/*  This file is part of YUView - The YUV player with advanced analytics toolset
*   <https://github.com/IENT/YUView>
*   Copyright (C) 2015  Institut für Nachrichtentechnik, RWTH Aachen University, GERMANY
*
*   This program is free software; you can redistribute it and/or modify
*   it under the terms of the GNU General Public License as published by
*   the Free Software Foundation; either version 3 of the License, or
*   (at your option) any later version.
*
*   In addition, as a special exception, the copyright holders give
*   permission to link the code of portions of this program with the
*   OpenSSL library under certain conditions as described in each
*   individual source file, and distribute linked combinations including
*   the two.
*   
*   You must obey the GNU General Public License in all respects for all
*   of the code used other than OpenSSL. If you modify file(s) with this
*   exception, you may extend this exception to your version of the
*   file(s), but you are not obligated to do so. If you do not wish to do
*   so, delete this exception statement from your version. If you delete
*   this exception statement from all source files in the program, then
*   also delete it here.
*
*   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 General Public License for more details.
*
*   You should have received a copy of the GNU General Public License
*   along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

#pragma once

#include <QObject>
#include <QTimer>

class EventSubsampler : public QObject
{
  Q_OBJECT

public:
  EventSubsampler(unsigned eventsPerSecond = 5) : eventsPerSecond(eventsPerSecond) {}

signals:
  void subsampledEvent();

public slots:
  void postEvent()
  {
    if (this->state == State::Idle)
    {
      const auto timeoutMs = 1000 / this->eventsPerSecond;
      QTimer::singleShot(timeoutMs, this, &EventSubsampler::timerTimeout);
      this->state = State::CoolDown;
      emit subsampledEvent();
    }
    else if (this->state == State::CoolDown)
    {
      this->state = State::PendingEvent;
    }
  }

private slots:
  void timerTimeout()
  {
    if (this->state == State::PendingEvent)
    {
      const auto timeoutMs = 1000 / this->eventsPerSecond;
      QTimer::singleShot(timeoutMs, this, &EventSubsampler::timerTimeout);
      emit subsampledEvent();
      this->state = State::CoolDown;
    }
    else
      this->state = State::Idle;
  }

private:
  enum class State
  {
    Idle,         // No event occured yet. Time inactive.
    CoolDown,     // Timer running but no additional event yet
    PendingEvent  // Timer running and an additional event was also recieved
  };
  State state {State::Idle};

  unsigned eventsPerSecond {1};
};
