculateHash( dl.getTorrent().getHash()));
								
								dl.setAttribute( ta_sha1, sha1 );
							}
							
							if ( sha1.equals( search_sha1 )){
								
								download	= dl;
													
								break;
							}
						}
					}
				}
			}
			
			String	originator = contact.getName();
			
			if ( download == null ){
				
				String msg = "TorrentDownload: request from " + originator + " for '" + pi.getUtilities().getFormatters().encodeBytesToString( search_key ) + "' not found";
				
				if ( TRACE ){
					
					System.out.println( msg );
				}
				
				ddb.log( msg );
				
					// torrent not found - probably been removed whilst info still published in DHT
				
				return( null );
				
			}
			
			Torrent	torrent = download.getTorrent();
			
			if ( torrent.isPrivate()){
				
				Debug.out( "Attempt to download private torrent" );
				
				ddb.log( "TorrentDownload: request from " + originator + "  for '" + download.getName() + "' denied as it is private" );
				
					// should never happen as private torrents are not tracked so they can't be found for
					// download
				
				return( null );
			}
			
			try{
					// apparently there are some trackers using non-private torrents with passkeys. Crazy, however to give users at
					// least the opportunity to prevent .torrent transfer for these torrents we deny this if the DHT peer source has
					// been disabled by the user
				
				DownloadManager dm = PluginCoreUtils.unwrapIfPossible( download );
				
				if ( dm != null && !dm.getDownloadState().isPeerSourceEnabled( PEPeerSource.PS_DHT )){
					
					ddb.log( "TorrentDownload: request from " + originator + "  for '" + download.getName() + "' denied as DHT peer source disabled" );
					
					return( null );
				}
			}catch( Throwable e ){
				
				Debug.out( e );
			}
			
			String	msg = "TorrentDownload: request from " + originator + "  for '" + download.getName() + "' OK";		

			if ( TRACE ){
				
				System.out.println( msg );
			}
			
			ddb.log( msg );
			
			HashWrapper	hw = new HashWrapper( torrent.getHash());
			
			synchronized( data_cache ){
				
				Object[]	data = (Object[])data_cache.get( hw );
				
				if ( data != null ){
										
					data[1] = new Long( SystemTime.getCurrentTime());
					
					return( ddb.createValue((byte[])data[0]));
				}
			}
			
			
			torrent = torrent.removeAdditionalProperties();
			
				// when clients get a torrent from the DHT they take on
				// responsibility for tracking it too
			
			torrent.setDecentralisedBackupRequested( true );
			
			byte[] data = torrent.writeToBEncodedData();
							
			data = encrypt( torrent.getHash(), data );
				
			if ( data == null ){
					
				return( null );
			}
			
			synchronized( data_cache ){

				if ( data_cache.size() == 0 ){
					
					final TimerEventPeriodic[]pe = { null };
					
					pe[0] = SimpleTimer.addPeriodicEvent(
						"DDBTorrent:timeout",
						30*1000,
						new TimerEventPerformer()
						{
							public void
							perform(
								TimerEvent	event )
							{								
								long now = SystemTime.getCurrentTime();
								
								synchronized( data_cache ){

									Iterator	it = data_cache.values().iterator();
									
									while( it.hasNext()){
										
										long	time = ((Long)((Object[])it.next())[1]).longValue();
								
										if ( now < time || now - time > 120*1000 ){
											
											it.remove();
										}
									}
									
									if ( data_cache.size() == 0 ){
										
										pe[0].cancel();
									}
								}
							}	
						});
				}
				
				data_cache.put( hw, new Object[]{ data, new Long( SystemTime.getCurrentTime())});
			}
				
			return( ddb.createValue( data ));
			
		}catch( Throwable e ){
			
			throw( new DistributedDatabaseException("Torrent write fails", e ));
		}
	}
	
		// server side write
	
	public DistributedDatabaseValue
	write(
		DistributedDatabaseContact			contact,
		DistributedDatabaseTransferType		type,
		DistributedDatabaseKey				key,
		DistributedDatabaseValue			value )
	
		throws DistributedDatabaseException
	{
		throw( new DistributedDatabaseException( "not supported" ));
	}
	
		// client side read
	
	protected DistributedDatabaseValue
	read(
		DDBaseContactImpl							contact,
		final DistributedDatabaseProgressListener	listener,
		DistributedDatabaseTransferType				type,
		DistributedDatabaseKey						key,
		long										timeout )
	
		throws DistributedDatabaseException
	{
		byte[]	torrent_hash	= ((DDBaseKeyImpl)key).getBytes();
		
		byte[]	lookup_key	= new SHA1Simple().calculateHash( torrent_hash );
					
		if ( TRACE ){
			System.out.println( "TorrentXfer: sending via sha1(hash)" );
		}
		
		byte[]	data = contact.getContact().read( 
							new DHTPluginProgressListener()
							{
								public void
								reportSize(
									long	size )
								{
									listener.reportSize( size );
								}
								
								public void
								reportActivity(
									String	str )
								{
									listener.reportActivity( str );
								}
								
								public void
								reportCompleteness(
									int		percent )
								{
									listener.reportCompleteness( percent );
								}
							},
							DDBaseHelpers.getKey(type.getClass()).getHash(),
							lookup_key,
							timeout );
							
		if ( data == null ){
			
			return( null );
		}
		
		data = decrypt( torrent_hash, data );
			
		if ( data == null ){
				
			return( null );
		}
		
		return( new DDBaseValueImpl( contact, data, SystemTime.getCurrentTime(), -1));
	}
	
	protected byte[]
   	encrypt(
   		byte[]		hash,
   		byte[]		data )
   	{
		if ( !testCrypto()){
			
			return( null );
		}
		
   		byte[]	enc = doCrypt( Cipher.ENCRYPT_MODE, hash, data, 0 );
		
		if ( enc == null ){
			
			if ( TRACE ){
				
				System.out.println( "TorrentXfer: encryption failed, using plain" );
			}
			
			byte[]	res = new byte[data.length+2];
			
			res[0] = CRYPTO_VERSION;
			res[1] = 0;	// not encrypted

			System.arraycopy( data, 0, res, 2, data.length );
			
			return( res );
			
		}else{
		
			if ( TRACE ){
				
				System.out.println( "TorrentXfer: encryption ok" );
			}

			byte[]	res = new byte[enc.length+2];
			
			res[0] = CRYPTO_VERSION;
			res[1] = 1;	// encrypted

			System.arraycopy( enc, 0, res, 2, enc.length );

			return( res );
		}
   	}
	
	protected byte[]
  	decrypt(
  		byte[]		hash,
  		byte[]		data )
  	{
		if ( !testCrypto()){
			
			return( null );
		}
		
		if ( data[0] != CRYPTO_VERSION ){
			
			Debug.out( "Invalid crypto version received" );
			
			return( data );
		}
		
		if ( data[1] == 0 ){
			
				// encryption failed, in plain
			
			if ( TRACE ){
				System.out.println( "TorrentXfer: encryption failed, retrieving plain" );
			}

			byte[]	res = new byte[data.length-2];
			
			System.arraycopy( data, 2, res, 0, res.length );
			
			return( res );
			
		}else{
  		
			if ( TRACE ){
				System.out.println( "TorrentXfer: encryption ok, decrypting" );
			}

			byte[]	res =  doCrypt( Cipher.DECRYPT_MODE, hash, data, 2 );
			
			return( res );
		}
  	}
	
	protected byte[]
	doCrypt(
		int			mode,
		byte[]		hash,
		byte[]		data,
		int			data_offset )
	{
		try{
			byte[]	key_data = new byte[24];
			
				// hash is 20 bytes so we've got 4 zeros at the end. tough
			
			System.arraycopy( hash, 0, key_data, 0, hash.length );
			
			SecretKey tdes_key = new SecretKeySpec( key_data, "DESede" );

			Cipher cipher = Cipher.getInstance("DESede");  // Triple-DES encryption

			cipher.init(mode, tdes_key );
						
			return( cipher.doFinal(data, data_offset, data.length - data_offset ));
						
		}catch( Throwable e ){
			
			Debug.out( e );
			
			return( null );
		}
	}
	
	protected boolean
	testCrypto()
	{
		if ( !crypto_tested ){
			
			crypto_tested	= true;
		
			try{
				Cipher.getInstance("DESede");  // Triple-DES encryption
	
				crypto_available	= true;
				
			}catch( Throwable e ){
				
				Logger.log(new LogAlert(LogAlert.UNREPEATABLE,
						"Unable to initialise cryptographic framework for magnet-based "
								+ "torrent downloads, please re-install Java", e));
			}
		}
		
		return( crypto_available );
	}
}
