/*=============================================================================
    Copyright (c) 2014 Joel de Guzman

    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)
=============================================================================*/
#ifndef BOOST_SPIRIT_X3_DIRECTIVE_WITH_HPP
#define BOOST_SPIRIT_X3_DIRECTIVE_WITH_HPP

#include <boost/spirit/home/x3/support/unused.hpp>
#include <boost/spirit/home/x3/core/parser.hpp>

namespace boost {
namespace spirit {
namespace x3 {
///////////////////////////////////////////////////////////////////////////
// with directive injects a value into the context prior to parsing.
///////////////////////////////////////////////////////////////////////////
template <typename Subject, typename Derived, typename T>
struct with_value_holder
    : unary_parser<Subject, Derived>
{
    typedef unary_parser<Subject, Derived> base_type;
    mutable T val;
    constexpr
    with_value_holder(Subject const& subject, T&& val)
        : base_type(subject)
        , val(std::forward<T>(val)) {}
};

template <typename Subject, typename Derived, typename T>
struct with_value_holder<Subject, Derived, T&>
    : unary_parser<Subject, Derived>
{
    typedef unary_parser<Subject, Derived> base_type;
    T& val;
    constexpr
    with_value_holder(Subject const& subject, T& val)
        : base_type(subject)
        , val(val) {}
};

template <typename Subject, typename ID, typename T>
struct with_directive
    : with_value_holder<Subject, with_directive<Subject, ID, T>, T>
{
    typedef with_value_holder<Subject, with_directive<Subject, ID, T>, T> base_type;
    static bool const is_pass_through_unary = true;
    static bool const handles_container = Subject::handles_container;

    typedef Subject subject_type;

    constexpr
    with_directive(Subject const& subject, T&& val)
        : base_type(subject, std::forward<T>(val)) {}

    template <typename Iterator, typename Context
              , typename RContext, typename Attribute>
    bool
    parse(Iterator& first, Iterator const& last
          , Context const& context, RContext& rcontext, Attribute& attr) const
    {
        return this->subject.parse(
                   first, last
                   , make_context<ID>(this->val, context)
                   , rcontext
                   , attr);
    }
};

template <typename ID, typename T>
struct with_gen
{
    T&& val;

    template <typename Subject>
    constexpr with_directive<typename extension::as_parser<Subject>::value_type, ID, T>
    operator[](Subject const& subject) const
    {
        return { as_parser(subject), std::forward<T>(val) };
    }
};

template <typename ID, typename T>
constexpr with_gen<ID, T>
with(T&& val)
{
    return { std::forward<T>(val) };
}
}
}
}

#endif
