/*************************************************************************
 *                                                                       *
 *  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.Date;
import java.util.List;

import javax.persistence.EntityManager;

import org.signserver.common.SignServerException;
import org.signserver.common.WorkerConfig;
import org.signserver.server.statistics.StatisticsEntry;

/**
 * TODO: Document me!
 * 
 * @author Philip Vendil 28 apr 2008
 * @version $Id: IStatisticsCollector.java 2345 2012-05-06 09:03:57Z netmackan $
 */
public interface IStatisticsCollector {

    /**
     * Method called  after instantiation.
     * 
     * @param workerId id of worker.
     * @param config active worker configuration of worker
     * @param em the SignServer EntityManager
     * @throws SignServerException if unexpected error occurred during initialization.
     */
    void init(int workerId, WorkerConfig config, EntityManager em) throws SignServerException;

    /**
     * Main method used to add an event to this StatisticsCollector. It is
     * up to the implementation to decide how.
     * 
     * @param event the event to perform statistics on.
     * @throws SignServerException if unexpected error occurred when collecting the statistics, such
     * as DB failure or other IO problems.
     */
    void addEvent(Event event) throws SignServerException;

    /**
     * Signal to the Statistics Collector to flush all data and start again.
     */
    void flush();

    /**
     * Method used to fetch a list of StatisticsEntries maintained
     * by the statistics collector.
     * 
     * @param type a defined String specifying what type of statistics
     * that is requested. It's up to the implementation and the viewer of
     * statistics to define the value of the type, but it should be unique.
     * The value "ALL" should always return all statistics. Cannot be null. 
     * @param startTime for statistics entries in the query, null gives no start time
     * @param endTime for started statistics entries in the query, null gives no end time.
     * @return A list of matching StatisticsEntry, never null.
     */
    List<StatisticsEntry> fetchStatistics(String type, Date startTime, Date endTime);
}