/////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Gordon Woodhull  2008
//
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          http://www.boost.org/LICENSE_1_0.txt)
//
// This is a contribution to Boost.Intrusive to support hooks as
// elements in Boost.Fusion containers
//
/////////////////////////////////////////////////////////////////////////////
#ifndef BOOST_INTRUSIVE_PARENT_FROM_MEMBER_HPP
#define BOOST_INTRUSIVE_PARENT_FROM_MEMBER_HPP

#include <boost/intrusive/detail/config_begin.hpp>
#include <boost/static_assert.hpp>
#include <cstddef>
#include <boost/fusion/include/end.hpp>
#include <boost/fusion/include/find.hpp>
#include <boost/intrusive/detail/parent_from_member.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/mpl/assert.hpp>

#include "vector_pointer_to_member.hpp"

namespace boost {
namespace intrusive {
namespace detail {
    
    // this would be better a metafunction but that would mean converting parent_from_member first
    template<typename FusionMap, typename ElementKey>
    inline std::size_t offset_from_fusion_map_to_element()
    {
        // this attempts to use the offset of the element in the fusion::vector implementation of fusion::map
        // which would work if a class with one member has the same address as its member
        // however, probably a bad assumption and would need a sequence of pointers-to-members
        // also this should be metafunction
        typedef typename fusion::result_of::template find<FusionMap,ElementKey>::type found_iter;
        // this line causes gcc bus error??
        //typedef typename fusion::template end<FusionMap>::type end_type
        //BOOST_MPL_ASSERT_NOT((is_same<found_iter, end_type>));
        // this does not compile because vector_ptr_to_member only works with fusion::vector##<> not fusion::vector<>
        typename fusish::template vector_ptr_to_member_type<typename FusionMap::storage_type, typename found_iter::index>::type
            p2m = fusish::vector_ptr_to_member<typename FusionMap::storage_type, found_iter::index::value>();
        return boost::intrusive::detail::offset_from_pointer_to_member(p2m);
    }

    template<class Element, class FusionMap, class ElementKey>
    inline FusionMap *fusion_map_from_element(Element *element)
    {
       return (FusionMap*)((char*)element - 
          offset_from_fusion_map_to_element<FusionMap,ElementKey>());
    }

    template<class Element, class FusionMap, class ElementKey>
    inline const FusionMap *fusion_map_from_element(const Element *element)
    {
       return (const FusionMap*)((const char*)element - 
          offset_from_fusion_map_to_element<FusionMap,ElementKey>());
    }

}  //namespace detail {
}  //namespace intrusive {
}  //namespace boost {

#include <boost/intrusive/detail/config_end.hpp>

#endif   //#ifndef BOOST_INTRUSIVE_PARENT_FROM_MEMBER_HPP