/*
 * 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.host.network.internal;

import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.logging.Logger;

import com.redhat.thermostat.backend.Backend;
import com.redhat.thermostat.backend.HostPollingAction;
import com.redhat.thermostat.backend.HostPollingBackend;
import com.redhat.thermostat.common.Version;
import com.redhat.thermostat.common.Clock;
import com.redhat.thermostat.common.SystemClock;
import com.redhat.thermostat.common.utils.LoggingUtils;
import com.redhat.thermostat.host.network.model.NetworkInfoList;
import com.redhat.thermostat.host.network.model.NetworkInterfaceInfo;
import com.redhat.thermostat.storage.core.WriterID;

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.Deactivate;
import org.apache.felix.scr.annotations.Modified;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.Service;
import org.osgi.framework.BundleContext;

@Component(
        policy = ConfigurationPolicy.REQUIRE,
        configurationPid = "host-network"
)
@Service(value = Backend.class)
public class HostNetworkBackend extends HostPollingBackend {

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

    private final long procCheckInterval = 1000; // TODO make this configurable.
    private final Clock clock;

    @Reference
    private NetworkInfoListDAO networkInterfaceInfoDAO;

    @Reference
    private WriterID writerID;

    public HostNetworkBackend() {
        this(Executors.newSingleThreadScheduledExecutor());
    }

    private HostNetworkBackend(ScheduledExecutorService executor) {
        this("Host Network Backend",
                "Gathers network interface information from the system",
                "Red Hat, Inc.", new Version(), executor);
    }

    HostNetworkBackend(String name, String descr, String vendor, Version version, ScheduledExecutorService executor) {
        super(name, descr, vendor, version, executor);
        this.clock = new SystemClock();
    }

    @Activate
    public void componentActivated(BundleContext context) {
        Version version = new Version(context.getBundle());
        setVersion(version.getVersionNumber());
        registerAction(new BackendAction(writerID, clock, networkInterfaceInfoDAO));
    }

    /*
     * 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 host-network");
    }

    @Deactivate
    protected void componentDeactivated() {
        if (isActive()) {
            deactivate();
        }
    }

    private static class BackendAction implements HostPollingAction {

        private final NetworkInfoBuilder builder;
        private final NetworkInfoListDAO dao;
        private WriterID writerID;
        private Clock clock;
        private int oldHash = 0;

        BackendAction(WriterID writerID, Clock clock, NetworkInfoListDAO dao) {
            builder = new NetworkInfoBuilder();
            this.writerID = writerID;
            this.clock = clock;
            this.dao = dao;
        }

        @Override
        public void run() {
            final List<NetworkInterfaceInfo> ifaceList = builder.build();
            int hash = ifaceList.hashCode();
            if (hash != oldHash) {
                NetworkInfoList obj = new NetworkInfoList(writerID.getWriterID(), clock.getRealTimeMillis(), ifaceList);
                dao.put(obj);
                oldHash = hash;
            }
        }

    }
}