#ifndef BOOST_EXT_SPIRIT_NONSTANDARD_QI_DIRECTIVE_IDENTITY_HPP
#define BOOST_EXT_SPIRIT_NONSTANDARD_QI_DIRECTIVE_IDENTITY_HPP

#include <boost/spirit/home/qi/meta_compiler.hpp>
#include <boost/spirit/home/qi/parser.hpp>
#include <boost/spirit/home/support/attributes.hpp>
#include <boost/spirit/home/support/info.hpp>
#include <boost/spirit/home/support/terminal.hpp>
#include <boost/fusion/include/at.hpp>

namespace boost {
namespace spirit {

BOOST_SPIRIT_TERMINAL_EX(identity)

template <>   // enable identity[p] 
struct use_directive<qi::domain, tag::identity> : mpl::true_ {};

namespace qi {

    template <typename Subject>
    struct identity_parser : unary_parser<identity_parser<Subject> >
    {
        typedef Subject subject_type;

        template <typename Context, typename Iterator>
        struct attribute
        {
            typedef typename traits::attribute_of<Subject, Context, Iterator>::type type;
        };

        identity_parser(Subject const& subject)
          : subject(subject) {}

        template <typename Iterator, typename Context
          , typename Skipper, typename Attribute>
        bool parse(Iterator& first, Iterator const& last
          , Context& context, Skipper const& skipper
          , Attribute& attr) const
        {
            return subject.parse(first, last, context, skipper, attr);
        }

        template <typename Context>
        info what(Context& context) const
        {
            return info("identity", subject.what(context));
        }

        Subject subject;

    private:
        // silence MSVC warning C4512: assignment operator could not be generated
        identity_parser& operator= (identity_parser const&);
    };

    template <typename Subject, typename Modifiers>
    struct make_directive<tag::identity, Subject, Modifiers>
    {
        typedef identity_parser<Subject> result_type;

        template <typename Terminal>
        result_type operator()(
            Terminal const& term, Subject const& subject, unused_type) const
        {
            return result_type(subject);
        }
    };
}
namespace traits
{
    template <typename Subject>
    struct has_semantic_action<qi::identity_parser<Subject> >
      : unary_has_semantic_action<Subject> {};
} 

}} // boost::spirit
  
#endif//BOOST_EXT_SPIRIT_NONSTANDARD_QI_DIRECTIVE_IDENTITY_HPP