robot/include/rttr/detail/default_arguments/default_arguments.h

/************************************************************************************
*                                                                                   *
*   Copyright (c) 2014 - 2018 Axel Menzel <info@rttr.org>                           *
*                                                                                   *
*   This file is part of RTTR (Run Time Type Reflection)                            *
*   License: MIT License                                                            *
*                                                                                   *
*   Permission is hereby granted, free of charge, to any person obtaining           *
*   a copy of this software and associated documentation files (the "Software"),    *
*   to deal in the Software without restriction, including without limitation       *
*   the rights to use, copy, modify, merge, publish, distribute, sublicense,        *
*   and/or sell copies of the Software, and to permit persons to whom the           *
*   Software is furnished to do so, subject to the following conditions:            *
*                                                                                   *
*   The above copyright notice and this permission notice shall be included in      *
*   all copies or substantial portions of the Software.                             *
*                                                                                   *
*   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR      *
*   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,        *
*   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE     *
*   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER          *
*   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,   *
*   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE   *
*   SOFTWARE.                                                                       *
*                                                                                   *
*************************************************************************************/

#ifndef RTTR_DEFAULT_ARGUMENTS_H_
#define RTTR_DEFAULT_ARGUMENTS_H_

#include "rttr/detail/base/core_prerequisites.h"
#include "rttr/detail/misc/misc_type_traits.h"
#include "rttr/detail/misc/argument_extractor.h"
#include "rttr/detail/misc/function_traits.h"

#include <tuple>

namespace rttr
{
namespace detail
{

/*!
 * This class holds the data for the default arguments.
 */
template<typename...T>
struct default_args
{
    default_args() {}
    default_args(T&&... args) : m_args(std::forward<T>(args)...) {}

    std::tuple<T...> m_args;
};

template<>
struct default_args<>
{
    default_args() {}
    std::tuple<> m_args;
};

struct constructor_type {};
struct function_type {};

/////////////////////////////////////////////////////////////////////////////////////////
// a helper class to store two default list, the user provided, with std::nullptr_t
// and the function signature:
// e.g. default_args<int, bool*> , default_args<int, nullptr>
// this is needed for the get_default_args() function, to copy the values from the std::nullptr_t list
// to the function signature list
template<typename T1, typename T2>
struct default_list
{
    using default_types_func        = T1;
    using default_types_provided    = T2;
};

// short cut for an empty list
using empty_defaults = default_list<default_args<>, default_args<>>;

/////////////////////////////////////////////////////////////////////////////////////////

// This type trait will check whether a signature (given via \p Arg_list) match the \o Default_Arg_List types.
// It will check the signature recursively, beginning with the complete signature,
// then removing the first argument and check against Default_Arg_List, then removing the second...
template<typename Arg_list, typename Default_Arg_List>
struct find_default_args_impl;

template<typename Default_Arg_List, typename T, typename...TArgs>
struct find_default_args_impl<type_list<T, TArgs...>, Default_Arg_List>
{
    template<typename Tx>
    using decay_type = remove_cv_t<remove_reference_t< Tx >>;

    using func_args = default_args< decay_type< T>,
                                    decay_type< TArgs>...
                                  >;

    using type = conditional_t< is_same_nullptr<func_args, Default_Arg_List>::value,
                                default_list<func_args, Default_Arg_List>,
                                typename find_default_args_impl<type_list<TArgs...>, Default_Arg_List >::type
                               >;
};

template<typename Default_Arg_List>
struct find_default_args_impl<type_list<>, Default_Arg_List>
{
    using type = default_list<default_args<>, default_args<>>;
};

/////////////////////////////////////////////////////////////////////////////////////////

/*!
 * This helper struct is needed to call `find_default_args_t` with a function signature,
 * or a constructor signature (a list of arguments), i.e. I have only one interface to invoke.
 *
 * This avoid code distinction in `has_default_types`or `get_default_args`.
 */
template<typename Default_Arg_List, typename T, typename Acc_Type, typename Enable = void>
struct find_default_args_helper;

// is function
template<typename Default_Arg_List, typename T, typename Acc_Type>
struct find_default_args_helper<Default_Arg_List, type_list<T>, Acc_Type, enable_if_t< std::is_same<Acc_Type, function_type>::value >>
:   find_default_args_impl< as_type_list_t< typename function_traits<T>::arg_types >, Default_Arg_List>
{
};

// is ctor with one argument
template<typename Default_Arg_List, typename T>
struct find_default_args_helper<Default_Arg_List, type_list<T>, constructor_type, enable_if_t< is_one_argument<T>::value >>
:   find_default_args_impl<type_list<T>, Default_Arg_List>
{
};

// is ctor with zero or more then one argument
template<typename Default_Arg_List, typename...TArgs>
struct find_default_args_helper<Default_Arg_List, type_list<TArgs...>, constructor_type, enable_if_t< !is_one_argument<TArgs...>::value >>
:   find_default_args_impl<type_list<TArgs...>, Default_Arg_List>
{
};


/*!
 * This type traits will check whether it is possible to call
 * a function type or a list of argument types (e.g. constructor arguments)
 * depending on a list of default argument types, \p Default_Arg_List.
 * When it is possible \p Default_Arg_List will be returned as type;
 * Otherwise an empty 'default_args<>' will be returned
 *
 * e.g.:
 * ctor_list => <bool, int, double>;    Default_Arg_List => default_args<bool, int, double> will return:    default_args<bool, int, double>
 * ctor_list => <bool, int, double>;    Default_Arg_List => default_args<int, double>       will return:    default_args<int, double>
 * ctor_list => <bool, int, double>;    Default_Arg_List => default_args<double>            will return:    default_args<double>
 * ctor_list => <bool, int, double>;    Default_Arg_List => default_args<int>               will return:    default_args<> (cannot be called; right most argument is missing)
 */
template<typename Default_Arg_List, typename Acc_Args, typename Acc_Type>
using find_default_args_t = typename find_default_args_helper<Default_Arg_List, Acc_Args, Acc_Type>::type;


/////////////////////////////////////////////////////////////////////////////////////////

template<typename T>
struct is_def_type : std::false_type { };

template<typename... TArgs>
struct is_def_type<default_args<TArgs...> > : std::true_type { };

/////////////////////////////////////////////////////////////////////////////////////////

template<typename T>
struct get_default_args_impl;

template<typename T, typename...TArgs>
struct get_default_args_impl<type_list<T, TArgs...>>
{
    using type = conditional_t< is_def_type<T>::value,
                                T,
                                typename get_default_args_impl<type_list<TArgs...>>::type
                               >;
};

template<>
struct get_default_args_impl<type_list<>>
{
    using type = default_args<>;
};

//! This type trait will return the first type which matches the template type `default_args<T...>`
template<typename...TArgs>
using get_default_args_t = typename get_default_args_impl< type_list< TArgs... > >::type;

/////////////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////////////

/*!
 * Evaluates to 'std::true_type' when the given arguments contains one 'def_args<T...>' argument;
 * Otherwise to 'std::false_type'
 */
template<typename...Args>
using has_default_args = std::integral_constant<bool, !std::is_same<get_default_args_t<Args...>, default_args<>>::value>;

template<typename T1, typename T2, typename Acc_Type>
struct has_default_types;


/*!
 * Evaluates to 'std::true_type' when the given arguments contains one valid 'def_args<T...>' argument,
 * that can be used to invoke the signature \p Acc_Args;
 * Otherwise to 'std::false_type'
 */
template<typename Acc_Args, typename Acc_Type, typename... TArgs>
struct has_default_types<Acc_Args, type_list<TArgs...>, Acc_Type>
:   std::integral_constant<bool, !std::is_same<find_default_args_t<get_default_args_t<TArgs...>, Acc_Args, Acc_Type>, empty_defaults>::value>
{
};

/////////////////////////////////////////////////////////////////////////////////////////

template<typename Acc_Args, typename Acc_Type, typename... TArgs>
using default_types_t = find_default_args_t<get_default_args_t<TArgs...>, Acc_Args, Acc_Type>;

/////////////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////////////
// returns the number of types 'default_args<T...>' provided in the given list of arguments TArgs...
template<typename...TArgs>
using count_default_args = count_if<is_def_type, raw_type_t<TArgs>... >;

/////////////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////////////

template<typename Acc_Args, typename Acc_Type, typename... Args, typename Default_Type = find_default_args_t<get_default_args_t<Args...>, Acc_Args, Acc_Type> >
static RTTR_INLINE
enable_if_t< std::is_same<Default_Type, empty_defaults>::value, typename Default_Type::default_types_func>
get_default_args(Args&&... arg)
{
    return default_args<>(); // no default arguments provided
}

/////////////////////////////////////////////////////////////////////////////////////////

template<typename Acc_Args, typename Acc_Type, typename... Args, typename Default_Type = find_default_args_t<get_default_args_t<Args...>, Acc_Args, Acc_Type> >
static RTTR_INLINE
enable_if_t< !std::is_same<Default_Type, empty_defaults>::value, typename Default_Type::default_types_func>
get_default_args(Args&&... arg)
{
    // default arguments are provided, extract them
    auto result = forward_to_array<typename Default_Type::default_types_provided>(std::forward<Args>(arg)...);
    // because we knew there is exactly one detail::default_argument,
    // we can extract it without worry to check
    typename Default_Type::default_types_func ret;
    ret.m_args = std::move(result[0].m_args);
    return ret;
}

/////////////////////////////////////////////////////////////////////////////////////////

} // end namespace detail
} // end namespace rttr

#endif // RTTR_DEFAULT_ARGUMENTS_H_