/*

 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

import java.io.IOException;

import java.net.ServerSocket;

import java.net.Socket;

import java.util.Objects;

import java.util.function.Consumer;

import javax.net.ServerSocketFactory;

/*

 * A simple socks4 proxy for traveling socket.

 */

class SocksProxy implements Runnable, AutoCloseable {

    private ServerSocket server;

    private Consumer<Socket> socketConsumer;

    private SocksProxy(ServerSocket server, Consumer<Socket> socketConsumer) {

        this.server = server;

        this.socketConsumer = socketConsumer;

    }

    static SocksProxy startProxy(Consumer<Socket> socketConsumer)

            throws IOException {

        Objects.requireNonNull(socketConsumer, "socketConsumer cannot be null");

        ServerSocket server

                = ServerSocketFactory.getDefault().createServerSocket(0);

        System.setProperty("socksProxyHost", "127.0.0.1");

        System.setProperty("socksProxyPort",

                String.valueOf(server.getLocalPort()));

        System.setProperty("socksProxyVersion", "4");

        SocksProxy proxy = new SocksProxy(server, socketConsumer);

        Thread proxyThread = new Thread(proxy, "Proxy");

        proxyThread.setDaemon(true);

        proxyThread.start();

        return proxy;

    }

    @Override

    public void run() {

        while (!server.isClosed()) {

            try(Socket socket = server.accept()) {

                System.out.println("Server: accepted connection");

                if (socketConsumer != null) {

                    socketConsumer.accept(socket);

                }

            } catch (IOException e) {

                if (!server.isClosed()) {

                    throw new RuntimeException(

                            "Server: accept connection failed", e);

                } else {

                    System.out.println("Server is closed.");

                }

            }

        }

    }

    @Override

    public void close() throws Exception {

        if (!server.isClosed()) {

            server.close();

        }

    }

    int getPort() {

        return server.getLocalPort();

    }

}