/*
 * Copyright 2012, 2013 Red Hat, Inc.
 *
 * This file is part of Thermostat.
 *
 * Thermostat is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2, or (at your
 * option) any later version.
 *
 * Thermostat 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Thermostat; see the file COPYING.  If not see
 * <http://www.gnu.org/licenses/>.
 *
 * Linking this code with other modules is making a combined work
 * based on this code.  Thus, the terms and conditions of the GNU
 * General Public License cover the whole combination.
 *
 * As a special exception, the copyright holders of this code give
 * you permission to link this code with independent modules to
 * produce an executable, regardless of the license terms of these
 * independent modules, and to copy and distribute the resulting
 * executable under terms of your choice, provided that you also
 * meet, for each linked independent module, the terms and conditions
 * of the license of that module.  An independent module is a module
 * which is not derived from or based on this code.  If you modify
 * this code, you may extend this exception to your version of the
 * library, but you are not obligated to do so.  If you do not wish
 * to do so, delete this exception statement from your version.
 */

package com.redhat.thermostat.agent;

import com.redhat.thermostat.annotations.ExtensionPoint;

/**
 * A listener that is notified when a JVM starts or is stopped.
 * <p>
 * Register an instance of this class as an OSGi service, and it will be
 * notified of all VM {@link Status} events.
 */
@ExtensionPoint
public interface VmStatusListener {

    enum Status {

        /** A VM has just started now */
        VM_STARTED,

        /**
         * A delayed version of {@link #VM_STARTED}. A VM was started at some
         * point in the past. The listener was not informed about it then
         * (probably because the listener was not registered at the time), but
         * is being informed about it now.
         */
        VM_ACTIVE,

        /** A VM was stopped just now */
        VM_STOPPED,
    }

    // TODO what other information other than pid may be useful for plugins?

    public void vmStatusChanged(Status newStatus, int pid);

}