eventBus.hpp

/*
  ANCH Framework: ANother C++ Hack is a C++ framework based on C++11 standard
  Copyright (C) 2012 Vincent Lachenal

  This file is part of ANCH Framework.

  ANCH Framework is free software: you can redistribute it and/or modify
  it under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  ANCH Framework 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 Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with ANCH Framework.  If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _ANCH_EVENTS_EVENT_BUS_H_
#define _ANCH_EVENTS_EVENT_BUS_H_

#include <thread>
#include <mutex>
#include <queue>
#include <set>

#include "events/observer.hpp"
#include "lessPtrCompare.hpp"
#include "singleton.hpp"


namespace anch {
  namespace events {

    template<typename Event>
    class EventBus: public anch::Singleton<EventBus<Event> > {
      friend class anch::Singleton<EventBus<Event> >; 

      // Attributes +
    private:
      std::mutex _eventMutex;

      std::mutex _queueMutex;

      std::thread* _thread;

      std::queue<Event> _events;

      std::set<anch::events::Observer<Event>*, anch::LessPtrCompare<Observer<Event> > > _observers;
      // Attributes -


      // Constructors +
    private:
      EventBus(): _eventMutex(), _queueMutex(), _thread(NULL), _events(), _observers() {
        // Nothing to do
      }
      // Constructors -

      // Destructor +
      virtual ~EventBus() {
        if(_thread != NULL) {
          _thread->join();
          delete _thread;
        }
      }
      // Destructor -


      // Methods +
    public:
      bool addObserver(anch::events::Observer<Event>& observer) noexcept {
        std::lock_guard<std::mutex> lock(_eventMutex);
        bool added = _observers.insert(&observer).second;
        return added;
      }

      static bool AddObserver(anch::events::Observer<Event>& observer) noexcept {
        return EventBus<Event>::getInstance().addObserver(observer);
      }

      void removeObserver(anch::events::Observer<Event>& observer) noexcept {
        std::lock_guard<std::mutex> lock(_eventMutex);
        _observers.erase(&observer);
      }

      static void RemoveObserver(anch::events::Observer<Event>& observer) noexcept {
        EventBus<Event>::getInstance().removeObserver(observer);
      }

      void fireEvent(const Event& event) noexcept {
        std::lock_guard<std::mutex> lock(_eventMutex);
        for(anch::events::Observer<Event>* observer : _observers) {
          observer->notify(event);
        }
      }

      static void FireEvent(const Event& event) noexcept {
        EventBus<Event>::getInstance().fireEvent(event);
      }

      void scheduleDeferred(const Event& event) noexcept {
        std::lock_guard<std::mutex> lock(_queueMutex);
        bool empty = _events.empty();
        _events.push(event);
        if(empty) {
          if(_thread != NULL) {
            _thread->join();
            delete _thread;
          }
          _thread = new std::thread(&EventBus<Event>::processEvents,this);
        }
      }

      static void ScheduleDeferred(const Event& event) noexcept {
        EventBus<Event>::getInstance().scheduleDeferred(event);
      }

    private:
      void processEvents() noexcept {
        bool empty = false;
        do {
          _queueMutex.lock();
          Event event = _events.front();
          _events.pop();
          empty = _events.empty();
          _queueMutex.unlock();

          fireEvent(event);

        } while(!empty);
      }
      // Methods -

    };

  }
}

#endif // _ANCH_EVENTS_EVENT_BUS_H_