/**
 * Copyright 2011 JogAmp Community. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are
 * permitted provided that the following conditions are met:
 *
 *    1. Redistributions of source code must retain the above copyright notice, this list of
 *       conditions and the following disclaimer.
 *
 *    2. Redistributions in binary form must reproduce the above copyright notice, this list
 *       of conditions and the following disclaimer in the documentation and/or other materials
 *       provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY JogAmp Community ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JogAmp Community OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and documentation are those of the
 * authors and should not be interpreted as representing official policies, either expressed
 * or implied, of JogAmp Community.
 */

package jogamp.common.util.locks;

import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;
import com.jogamp.common.util.locks.SingletonInstance;

public class SingletonInstanceServerSocket extends SingletonInstance {

    private final Server singletonServer;
    private final String fullName;

    public SingletonInstanceServerSocket(final long poll_ms, final int portNumber) {
        super(poll_ms);

        // Gather the local InetAddress, loopback is prioritized
        InetAddress ilh = null;
        try {
            ilh = InetAddress.getByName(null); // loopback
        } catch (final UnknownHostException e1) { }
        if(null == ilh) {
            try {
                ilh = InetAddress.getByName("localhost");
                if(null!=ilh && !ilh.isLoopbackAddress()) { ilh = null; }
            } catch (final UnknownHostException e1) { }
        }
        if(null == ilh) {
            try {
                ilh = InetAddress.getByAddress(new byte[] { 127, 0, 0, 1 } );
                if(null!=ilh && !ilh.isLoopbackAddress()) { ilh = null; }
            } catch (final UnknownHostException e) { }
        }
        if(null == ilh) {
            try {
                ilh = InetAddress.getLocalHost();
            } catch (final UnknownHostException e) { }
        }
        if(null == ilh) {
            throw new RuntimeException(infoPrefix()+" EEE Could not determine local InetAddress");
        }

        fullName = ilh.toString()+":"+portNumber;
        singletonServer = new Server(ilh, portNumber);
        Runtime.getRuntime().addShutdownHook(new Thread() {
            @Override
            public void run() {
                singletonServer.kill();
            }
        });
    }

    public final InetAddress getLocalInetAddress() {
        return singletonServer.getLocalInetAddress();
    }

    public final int getPortNumber() {
        return singletonServer.getPortNumber();
    }

    @Override
    public final String getName() { return fullName; }

    @Override
    protected boolean tryLockImpl() {
        if( singletonServer.isRunning() ) {
            return false; // same JVM .. server socket already installed !
        }

        // check if other JVM's locked the server socket ..
        final Socket clientSocket = singletonServer.connect();
        if(null != clientSocket) {
            try {
                clientSocket.close();
            } catch (final IOException e) { }
            return false;
        }

        if( !singletonServer.start() ) {
            return false;
        }

        return true;
    }

    @Override
    protected boolean unlockImpl() {
        return singletonServer.shutdown();
    }

    public class Server implements Runnable {
       private final InetAddress localInetAddress;
       private final int portNumber;

       private volatile boolean shallQuit = false;
       private volatile boolean alive = false;

       private final Object syncOnStartStop = new Object();
       private ServerSocket serverSocket = null;
       private Thread serverThread = null;  // allowing kill() to force-stop last server-thread

       public Server(final InetAddress localInetAddress, final int portNumber) {
           this.localInetAddress = localInetAddress;
           this.portNumber = portNumber;
       }

       public final InetAddress getLocalInetAddress() { return localInetAddress; }
       public final int getPortNumber() { return portNumber; }

       public final boolean start() {
           if(alive) return true;

           synchronized (syncOnStartStop) {
               serverThread = new Thread(this);
               serverThread.setDaemon(true);  // be a daemon, don't keep the JVM running
               serverThread.start();
               try {
                   syncOnStartStop.wait();
               } catch (final InterruptedException ie) {
                   ie.printStackTrace();
               }
           }
           final boolean ok = isBound();
           if(!ok) {
               shutdown();
           }
           return ok;
       }

       public final boolean shutdown() {
           if(!alive) return true;

           synchronized (syncOnStartStop) {
               shallQuit = true;
               connect();
               try {
                   syncOnStartStop.wait();
               } catch (final InterruptedException ie) {
                   ie.printStackTrace();
               }
           }
           if(alive) {
               System.err.println(infoPrefix()+" EEE "+getName()+" - Unable to remove lock: ServerThread still alive ?");
               kill();
           }
           return true;
       }

       /**
        * Brutally kill server thread and close socket regardless.
        * This is out last chance for JVM shutdown.
        */
       @SuppressWarnings("deprecation")
       public final void kill() {
           if(alive) {
                System.err.println(infoPrefix()+" XXX "+getName()+" - Kill @ JVM Shutdown");
           }
           alive = false;
           if(null != serverThread) {
               try {
                   serverThread.stop();
               } catch(final Throwable t) { }
           }
           if(null != serverSocket) {
               try {
                   final ServerSocket ss = serverSocket;
                   serverSocket = null;
                   ss.close();
               } catch (final Throwable t) { }
           }
       }

       public final boolean isRunning() { return alive; }

       public final boolean isBound() {
           return alive && null != serverSocket && serverSocket.isBound() ;
       }

       public final Socket connect() {
           try {
               return new Socket(localInetAddress, portNumber);
           } catch (final Exception e) { }
           return null;
       }

       @Override
       public void run() {
           {
               final Thread currentThread = Thread.currentThread();
               currentThread.setName(currentThread.getName() + " - SISock: "+getName());
               if(DEBUG) {
                   System.err.println(currentThread.getName()+" - started");
               }
           }
           alive = false;
           synchronized (syncOnStartStop) {
               try {
                   serverSocket = new ServerSocket(portNumber, 1, localInetAddress);
                   serverSocket.setReuseAddress(true); // reuse same port w/ subsequent instance, i.e. overcome TO state when JVM crashed
                   alive = true;
               } catch (final IOException e) {
                    System.err.println(infoPrefix()+" III - Unable to install ServerSocket: "+e.getMessage());
                    shallQuit = true;
               } finally {
                    syncOnStartStop.notifyAll();
               }
           }

           while (!shallQuit) {
               try {
                   final Socket clientSocket = serverSocket.accept();
                   clientSocket.close();
               } catch (final IOException ioe) {
                   System.err.println(infoPrefix()+" EEE - Exception during accept: " + ioe.getMessage());
               }
           }

           synchronized (syncOnStartStop) {
               try {
                   if(null != serverSocket) {
                       serverSocket.close();
                   }
               } catch (final IOException e) {
                   System.err.println(infoPrefix()+" EEE - Exception during close: " + e.getMessage());
               } finally {
                   serverSocket = null;
                   alive = false;
                   shallQuit = false;
                   syncOnStartStop.notifyAll();
               }
           }
       }
    }
}