/*
 *  PHEX - The pure-java Gnutella-servent.
 *  Copyright (C) 2001 - 2008 Phex Development Group
 *
 *  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
 * 
 *  --- SVN Information ---
 *  $Id: ConnectionEngine.java 4205 2008-06-18 09:49:16Z gregork $
 */
package phex.connection;

import java.io.IOException;
import java.util.StringTokenizer;

import phex.common.address.AddressUtils;
import phex.common.address.DefaultDestAddress;
import phex.common.address.DestAddress;
import phex.common.address.IpAddress;
import phex.common.address.MalformedDestAddressException;
import phex.common.log.NLogger;
import phex.connection.handshake.HandshakeHandler;
import phex.connection.handshake.HandshakeStatus;
import phex.host.CaughtHostsContainer;
import phex.host.Host;
import phex.host.HostStatus;
import phex.http.GnutellaHeaderNames;
import phex.http.HTTPHeader;
import phex.http.HTTPHeaderGroup;
import phex.http.HTTPHeaderNames;
import phex.http.HTTPProcessor;
import phex.io.buffer.ByteBuffer;
import phex.msg.InvalidMessageException;
import phex.msg.Message;
import phex.msg.MessageProcessor;
import phex.msg.MsgHeader;
import phex.msg.vendor.CapabilitiesVMsg;
import phex.msg.vendor.MessagesSupportedVMsg;
import phex.msghandling.MessageService;
import phex.net.connection.Connection;
import phex.net.repres.PresentationManager;
import phex.prefs.core.MessagePrefs;
import phex.query.DynamicQueryConstants;
import phex.security.AccessType;
import phex.security.PhexSecurityManager;
import phex.servent.Servent;
import phex.utils.HexConverter;
import phex.utils.Localizer;

/**
 * <p>A worker that handles the communication between this and another gnutella
 * node.</p>
 *
 * <p>The remote node is represented as a Host object. Depending on whether the
 * host is in incoming or outgoing mode, this will perform the relevant
 * handshake negotiations. If this was an
 * outgoing connection, or during negotiations it becomes clear that the Host
 * wishes to partake in a Gnutella network, then enter a message handling loop
 * to forward all messages as necessary. This will usualy result in a message
 * being read, some bookkeeping to keep track of the message, discarding bad
 * messages and finally queuing a request with the Message Manager to pass on any
 * messages that must be generated in response.</p>
 */
public class ConnectionEngine implements ConnectionConstants
{
    private final Servent servent;
    private final MessageService messageService;
    private final PhexSecurityManager securityService;

    /**
     * pre-allocated buffer for repeated uses.
     */
    private byte[] headerBuffer;

    private final Host connectedHost;
    private final Connection connection; 
    private HTTPHeaderGroup headersRead;
    private HTTPHeaderGroup headersSend;

    public ConnectionEngine( Servent servent, Host connectedHost )
    {
        this.servent = servent;
        this.messageService = servent.getMessageService();
        this.securityService = servent.getSecurityService();
        this.connectedHost = connectedHost;
        this.connection = connectedHost.getConnection();
    }

    public void processIncomingData()
        throws IOException
    {
        headerBuffer = new byte[ MsgHeader.DATA_LENGTH ];
        try
        {
            while ( true )
            {
                MsgHeader header = readHeader();
                byte[] body = MessageProcessor.readMessageBody( connection,
                    header.getDataLength() );

                connectedHost.incReceivedCount();

                int ttl = header.getTTL();
                int hops = header.getHopsTaken();
                // verify valid ttl and hops data
                if ( ttl < 0 || hops < 0 )
                {
                    messageService.dropMessage( header, body, 
                        "TTL or hops below 0", connectedHost );
                    continue;
                }
                // if message traveled too far already... drop it.
                if ( hops > MessagePrefs.MaxNetworkTTL.get().intValue() )
                {
                    messageService.dropMessage( header, body, 
                        "Hops larger then maxNetworkTTL", connectedHost );
                    continue;
                }
                // limit TTL if too high!
                if ( ttl >= MessagePrefs.MaxNetworkTTL.get().intValue() )
                {
                    header.setTTL( (byte)(MessagePrefs.MaxNetworkTTL.get().intValue() - hops) );
                }

                Message message;
                try
                {
                    message = MessageProcessor.createMessageFromBody(
                        header, body, securityService );
                    if ( message == null )
                    { // unknown message type...
                        messageService.dropMessage( header, body, 
                            "Unknown message type", connectedHost );
                        continue;
                    }
                }
                catch ( InvalidMessageException exp )
                {
                    messageService.dropMessage( header, body,
                        "Invalid message: " + exp.getMessage(), connectedHost );
                    NLogger.warn( ConnectionEngine.class, exp, exp );
                    continue;
                }

                // count the hop and decrement TTL...
                header.countHop();

                messageService.dispatchMessage( message, connectedHost );
            }
        }
        catch ( IOException exp )
        {
            NLogger.debug( ConnectionEngine.class, exp, exp );
            if ( connectedHost.isConnected() )
            {
                connectedHost.setStatus( HostStatus.ERROR, exp.getMessage());
                connectedHost.disconnect();
            }
            throw exp;
        }
        catch ( Exception exp )
        {
            NLogger.warn( ConnectionEngine.class, exp, exp );
            if (connectedHost.isConnected() )
            {
                connectedHost.setStatus( HostStatus.ERROR, exp.getMessage());
                connectedHost.disconnect();
            }
            throw new IOException( "Exception occured: " + exp.getMessage() );
        }
    }

    private MsgHeader readHeader()
        throws IOException
    {
        MsgHeader header = MessageProcessor.parseMessageHeader( connection,
            headerBuffer );
        if ( header == null )
        {
            throw new ConnectionClosedException("Connection closed by remote host");
        }

        int length = header.getDataLength();
        if ( length < 0 )
        {
            throw new IOException( "Negative body size. Disconnecting the remote host." );
        }
        else if ( length > MessagePrefs.MaxLength.get().intValue() )
        {
            // Packet looks suspiciously too big.  Disconnect them.
            if ( NLogger.isWarnEnabled( ConnectionEngine.class ) )
            {
                // max 256KB when over 64KB max message length
                byte[] body = MessageProcessor.readMessageBody(
                    connection, 262144 );
                String hexBody = HexConverter.toHexString( body );
                NLogger.warn( ConnectionEngine.class, connectedHost + 
                    " - Body too big. Header: " + header + "\nBody(256KB): " + hexBody );
            }

            throw new IOException("Packet too big. Disconnecting the remote host.");
        }

        header.setArrivalTime( System.currentTimeMillis() );
        header.setFromHost( connectedHost );

        return header;
    }

    //////////////////// Connection Intialization //////////////////////////////
    
    public void initHostHandshake( )
        throws IOException
    {
        try
        {
            if ( connectedHost.isIncomming() )
            {
                initializeIncomingWith06();
            }
            else
            {
                initializeOutgoingWith06();
            }
            configureConnectionType( headersSend, headersRead );
            postHandshakeConfiguration( headersSend, headersRead );
        }
        finally
        {
            if ( headersRead != null )
            {
                // use the connection header whether connection was ok or not
                handleXTryHeaders( headersRead );
                // give free to gc
                headersRead = null;
                headersSend = null;
            }
        }
        
        // Connection to remote gnutella host is completed at this point.
        connectedHost.setStatus( HostStatus.CONNECTED );
        if ( connectedHost.isIncomming() )
        {
            servent.getHostService().addIncomingHost( connectedHost );
        }
        else
        {
            servent.getHostService().addConnectedHost( connectedHost );
        }
        
        // send UDP ping as soon as we have recognized host
        servent.getMessageService().sendUdpPing( connectedHost.getHostAddress() );

        // queue first Ping msg to send.
        // add ping routing to local host to track my initial pings...
        servent.getMessageService().pingHost( connectedHost, 
            MessagePrefs.TTL.get().byteValue() );
        
        // after initial handshake ping send message supported VM.
        if ( connectedHost.isVendorMessageSupported( ) )
        {
            MessagesSupportedVMsg vMsg = MessagesSupportedVMsg.getMyMsgSupported();
            connectedHost.queueMessageToSend( vMsg );
            
            CapabilitiesVMsg capVMsg = CapabilitiesVMsg.getMyCapabilitiesVMsg();
            connectedHost.queueMessageToSend( capVMsg );
        }
    }

    private void initializeIncomingWith06()
        throws IOException
    {
        // read connect headers
        headersRead = HTTPProcessor.parseHTTPHeaders( connection );
        if ( NLogger.isDebugEnabled( ConnectionEngine.class ) )
        {
            NLogger.debug( ConnectionEngine.class, connectedHost + 
                " - Connect headers: " + headersRead.buildHTTPHeaderString() );
        }
        configureRemoteHost( headersRead );

        // create appropriate handshake handler that takes care about headers
        // and logic...
        HandshakeHandler handshakeHandler = HandshakeHandler.createHandshakeHandler(
            servent, connectedHost );
        HandshakeStatus myResponse = handshakeHandler.createHandshakeResponse(
            new HandshakeStatus( headersRead ), false );
        headersSend = myResponse.getResponseHeaders();

        // send answer to host...
        sendStringToHost( GNUTELLA_06 + " " + myResponse.getStatusCode() + " " +
            myResponse.getStatusMessage() + "\r\n" );
        String httpHeaderString = myResponse.getResponseHeaders().buildHTTPHeaderString();
        sendStringToHost( httpHeaderString );
        sendStringToHost( "\r\n" );

        if ( myResponse.getStatusCode() != STATUS_CODE_OK )
        {
            throw new IOException( "Connection not accepted: " +
                myResponse.getStatusCode() + " " + myResponse.getStatusMessage() );
        }

        HandshakeStatus inResponse = HandshakeStatus.parseHandshakeResponse(
            connection );
        if ( NLogger.isDebugEnabled( ConnectionEngine.class ) )
        {
            NLogger.debug( ConnectionEngine.class, connectedHost +
                " - Response Code: '" + inResponse.getStatusCode() + "'." );
            NLogger.debug( ConnectionEngine.class, connectedHost +
                " - Response Message: '" + inResponse.getStatusMessage() + "'."  );
            NLogger.debug( ConnectionEngine.class, connectedHost +
                " - Response Headers: "
                + inResponse.getResponseHeaders().buildHTTPHeaderString() );
        }

        if ( inResponse.getStatusCode() != STATUS_CODE_OK )
        {
            throw new IOException( "Host rejected connection: " +
                inResponse.getStatusCode() + " " +
                inResponse.getStatusMessage() );
        }
        headersRead.replaceHeaders( inResponse.getResponseHeaders() );
    }

    private void initializeOutgoingWith06()
        throws IOException
    {
        connectedHost.setStatus( HostStatus.CONNECTING,
            Localizer.getString( "Negotiate0_6Handshake") );

        // Send the first handshake greeting to the remote host.
        String greeting = servent.getGnutellaNetwork().getNetworkGreeting();

        String requestLine = greeting + '/' + PROTOCOL_06 + "\r\n";
        StringBuffer requestBuffer = new StringBuffer( 100 );
        requestBuffer.append( requestLine );

        // create appropriate handshake handler that takes care about headers
        // and logic...
        HandshakeHandler handshakeHandler = HandshakeHandler.createHandshakeHandler(
            servent, connectedHost );

        HTTPHeaderGroup handshakeHeaders =  
            handshakeHandler.createOutgoingHandshakeHeaders();
        requestBuffer.append( handshakeHeaders.buildHTTPHeaderString() );
        requestBuffer.append( "\r\n" );
        headersSend = handshakeHeaders;

        String requestStr = requestBuffer.toString();
        sendStringToHost( requestStr );

        HandshakeStatus handshakeResponse = HandshakeStatus.parseHandshakeResponse(
            connection );
        headersRead = handshakeResponse.getResponseHeaders();
        if ( NLogger.isDebugEnabled( ConnectionEngine.class ) )
        {
            NLogger.debug( ConnectionEngine.class, connectedHost +
                " - Response Code: '" + handshakeResponse.getStatusCode() + "'." );
            NLogger.debug( ConnectionEngine.class, connectedHost +
                " - Response Message: '" + handshakeResponse.getStatusMessage() + "'."  );
            NLogger.debug( ConnectionEngine.class, connectedHost +
                " - Response Headers: "
                + headersRead.buildHTTPHeaderString() );
        }

        if ( handshakeResponse.getStatusCode() != STATUS_CODE_OK )
        {
            if ( handshakeResponse.getStatusCode() == STATUS_CODE_REJECTED )
            {
                throw new ConnectionRejectedException(
                    handshakeResponse.getStatusCode() + " "
                    + handshakeResponse.getStatusMessage() );
            }
            throw new ConnectionRejectedException(
                "Gnutella 0.6 connection rejected. Status: " +
                handshakeResponse.getStatusCode() + " - " +
                handshakeResponse.getStatusMessage() );
        }

        configureRemoteHost( headersRead );

        HandshakeStatus myResponse = handshakeHandler.createHandshakeResponse(
            handshakeResponse, true );
        HTTPHeaderGroup myResponseHeaders = myResponse.getResponseHeaders();
        headersSend.replaceHeaders( myResponseHeaders );
        // send answer to host...
        sendStringToHost( GNUTELLA_06 + " " + myResponse.getStatusCode() + " " +
            myResponse.getStatusMessage() + "\r\n" );
        String httpHeaderString = myResponseHeaders.buildHTTPHeaderString();
        sendStringToHost( httpHeaderString );
        sendStringToHost( "\r\n" );

        if ( myResponse.getStatusCode() != STATUS_CODE_OK )
        {
            throw new ConnectionRejectedException( "Connection not accepted: " +
                myResponse.getStatusCode() + " " + myResponse.getStatusMessage() );
        }
    }

    private void configureConnectionType( HTTPHeaderGroup myHeadersSend,
       HTTPHeaderGroup theirHeadersRead )
    {
        HTTPHeader myUPHeader = myHeadersSend.getHeader(
            GnutellaHeaderNames.X_ULTRAPEER );
        HTTPHeader theirUPHeader = theirHeadersRead.getHeader(
            GnutellaHeaderNames.X_ULTRAPEER );
        if ( myUPHeader == null || theirUPHeader == null )
        {
            connectedHost.setConnectionType( Host.CONNECTION_NORMAL );
        }
        else if ( myUPHeader.booleanValue() )
        {
            if ( theirUPHeader.booleanValue() )
            {
                connectedHost.setConnectionType( Host.CONNECTION_UP_UP );
            }
            else
            {
                connectedHost.setConnectionType( Host.CONNECTION_UP_LEAF );
            }
        }
        else // !myUPHeader.booleanValue()
        {
            if ( theirUPHeader.booleanValue() )
            {
                connectedHost.setConnectionType( Host.CONNECTION_LEAF_UP );
            }
            else
            {
                connectedHost.setConnectionType( Host.CONNECTION_NORMAL );
            }
        }
    }

    private void handleXTryHeaders( HTTPHeaderGroup headers )
    {
        // X-Try header is not used by most servents anymore... (2003-02-25)
        // we read still read it a while though...
        // http://groups.yahoo.com/group/the_gdf/message/14316
        HTTPHeader[] hostAddresses = headers.getHeaders(
            GnutellaHeaderNames.X_TRY );
        if ( hostAddresses != null )
        {
            handleXTryHosts( hostAddresses, true );
        }
        // for us ultrapeers have low priority other high.. since we cant connect to UP..
        hostAddresses = headers.getHeaders(
            GnutellaHeaderNames.X_TRY_ULTRAPEERS );
        if ( hostAddresses != null )
        {
            handleXTryHosts( hostAddresses, false );
        }
    }

    private void handleXTryHosts( HTTPHeader[] xtryHostAdresses, boolean isUltrapeerList )
    {
        short priority;
        if ( isUltrapeerList )
        {
            priority = CaughtHostsContainer.HIGH_PRIORITY;
        }
        else
        {
            priority = CaughtHostsContainer.NORMAL_PRIORITY;
        }
        CaughtHostsContainer hostContainer = servent.getHostService().getCaughtHostsContainer();

        for ( int i = 0; i < xtryHostAdresses.length; i++ )
        {
            StringTokenizer tokenizer = new StringTokenizer(
                xtryHostAdresses[i].getValue(), "," );
            while( tokenizer.hasMoreTokens() )
            {
                String hostAddressStr = tokenizer.nextToken().trim();
                try
                {
                    DestAddress address = PresentationManager.getInstance()
                        .createHostAddress( hostAddressStr, DefaultDestAddress.DEFAULT_PORT );
                    AccessType access = securityService.controlHostAddressAccess( address );
                    switch ( access )
                    {
                        case ACCESS_DENIED:
                        case ACCESS_STRONGLY_DENIED:
                            // skip host address...
                            continue;
                    }
                    IpAddress ipAddress = address.getIpAddress();
                    if ( !isUltrapeerList && ipAddress != null && ipAddress.isSiteLocalIP() )
                    { // private IP have low priority except for ultrapeers.
                        priority = CaughtHostsContainer.LOW_PRIORITY;
                    }
                    hostContainer.addCaughtHost( address, priority );
                }
                catch ( MalformedDestAddressException exp )
                {
                }
            }
        }
    }
    
    /**
     * This method uses the header fields to set attributes of the remote host
     * accordingly.
     */
    private void configureRemoteHost( HTTPHeaderGroup headers )
    {
        HTTPHeader header = headers.getHeader( HTTPHeaderNames.USER_AGENT );
        if ( header != null )
        {
            connectedHost.setVendor( header.getValue() );
        }

        if ( connectedHost.isIncomming() )
        {
            header = headers.getHeader( GnutellaHeaderNames.LISTEN_IP );
            if ( header == null )
            {
                header = headers.getHeader( GnutellaHeaderNames.X_MY_ADDRESS );
            }
            if ( header != null )
            {
                DestAddress addi = connectedHost.getHostAddress();
                // parse port
                int port = AddressUtils.parsePort( header.getValue() );
                if ( port > 0 )
                {
                    addi.setPort( port );
                }
            }
        }
        
        header = headers.getHeader( GnutellaHeaderNames.REMOTE_IP );
        if ( header != null )
        {
            byte[] remoteIP = AddressUtils.parseIP( header.getValue() );
            if ( remoteIP != null )
            {
                IpAddress ip = new IpAddress( remoteIP );
                DestAddress address = PresentationManager.getInstance().createHostAddress(ip, -1);
                servent.updateLocalAddress( address );                
            }
        }

        header = headers.getHeader( GnutellaHeaderNames.X_QUERY_ROUTING );
        if ( header != null )
        {
            try
            {
                float version = Float.parseFloat( header.getValue() );
                if ( version >= 0.1f )
                {
                    connectedHost.setQueryRoutingSupported( true );
                }
            }
            catch ( NumberFormatException e )
            { // no qr supported... don't care
            }
        }

        header = headers.getHeader( GnutellaHeaderNames.X_UP_QUERY_ROUTING );
        if ( header != null )
        {
            try
            {
                float version = Float.parseFloat( header.getValue() );
                if ( version >= 0.1f )
                {
                    connectedHost.setUPQueryRoutingSupported( true );
                }
            }
            catch ( NumberFormatException e )
            { // no qr supported... don't care
            }
        }
        
        header = headers.getHeader( GnutellaHeaderNames.X_DYNAMIC_QUERY );
        if ( header != null )
        {
            try
            {
                float version = header.floatValue();
                if ( version >= 0.1f )
                {
                    connectedHost.setDynamicQuerySupported( true );
                }
            }
            catch ( NumberFormatException e)
            {// no dynamiy query supported... don't care
            }
        }
        
        byte maxTTL = headers.getByteHeaderValue( GnutellaHeaderNames.X_MAX_TTL, 
            DynamicQueryConstants.DEFAULT_MAX_TTL );
        connectedHost.setMaxTTL( maxTTL );
        
        int degree = headers.getIntHeaderValue( GnutellaHeaderNames.X_DEGREE, 
            DynamicQueryConstants.NON_DYNAMIC_QUERY_DEGREE );
        connectedHost.setUltrapeerDegree( degree );
    }
    
    private void postHandshakeConfiguration( HTTPHeaderGroup myHeadersSend,
       HTTPHeaderGroup theirHeadersRead )
       throws IOException

    {
        if ( myHeadersSend.isHeaderValueContaining( HTTPHeaderNames.ACCEPT_ENCODING,
            "deflate" ) && theirHeadersRead.isHeaderValueContaining(
            HTTPHeaderNames.CONTENT_ENCODING, "deflate" ) )
        {
            connectedHost.activateInputInflation();
        }
        if ( theirHeadersRead.isHeaderValueContaining( HTTPHeaderNames.ACCEPT_ENCODING,
            "deflate" ) && myHeadersSend.isHeaderValueContaining(
            HTTPHeaderNames.CONTENT_ENCODING, "deflate" ) )
        {
            connectedHost.activateOutputDeflation();
        }
        
        
        HTTPHeader header = theirHeadersRead.getHeader( 
            GnutellaHeaderNames.VENDOR_MESSAGE );
        if ( header != null && !header.getValue().equals("") )
        {
            connectedHost.setVendorMessageSupported( true );
        }
    }

    private void sendStringToHost( String str )
        throws IOException
    {
        NLogger.debug( ConnectionEngine.class, connectedHost +
            " - Send: " + str );
        byte[] bytes = str.getBytes( "ISO8859-1" );
        connection.write( ByteBuffer.wrap( bytes ) );
        connection.flush();
    }
}