coordinate_descriptor_traits.hpp

/* This file is part of OpenKalman, a header-only C++ library for
 * Kalman filters and other recursive filters.
 *
 * Copyright (c) 2022-2025 Christopher Lee Ogden <ogden@gatech.edu>
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

#ifndef OPENKALMAN_VECTOR_SPACE_TRAITS_HPP
#define OPENKALMAN_VECTOR_SPACE_TRAITS_HPP

#include <type_traits>
#include <typeindex>
#ifdef __cpp_lib_ranges
#include <ranges>
#else
#include "basics/compatibility/ranges.hpp"
#endif
#include "values/concepts/index.hpp"
#include "collections/concepts/collection_view.hpp"
#include "collections/traits/size_of.hpp"

namespace OpenKalman::interface
{
#ifdef __cpp_concepts
  template<typename T>
#else
  template<typename T, typename = void>
#endif
  struct coordinate_descriptor_traits
  {
    static constexpr bool
    is_specialized = false;


    static constexpr auto
    dimension =
      [](const T&) noexcept
#ifdef __cpp_concepts
        -> values::index auto
#endif
      { return std::integral_constant<std::size_t, 0_uz>{}; };


    static constexpr auto stat_dimension = [](const T&) noexcept -> values::index auto
      { return std::integral_constant<std::size_t, 0_uz>{}; };


    static constexpr auto
    is_euclidean =
      [](const T&) noexcept
#ifdef __cpp_concepts
        -> std::convertible_to<bool> auto
#endif
      { return std::false_type {}; };

    static constexpr auto
    hash_code = [](const T&) noexcept -> std::size_t { return typeid(T).hash_code(); };


    static constexpr auto
    to_stat_space =
#ifdef __cpp_concepts
      [](const T& t, collections::collection_view auto&& data_view) noexcept -> collections::collection_view decltype(auto)
#else
      [](const T& t, auto&& data_view) noexcept
#endif
    {
      return std::forward<decltype(data_view)>(data_view);
    };


    static constexpr auto
    from_stat_space =
#ifdef __cpp_concepts
      [](const T& t, collections::collection_view auto&& data_view) noexcept -> collections::collection_view decltype(auto)
#else
      [](const T& t, auto&& data_view) noexcept
#endif
    {
      return std::forward<decltype(data_view)>(data_view);
    };


    static constexpr auto
    wrap =
#ifdef __cpp_concepts
      [](const T& t, collections::collection_view auto&& data_view) noexcept -> collections::collection_view decltype(auto)
#else
      [](const T& t, auto&& data_view) noexcept
#endif
    {
      return std::forward<decltype(data_view)>(data_view);
    };

  };


#ifdef __cpp_concepts
  template<values::index T>
  struct coordinate_descriptor_traits<T>
#else
  template<typename T>
  struct coordinate_descriptor_traits<T, std::enable_if_t<values::index<T>>>
#endif
  {
    static constexpr bool is_specialized = true;

    using scalar_type = values::number_type_of_t<T>;

    static constexpr auto
    dimension = [](const T& t) { return t; };

    static constexpr auto
    stat_dimension = [](const T& t) { return t; };

    static constexpr auto
    is_euclidean = [](const T&) { return std::true_type {}; };

    static constexpr auto
    hash_code = [](const T& t) -> std::size_t { return t; };

  };


} // namespace OpenKalman::interface



#endif //OPENKALMAN_VECTOR_SPACE_TRAITS_HPP