/*
 *  PHEX - The pure-java Gnutella-servent.
 *  Copyright (C) 2001 - 2007 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: ConnectionObserver.java 4117 2008-01-26 18:29:20Z gregork $
 */
package phex.connection;


import java.util.ArrayList;
import java.util.List;

import phex.common.ThreadTracking;
import phex.common.log.NLogger;
import phex.host.Host;
import phex.host.HostStatus;
import phex.host.NetworkHostsContainer;
import phex.msghandling.MessageService;
import phex.utils.Localizer;


/**
 * Observes the connected hosts to find sleeping connections. It verifies if
 * these connection still respond to incoming ping. In case they don't respond
 * the connections are dropped.
 */
public class ConnectionObserver implements Runnable
{
    private long SLEEP_TIME = 30000;
    private long PING_WAIT_TIME = 20000;

    private List<ConnectionSnapshoot> snapshootList;
    private List<Host> quiteList;
    private final NetworkHostsContainer networkHostsContainer;
    private final MessageService messageService;

    public ConnectionObserver( NetworkHostsContainer networkHostsContainer,
        MessageService messageService )
    {
        this.networkHostsContainer = networkHostsContainer;
        this.messageService = messageService;
    }

    public void start()
    {
        Thread thread = new Thread( ThreadTracking.rootThreadGroup, this,
            "ConnectionObserver-" + Integer.toHexString( hashCode() ) );
        thread.setPriority( Thread.NORM_PRIORITY );
        thread.setDaemon( true );
        thread.start();
    }

    public void run()
    {
        snapshootList = new ArrayList<ConnectionSnapshoot>();
        quiteList = new ArrayList<Host>();
        while( true )
        {
            snapshootList.clear();
            quiteList.clear();

            Host[] hosts = networkHostsContainer.getUltrapeerConnections();
            createSnapshoots(hosts);
            hosts = networkHostsContainer.getLeafConnections();
            createSnapshoots(hosts);
            hosts = networkHostsContainer.getPeerConnections();
            createSnapshoots(hosts);

            //Sleep some time...
            try
            {
                Thread.sleep( SLEEP_TIME );
            }
            catch (InterruptedException e)
            {
            }

            // Find connections that where quite in the meantime
            hosts = networkHostsContainer.getUltrapeerConnections();
            findQuiteHosts( hosts );
            hosts = networkHostsContainer.getLeafConnections();
            findQuiteHosts( hosts );
            hosts = networkHostsContainer.getPeerConnections();
            findQuiteHosts( hosts );

            if ( quiteList.size() > 0 )
            {
                // send a ping to each connection in the hope they respond to it.
                int size = quiteList.size();
                for ( int i = 0; i < size; i++ )
                {
                    Host host = quiteList.get( i );
                    NLogger.debug(ConnectionObserver.class,
                        host + " - Sending keep alive ping. " );
                    // first ping all hosts in the quite host list.
                    messageService.pingHost( host );
                }
                //Wait some time for the pinged hosts to respond...
                try
                {
                    Thread.sleep( PING_WAIT_TIME );
                }
                catch (InterruptedException e)
                {
                }
                for ( int i = 0; i < size; i++ )
                {
                    Host host = quiteList.get( i );
                    // Disconnect connection if it was still quite in the meantime
                    ConnectionSnapshoot shoot = findSnapshoot( host );
                    if ( shoot.hasBeenQuite( ) )
                    {
                        host.setStatus( HostStatus.ERROR,
                            Localizer.getString( "HostNotResponding" ) );
                        NLogger.debug(ConnectionObserver.class,
                            host + " - Host not responding, disconnecting.." );
                        host.disconnect();
                    }
                }
            }
        }
    }

    private void findQuiteHosts( Host[] hosts )
    {
        for ( int i = 0; i < hosts.length; i++ )
        {
            ConnectionSnapshoot shoot = findSnapshoot( hosts[i] );
            if ( shoot == null )
            {// this is a new host...
                continue;
            }

            if ( shoot.hasBeenQuite( ) )
            {
                quiteList.add( hosts[i] );
            }
        }
    }

    private void createSnapshoots( Host[] hosts )
    {
        for ( int i = 0; i < hosts.length; i++ )
        {
            snapshootList.add( new ConnectionSnapshoot( hosts[i] ) );
        }
    }

    private ConnectionSnapshoot findSnapshoot( Host host )
    {
        int size = snapshootList.size();
        for ( int i = 0; i < size; i++ )
        {
            ConnectionSnapshoot shoot = snapshootList.get( i );
            if ( shoot.host == host )
            {
                return shoot;
            }
        }
        return null;
    }

    private class ConnectionSnapshoot
    {
        Host host;
        int receivedCount;
        int sentCount;
        int sendDropCount;

        ConnectionSnapshoot( Host host )
        {
            this.host = host;
            receivedCount = host.getReceivedCount();
            sentCount = host.getSentCount();
            sendDropCount = host.getSendDropCount();
        }

        /**
         * Returns true if the data has not changed. This means we have received
         * no new data, or all sent packages have been dropped.
         * @return true if the host has been quite, false others.
         */
        public boolean hasBeenQuite( )
        {
            int receivedDiff = host.getReceivedCount() - receivedCount;
            int sentDiff = host.getSentCount() - sentCount;
            int sendDropDiff = host.getSendDropCount() - sendDropCount;

            if ( receivedDiff == 0 )
            {
                return true;
            }

            if ( sentDiff == sendDropDiff && sentDiff != 0 )
            {
                return true;
            }

            return false;
        }
    }
}