/*
 * Copyright 2012-2017 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.vm.gc.agent.internal;

import java.util.logging.Logger;

import com.redhat.thermostat.common.utils.LoggingUtils;
import com.redhat.thermostat.jvm.overview.agent.VmListenerBackend;
import com.redhat.thermostat.jvm.overview.agent.VmStatusListenerRegistrar;
import com.redhat.thermostat.jvm.overview.agent.VmUpdateListener;
import org.apache.felix.scr.annotations.Activate;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.ConfigurationPolicy;
import org.apache.felix.scr.annotations.Modified;
import org.apache.felix.scr.annotations.Deactivate;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.Service;
import org.osgi.framework.BundleContext;
import com.redhat.thermostat.backend.Backend;
import com.redhat.thermostat.common.Version;
import com.redhat.thermostat.storage.core.WriterID;
import com.redhat.thermostat.vm.gc.agent.internal.models.VmGcStatDAO;

@Component(
        policy = ConfigurationPolicy.REQUIRE,
        configurationPid = "vm-gc"
)
@Service(value = Backend.class)
public class VmGcBackend extends VmListenerBackend {

    private static final Logger logger = LoggingUtils.getLogger(VmGcBackend.class);

    private final ListenerCreator listenerCreator;
    
    @Reference
    private VmGcStatDAO vmGcStats;
    @Reference
    private WriterID writerId;
    
    public VmGcBackend() {
        this(new ListenerCreator());
    }
    
    VmGcBackend(ListenerCreator creator) {
        super("VM GC Backend", "Gathers garbage collection statistics about a JVM", "Red Hat, Inc.", true);
        this.listenerCreator = creator;
    }

    @Override
    protected VmUpdateListener createVmListener(String writerId, String vmId, int pid) {
        return listenerCreator.create(writerId, vmGcStats, vmId);
    }

    @Activate
    protected void componentActivated(BundleContext context) {
        VmStatusListenerRegistrar registrar = new VmStatusListenerRegistrar(context);
        Version version = new Version(context.getBundle());
        initialize(writerId, registrar, version.getVersionNumber());
    }

    /*
     * Default OSGI behaviour is to restart the component when configuration changes.
     * The @modified method acts as a callback to prevent this from happening since
     * we don't need to restart the component for our use-case.
     */
    @Modified
    protected void modified() {
        logger.config("Doing nothing on configuration change for plugin vm-gc");
    }
    
    @Deactivate
    protected void componentDeactivated() {
        if (isActive()) {
            deactivate();
        }
    }
    
    // DS bind method
    protected void bindVmGcStats(VmGcStatDAO dao) {
        this.vmGcStats = dao;
    }
    
    // DS bind method
    protected void bindWriterId(WriterID id) {
        this.writerId = id;
    }
    
    // For testing purposes
    static class ListenerCreator {
        VmGcVmListener create(String writerId, VmGcStatDAO dao, String vmId) {
            return new VmGcVmListener(writerId, dao, vmId);
        }
    }
    
}