//
//  ========================================================================
//  Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.server.nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.nio.channels.SelectionKey;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;

import org.eclipse.jetty.continuation.Continuation;
import org.eclipse.jetty.io.AsyncEndPoint;
import org.eclipse.jetty.io.ConnectedEndPoint;
import org.eclipse.jetty.io.Connection;
import org.eclipse.jetty.io.EndPoint;
import org.eclipse.jetty.io.nio.AsyncConnection;
import org.eclipse.jetty.io.nio.SelectChannelEndPoint;
import org.eclipse.jetty.io.nio.SelectorManager;
import org.eclipse.jetty.io.nio.SelectorManager.SelectSet;
import org.eclipse.jetty.server.AsyncHttpConnection;
import org.eclipse.jetty.server.Request;

/* ------------------------------------------------------------------------------- */
/**
 * Selecting NIO connector.
 * <p>
 * This connector uses efficient NIO buffers with a non blocking threading model. Direct NIO buffers
 * are used and threads are only allocated to connections with requests. Synchronization is used to
 * simulate blocking for the servlet API, and any unflushed content at the end of request handling
 * is written asynchronously.
 * </p>
 * <p>
 * This connector is best used when there are a many connections that have idle periods.
 * </p>
 * <p>
 * When used with {@link org.eclipse.jetty.continuation.Continuation}, threadless waits are supported.
 * If a filter or servlet returns after calling {@link Continuation#suspend()} or when a
 * runtime exception is thrown from a call to {@link Continuation#undispatch()}, Jetty will
 * will not send a response to the client. Instead the thread is released and the Continuation is
 * placed on the timer queue. If the Continuation timeout expires, or it's
 * resume method is called, then the request is again allocated a thread and the request is retried.
 * The limitation of this approach is that request content is not available on the retried request,
 * thus if possible it should be read after the continuation or saved as a request attribute or as the
 * associated object of the Continuation instance.
 * </p>
 *
 * @org.apache.xbean.XBean element="nioConnector" description="Creates an NIO based socket connector"
 */
public class SelectChannelConnector extends AbstractNIOConnector
{
	protected ServerSocketChannel _acceptChannel;
	private int _lowResourcesConnections;
	private int _lowResourcesMaxIdleTime;
	private int _localPort=-1;

	private final SelectorManager _manager = new ConnectorSelectorManager();

	/* ------------------------------------------------------------------------------- */
	/**
	 * Constructor.
	 *
	 */
	public SelectChannelConnector()
	{
		_manager.setMaxIdleTime(getMaxIdleTime());
		addBean(_manager,true);
		setAcceptors(Math.max(1,(Runtime.getRuntime().availableProcessors()+3)/4));
	}
	
	/* ------------------------------------------------------------ */
	@Override
	public void accept(int acceptorID) throws IOException
	{
		ServerSocketChannel server;
		synchronized(this)
		{
			server = _acceptChannel;
		}

		if (server!=null && server.isOpen() && _manager.isStarted())
		{
			SocketChannel channel = server.accept();
			channel.configureBlocking(false);
			Socket socket = channel.socket();
			configure(socket);
			_manager.register(channel);
		}
	}

	/* ------------------------------------------------------------ */
	public void close() throws IOException
	{
		synchronized(this)
		{
			if (_acceptChannel != null)
			{
				removeBean(_acceptChannel);
				if (_acceptChannel.isOpen())
					_acceptChannel.close();
			}
			_acceptChannel = null;
			_localPort=-2;
		}
	}

	/* ------------------------------------------------------------------------------- */
	@Override
	public void customize(EndPoint endpoint, Request request) throws IOException
	{
		request.setTimeStamp(System.currentTimeMillis());
		endpoint.setMaxIdleTime(_maxIdleTime);
		super.customize(endpoint, request);
	}

	/* ------------------------------------------------------------------------------- */
	@Override
	public void persist(EndPoint endpoint) throws IOException
	{
		AsyncEndPoint aEndp = ((AsyncEndPoint)endpoint);
		aEndp.setCheckForIdle(true);
		super.persist(endpoint);
	}

	/* ------------------------------------------------------------ */
	public SelectorManager getSelectorManager()
	{
		return _manager;
	}

	/* ------------------------------------------------------------ */
	public synchronized Object getConnection()
	{
		return _acceptChannel;
	}

	/* ------------------------------------------------------------------------------- */
	public int getLocalPort()
	{
		synchronized(this)
		{
			return _localPort;
		}
	}

	/* ------------------------------------------------------------ */
	public void open() throws IOException
	{
		synchronized(this)
		{
			if (_acceptChannel == null)
			{
				// Create a new server socket
				_acceptChannel = ServerSocketChannel.open();
				// Set to blocking mode
				_acceptChannel.configureBlocking(true);

				// Bind the server socket to the local host and port
				_acceptChannel.socket().setReuseAddress(getReuseAddress());
				InetSocketAddress addr = getHost()==null?new InetSocketAddress(getPort()):new InetSocketAddress(getHost(),getPort());
				_acceptChannel.socket().bind(addr,getAcceptQueueSize());

				_localPort=_acceptChannel.socket().getLocalPort();
				if (_localPort<=0)
					throw new IOException("Server channel not bound");

				addBean(_acceptChannel);
			}
		}
	}

	/* ------------------------------------------------------------ */
	@Override
	public void setMaxIdleTime(int maxIdleTime)
	{
		_manager.setMaxIdleTime(maxIdleTime);
		super.setMaxIdleTime(maxIdleTime);
	}

	/* ------------------------------------------------------------ */
	/**
	 * @return the lowResourcesConnections
	 */
	public int getLowResourcesConnections()
	{
		return _lowResourcesConnections;
	}

	/* ------------------------------------------------------------ */
	/**
	 * Set the number of connections, which if exceeded places this manager in low resources state.
	 * This is not an exact measure as the connection count is averaged over the select sets.
	 * @param lowResourcesConnections the number of connections
	 * @see #setLowResourcesMaxIdleTime(int)
	 */
	public void setLowResourcesConnections(int lowResourcesConnections)
	{
		_lowResourcesConnections=lowResourcesConnections;
	}

	/* ------------------------------------------------------------ */
	/**
	 * @return the lowResourcesMaxIdleTime
	 */
	@Override
	public int getLowResourcesMaxIdleTime()
	{
		return _lowResourcesMaxIdleTime;
	}

	/* ------------------------------------------------------------ */
	/**
	 * Set the period in ms that a connection is allowed to be idle when this there are more
	 * than {@link #getLowResourcesConnections()} connections.  This allows the server to rapidly close idle connections
	 * in order to gracefully handle high load situations.
	 * @param lowResourcesMaxIdleTime the period in ms that a connection is allowed to be idle when resources are low.
	 * @see #setMaxIdleTime(int)
	 */
	@Override
	public void setLowResourcesMaxIdleTime(int lowResourcesMaxIdleTime)
	{
		_lowResourcesMaxIdleTime=lowResourcesMaxIdleTime;
		super.setLowResourcesMaxIdleTime(lowResourcesMaxIdleTime);
	}


	/* ------------------------------------------------------------ */
	/*
	 * @see org.eclipse.jetty.server.server.AbstractConnector#doStart()
	 */
	@Override
	protected void doStart() throws Exception
	{
		_manager.setSelectSets(getAcceptors());
		_manager.setMaxIdleTime(getMaxIdleTime());
		_manager.setLowResourcesConnections(getLowResourcesConnections());
		_manager.setLowResourcesMaxIdleTime(getLowResourcesMaxIdleTime());

		super.doStart();
	}

	/* ------------------------------------------------------------ */
	protected SelectChannelEndPoint newEndPoint(SocketChannel channel, SelectSet selectSet, SelectionKey key) throws IOException
	{
		SelectChannelEndPoint endp= new SelectChannelEndPoint(channel,selectSet,key, SelectChannelConnector.this._maxIdleTime);
		endp.setConnection(selectSet.getManager().newConnection(channel,endp, key.attachment()));
		return endp;
	}

	/* ------------------------------------------------------------------------------- */
	protected void endPointClosed(SelectChannelEndPoint endpoint)
	{
		connectionClosed(endpoint.getConnection());
	}

	/* ------------------------------------------------------------------------------- */
	protected AsyncConnection newConnection(SocketChannel channel,final AsyncEndPoint endpoint)
	{
		return new AsyncHttpConnection(SelectChannelConnector.this,endpoint,getServer());
	}


	/* ------------------------------------------------------------ */
	/* ------------------------------------------------------------ */
	/* ------------------------------------------------------------ */
	private final class ConnectorSelectorManager extends SelectorManager
	{
		@Override
		public void execute(Runnable task)
		{
			getThreadPool().execute(task);
		}

		@Override
		protected void endPointClosed(final SelectChannelEndPoint endpoint)
		{
			SelectChannelConnector.this.endPointClosed(endpoint);
		}

		@Override
		protected void endPointOpened(SelectChannelEndPoint endpoint)
		{
			// TODO handle max connections and low resources
			connectionOpened(endpoint.getConnection());
		}

		@Override
		protected void endPointUpgraded(ConnectedEndPoint endpoint, Connection oldConnection)
		{
			connectionUpgraded(oldConnection,endpoint.getConnection());
		}

		@Override
		public AsyncConnection newConnection(SocketChannel channel,AsyncEndPoint endpoint, Object attachment)
		{
			return SelectChannelConnector.this.newConnection(channel,endpoint);
		}

		@Override
		protected SelectChannelEndPoint newEndPoint(SocketChannel channel, SelectSet selectSet, SelectionKey sKey) throws IOException
		{
			return SelectChannelConnector.this.newEndPoint(channel,selectSet,sKey);
		}
	}
}