/*=============================================================================
    Copyright (c) 2001-2014 Joel de Guzman
    Copyright (c) 2001-2011 Hartmut Kaiser

    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_OPTIONAL_MARCH_23_2007_1117PM)
#define BOOST_SPIRIT_X3_OPTIONAL_MARCH_23_2007_1117PM

#include <boost/spirit/home/x3/core/proxy.hpp>
#include <boost/spirit/home/x3/core/detail/parse_into_container.hpp>
#include <boost/spirit/home/x3/support/traits/attribute_of.hpp>
#include <boost/spirit/home/x3/support/traits/move_to.hpp>
#include <boost/spirit/home/x3/support/traits/optional_traits.hpp>
#include <boost/spirit/home/x3/support/traits/attribute_category.hpp>

namespace boost {
namespace spirit {
namespace x3 {
template <typename Subject>
struct optional : proxy<Subject, optional<Subject>>
{
    typedef proxy<Subject, optional<Subject>> base_type;
    static bool const is_pass_through_unary = false;
    static bool const handles_container = true;

    constexpr
    optional(Subject const& subject)
        : base_type(subject) {}

    using base_type::parse_subject;

    // Attribute is a container
    template <typename Iterator, typename Context
              , typename RContext, typename Attribute>
    bool
    parse_subject(Iterator& first, Iterator const& last
                  , Context const& context, RContext& rcontext, Attribute& attr
                  , traits::container_attribute) const
    {
        detail::parse_into_container(
            this->subject, first, last, context, rcontext, attr);
        return true;
    }

    // Attribute is an optional
    template <typename Iterator, typename Context
              , typename RContext, typename Attribute>
    bool
    parse_subject(Iterator& first, Iterator const& last
                  , Context const& context, RContext& rcontext, Attribute& attr
                  , traits::optional_attribute) const
    {
        typedef typename
        x3::traits::optional_value<Attribute>::type
        value_type;

        // create a local value
        value_type val{};

        if (this->subject.parse(first, last, context, rcontext, val))
        {
            // assign the parsed value into our attribute
            x3::traits::move_to(val, attr);
        }

        return true;
    }
};

template <typename Subject>
constexpr optional<typename extension::as_parser<Subject>::value_type>
operator-(Subject const& subject)
{
    return { as_parser(subject) };
}
}
}
}

namespace boost {
namespace spirit {
namespace x3 {
namespace traits {
template <typename Subject, typename Context>
struct attribute_of<x3::optional<Subject>, Context>
    : build_optional<
      typename attribute_of<Subject, Context>::type> {};
}
}
}
}

#endif
