/*************************************************************************
 *                                                                       *
 *  SignServer: The OpenSource Automated Signing Server                  *
 *                                                                       *
 *  This software is free software; you can redistribute it and/or       *
 *  modify it under the terms of the GNU Lesser General Public           *
 *  License as published by the Free Software Foundation; either         *
 *  version 2.1 of the License, or any later version.                    *
 *                                                                       *
 *  See terms of license at gnu.org.                                     *
 *                                                                       *
 *************************************************************************/
package org.signserver.server.statistics;

import java.util.HashMap;

import javax.persistence.EntityManager;

import org.apache.log4j.Logger;
import org.signserver.common.SignServerException;
import org.signserver.common.StatisticsConstants;
import org.signserver.common.WorkerConfig;
import org.signserver.server.statistics.csvfilewriter.CSVFileStatisticsCollector;
import org.signserver.server.statistics.nonpersistent.NonPersistantStatisticsCollector;

/**
 * Class managing all statistics instances.
 * 
 * The methods are startEvent and endEvent, startEvent that creates and maintains
 * a statistics collector for a worker if it's configured to do so, and endEvent
 * managing the storage of that event.
 *
 * @author Philip Vendil 9 maj 2008
 * @version $Id: StatisticsManager.java 1825 2011-08-10 10:21:18Z netmackan $
 */
public class StatisticsManager {

    /** Logger for this class. */
    private static final Logger LOG = Logger.getLogger(StatisticsManager.class);

    private static HashMap<Integer, IStatisticsCollector> instances = new HashMap<Integer, IStatisticsCollector>();

    /**
     * Method used to signal to the StatisticsManager to create a statistics event using the
     * configure statistics manager.
     * 
     * @param workerId id of the worker calling
     * @param config the active configuration of the worker
     * @param em the EntityManager used by the worker.
     * @return an Event if statistics is going to be used or null if statistics is disabled.
     */
    public static Event startEvent(int workerId, WorkerConfig config, EntityManager em) {
        Event retval = null;
        IStatisticsCollector sc = getStatisticsCollector(workerId, config, em);
        if (sc != null) {
            retval = new Event(workerId);
            retval.start();
        }
        return retval;
    }

    /**
     * Method signaling that the given event has ended and should be stored in the configure
     * statistics collector. 
     * 
     * @param workerId id of the worker calling
     * @param config the active configuration of the worker
     * @param em the EntityManager used by the worker.
     * @param event the event created by the startEvent method.
     * @throws SignServerException if unexpected error occurred when collecting the statistics, such
     * as DB failure or other IO problems.
     */
    public static void endEvent(int workerId, WorkerConfig config, EntityManager em, Event event) throws SignServerException {
        if (event != null) {
            event.stop();
            IStatisticsCollector sc = getStatisticsCollector(workerId, config, em);
            if (sc != null) {
                sc.addEvent(event);
            }
        }
    }

    /**
     * Method in charge of creating and maintaining an workers statistics collector.
     * @param workerId 
     * @param config the active worker configuration
     */
    public static IStatisticsCollector getStatisticsCollector(int workerId,
            WorkerConfig config, EntityManager em) {
        if (config.getProperty(StatisticsConstants.TYPE) == null) {
            return null;
        }

        if (instances.get(workerId) != null) {
            return instances.get(workerId);
        }

        return genStatisticsCollector(workerId,
                config, em);

    }

    private synchronized static IStatisticsCollector genStatisticsCollector(int workerId,
            WorkerConfig config, EntityManager em) {

        String typeValue = config.getProperty(StatisticsConstants.TYPE);

        String classPath = null;
        if (typeValue.equalsIgnoreCase(StatisticsConstants.TYPE_NONPERSISTANT)) {
            classPath = NonPersistantStatisticsCollector.class.getName();
        }
        if (typeValue.equalsIgnoreCase(StatisticsConstants.TYPE_CSVFILEWRITER)) {
            classPath = CSVFileStatisticsCollector.class.getName();
        }

        if (classPath == null) {
            classPath = typeValue;
        }

        try {
            IStatisticsCollector sc = (IStatisticsCollector) StatisticsManager.class.getClassLoader().loadClass(classPath).newInstance();
            sc.init(workerId, config, em);
            instances.put(workerId, sc);
            return sc;
        } catch (Exception e) {
            LOG.error("Error generating statistics for worker with id " + workerId + " check that the worker property " + StatisticsConstants.TYPE + " is configured propertly. It currently have the value '" + typeValue + " the error was of type " + e.getClass().getName() + " and had the following message : " + e.getMessage() + ". Statistics will be disabled until next reload.");
            LOG.debug("Stacktrace :", e);
        }
        return null;
    }

    /**
     * resets the statistics of the given workerId
     * @param workerId of worker to reset statistics for or '0' for all workers.
     */
    public static void flush(int workerId) {
        if (workerId == 0) {
            instances.clear();
        } else {
            instances.remove(workerId);
        }
    }
}