/*

 * 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

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

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

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * 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.

 */

package sun.management.jdp;

import java.io.IOException;

import java.lang.management.ManagementFactory;

import java.lang.management.RuntimeMXBean;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

/**

 * JdpController is responsible to create and manage a broadcast loop.

 *

 * <p> Other part of code has no access to broadcast loop and have to use

 * provided static methods

 * {@link #startDiscoveryService(InetAddress,int,String,String) startDiscoveryService}

 * and {@link #stopDiscoveryService() stopDiscoveryService}

 * <p>{@link #startDiscoveryService(InetAddress,int,String,String) startDiscoveryService} could be called multiple

 * times as it stops the running service if it is necessary.

 * Call to {@link #stopDiscoveryService() stopDiscoveryService}

 * ignored if service isn't run.

 *

 *

 * <p> System properties below could be used to control broadcast loop behavior.

 * Property below have to be set explicitly in command line. It's not possible to

 * set it in management.config file.  Careless changes of these properties could

 * lead to security or network issues.

 * <ul>

 *     <li>com.sun.management.jdp.ttl         - set ttl for broadcast packet</li>

 *     <li>com.sun.management.jdp.pause       - set broadcast interval in seconds</li>

 *     <li>com.sun.management.jdp.source_addr - an address of interface to use for broadcast</li>

 * </ul>

 *

 * <p>null parameters values are filtered out on {@link JdpPacketWriter} level and

 * corresponding keys are not placed to packet.

 */

public final class JdpController {

    private static class JDPControllerRunner implements Runnable {

        private final JdpJmxPacket packet;

        private final JdpBroadcaster bcast;

        private final int pause;

        private volatile boolean shutdown = false;

        private JDPControllerRunner(JdpBroadcaster bcast, JdpJmxPacket packet, int pause) {

            this.bcast = bcast;

            this.packet = packet;

            this.pause = pause;

        }

        @Override

        public void run() {

            try {

                while (!shutdown) {

                    bcast.sendPacket(packet);

                    try {

                        Thread.sleep(this.pause);

                    } catch (InterruptedException e) {

                        // pass

                    }

                }

            } catch (IOException e) {

              // pass;

            }

            // It's not possible to re-use controller,

            // nevertheless reset shutdown variable

            try {

                stop();

                bcast.shutdown();

            } catch (IOException ex) {

                // pass - ignore IOException during shutdown

            }

        }

        public void stop() {

            shutdown = true;

        }

    }

    private static JDPControllerRunner controller = null;

    private JdpController(){

        // Don't allow to instantiate this class.

    }

    // Utility to handle optional system properties

    // Parse an integer from string or return default if provided string is null

    private static int getInteger(String val, int dflt, String msg) throws JdpException {

        try {

            return (val == null) ? dflt : Integer.parseInt(val);

        } catch (NumberFormatException ex) {

            throw new JdpException(msg);

        }

    }

    // Parse an inet address from string or return default if provided string is null

    private static InetAddress getInetAddress(String val, InetAddress dflt, String msg) throws JdpException {

        try {

            return (val == null) ? dflt : InetAddress.getByName(val);

        } catch (UnknownHostException ex) {

            throw new JdpException(msg);

        }

    }

    // Get the process id of the current running Java process

    private static Long getProcessId() {

        try {

            // Get the current process id

            return ProcessHandle.current().pid();

        } catch(UnsupportedOperationException ex) {

            return null;

        }

    }

    /**

     * Starts discovery service

     *

     * @param address - multicast group address

     * @param port - udp port to use

     * @param instanceName - name of running JVM instance

     * @param url - JMX service url

     * @throws IOException

     */

    public static synchronized void startDiscoveryService(InetAddress address, int port, String instanceName, String url)

            throws IOException, JdpException {

        // Limit packet to local subnet by default

        int ttl = getInteger(

                System.getProperty("com.sun.management.jdp.ttl"), 1,

                "Invalid jdp packet ttl");

        // Broadcast once a 5 seconds by default

        int pause = getInteger(

                System.getProperty("com.sun.management.jdp.pause"), 5,

                "Invalid jdp pause");

        // Converting seconds to milliseconds

        pause = pause * 1000;

        // Allow OS to choose broadcast source

        InetAddress sourceAddress = getInetAddress(

                System.getProperty("com.sun.management.jdp.source_addr"), null,

                "Invalid source address provided");

        // Generate session id

        UUID id = UUID.randomUUID();

        JdpJmxPacket packet = new JdpJmxPacket(id, url);

        // Don't broadcast whole command line for security reason.

        // Strip everything after first space

        String javaCommand = System.getProperty("sun.java.command");

        if (javaCommand != null) {

            String[] arr = javaCommand.split(" ", 2);

            packet.setMainClass(arr[0]);

        }

        // Put optional explicit java instance name to packet, if user doesn't specify

        // it the key is skipped. PacketWriter is responsible to skip keys having null value.

        packet.setInstanceName(instanceName);

        // Set rmi server hostname if it explicitly specified by user with

        // java.rmi.server.hostname

        String rmiHostname = System.getProperty("java.rmi.server.hostname");

        packet.setRmiHostname(rmiHostname);

        // Set broadcast interval

        packet.setBroadcastInterval(Integer.toString(pause));

        // Set process id

        Long pid = getProcessId();

        if (pid != null) {

           packet.setProcessId(pid.toString());

        }

        JdpBroadcaster bcast = new JdpBroadcaster(address, sourceAddress, port, ttl);

        // Stop discovery service if it's already running

        stopDiscoveryService();

        controller = new JDPControllerRunner(bcast, packet, pause);

        Thread t = new Thread(null, controller, "JDP broadcaster", 0, false);

        t.setDaemon(true);

        t.start();

    }

    /**

     * Stop running discovery service,

     * it's safe to attempt to stop not started service

     */

    public static synchronized void stopDiscoveryService() {

        if ( controller != null ){

             controller.stop();

             controller = null;

        }

    }

}