package org.jgroups.blocks.cs;

import org.jgroups.Address;
import org.jgroups.annotations.ManagedOperation;
import org.jgroups.util.*;

import java.net.InetAddress;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;

/**
 * Server for sending and receiving messages via NIO channels. Uses only a single thread to accept, connect, write and
 * read connections. Read messages are passed to a receiver, which typically uses a thread pool to process messages.<p/>
 * Note that writes can get dropped, e.g. in the case where we have a previous write pending and a new write is received.
 * This is typically not an issue as JGroups retransmits messages, but might become one when using NioServer standalone,
 * ie. outside of JGroups.
 * @author Bela Ban
 * @since  3.6.5
 */
public class NioServer extends NioBaseServer {
    protected ServerSocketChannel channel;  // used to accept connections from peers



    /**
     * Creates an instance of {@link NioServer} that opens a server channel and listens for connections.
     * Needs to be started next.
     * @param bind_addr The local address to bind to. If null, the address will be picked by the OS
     * @param port The local port to bind to
     * @throws Exception Thrown if the creation failed
     */
    public NioServer(InetAddress bind_addr, int port) throws Exception {
        this(new DefaultThreadFactory("nio", false), new DefaultSocketFactory(),
             bind_addr, port, port+50, null, 0, 0);
    }



    /**
     * Creates an instance of {@link NioServer} that opens a server channel and listens for connections.
     * Needs to be started next.
     * @param thread_factory The thread factory used to create new threads
     * @param socket_factory The socket factory used to create socket channels
     * @param bind_addr The local address to bind to. If null, the address will be picked by the OS
     * @param srv_port The local port to bind to If 0, the port will be picked by the OS.
     * @param end_port If srv_port is taken, the next port is tried, until end_port has been reached, in which case an
     *                 exception will be thrown. If srv_port == end_port, only 1 port will be tried.
     * @param external_addr The external address in case of NAT. Ignored if null.
     * @param external_port The external port on the NA. If 0, srv_port is used.
     * @param recv_buf_size The size of the initial TCP receive window (in bytes)
     * @throws Exception Thrown if the creation failed
     */
    public NioServer(ThreadFactory thread_factory, SocketFactory socket_factory, InetAddress bind_addr, int srv_port, int end_port,
                     InetAddress external_addr, int external_port, int recv_buf_size) throws Exception {
        super(thread_factory, socket_factory, recv_buf_size);
        channel=Util.createServerSocketChannel(this.socket_factory, "jgroups.nio.server", bind_addr,
                                               srv_port, end_port, recv_buf_size);
        channel.configureBlocking(false);
        selector=Selector.open();
        acceptor=factory.newThread(new Acceptor(), "NioServer.Selector [" + channel.getLocalAddress() + "]");
        channel.register(selector, SelectionKey.OP_ACCEPT, null);
        local_addr=localAddress(bind_addr, channel.socket().getLocalPort(), external_addr, external_port);
    }



    @Override
    protected void handleAccept(SelectionKey key) throws Exception {
        SocketChannel client_channel=channel.accept();
        NioConnection conn=null;
        if(client_channel == null) return; // can happen if no connection is available to accept
        try {
            conn=new NioConnection(client_channel, NioServer.this);
            SelectionKey client_key=client_channel.register(selector, SelectionKey.OP_READ, conn);
            conn.key(client_key); // we need to set the selection key of the client channel *not* the server channel
            Address peer_addr=conn.peerAddress();
            if(use_peer_connections)
                return;

            synchronized(this) {
                replaceConnection(peer_addr, conn); // closes old conn
                conn.start();
                log.trace("%s: accepted connection from %s", local_addr, peer_addr);
            }
        }
        catch(Throwable ex) {
            Util.close(conn);
            removeConnectionIfPresent(conn.peerAddress(), conn);
            throw ex;
        }
    }


    @Override
    @ManagedOperation(description="Starts the server")
    public synchronized void start() throws Exception {
        if(running.compareAndSet(false, true)) {
            acceptor.start();
            super.start();
        }
    }

    @Override
    @ManagedOperation(description="Stops the server")
    public synchronized void stop() {
        super.stop();
        if(running.compareAndSet(true, false)) {
            // Util.close(selector); // closing the selector also stops the acceptor thread
            // socket_factory.close(channel);
            selector.wakeup();
        }
    }

    protected void acceptorDone() {
        Util.close(selector); // closing the selector also stops the acceptor thread
        socket_factory.close(channel);
    }
}
