#ifndef DATETIME_TIMER_HPP__
#define DATETIME_TIMER_HPP__


template <class timer_traits>
class timer
{
public:
  typedef timer_traits traits_type;
  typedef typename timer_traits::time_rep time_rep;
  typedef typename timer_traits::time_duration_type time_duration_type;
  
  timer () :
    running(false),
    started_at(timer_traits::init_zero()),
    total_elapsed(0,0,0,0)
  {}
  bool is_running() const
  {
    return running;
  }
  void start()
  { 
    if (!running) {
      running = true;
      started_at = timer_traits::get_current_time();
    }
  }
  time_duration_type elapsed() const
  {
    if (!running) {
      return total_elapsed;
    }
    return total_elapsed + timer_traits::make_time_duration(started_at, timer_traits::get_current_time());
  }
  void stop() 
  { 
    if (running) {
      running = false;
      total_elapsed = total_elapsed + 
        timer_traits::make_time_duration(started_at, timer_traits::get_current_time());
    }
  }
  void restart() 
  {
    clear_elapsed();
    running = true;
    started_at = timer_traits::get_current_time();    
  }
  void clear_elapsed() 
  { 
    total_elapsed = time_duration_type(0,0,0,0);
  }
    
private:
  bool running;
  time_rep started_at;
  time_duration_type total_elapsed;
};

#endif