/*
 * Copyright 2004 Sun Microsystems, Inc.  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.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package sun.jvmstat.perfdata.monitor.protocol.rmi;

import sun.jvmstat.monitor.*;
import sun.jvmstat.monitor.event.*;
import sun.jvmstat.monitor.remote.*;
import sun.jvmstat.perfdata.monitor.*;
import java.util.*;
import java.net.*;
import java.io.*;
import java.rmi.*;
import java.util.HashMap;

/**
 * Concrete implementation of the MonitoredHost interface for the
 * <em>rmi</em> protocol of the HotSpot PerfData monitoring implementation.
 *
 * @author Brian Doherty
 * @since 1.5
 */
public class MonitoredHostProvider extends MonitoredHost {
    private static final String serverName = "/JStatRemoteHost";
    private static final int DEFAULT_POLLING_INTERVAL = 1000;

    private ArrayList<HostListener> listeners;
    private NotifierTask task;
    private HashSet<Integer> activeVms;
    private RemoteVmManager vmManager;
    private RemoteHost remoteHost;
    private Timer timer;

    /**
     * Create a MonitoredHostProvider instance using the given HostIdentifier.
     *
     * @param hostId the host identifier for this MonitoredHost
     * @throws MonitorException Thrown on any error encountered while
     *                          communicating with the remote host.
     */
    public MonitoredHostProvider(HostIdentifier hostId)
           throws MonitorException {
        this.hostId = hostId;
        this.listeners = new ArrayList<HostListener>();
        this.interval = DEFAULT_POLLING_INTERVAL;
        this.activeVms = new HashSet<Integer>();

        String rmiName;
        String sn = serverName;
        String path = hostId.getPath();

        if ((path != null) && (path.length() > 0)) {
            sn = path;
        }

        if (hostId.getPort() != -1) {
            rmiName = "rmi://" + hostId.getHost() + ":" + hostId.getPort() + sn;
        } else {
            rmiName = "rmi://" + hostId.getHost() + sn;
        }

        try {
            remoteHost = (RemoteHost)Naming.lookup(rmiName);

        } catch (RemoteException e) {
            /*
             * rmi registry not available
             *
             * Access control exceptions, where the rmi server refuses a
             * connection based on policy file configuration, come through
             * here on the client side. Unfortunately, the RemoteException
             * doesn't contain enough information to determine the true cause
             * of the exception. So, we have to output a rather generic message.
             */
            String message = "RMI Registry not available at "
                             + hostId.getHost();

            if (hostId.getPort() == -1) {
                message = message + ":"
                          + java.rmi.registry.Registry.REGISTRY_PORT;
            } else {
                message = message + ":" + hostId.getPort();
            }

            if (e.getMessage() != null) {
                throw new MonitorException(message + "\n" + e.getMessage(), e);
            } else {
                throw new MonitorException(message, e);
            }

        } catch (NotBoundException e) {
            // no server with given name
            String message = e.getMessage();
            if (message == null) message = rmiName;
            throw new MonitorException("RMI Server " + message
                                       + " not available", e);
        } catch (MalformedURLException e) {
            // this is a programming problem
            e.printStackTrace();
            throw new IllegalArgumentException("Malformed URL: " + rmiName);
        }
        this.vmManager = new RemoteVmManager(remoteHost);
        this.timer = new Timer(true);
    }

    /**
     * {@inheritDoc}
     */
    public MonitoredVm getMonitoredVm(VmIdentifier vmid)
                       throws MonitorException {
        return getMonitoredVm(vmid, DEFAULT_POLLING_INTERVAL);
    }

    /**
     * {@inheritDoc}
     */
    public MonitoredVm getMonitoredVm(VmIdentifier vmid, int interval)
                       throws MonitorException {
        VmIdentifier nvmid = null;
        try {
            nvmid = hostId.resolve(vmid);
            RemoteVm rvm = remoteHost.attachVm(vmid.getLocalVmId(),
                                               vmid.getMode());
            RemoteMonitoredVm rmvm = new RemoteMonitoredVm(rvm, nvmid, timer,
                                                           interval);
            rmvm.attach();
            return rmvm;

        } catch (RemoteException e) {
            throw new MonitorException("Remote Exception attaching to "
                                       + nvmid.toString(), e);
        } catch (URISyntaxException e) {
            /*
             * the VmIdentifier is expected to be a valid and should resolve
             * easonably against the host identifier. A URISyntaxException
             * here is most likely a programming error.
             */
            throw new IllegalArgumentException("Malformed URI: "
                                               + vmid.toString(), e);
        }
    }

    /**
     * {@inheritDoc}
     */
    public void detach(MonitoredVm vm) throws MonitorException {
        RemoteMonitoredVm rmvm = (RemoteMonitoredVm)vm;
        rmvm.detach();
        try {
            remoteHost.detachVm(rmvm.getRemoteVm());

        } catch (RemoteException e) {
            throw new MonitorException("Remote Exception detaching from "
                                       + vm.getVmIdentifier().toString(), e);
        }
    }

    /**
     * {@inheritDoc}
     */
    public void addHostListener(HostListener listener) {
        synchronized(listeners) {
            listeners.add(listener);
            if (task == null) {
                task = new NotifierTask();
                timer.schedule(task, 0, interval);
            }
        }
    }

    /**
     * {@inheritDoc}
     */
    public void removeHostListener(HostListener listener) {
        /*
         * XXX: if a disconnect method is added, make sure it calls
         * this method to unregister this object from the watcher. otherwise,
         * an unused MonitoredHostProvider instance may go uncollected.
         */
        synchronized(listeners) {
            listeners.remove(listener);
            if (listeners.isEmpty() && (task != null)) {
                task.cancel();
                task = null;
            }
        }
    }

    public void setInterval(int newInterval) {
        synchronized(listeners) {
            if (newInterval == interval) {
                return;
            }

            int oldInterval = interval;
            super.setInterval(newInterval);

            if (task != null) {
                task.cancel();
                NotifierTask oldTask = task;
                task = new NotifierTask();
                CountedTimerTaskUtils.reschedule(timer, oldTask, task,
                                                 oldInterval, newInterval);
            }
        }
    }

    /**
     * {@inheritDoc}
     */
    public Set<Integer> activeVms() throws MonitorException {
        return vmManager.activeVms();
    }

    /**
     * Fire VmStatusChangeEvent events to HostListener objects
     *
     * @param active Set of Integer objects containing the local
     *               Vm Identifiers of the active JVMs
     * @param started Set of Integer objects containing the local
     *                Vm Identifiers of new JVMs started since last
     *                interval.
     * @param terminated Set of Integer objects containing the local
     *                   Vm Identifiers of terminated JVMs since last
     *                   interval.
     */
    private void fireVmStatusChangedEvents(Set active, Set started,
                                           Set terminated) {
        ArrayList registered = null;
        VmStatusChangeEvent ev = null;

        synchronized(listeners) {
            registered = (ArrayList)listeners.clone();
        }

        for (Iterator i = registered.iterator(); i.hasNext(); /* empty */) {
            HostListener l = (HostListener)i.next();
            if (ev == null) {
                ev = new VmStatusChangeEvent(this, active, started, terminated);
            }
            l.vmStatusChanged(ev);
        }
    }

    /**
     * Fire hostDisconnectEvent events.
     */
    void fireDisconnectedEvents() {
        ArrayList registered = null;
        HostEvent ev = null;

        synchronized(listeners) {
            registered = (ArrayList)listeners.clone();
        }

        for (Iterator i = registered.iterator(); i.hasNext(); /* empty */) {
            HostListener l = (HostListener)i.next();
            if (ev == null) {
                ev = new HostEvent(this);
            }
            l.disconnected(ev);
        }
    }

    /**
     * class to poll the remote machine and generate local event notifications.
     */
    private class NotifierTask extends CountedTimerTask {
        public void run() {
            super.run();

            // save the last set of active JVMs
            Set lastActiveVms = activeVms;

            try {
                // get the current set of active JVMs
                activeVms = (HashSet<Integer>)vmManager.activeVms();

            } catch (MonitorException e) {
                // XXX: use logging api
                System.err.println("MonitoredHostProvider: polling task "
                                   + "caught MonitorException:");
                e.printStackTrace();

                // mark the HostManager as errored and notify listeners
                setLastException(e);
                fireDisconnectedEvents();
            }

            if (activeVms.isEmpty()) {
                return;
            }

            Set<Integer> startedVms = new HashSet<Integer>();
            Set<Object> terminatedVms = new HashSet<Object>();

            for (Iterator i = activeVms.iterator(); i.hasNext(); /* empty */ ) {
                Integer vmid = (Integer)i.next();
                if (!lastActiveVms.contains(vmid)) {
                    // a new file has been detected, add to set
                    startedVms.add(vmid);
                }
            }

            for (Iterator i = lastActiveVms.iterator(); i.hasNext();
                    /* empty */ ) {
                Object o = i.next();
                if (!activeVms.contains(o)) {
                    // JVM has terminated, remove it from the active list
                    terminatedVms.add(o);
                }
            }

            if (!startedVms.isEmpty() || !terminatedVms.isEmpty()) {
                fireVmStatusChangedEvents(activeVms, startedVms, terminatedVms);
            }
        }
    }
}