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 * Copyright (c) 2018, TechEmpower, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
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 *       notice, this list of conditions and the following disclaimer.
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 *       notice, this list of conditions and the following disclaimer in the
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 *     * Neither the name TechEmpower, Inc. nor the names of its
 *       contributors may be used to endorse or promote products derived from
 *       this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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package com.techempower.scheduler;

import java.util.*;

import com.techempower.helper.*;
import com.techempower.util.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * An event that is executed on a daily basis at a given hour-minute
 * combination.  This is a convenience subclass to ScheduledEvent that leaves
 * you to implement a call to the constructor and a method named "doIt" where
 * you do your business.
 */
public abstract class DailyEvent
  extends ScheduledEvent
{

  //
  // Member variables.
  //

  private final Logger log = LoggerFactory.getLogger(getClass());
  private final int    hour;
  private final int minute;
  
  //
  // Member methods.
  //
  
  /**
   * Constructor.
   * 
   * @param name The event's name.
   * @param description A description to display to administrators.
   * @param hour An hour on a zero-indexed 24-hour clock (0 to 23).
   * @param minute A minute from 0 to 59.
   */
  public DailyEvent(String name, String description, int hour, 
      int minute)
  {
    super(name, description);
    
    // Bounds check.
    Args.intBound(minute, "minute", 0, 59);
    Args.intBound(hour, "hour", 0, 23);
    
    this.hour = hour;
    this.minute = minute;
  }

  /**
   * Gets a default scheduled time for this event.
   */
  @Override
  public long getDefaultScheduledTime()
  {
    return getNextRun().getTimeInMillis();
  }

  /**
   * Moves a Calendar object forward until the next run date.
   */
  protected Calendar getNextRun()
  {
    // Move to the upcoming midnight.
    final Calendar cal = DateHelper.getCalendarInstance();
    cal.add(Calendar.HOUR_OF_DAY, 1);
    
    // Keep moving until we get to the right day.
    while (cal.get(Calendar.HOUR_OF_DAY) != this.hour)
    {
      cal.add(Calendar.HOUR_OF_DAY, 1);
    }

    // Set the remaining bits.
    cal.set(Calendar.MINUTE, this.minute);
    cal.set(Calendar.SECOND, 0);
    cal.set(Calendar.MILLISECOND, 0);
    
    return cal;
  }

  /**
   * Executes this event.
   */
  @Override
  public void execute(Scheduler scheduler, boolean onDemandExecution)
  {
    try
    {
      doIt();
    }
    catch (Exception exc)
    {
      log.error("Exception while executing {}", this, exc);
    }
    finally
    {
      // Reschedule this event.
      scheduler.scheduleEvent(this, getDefaultScheduledTime());
    }
  }
  
  /**
   * Subclasses implement this to do their business.
   */
  protected abstract void doIt();
  
}