/*

 * Copyright (c) 2002, 2012, 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.  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 com.sun.jmx.remote.internal;

import java.io.IOException;

import java.io.NotSerializableException;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import java.util.concurrent.Executor;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.PrivilegedAction;

import javax.security.auth.Subject;

import javax.management.Notification;

import javax.management.NotificationListener;

import javax.management.NotificationFilter;

import javax.management.ObjectName;

import javax.management.MBeanServerNotification;

import javax.management.InstanceNotFoundException;

import javax.management.ListenerNotFoundException;

import javax.management.remote.NotificationResult;

import javax.management.remote.TargetedNotification;

import com.sun.jmx.remote.util.ClassLogger;

import com.sun.jmx.remote.util.EnvHelp;

import java.rmi.UnmarshalException;

public abstract class ClientNotifForwarder {

    private final AccessControlContext acc;

    public ClientNotifForwarder(Map<String, ?> env) {

        this(null, env);

    }

    private static int threadId;

    /* An Executor that allows at most one executing and one pending

       Runnable.  It uses at most one thread -- as soon as there is

       no pending Runnable the thread can exit.  Another thread is

       created as soon as there is a new pending Runnable.  This

       Executor is adapted for use in a situation where each Runnable

       usually schedules up another Runnable.  On return from the

       first one, the second one is immediately executed.  So this

       just becomes a complicated way to write a while loop, but with

       the advantage that you can replace it with another Executor,

       for instance one that you are using to execute a bunch of other

       unrelated work.

       You might expect that a java.util.concurrent.ThreadPoolExecutor

       with corePoolSize=0 and maximumPoolSize=1 would have the same

       behavior, but it does not.  A ThreadPoolExecutor only creates

       a new thread when a new task is submitted and the number of

       existing threads is < corePoolSize.  This can never happen when

       corePoolSize=0, so new threads are never created.  Surprising,

       but there you are.

    */

    private static class LinearExecutor implements Executor {

        public synchronized void execute(Runnable command) {

            if (this.command != null)

                throw new IllegalArgumentException("More than one command");

            this.command = command;

            if (thread == null) {

                thread = new Thread() {

                    @Override

                    public void run() {

                        while (true) {

                            Runnable r;

                            synchronized (LinearExecutor.this) {

                                if (LinearExecutor.this.command == null) {

                                    thread = null;

                                    return;

                                } else {

                                    r = LinearExecutor.this.command;

                                    LinearExecutor.this.command = null;

                                }

                            }

                            r.run();

                        }

                    }

                };

                thread.setDaemon(true);

                thread.setName("ClientNotifForwarder-" + ++threadId);

                thread.start();

            }

        }

        private Runnable command;

        private Thread thread;

    }

    public ClientNotifForwarder(ClassLoader defaultClassLoader, Map<String, ?> env) {

        maxNotifications = EnvHelp.getMaxFetchNotifNumber(env);

        timeout = EnvHelp.getFetchTimeout(env);

        /* You can supply an Executor in which the remote call to

           fetchNotifications will be made.  The Executor's execute

           method reschedules another task, so you must not use

           an Executor that executes tasks in the caller's thread.  */

        Executor ex = (Executor)

            env.get("jmx.remote.x.fetch.notifications.executor");

        if (ex == null)

            ex = new LinearExecutor();

        else if (logger.traceOn())

            logger.trace("ClientNotifForwarder", "executor is " + ex);

        this.defaultClassLoader = defaultClassLoader;

        this.executor = ex;

        this.acc = AccessController.getContext();

    }

    /**

     */

    abstract protected NotificationResult fetchNotifs(long clientSequenceNumber,

                                                      int maxNotifications,

                                                      long timeout)

            throws IOException, ClassNotFoundException;

    abstract protected Integer addListenerForMBeanRemovedNotif()

        throws IOException, InstanceNotFoundException;

    abstract protected void removeListenerForMBeanRemovedNotif(Integer id)

        throws IOException, InstanceNotFoundException,

               ListenerNotFoundException;

    /**

     * Used to send out a notification about lost notifs

     */

    abstract protected void lostNotifs(String message, long number);

    public synchronized void addNotificationListener(Integer listenerID,

                                        ObjectName name,

                                        NotificationListener listener,

                                        NotificationFilter filter,

                                        Object handback,

                                        Subject delegationSubject)

            throws IOException, InstanceNotFoundException {

        if (logger.traceOn()) {

            logger.trace("addNotificationListener",

                         "Add the listener "+listener+" at "+name);

        }

        infoList.put(listenerID,

                     new ClientListenerInfo(listenerID,

                                            name,

                                            listener,

                                            filter,

                                            handback,

                                            delegationSubject));

        init(false);

    }

    public synchronized Integer[]

        removeNotificationListener(ObjectName name,

                                   NotificationListener listener)

        throws ListenerNotFoundException, IOException {

        beforeRemove();

        if (logger.traceOn()) {

            logger.trace("removeNotificationListener",

                         "Remove the listener "+listener+" from "+name);

        }

        List<Integer> ids = new ArrayList<Integer>();

        List<ClientListenerInfo> values =

                new ArrayList<ClientListenerInfo>(infoList.values());

        for (int i=values.size()-1; i>=0; i--) {

            ClientListenerInfo li = values.get(i);

            if (li.sameAs(name, listener)) {

                ids.add(li.getListenerID());

                infoList.remove(li.getListenerID());

            }

        }

        if (ids.isEmpty())

            throw new ListenerNotFoundException("Listener not found");

        return ids.toArray(new Integer[0]);

    }

    public synchronized Integer

        removeNotificationListener(ObjectName name,

                                   NotificationListener listener,

                                   NotificationFilter filter,

                                   Object handback)

            throws ListenerNotFoundException, IOException {

        if (logger.traceOn()) {

            logger.trace("removeNotificationListener",

                         "Remove the listener "+listener+" from "+name);

        }

        beforeRemove();

        Integer id = null;

        List<ClientListenerInfo> values =

                new ArrayList<ClientListenerInfo>(infoList.values());

        for (int i=values.size()-1; i>=0; i--) {

            ClientListenerInfo li = values.get(i);

            if (li.sameAs(name, listener, filter, handback)) {

                id=li.getListenerID();

                infoList.remove(id);

                break;

            }

        }

        if (id == null)

            throw new ListenerNotFoundException("Listener not found");

        return id;

    }

    public synchronized Integer[] removeNotificationListener(ObjectName name) {

        if (logger.traceOn()) {

            logger.trace("removeNotificationListener",

                         "Remove all listeners registered at "+name);

        }

        List<Integer> ids = new ArrayList<Integer>();

        List<ClientListenerInfo> values =

                new ArrayList<ClientListenerInfo>(infoList.values());

        for (int i=values.size()-1; i>=0; i--) {

            ClientListenerInfo li = values.get(i);

            if (li.sameAs(name)) {

                ids.add(li.getListenerID());

                infoList.remove(li.getListenerID());

            }

        }

        return ids.toArray(new Integer[0]);

    }

    /*

     * Called when a connector is doing reconnection. Like <code>postReconnection</code>,

     * this method is intended to be called only by a client connector:

     * <code>RMIConnector</code> and <code>ClientIntermediary</code>.

     * Call this method will set the flag beingReconnection to <code>true</code>,

     * and the thread used to fetch notifis will be stopped, a new thread can be

     * created only after the method <code>postReconnection</code> is called.

     *

     * It is caller's responsiblity to not re-call this method before calling

     * <code>postReconnection</code>.

     */

    public synchronized ClientListenerInfo[] preReconnection() throws IOException {

        if (state == TERMINATED || beingReconnected) { // should never

            throw new IOException("Illegal state.");

        }

        final ClientListenerInfo[] tmp =

            infoList.values().toArray(new ClientListenerInfo[0]);

        beingReconnected = true;

        infoList.clear();

        return tmp;

    }

    /**

     * Called after reconnection is finished.

     * This method is intended to be called only by a client connector:

     * <code>RMIConnector</code> and <code>ClientIntermediary</code>.

     */

    public synchronized void postReconnection(ClientListenerInfo[] listenerInfos)

        throws IOException {

        if (state == TERMINATED) {

            return;

        }

        while (state == STOPPING) {

            try {

                wait();

            } catch (InterruptedException ire) {

                IOException ioe = new IOException(ire.toString());

                EnvHelp.initCause(ioe, ire);

                throw ioe;

            }

        }

        final boolean trace = logger.traceOn();

        final int len   = listenerInfos.length;

        for (int i=0; i<len; i++) {

            if (trace) {

                logger.trace("addNotificationListeners",

                             "Add a listener at "+

                             listenerInfos[i].getListenerID());

            }

            infoList.put(listenerInfos[i].getListenerID(), listenerInfos[i]);

        }

        beingReconnected = false;

        notifyAll();

        if (currentFetchThread == Thread.currentThread() ||

              state == STARTING || state == STARTED) { // doing or waiting reconnection

              // only update mbeanRemovedNotifID

            try {

                mbeanRemovedNotifID = addListenerForMBeanRemovedNotif();

            } catch (Exception e) {

                final String msg =

                    "Failed to register a listener to the mbean " +

                    "server: the client will not do clean when an MBean " +

                    "is unregistered";

                if (logger.traceOn()) {

                    logger.trace("init", msg, e);

                }

            }

        } else {

              while (state == STOPPING) {

                  try {

                      wait();

                  } catch (InterruptedException ire) {

                      IOException ioe = new IOException(ire.toString());

                      EnvHelp.initCause(ioe, ire);

                      throw ioe;

                  }

              }

              if (listenerInfos.length > 0) { // old listeners are re-added

                  init(true); // not update clientSequenceNumber

              } else if (infoList.size() > 0) { // only new listeners added during reconnection

                  init(false); // need update clientSequenceNumber

              }

          }

    }

    public synchronized void terminate() {

        if (state == TERMINATED) {

            return;

        }

        if (logger.traceOn()) {

            logger.trace("terminate", "Terminating...");

        }

        if (state == STARTED) {

           infoList.clear();

        }

        setState(TERMINATED);

    }

    // -------------------------------------------------

    // private classes

    // -------------------------------------------------

    //

    private class NotifFetcher implements Runnable {

        private volatile boolean alreadyLogged = false;

        private void logOnce(String msg, SecurityException x) {

            if (alreadyLogged) return;

            // Log only once.

            logger.config("setContextClassLoader",msg);

            if (x != null) logger.fine("setContextClassLoader", x);

            alreadyLogged = true;

        }

        // Set new context class loader, returns previous one.

        private final ClassLoader setContextClassLoader(final ClassLoader loader) {

            final AccessControlContext ctxt = ClientNotifForwarder.this.acc;

            // if ctxt is null, log a config message and throw a

            // SecurityException.

            if (ctxt == null) {

                logOnce("AccessControlContext must not be null.",null);

                throw new SecurityException("AccessControlContext must not be null");

            }

            return AccessController.doPrivileged(

                new PrivilegedAction<ClassLoader>() {

                    public ClassLoader run() {

                        try {

                            // get context class loader - may throw

                            // SecurityException - though unlikely.

                            final ClassLoader previous =

                                Thread.currentThread().getContextClassLoader();

                            // if nothing needs to be done, break here...

                            if (loader == previous) return previous;

                            // reset context class loader - may throw

                            // SecurityException

                            Thread.currentThread().setContextClassLoader(loader);

                            return previous;

                        } catch (SecurityException x) {

                            logOnce("Permission to set ContextClassLoader missing. " +

                                    "Notifications will not be dispatched. " +

                                    "Please check your Java policy configuration: " +

                                    x, x);

                            throw x;

                        }

                    }

                }, ctxt);

        }

        public void run() {

            final ClassLoader previous;

            if (defaultClassLoader != null) {

                previous = setContextClassLoader(defaultClassLoader);

            } else {

                previous = null;

            }

            try {

                doRun();

            } finally {

                if (defaultClassLoader != null) {

                    setContextClassLoader(previous);

                }

            }

        }

        private void doRun() {

            synchronized (ClientNotifForwarder.this) {

                currentFetchThread = Thread.currentThread();

                if (state == STARTING) {

                    setState(STARTED);

                }

            }

            NotificationResult nr = null;

            if (!shouldStop() && (nr = fetchNotifs()) != null) {

                // nr == null means got exception

                final TargetedNotification[] notifs =

                    nr.getTargetedNotifications();

                final int len = notifs.length;

                final Map<Integer, ClientListenerInfo> listeners;

                final Integer myListenerID;

                long missed = 0;

                synchronized(ClientNotifForwarder.this) {

                    // check sequence number.

                    //

                    if (clientSequenceNumber >= 0) {

                        missed = nr.getEarliestSequenceNumber() -

                            clientSequenceNumber;

                    }

                    clientSequenceNumber = nr.getNextSequenceNumber();

                    listeners = new HashMap<Integer, ClientListenerInfo>();

                    for (int i = 0 ; i < len ; i++) {

                        final TargetedNotification tn = notifs[i];

                        final Integer listenerID = tn.getListenerID();

                        // check if an mbean unregistration notif

                        if (!listenerID.equals(mbeanRemovedNotifID)) {

                            final ClientListenerInfo li = infoList.get(listenerID);

                            if (li != null) {

                                listeners.put(listenerID, li);

                            }

                            continue;

                        }

                        final Notification notif = tn.getNotification();

                        final String unreg =

                            MBeanServerNotification.UNREGISTRATION_NOTIFICATION;

                        if (notif instanceof MBeanServerNotification &&

                            notif.getType().equals(unreg)) {

                            MBeanServerNotification mbsn =

                                (MBeanServerNotification) notif;

                            ObjectName name = mbsn.getMBeanName();

                            removeNotificationListener(name);

                        }

                    }