/**
 * ServletMaintenance.java
 * Matt Tucker
 * CoolServlets.com
 * June 10, 1999
 * Version 1.0.2
 *
 *    Copyright (C) 1999  Matt Tucker
 *
 *    This library is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU Library General Public
 *    License as published by the Free Software Foundation; either
 *    version 2 of the License, or (at your option) any later version.
 *
 *    This library 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
 *    Library General Public License for more details.
 *
 *    You should have received a copy of the GNU Library General Public
 *    License along with this library; if not, write to the
 *    Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 *    Boston, MA  02111-1307, USA.
 */

package com.coolservlets.util;

/**
 * A thread that helps a servlet perform time based actions. This system
 * is useful for doing things such as saving the servlet's state or performing
 * other periodic tasks.
 * <p>
 * The user of this class specifies a number of minutes and hours to wait
 * before invoking the doMaintenance() function of the passed in
 * MaintainedServlet object.
 * <p>
 * For example, a servlet should "implement ServletMaintenace" and then have
 * a doMainenance() method that contains actions that should be performed
 * periodically. Then, the servlet should define a ServletMaintenance object
 * as something like:
 * <p>
 * ServletMaintenance timer = new ServletMaintenance(this,30,ServletMaintenance.MINUTES);
 * </pre>
 * <p>
 * This starts up a timer that will call doMaintenance() every thirty minutes.
 * When the thread needs to be stopped, the shutDown() method should be called.
 *
 * @author Matt Tucker
 * @version 1.0.2
 */
public class ServletMaintenance extends Thread {
    /**
     * Class users must pass in a servlet that implements the MaintainedServlet
     * interface as well as a length of time that this thread
     * will wait during each interval. Note, after calling the constructor, the
     * thread will automatically start running.
     * <p>
     * The third argument to the constructor should be one of the following:
     * <ul>
ServletMaintenance.SECONDS
     *     <li>ServletMaintenance.MINUTES
     *     <li>ServletMaintenance.HOURS
     *     <li>ServletMaintenance.DAYS
     * </ul>
     *
     * @param reference  some object that implements MaintainedServlet
     * @param lengthTime  a length of time to wait
     * @param timeType  the time unit that should be used
     */
     public ServletMaintenance(MaintainedServlet reference, int lengthTime, int timeType) {
        servletReference = reference;
        secondsToWait = 0;
        minutesToWait = 0;
        hoursToWait = 0;
        daysToWait = 0;

        if (timeType == ServletMaintenance.SECONDS) {
            secondsToWait = lengthTime;
        }
        else if (timeType == ServletMaintenance.MINUTES) {
            minutesToWait = lengthTime;
        }
        else if (timeType == ServletMaintenance.HOURS) {
            hoursToWait = lengthTime;
        }
        else if (timeType == ServletMaintenance.DAYS) {
            daysToWait = lengthTime;
        }

        //Start this thread
        start();
    }

    /**
     * Returns the number of seconds the thread waits before executing.
     */
    public int getSeconds() {
        return secondsToWait;
    }

    /**
     * Returns the number of minutes the thread waits before executing.
     */
    public int getMinutes() {
        return minutesToWait;
    }

    /**
     * Returns the number of hours the thread waits before executing.
     */
    public int getHours() {
        return hoursToWait;
    }

    /**
     * Returns the number of days the thread waits before executing.
     */
    public int getDays() {
        return daysToWait;
    }

    /**
     * Sets the number of seconds the thread waits before executing. The change
     * will not take effect until the next time the thread loops through a
     * wait cycle.
     *
     * @param minutes the number of hours to wait.
     */
    public void setSeconds(int seconds) {
        secondsToWait = seconds;
    }

    /**
     * Sets the number of minutes the thread waits before executing. The change
     * will not take effect until the next time the thread loops through a
     * wait cycle.
     *
     * @param minutes the number of minutes to wait.
     */
    public void setMinutes(int minutes) {
        minutesToWait = minutes;
    }

    /**
     * Sets the number of hours the thread waits before executing. The change
     * will not take effect until the next time the thread loops through a
     * wait cycle.
     *
     * @param minutes the number of hours to wait.
     */
    public void setHours(int hours) {
        hoursToWait = hours;
    }

    /**
     * Sets the number of hours the thread waits before executing. The change
     * will not take effect until the next time the thread loops through a
     * wait cycle.
     *
     * @param minutes the number of hours to wait.
     */
    public void setDays(int days) {
        daysToWait = days;
    }

    /**
     * This should be called when the thread needs to be shut-down.
     */
    public void shutDown() {
        done = true;
    }

    /**
     * Calls the doMaintenance() method of the MaintainedServlet object and then
     * sleeps for the desired interval. This process will continue until the
     * shutDown() method is called. This method will be automatically started
     * when the object is constructed. You should not call the run method or
     * the start method in your code.
     */
    public void run() {
        //While the user has not called the shutDown() method.
        while (!done) {
            try {
                //Wait for the specified amount of time before continuing.
                long timeToWait = secondsToWait*SECOND;
                timeToWait += minutesToWait*MINUTE;
                timeToWait += hoursToWait*HOUR;
                timeToWait += daysToWait*DAY;
                sleep(timeToWait);
                //Tell the servlet to perform the maintenance function
                if (!done) {
                    servletReference.doMaintenance();
                }
            }
            catch (Exception e) {
                //we'll ignore errors...
            }
        }
    }

    /* Constant representing seconds. */
    public static final int SECONDS = 0;

    /* Constant representing minutes. */
    public static final int MINUTES = 1;

    /* Constant representing hours. */
    public static final int HOURS = 2;

    /* Constant representing days. */
    public static final int DAYS = 3;

    private MaintainedServlet servletReference;
    private boolean done = false;
    private int secondsToWait;
    private int minutesToWait;
    private int hoursToWait;
    private int daysToWait;
    //A series of time constants to make the source more readable.
    //They are measured in milleseconds.
    private final long SECOND = 1000;
    private final long MINUTE = SECOND*60;
    private final long HOUR = MINUTE*60;
    private final long DAY = HOUR*24;
}