/*=============================================================================
    Copyright (c) 2001-2014 Joel de Guzman
    Copyright (c) 2013 Agustin Berge
    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_ATTRIBUTE_OF_JAN_7_2012_0914AM)
#define BOOST_SPIRIT_X3_ATTRIBUTE_OF_JAN_7_2012_0914AM

#include <boost/spirit/home/x3/support/utility/sfinae.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/utility/enable_if.hpp>

namespace boost {
namespace spirit {
namespace x3 {
namespace traits {
///////////////////////////////////////////////////////////////////////////
// Get the attribute type of a component. By default, this gets the
// Component's attribute_type typedef or instantiates a nested attribute
// metafunction. Components may specialize this if such an attribute_type
// is not readily available (e.g. expensive to compute at compile time).
///////////////////////////////////////////////////////////////////////////
template <typename Component, typename Context, typename Enable = void>
struct attribute_of;

namespace detail {
template <typename Component, typename Context, typename Enable = void>
struct default_attribute_of;

template <typename Component, typename Context>
struct default_attribute_of<Component, Context,
           typename disable_if_substitution_failure<
           typename Component::attribute_type>::type>
           : mpl::identity<typename Component::attribute_type> {};

template <typename Component, typename Context>
struct default_attribute_of<Component, Context,
           typename disable_if_substitution_failure<
           typename Component::template attribute<Context>::type>::type>
    : Component::template attribute<Context> {};

template <typename Component, typename Context>
struct default_attribute_of<Component, Context,
           typename enable_if_c<Component::is_pass_through_unary>::type>
           : attribute_of<typename Component::subject_type, Context> {};
}

template <typename Component, typename Context, typename Enable>
struct attribute_of : detail::default_attribute_of<Component, Context> {};
}
}
}
}

#endif
