/*==============================================================================
    Copyright (c) 2005-2010 Joel de Guzman
    Copyright (c) 2010 Thomas Heller

    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_PHOENIX_CORE_FUNCTION_EQUAL_HPP
#define BOOST_PHOENIX_CORE_FUNCTION_EQUAL_HPP

#include <boost/phoenix/core/limits.hpp>
#include <boost/is_placeholder.hpp>
#include <boost/mpl/bool.hpp>
#include <boost/phoenix/core/terminal.hpp>
#include <boost/proto/matches.hpp>

#ifndef BOOST_PHOENIX_NO_VARIADIC_FUNCTION_EQUAL
#   include <boost/phoenix/core/detail/index_sequence.hpp>
#endif

namespace boost
{
    template <typename> class weak_ptr;
}

namespace boost { namespace phoenix
{
    template <typename>
    struct actor;

    namespace detail
    {
        struct compare
            : proto::callable
        {
            typedef bool result_type;

            template <typename A0, typename A1>
            result_type operator()(A0 const & a0, A1 const & a1) const
            {
                return a0 == a1;
            }

            // hard wiring reference_wrapper and weak_ptr here ...
            // **TODO** find out why boost bind does this ...
            template <typename A0, typename A1>
            result_type
            operator()(
                reference_wrapper<A0> const & a0
              , reference_wrapper<A1> const & a1
            ) const
            {
                return a0.get_pointer() == a1.get_pointer();
            }

            template <typename A0, typename A1>
            result_type
            operator()(weak_ptr<A0> const & a0, weak_ptr<A1> const & a1) const
            {
                return !(a0 < a1) && !(a1 < a0);
            }
        };

        struct function_equal_otherwise;

        struct function_equal_
            : proto::when<
                proto::if_<
                    proto::matches<proto::_, proto::_state>()
                  , proto::or_<
                        proto::when<
                            proto::terminal<proto::_>
                          , compare(
                                proto::_value
                              , proto::call<
                                    proto::_value(proto::_state)
                                >
                            )
                        >
                      , proto::otherwise<function_equal_otherwise(proto::_, proto::_state)>
                    >
                  , proto::call<function_equal_otherwise()>
                >
            >
        {};

        struct function_equal_otherwise
            : proto::callable
        {
            typedef bool result_type;

            result_type operator()() const
            {
                return false;
            }

#ifdef BOOST_PHOENIX_NO_VARIADIC_FUNCTION_EQUAL
            template <typename Expr1>
            result_type operator()(Expr1 const& e1, Expr1 const& e2) const
            {
                return
                    this->evaluate(
                        e1
                      , e2
                      , typename proto::arity_of<Expr1>::type()
                    );
            }

            private:
            #include <boost/phoenix/core/detail/cpp03/function_equal.hpp>
#else
            template <typename Expr1>
            result_type operator()(Expr1 const& e1, Expr1 const& e2) const
            {
                return
                    this->evaluate(
                        e1
                      , e2
                      , typename make_index_sequence<proto::arity_of<Expr1>::value>::type()
                    );
            }

            private:
            template <typename Expr1>
            result_type
            evaluate(Expr1 const& /*e1*/, Expr1 const& /*e2*/, index_sequence<>) const
            {
                return true;
            }
            template <typename Expr1, std::size_t Head, std::size_t... Tail>
            result_type
            evaluate(Expr1 const& e1, Expr1 const& e2, index_sequence<Head, Tail...>) const
            {
                return
                  function_equal_()(proto::child_c<Head>(e1), proto::child_c<Head>(e2)) &&
                  this->evaluate(
                      e1
                    , e2
                    , index_sequence<Tail...>()
                  );
            }
#endif
        };
    }

    template <typename Expr1, typename Expr2>
    inline bool function_equal_impl(actor<Expr1> const& a1, actor<Expr2> const& a2)
    {
        return detail::function_equal_()(a1, a2);
    }

    template <typename Expr1, typename Expr2>
    inline bool function_equal(actor<Expr1> const& a1, actor<Expr2> const& a2)
    {
        return function_equal_impl(a1, a2);
    }

}}

#endif