/*
 * EntityObserver.hpp
 *
 *  Created on: Dec 29, 2015
 *      Author: heber
 */


#ifndef ENTITYOBSERVER_HPP_
#define ENTITYOBSERVER_HPP_

// include config.h
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "CodePatterns/Observer/Relay.hpp"

/** The EntityObserver is a central instance to all changes occuring within a set entities such as
 * all atoms or all molecules.
 *
 * The intent is that if a class wants to know about changes in just _any_ single entity,
 * he may register singly to this class and not to each and every one. This also
 * keeps him updated in case of removed or added entities.
 *
 * \warning EntityObserver must get purged \b after World as we do not keep an
 * an internal list of all entities. Hence, each one must get destroyed while
 * the EntityObserver instance is still intact or segfault will occur.
 *
 * \section howto How to use EntityObserver
 *
 * All your template class, here T, needs to do is call Inserted() and Removed() functions
 * in its cstor and dstor, respectively.
 *
 * Make this a singleton and add some static variables (for channels) in a derived class
 * (derive both the singleton pattern and this template class).
 *
 */
template <class T>
class EntityObserver : public Relay
{
  //!> grant template class access to inserted and removed functions
  friend T;

  /** Inform all Observers of this EntityObserver that a new entity has been inserted.
   *
   * \param res the inserted entity
   */
  void Inserted(Observable *res);

  /** Inform all Observers of this EntityObserver that a new entity has been removed.
   *
   * \param res the removed entity
   */
  void Removed(Observable *res);

protected:

  /** Constructor for EntityObserver.
   *
   * \param _Channels a set of channels for the entity to observe (e.g. all of them)
   * \param _name name for this for the ObserverLog
   */
  EntityObserver(const Observable::channels_t &_Channels, const std::string &_name);

  //!> ref to list of channels we observe
  const Observable::channels_t &EntityChannels;
};

#include "EntityObserver_impl.hpp"

#endif /* ENTITYOBSERVER_HPP_ */