/*=============================================================================
    Copyright (c) 2001-2014 Joel de Guzman
    http://spirit.sourceforge.net/

    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)
=============================================================================*/
#if !defined(BOOST_SPIRIT_X3_CONTEXT_JAN_4_2012_1215PM)
#define BOOST_SPIRIT_X3_CONTEXT_JAN_4_2012_1215PM

#include <boost/spirit/home/x3/support/unused.hpp>
#include <boost/mpl/identity.hpp>

namespace boost {
namespace spirit {
namespace x3 {
template <typename ID, typename T, typename Next = unused_type>
struct context
{
    context(T& val, Next const& next)
        : val(val), next(next) {}

    T&
    get(mpl::identity<ID>) const
    {
        return val;
    }

    template <typename ID_>
    decltype(auto) get(ID_ id) const
    {
        return next.get(id);
    }

    T& val;
    Next const& next;
};

template <typename ID, typename T>
struct context<ID, T, unused_type>
{
    context(T& val)
        : val(val) {}

    context(T& val, unused_type)
        : val(val) {}

    T&
    get(mpl::identity<ID>) const
    {
        return val;
    }

    template <typename ID_>
    unused_type
    get(ID_) const
    {
        return {};
    }

    T& val;
};

template <typename Tag, typename Context>
inline
decltype(auto) get(Context const& context)
{
    return context.get(mpl::identity<Tag>());
}

template <typename ID, typename T, typename Next>
inline context<ID, T, Next>
make_context(T& val, Next const& next)
{
    return { val, next };
}

template <typename ID, typename T>
inline context<ID, T>
make_context(T& val)
{
    return { val };
}

namespace detail {
template <typename ID, typename T, typename Next, typename FoundVal>
inline Next const&
make_unique_context(T& /* val */, Next const& next, FoundVal&)
{
    return next;
}

template <typename ID, typename T, typename Next>
inline context<ID, T, Next>
make_unique_context(T& val, Next const& next, unused_type)
{
    return { val, next };
}
}

template <typename ID, typename T, typename Next>
inline auto
make_unique_context(T& val, Next const& next)
{
    return detail::make_unique_context<ID>(val, next, x3::get<ID>(next));
}
}
}
}

#endif
