#ifndef TCG_OBSERVER_NOTIFIER_H

#define TCG_OBSERVER_NOTIFIER_H

// tcg includes

#include "base.h"

// STD includes

#include <set></set>

/*!

  \file     tcg_observer_notifier.h

  \brief    This file contains the barebone of an elementary, classical

            implementation of the Observer pattern requiring derivation.

  \details  This is intended as a convenient and lightweight predefined

            implementation when hardwiring the Observer pattern in a

            known class using derivation.

            Observe that this implementation does not deal with the

            actual notifications forwarding - it just manages the

            set of observers/notifiers in a notifier/observer instance.

            No multithreading is taken into consideration.

  \remark   See elsewhere for more advanced implementations.

*/

namespace tcg

{

//************************************************************************

//    Observer/notifier  base polymorphic classes

//************************************************************************

class observer_base;

class notifier_base;

//------------------------------------------------------------

class observer_base

{

public:

	virtual ~observer_base() {}

	virtual void attach(notifier_base *notifier) = 0; //!< Adds the specified notifier to the internal set of notifiers.

	virtual void detach(notifier_base *notifier) = 0; //!< Removes the specified notifier from the internal set of notifiers.

};

//------------------------------------------------------------

class notifier_base

{

public:

	virtual ~notifier_base() {}

	virtual void attach(observer_base *observer) = 0; //!< Adds the specified observer to the internal set of observers.

	virtual void detach(observer_base *observer) = 0; //!< Removes the specified observer from the internal set of observers.

};

//************************************************************************

//    Observer/notifier  with a single interacting object

//************************************************************************

template <typename base="observer_base" notifier="notifier_base," typename=""></typename>

class observer_single : public noncopyable<base>

{

	Notifier *m_notifier; // Not owned

public:

	typedef Notifier notifier_type;

public:

	observer_single() : m_notifier() {}

	~observer_single()

	{

		if (m_notifier)

			static_cast<notifier_base *="">(m_notifier)->detach(this); // The detaching function is most probably \a private in</notifier_base>

	}																// reimplemented notifier classes (like in this observer).

																	// Besides, it would be a virtual function call anyway.

	notifier_type *notifier() const { return m_notifier; }

private:

	void attach(notifier_base *notifier)

	{

		assert(notifier && !m_notifier);

		m_notifier = static_cast<notifier *="">(notifier);</notifier>

	}

	void detach(notifier_base *notifier)

	{

		assert(m_notifier && m_notifier == static_cast<notifier *="">(notifier));</notifier>

		m_notifier = 0;

	}

};

//------------------------------------------------------------

template <typename base="notifier_base" observer="observer_base," typename=""></typename>

class notifier_single : public noncopyable<base>

{

	Observer *m_observer; // Not owned

public:

	typedef Observer observer_type;

public:

	notifier_single() : m_observer() {}

	~notifier_single()

	{

		if (m_observer)

			static_cast<observer_base *="">(m_observer)->detach(this);</observer_base>

	}

	observer_type *observer() const { return m_observer; }

	void addObserver(observer_type *observer)

	{

		notifier_single::attach(observer);					  // No reason to go polymorphic here - it's this very class.

		static_cast<observer_base *="">(observer)->attach(this); // However, here it's necessary - like above, downcast to</observer_base>

	}														  // the very base.

	void removeObserver(observer_type *observer)

	{

		static_cast<observer_base *="">(observer)->detach(this);</observer_base>

		notifier_single::detach(observer);

	}

private:

	void attach(observer_base *observer)

	{

		assert(observer && !m_observer);

		m_observer = static_cast<observer *="">(observer);</observer>

	}

	void detach(observer_base *observer)

	{

		assert(m_observer && m_observer == static_cast<observer *="">(observer));</observer>

		m_observer = 0;

	}

};

//************************************************************************

//    Observer/notifier  with multiple interacting objects

//************************************************************************

template 

		  typename Set = std::set<notifier *="">></notifier>

class observer : public noncopyable<base>

{

	Set m_notifiers; // Not owned

public:

	typedef Notifier notifier_type;

	typedef Set notifiers_container;

public:

	~observer()

	{

		typename Set::iterator nt, nEnd = m_notifiers.end();

		for (nt = m_notifiers.begin(); nt != nEnd; ++nt)

			static_cast<notifier_base *="">(*nt)->detach(this);</notifier_base>

	}

	const notifiers_container ¬ifiers() const

	{

		return m_notifiers;

	}

private:

	void attach(notifier_base *notifier)

	{

		assert(notifier);

		m_notifiers.insert(static_cast<notifier *="">(notifier));</notifier>

	}

	void detach(notifier_base *notifier)

	{

		assert(!m_notifiers.empty());

		m_notifiers.erase(static_cast<notifier *="">(notifier));</notifier>

	}

};

//------------------------------------------------------------

template 

		  typename Set = std::set<observer *="">></observer>

class notifier : public noncopyable<base>

{

	Set m_observers; // Not owned

public:

	typedef Observer observer_type;

	typedef Set observers_container;

public:

	~notifier()

	{

		typename Set::iterator ot, oEnd = m_observers.end();

		for (ot = m_observers.begin(); ot != oEnd; ++ot)

			static_cast<observer_base *="">(*ot)->detach(this);</observer_base>

	}

	const observers_container &observers() const

	{

		return m_observers;

	}

	void addObserver(observer_type *observer)

	{

		notifier::attach(observer);

		static_cast<observer_base *="">(observer)->attach(this);</observer_base>

	}

	void removeObserver(observer_type *observer)

	{

		static_cast<observer_base *="">(observer)->detach(this);</observer_base>

		notifier::detach(observer);

	}

private:

	void attach(observer_base *observer)

	{

		assert(observer);

		m_observers.insert(static_cast<observer *="">(observer));</observer>

	}

	void detach(observer_base *observer)

	{

		assert(!m_observers.empty());

		m_observers.erase(static_cast<observer *="">(observer));</observer>

	}

};

} // namespace tcg

#endif // TCG_OBSERVER_NOTIFIER_H