/* 
 * Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights reserved.
 *
 * 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; version 2 of the
 * License.
 * 
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301  USA
 */

#ifndef _THREADED_TIMER_H_
#define _THREADED_TIMER_H_

#include "common.h"
#include "glib.h"
#include "base/threading.h"

#include <list>
#include <boost/function.hpp>

// The callback type used for timer events. It gets the id of the task returned from add_task
// and must return a boolean value which tells us if the task should continue to run or
// immediately be stopped. For one-shot tasks the return value has no meaning.
typedef boost::function<bool (int)> TimerFunction;

#ifdef _WIN32
  #pragma warning(disable: 4251) // We don't want to DLL export TimerTask, and we don't need a warning for that.
#endif

struct TimerTask {
  int task_id;
  gdouble next_time;         // Precomputed target time when this task must be triggered again.
  gdouble wait_time;         // The time in seconds to wait until this task is executed again.
  TimerFunction callback;    // The callback to trigger when the timer fires.
  bool stop;                 // Tells the scheduler to remove this task.
  bool single_shot;          // If true then this task will only run once.
  bool scheduled;            // True if the task has been scheduled currently (it is waiting in the pool to get executed).
};

typedef std::list<TimerTask> TaskList;

// The unit type of the timer value given to ThreadedTimer::add_task.
enum TimerUnit {
  TimerFrequency,
  TimerTimeSpan
};

/**
 * The threaded timer is supposed to run as a singleton and provide scheduled timer events. It takes orders when to trigger
 * a timer event, depending on the given frequency (if it is a repeating timer) or delay (for one-shot timers).
 * It forms the base for timed services like animations, server pings in the background etc.
 */
class BASELIBRARY_PUBLIC_FUNC ThreadedTimer
{
public:
  static ThreadedTimer* get();
  static void stop();
  
  static int add_task(TimerUnit unit, double value, bool single_shot, TimerFunction callback);
  static void remove_task(int task_id);
private:
  base::Mutex _timer_lock;  // Synchronize access to the timer class.
  GThreadPool* _pool;   // A number of threads which trigger the callbacks (to make them independant of each other).
  int _wait_time;       // The time the timer thread has to wait until looking for new tasks to execute.
  bool _terminate;      // Set to true when shutting down the timer.
  int _next_id;         // A counter for task ids.
  
  GThread *_thread;     // This thread loops endlessly executing tasks as they come in. 
  TaskList _tasks;

  ThreadedTimer(int base_frequency);
  ~ThreadedTimer();

  static gpointer start(gpointer data);
  static gpointer pool_function(gpointer data, gpointer user_data);
  void main_loop();
  void remove(int task_id);
};

#endif // _THREADED_TIMER_H_

