////////////////////////////////////////////////////////////////////////////////
// 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_MULTIMETHODS_INC_
#define LOKI_MULTIMETHODS_INC_

// $Id: MultiMethods.h 751 2006-10-17 19:50:37Z syntheticpp $


#include "Typelist.h"
#include "LokiTypeInfo.h"
#include "Functor.h"
#include "AssocVector.h"

////////////////////////////////////////////////////////////////////////////////
// IMPORTANT NOTE:
// The double dispatchers implemented below differ from the excerpts shown in
// the book - they are simpler while respecting the same interface.
////////////////////////////////////////////////////////////////////////////////

namespace Loki
{
////////////////////////////////////////////////////////////////////////////////
// class template InvocationTraits (helper)
// Helps implementing optional symmetry
////////////////////////////////////////////////////////////////////////////////

namespace Private
{
template < class SomeLhs, class SomeRhs,
         class Executor, typename ResultType >
struct InvocationTraits
{
    static ResultType
    DoDispatch(SomeLhs& lhs, SomeRhs& rhs,
               Executor& exec, Int2Type<false>)
    {
        return exec.Fire(lhs, rhs);
    }
    static ResultType
    DoDispatch(SomeLhs& lhs, SomeRhs& rhs,
               Executor& exec, Int2Type<true>)
    {
        return exec.Fire(rhs, lhs);
    }
};
}

////////////////////////////////////////////////////////////////////////////////
// class template StaticDispatcher
// Implements an automatic static double dispatcher based on two typelists
////////////////////////////////////////////////////////////////////////////////

template
<
class Executor,
      class BaseLhs,
      class TypesLhs,
      bool symmetric = true,
      class BaseRhs = BaseLhs,
      class TypesRhs = TypesLhs,
      typename ResultType = void
      >
class StaticDispatcher
{
    template <class SomeLhs>
    static ResultType DispatchRhs(SomeLhs& lhs, BaseRhs& rhs,
                                  Executor exec, NullType)
    { return exec.OnError(lhs, rhs); }

    template <class Head, class Tail, class SomeLhs>
    static ResultType DispatchRhs(SomeLhs& lhs, BaseRhs& rhs,
                                  Executor exec, Typelist<Head, Tail>)
    {
        if (Head* p2 = dynamic_cast<Head*>(&rhs))
        {
            Int2Type < (symmetric &&
                        int(TL::IndexOf<TypesRhs, Head>::value) <
                        int(TL::IndexOf<TypesLhs, SomeLhs>::value)) > i2t;

            typedef Private::InvocationTraits <
            SomeLhs, Head, Executor, ResultType > CallTraits;

            return CallTraits::DoDispatch(lhs, *p2, exec, i2t);
        }
        return DispatchRhs(lhs, rhs, exec, Tail());
    }

    static ResultType DispatchLhs(BaseLhs& lhs, BaseRhs& rhs,
                                  Executor exec, NullType)
    { return exec.OnError(lhs, rhs); }

    template <class Head, class Tail>
    static ResultType DispatchLhs(BaseLhs& lhs, BaseRhs& rhs,
                                  Executor exec, Typelist<Head, Tail>)
    {
        if (Head* p1 = dynamic_cast<Head*>(&lhs))
        {
            return DispatchRhs(*p1, rhs, exec, TypesRhs());
        }
        return DispatchLhs(lhs, rhs, exec, Tail());
    }

public:
    static ResultType Go(BaseLhs& lhs, BaseRhs& rhs,
                         Executor exec)
    { return DispatchLhs(lhs, rhs, exec, TypesLhs()); }
};

////////////////////////////////////////////////////////////////////////////////
// class template BasicDispatcher
// Implements a logarithmic double dispatcher for functors (or functions)
// Doesn't offer automated casts or symmetry
////////////////////////////////////////////////////////////////////////////////

template
<
class BaseLhs,
      class BaseRhs = BaseLhs,
      typename ResultType = void,
      typename CallbackType = ResultType (*)(BaseLhs&, BaseRhs&)
      >
class BasicDispatcher
{
    typedef std::pair<TypeInfo, TypeInfo> KeyType;
    typedef CallbackType MappedType;
    typedef AssocVector<KeyType, MappedType> MapType;
    MapType callbackMap_;

    void DoAdd(TypeInfo lhs, TypeInfo rhs, CallbackType fun);
    bool DoRemove(TypeInfo lhs, TypeInfo rhs);

public:
    template <class SomeLhs, class SomeRhs>
    void Add(CallbackType fun)
    {
        DoAdd(typeid(SomeLhs), typeid(SomeRhs), fun);
    }

    template <class SomeLhs, class SomeRhs>
    bool Remove()
    {
        return DoRemove(typeid(SomeLhs), typeid(SomeRhs));
    }

    ResultType Go(BaseLhs& lhs, BaseRhs& rhs);
};

// Non-inline to reduce compile time overhead...
template < class BaseLhs, class BaseRhs,
         typename ResultType, typename CallbackType >
void BasicDispatcher<BaseLhs, BaseRhs, ResultType, CallbackType>
::DoAdd(TypeInfo lhs, TypeInfo rhs, CallbackType fun)
{
    callbackMap_[KeyType(lhs, rhs)] = fun;
}

template < class BaseLhs, class BaseRhs,
         typename ResultType, typename CallbackType >
bool BasicDispatcher<BaseLhs, BaseRhs, ResultType, CallbackType>
::DoRemove(TypeInfo lhs, TypeInfo rhs)
{
    return callbackMap_.erase(KeyType(lhs, rhs)) == 1;
}

template < class BaseLhs, class BaseRhs,
         typename ResultType, typename CallbackType >
ResultType BasicDispatcher<BaseLhs, BaseRhs, ResultType, CallbackType>
::Go(BaseLhs& lhs, BaseRhs& rhs)
{
    typename MapType::key_type k(typeid(lhs), typeid(rhs));
    typename MapType::iterator i = callbackMap_.find(k);
    if (i == callbackMap_.end())
    {
        throw std::runtime_error("Function not found");
    }
    return (i->second)(lhs, rhs);
}

////////////////////////////////////////////////////////////////////////////////
// class template StaticCaster
// Implementation of the CastingPolicy used by FunctorDispatcher
////////////////////////////////////////////////////////////////////////////////

template <class To, class From>
struct StaticCaster
{
    static To& Cast(From& obj)
    {
        return static_cast<To&>(obj);
    }
};

////////////////////////////////////////////////////////////////////////////////
// class template DynamicCaster
// Implementation of the CastingPolicy used by FunctorDispatcher
////////////////////////////////////////////////////////////////////////////////

template <class To, class From>
struct DynamicCaster
{
    static To& Cast(From& obj)
    {
        return dynamic_cast<To&>(obj);
    }
};

////////////////////////////////////////////////////////////////////////////////
// class template Private::FnDispatcherHelper
// Implements trampolines and argument swapping used by FnDispatcher
////////////////////////////////////////////////////////////////////////////////

namespace Private
{
template < class BaseLhs, class BaseRhs,
         class SomeLhs, class SomeRhs,
         typename ResultType,
         class CastLhs, class CastRhs,
         ResultType (*Callback)(SomeLhs&, SomeRhs&) >
struct FnDispatcherHelper
{
    static ResultType Trampoline(BaseLhs& lhs, BaseRhs& rhs)
    {
        return Callback(CastLhs::Cast(lhs), CastRhs::Cast(rhs));
    }
    static ResultType TrampolineR(BaseRhs& rhs, BaseLhs& lhs)
    {
        return Trampoline(lhs, rhs);
    }
};
}

////////////////////////////////////////////////////////////////////////////////
// class template FnDispatcher
// Implements an automatic logarithmic double dispatcher for functions
// Features automated conversions
////////////////////////////////////////////////////////////////////////////////

template < class BaseLhs, class BaseRhs = BaseLhs,
         typename ResultType = void,
         template <class, class> class CastingPolicy = DynamicCaster,
         template <class, class, class, class>
         class DispatcherBackend = BasicDispatcher >
class FnDispatcher
{
    DispatcherBackend < BaseLhs, BaseRhs, ResultType,
                      ResultType (*)(BaseLhs&, BaseRhs&) > backEnd_;

public:
    template <class SomeLhs, class SomeRhs>
    void Add(ResultType (*pFun)(BaseLhs&, BaseRhs&))
    {
        return backEnd_.template Add<SomeLhs, SomeRhs>(pFun);
    }

    template < class SomeLhs, class SomeRhs,
             ResultType (*callback)(SomeLhs&, SomeRhs&) >
    void Add()
    {
        typedef Private::FnDispatcherHelper <
        BaseLhs, BaseRhs,
                 SomeLhs, SomeRhs,
                 ResultType,
                 CastingPolicy<SomeLhs, BaseLhs>,
                 CastingPolicy<SomeRhs, BaseRhs>,
                 callback > Local;

        Add<SomeLhs, SomeRhs>(&Local::Trampoline);
    }

    template < class SomeLhs, class SomeRhs,
             ResultType (*callback)(SomeLhs&, SomeRhs&),
             bool symmetric >
    void Add(bool = true) // [gcc] dummy bool
    {
        typedef Private::FnDispatcherHelper <
        BaseLhs, BaseRhs,
                 SomeLhs, SomeRhs,
                 ResultType,
                 CastingPolicy<SomeLhs, BaseLhs>,
                 CastingPolicy<SomeRhs, BaseRhs>,
                 callback > Local;

        Add<SomeLhs, SomeRhs>(&Local::Trampoline);
        if (symmetric)
        {
            Add<SomeRhs, SomeLhs>(&Local::TrampolineR);
        }
    }

    template <class SomeLhs, class SomeRhs>
    void Remove()
    {
        backEnd_.template Remove<SomeLhs, SomeRhs>();
    }

    ResultType Go(BaseLhs& lhs, BaseRhs& rhs)
    {
        return backEnd_.Go(lhs, rhs);
    }
};

////////////////////////////////////////////////////////////////////////////////
// class template FunctorDispatcherAdaptor
// permits use of FunctorDispatcher under gcc.2.95.2/3
///////////////////////////////////////////////////////////////////////////////

namespace Private
{
template < class BaseLhs, class BaseRhs,
         class SomeLhs, class SomeRhs,
         typename ResultType,
         class CastLhs, class CastRhs,
         class Fun, bool SwapArgs >
class FunctorDispatcherHelper
{
    Fun fun_;
    ResultType Fire(BaseLhs& lhs, BaseRhs& rhs, Int2Type<false>)
    {
        return fun_(CastLhs::Cast(lhs), CastRhs::Cast(rhs));
    }
    ResultType Fire(BaseLhs& rhs, BaseRhs& lhs, Int2Type<true>)
    {
        return fun_(CastLhs::Cast(lhs), CastRhs::Cast(rhs));
    }
public:
    FunctorDispatcherHelper(const Fun& fun) : fun_(fun) {}

    ResultType operator()(BaseLhs& lhs, BaseRhs& rhs)
    {
        return Fire(lhs, rhs, Int2Type<SwapArgs>());
    }
};
}

////////////////////////////////////////////////////////////////////////////////
// class template FunctorDispatcher
// Implements a logarithmic double dispatcher for functors
// Features automated casting
////////////////////////////////////////////////////////////////////////////////

template < class BaseLhs, class BaseRhs = BaseLhs,
         typename ResultType = void,
         template <class, class> class CastingPolicy = DynamicCaster,
         template <class, class, class, class>
         class DispatcherBackend = BasicDispatcher >
class FunctorDispatcher
{
    typedef LOKI_TYPELIST_2(BaseLhs&, BaseRhs&) ArgsList;
    typedef Functor<ResultType, ArgsList, LOKI_DEFAULT_THREADING> FunctorType;

    DispatcherBackend<BaseLhs, BaseRhs, ResultType, FunctorType> backEnd_;

public:
    template <class SomeLhs, class SomeRhs, class Fun>
    void Add(const Fun& fun)
    {
        typedef Private::FunctorDispatcherHelper <
        BaseLhs, BaseRhs,
                 SomeLhs, SomeRhs,
                 ResultType,
                 CastingPolicy<SomeLhs, BaseLhs>,
                 CastingPolicy<SomeRhs, BaseRhs>,
                 Fun, false > Adapter;

        backEnd_.template Add<SomeLhs, SomeRhs>(FunctorType(Adapter(fun)));
    }
    template <class SomeLhs, class SomeRhs, bool symmetric, class Fun>
    void Add(const Fun& fun)
    {
        Add<SomeLhs, SomeRhs>(fun);

        if (symmetric)
        {
            // Note: symmetry only makes sense where BaseLhs==BaseRhs
            typedef Private::FunctorDispatcherHelper <
            BaseLhs, BaseLhs,
                     SomeLhs, SomeRhs,
                     ResultType,
                     CastingPolicy<SomeLhs, BaseLhs>,
                     CastingPolicy<SomeRhs, BaseLhs>,
                     Fun, true > AdapterR;

            backEnd_.template Add<SomeRhs, SomeLhs>(FunctorType(AdapterR(fun)));
        }
    }

    template <class SomeLhs, class SomeRhs>
    void Remove()
    {
        backEnd_.template Remove<SomeLhs, SomeRhs>();
    }

    ResultType Go(BaseLhs& lhs, BaseRhs& rhs)
    {
        return backEnd_.Go(lhs, rhs);
    }
};
} // namespace Loki



#endif // end file guardian