//
//  ========================================================================
//  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;

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.LineNumberReader;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Properties;

import org.eclipse.jetty.util.StringUtil;
import org.eclipse.jetty.util.thread.ShutdownThread;

/**
 * Shutdown/Stop Monitor thread.
 * <p>
 * This thread listens on the port specified by the STOP.PORT system parameter (defaults to -1 for not listening) for request authenticated with the key given
 * by the STOP.KEY system parameter (defaults to "eclipse") for admin requests.
 * <p>
 * If the stop port is set to zero, then a random port is assigned and the port number is printed to stdout.
 * <p>
 * Commands "stop" and "status" are currently supported.
 */
public class ShutdownMonitor 
{
    // Implementation of safe lazy init, using Initialization on Demand Holder technique.
    static class Holder
    {
        static ShutdownMonitor instance = new ShutdownMonitor();
    }

    public static ShutdownMonitor getInstance()
    {
        return Holder.instance;
    }

    /**
     * ShutdownMonitorThread
     *
     * Thread for listening to STOP.PORT for command to stop Jetty.
     * If ShowndownMonitor.exitVm is true, then Sytem.exit will also be
     * called after the stop.
     *
     */
    public class ShutdownMonitorThread extends Thread
    {

        public ShutdownMonitorThread ()
        {
            setDaemon(true);
            setName("ShutdownMonitor");
        }
        
        @Override
        public void run()
        {
            if (serverSocket == null)
            {
                return;
            }

            while (serverSocket != null)
            {
                Socket socket = null;
                try
                {
                    socket = serverSocket.accept();

                    LineNumberReader lin = new LineNumberReader(new InputStreamReader(socket.getInputStream()));
                    String receivedKey = lin.readLine();
                    if (!key.equals(receivedKey))
                    {
                        System.err.println("Ignoring command with incorrect key");
                        continue;
                    }

                    OutputStream out = socket.getOutputStream();

                    String cmd = lin.readLine();
                    debug("command=%s",cmd);
                    if ("stop".equals(cmd))
                    {
                        // Graceful Shutdown
                        debug("Issuing graceful shutdown..");
                        ShutdownThread.getInstance().run();

                        // Reply to client
                        debug("Informing client that we are stopped.");
                        out.write("Stopped\r\n".getBytes(StringUtil.__UTF8));
                        out.flush();

                        // Shutdown Monitor
                        debug("Shutting down monitor");
                        close(socket);
                        socket = null;
                        close(serverSocket);
                        serverSocket = null;

                        if (exitVm)
                        {
                            // Kill JVM
                            debug("Killing JVM");
                            System.exit(0);
                        }
                    }
                    else if ("status".equals(cmd))
                    {
                        // Reply to client
                        out.write("OK\r\n".getBytes(StringUtil.__UTF8));
                        out.flush();
                    }
                }
                catch (Exception e)
                {
                    debug(e);
                    System.err.println(e.toString());
                }
                finally
                {
                    close(socket);
                    socket = null;
                }
            }
        }
        
        public void start()
        {
            if (isAlive())
            {
                System.err.printf("ShutdownMonitorThread already started");
                return; // cannot start it again
            }

            startListenSocket();
            
            if (serverSocket == null)
            {
                return;
            }
            if (DEBUG)
                System.err.println("Starting ShutdownMonitorThread");
            super.start();
        }
        
        private void startListenSocket()
        {
            if (port < 0)
            {            
                if (DEBUG)
                    System.err.println("ShutdownMonitor not in use (port < 0): " + port);
                return;
            }

            try
            {
                serverSocket = new ServerSocket(port,1,InetAddress.getByName("127.0.0.1"));
                if (port == 0)
                {
                    // server assigned port in use
                    port = serverSocket.getLocalPort();
                    System.out.printf("STOP.PORT=%d%n",port);
                }

                if (key == null)
                {
                    // create random key
                    key = Long.toString((long)(Long.MAX_VALUE * Math.random() + this.hashCode() + System.currentTimeMillis()),36);
                    System.out.printf("STOP.KEY=%s%n",key);
                }
            }
            catch (Exception e)
            {
                debug(e);
                System.err.println("Error binding monitor port " + port + ": " + e.toString());
                serverSocket = null;
            }
            finally
            {
                // establish the port and key that are in use
                debug("STOP.PORT=%d",port);
                debug("STOP.KEY=%s",key);
                debug("%s",serverSocket);
            }
        }

    }
    
    private boolean DEBUG;
    private int port;
    private String key;
    private boolean exitVm;
    private ServerSocket serverSocket;
    private ShutdownMonitorThread thread;
    
    

    /**
     * Create a ShutdownMonitor using configuration from the System properties.
     * <p>
     * <code>STOP.PORT</code> = the port to listen on (empty, null, or values less than 0 disable the stop ability)<br>
     * <code>STOP.KEY</code> = the magic key/passphrase to allow the stop (defaults to "eclipse")<br>
     * <p>
     * Note: server socket will only listen on localhost, and a successful stop will issue a System.exit() call.
     */
    private ShutdownMonitor()
    {
        Properties props = System.getProperties();

        this.DEBUG = props.containsKey("DEBUG");

        // Use values passed thru via /jetty-start/
        this.port = Integer.parseInt(props.getProperty("STOP.PORT","-1"));
        this.key = props.getProperty("STOP.KEY",null);
        this.exitVm = true;
    }

    private void close(ServerSocket server)
    {
        if (server == null)
        {
            return;
        }

        try
        {
            server.close();
        }
        catch (IOException ignore)
        {
            /* ignore */
        }
    }

    private void close(Socket socket)
    {
        if (socket == null)
        {
            return;
        }

        try
        {
            socket.close();
        }
        catch (IOException ignore)
        {
            /* ignore */
        }
    }

    private void debug(String format, Object... args)
    {
        if (DEBUG)
        {
            System.err.printf("[ShutdownMonitor] " + format + "%n",args);
        }
    }

    private void debug(Throwable t)
    {
        if (DEBUG)
        {
            t.printStackTrace(System.err);
        }
    }

    public String getKey()
    {
        return key;
    }

    public int getPort()
    {
        return port;
    }

    public ServerSocket getServerSocket()
    {
        return serverSocket;
    }

    public boolean isExitVm()
    {
        return exitVm;
    }


    public void setDebug(boolean flag)
    {
        this.DEBUG = flag;
    }

    public void setExitVm(boolean exitVm)
    {
        synchronized (this)
        {
            if (thread != null && thread.isAlive())
            {
                throw new IllegalStateException("ShutdownMonitorThread already started");
            }
            this.exitVm = exitVm;
        }
    }

    public void setKey(String key)
    {
        synchronized (this)
        {
            if (thread != null && thread.isAlive())
            {
                throw new IllegalStateException("ShutdownMonitorThread already started");
            }
            this.key = key;
        }
    }

    public void setPort(int port)
    {
        synchronized (this)
        {
            if (thread != null && thread.isAlive())
            {
                throw new IllegalStateException("ShutdownMonitorThread already started");
            }
            this.port = port;
        }
    }

    protected void start() throws Exception
    {
        ShutdownMonitorThread t = null;
        synchronized (this)
        {
            if (thread != null && thread.isAlive())
            {
                System.err.printf("ShutdownMonitorThread already started");
                return; // cannot start it again
            }
         
            thread = new ShutdownMonitorThread();
            t = thread;
        }
         
        if (t != null)
            t.start();
    }


    protected boolean isAlive ()
    {
        boolean result = false;
        synchronized (this)
        {
            result = (thread != null && thread.isAlive());
        }
        return result;
    }
    
 
    @Override
    public String toString()
    {
        return String.format("%s[port=%d]",this.getClass().getName(),port);
    }
}