/**
 * Copyright (c) 2002-2010 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package org.neo4j.ext.udc.impl;

import java.util.Properties;
import java.util.Timer;

import org.neo4j.ext.udc.UdcProperties;
import org.neo4j.helpers.Service;
import org.neo4j.kernel.Config;
import org.neo4j.kernel.KernelExtension;
import org.neo4j.kernel.Version;
import org.neo4j.kernel.impl.nioneo.xa.NeoStoreXaDataSource;

/**
 * Kernel extension for UDC, the Usage Data Collector. The UDC runs as a background
 * daemon, waking up once a day to collect basic usage information about a long
 * running graph database.
 * <p/>
 * The first update is delayed to avoid needless activity during integration
 * testing and short-run applications. Subsequent updates are made at regular
 * intervals. Both times are specified in milliseconds.
 *
 */
@Service.Implementation(KernelExtension.class)
public class UdcExtensionImpl extends KernelExtension implements UdcProperties {

    public static final String UDC_SOURCE_DISTRIBUTION_KEY = "neo4j.ext.udc.host";

    /**
     * Delay, in milliseconds, before the first UDC update is sent.
     *
     * Defaults to 10 minutes.
     */
    private int firstDelay = 10 * 1000 * 60;

    /**
     * Millisecond interval for subsequent updates.
     *
     * Defaults to 24 hours.
     */
    private int interval = 1000 * 60 * 60 * 24;

    /**
     * Host address to which UDC updates will be sent.
     */
    private String hostAddress = "udc.neo4j.org";

    /**
     * Disable the extension.
     *
     * Defaults to false.
     */
    private boolean disabled = false;

    /**
     * No-arg constructor, sets the extension key to "kernel udc".
     *  
     */
    public UdcExtensionImpl() {
        super("kernel udc");
    }

    /**
     * Lifecycle load event, which occurs during the startup of
     * a new GraphDbInstance.
     *
     * Configuration information is retrieved from the KernelData,
     * then a daemon thread is started to periodically collect
     * and submit usage data.
     *
     * @param kernel reference to the loading graph database kernel.
     */
    @Override
    protected void load(KernelData kernel) {
        configure(kernel.getConfig());

        // ABK: a hack to register this extension with the kernel, which
        // only knows about extensions that have a saved state
        kernel.setState(this, new Object());

        if (!disabled) {
            Timer timer = new Timer();
            NeoStoreXaDataSource ds = (NeoStoreXaDataSource) kernel.getConfig().getTxModule().getXaDataSourceManager().getXaDataSource("nioneodb");
            String storeId = Long.toHexString(ds.getRandomIdentifier());
            UdcTimerTask task = new UdcTimerTask(hostAddress, Version.VERSION.getRevision(), storeId);
            timer.scheduleAtFixedRate(task, firstDelay, interval);
        }
    }

    /**
     * Attempt to retrieve configuration provided by user.
     *
     * Configuration precedence is in this order:
     *
     * <ol>
     *   <li>value from config</li>
     *   <li>system property</li>
     *   <li>hard-coded default value</li>
     * <ol>
     * 
     * @param config user defined configuration parameters
     */
    private void configure(Config config) {
        Properties props = loadSystemProperties();
        try {
            String firstDelayAsString = (String) config.getParams().get(FIRST_DELAY_CONFIG_KEY);
            if (firstDelayAsString == null) {
                firstDelayAsString = (String)props.getProperty(FIRST_DELAY_CONFIG_KEY, "600000");
            }
            firstDelay = Integer.parseInt(firstDelayAsString);
        } catch (Exception e) {
           ; 
        }
        try {
            String intervalAsString = (String) config.getParams().get(INTERVAL_CONFIG_KEY);
            if (intervalAsString == null) {
                intervalAsString = (String)props.getProperty(INTERVAL_CONFIG_KEY, "86400000");
            }
            interval = Integer.parseInt(intervalAsString);
        } catch (Exception e) {
            ;
        }
        try {
            String possibleHost = (String)config.getParams().get(UDC_HOST_ADDRESS_KEY);
            if (null != possibleHost) hostAddress = possibleHost;
        } catch (Exception e) {
            ;
        }

        String disabledAsString = (String)config.getParams().get(UDC_DISABLE_KEY);
        if (disabledAsString == null) {
            disabledAsString = props.getProperty(UDC_DISABLE_KEY, "false");
        }
        disabled = Boolean.valueOf(disabledAsString);
    }

   private Properties loadSystemProperties() {
       Properties sysProps = System.getProperties();
       try {
           sysProps.load(getClass().getResourceAsStream("/org/neo4j/ext/udc/udc.properties"));
       } catch (Exception e) {
           System.err.println("failed to load udc.properties, because: " + e);
           ; // fail silently, 
       }
       return sysProps;
   }
}