////////////////////////////////////////////////////////////////////////////////
// The Loki Library
// Copyright (c) 2001 by Andrei Alexandrescu
// This code accompanies the book:
// Alexandrescu, Andrei. "Modern C++ Design: Generic Programming and Design
//     Patterns Applied". Copyright (c) 2001. Addison-Wesley.
// Permission to use, copy, modify, distribute and sell this software for any
//     purpose is hereby granted without fee, provided that the above copyright
//     notice appear in all copies and that both that copyright notice and this
//     permission notice appear in supporting documentation.
// The author or Addison-Wesley Longman make no representations about the
//     suitability of this software for any purpose. It is provided "as is"
//     without express or implied warranty.
////////////////////////////////////////////////////////////////////////////////
#ifndef LOKI_ABSTRACTFACTORY_INC_
#define LOKI_ABSTRACTFACTORY_INC_

// $Id: AbstractFactory.h 771 2006-10-27 18:05:03Z clitte_bbt $


#include "Typelist.h"
#include "Sequence.h"
#include "TypeManip.h"
#include "HierarchyGenerators.h"

#include <cassert>

/**
 * \defgroup	FactoriesGroup Factories
 * \defgroup	AbstractFactoryGroup Abstract Factory
 * \ingroup		FactoriesGroup
 * \brief		Implements an abstract object factory.
 */

/**
 * \class		AbstractFactory
 * \ingroup		AbstractFactoryGroup
 * \brief		Implements an abstract object factory.
 */

namespace Loki
{

////////////////////////////////////////////////////////////////////////////////
// class template AbstractFactoryUnit
// The building block of an Abstract Factory
////////////////////////////////////////////////////////////////////////////////

template <class T>
class AbstractFactoryUnit
{
public:
    virtual T* DoCreate(Type2Type<T>) = 0;
    virtual ~AbstractFactoryUnit() {}
};

////////////////////////////////////////////////////////////////////////////////
// class template AbstractFactory
// Defines an Abstract Factory interface starting from a typelist
////////////////////////////////////////////////////////////////////////////////

template
<
class TList,
      template <class> class Unit = AbstractFactoryUnit
      >
class AbstractFactory : public GenScatterHierarchy<TList, Unit>
{
public:
    typedef TList ProductList;

    template <class T> T* Create()
    {
        Unit<T>& unit = *this;
        return unit.DoCreate(Type2Type<T>());
    }
};

////////////////////////////////////////////////////////////////////////////////
// class template OpNewFactoryUnit
// Creates an object by invoking the new operator
////////////////////////////////////////////////////////////////////////////////

template <class ConcreteProduct, class Base>
class OpNewFactoryUnit : public Base
{
    typedef typename Base::ProductList BaseProductList;

protected:
    typedef typename BaseProductList::Tail ProductList;

public:
    typedef typename BaseProductList::Head AbstractProduct;
    ConcreteProduct* DoCreate(Type2Type<AbstractProduct>)
    {
        return new ConcreteProduct;
    }
};

////////////////////////////////////////////////////////////////////////////////
// class template PrototypeFactoryUnit
// Creates an object by cloning a prototype
// There is a difference between the implementation herein and the one described
//     in the book: GetPrototype and SetPrototype use the helper friend
//     functions DoGetPrototype and DoSetPrototype. The friend functions avoid
//     name hiding issues. Plus, GetPrototype takes a reference to pointer
//     instead of returning the pointer by value.
////////////////////////////////////////////////////////////////////////////////

template <class ConcreteProduct, class Base>
class PrototypeFactoryUnit : public Base
{
    typedef typename Base::ProductList BaseProductList;

protected:
    typedef typename BaseProductList::Tail ProductList;

public:
    typedef typename BaseProductList::Head AbstractProduct;

    PrototypeFactoryUnit(AbstractProduct* p = 0)
        : pPrototype_(p)
    {}

    template <class CP, class Base1>
    friend void DoGetPrototype(const PrototypeFactoryUnit<CP, Base1>& me,
                               typename Base1::ProductList::Head*& pPrototype);

    template <class CP, class Base1>
    friend void DoSetPrototype(PrototypeFactoryUnit<CP, Base1>& me,
                               typename Base1::ProductList::Head* pObj);

    template <class U>
    void GetPrototype(U*& p)
    { return DoGetPrototype(*this, p); }

    template <class U>
    void SetPrototype(U* pObj)
    { DoSetPrototype(*this, pObj); }

    AbstractProduct* DoCreate(Type2Type<AbstractProduct>)
    {
        assert(pPrototype_);
        return pPrototype_->Clone();
    }

private:
    AbstractProduct* pPrototype_;
};

template <class CP, class Base>
inline void DoGetPrototype(const PrototypeFactoryUnit<CP, Base>& me,
                           typename Base::ProductList::Head*& pPrototype)
{ pPrototype = me.pPrototype_; }

template <class CP, class Base>
inline void DoSetPrototype(PrototypeFactoryUnit<CP, Base>& me,
                           typename Base::ProductList::Head* pObj)
{ me.pPrototype_ = pObj; }

////////////////////////////////////////////////////////////////////////////////
// class template ConcreteFactory
// Implements an AbstractFactory interface
////////////////////////////////////////////////////////////////////////////////

template
<
class AbstractFact,
      template <class, class> class Creator = OpNewFactoryUnit,
      class TList = typename AbstractFact::ProductList
      >
class ConcreteFactory
    : public GenLinearHierarchy <
    typename TL::Reverse<TList>::Result, Creator, AbstractFact >
{
public:
    typedef typename AbstractFact::ProductList ProductList;
    typedef TList ConcreteProductList;
};

} // namespace Loki


#endif // end file guardian