draconisplusplus/include/rfl/internal/get_field_names.hpp

#ifndef RFL_INTERNAL_GETFIELDNAMES_HPP_
#define RFL_INTERNAL_GETFIELDNAMES_HPP_

#include <array>
#include <iostream>
#include <memory>
#include <source_location>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>

#include "../Literal.hpp"
#include "bind_fake_object_to_tuple.hpp"
#include "get_fake_object.hpp"
#include "is_flatten_field.hpp"
#include "is_rename.hpp"
#include "num_fields.hpp"

#if __GNUC__
#ifndef __clang__
#pragma GCC system_header
#endif
#endif

namespace rfl::internal {

  template <class T>
  struct Wrapper {
    using Type = T;
    T v;
  };

  template <class T>
  Wrapper(T) -> Wrapper<T>;

  // This workaround is necessary for clang.
  template <class T>
  constexpr auto wrap(const T& arg) noexcept {
    return Wrapper {arg};
  }

  template <class T, auto ptr>
  consteval auto get_field_name_str_view() {
    // Unfortunately, we cannot avoid the use of a compiler-specific macro for
    // Clang on Windows. For all other compilers, function_name works as
    // intended.
#if defined(__clang__) && defined(_MSC_VER)
    const auto func_name = std::string_view {__PRETTY_FUNCTION__};
#else
    const auto func_name =
        std::string_view {std::source_location::current().function_name()};
#endif
#if defined(__clang__)
    const auto split = func_name.substr(0, func_name.size() - 2);
    return split.substr(split.find_last_of(":.") + 1);
#elif defined(__GNUC__)
    const auto split = func_name.substr(0, func_name.size() - 2);
    return split.substr(split.find_last_of(":") + 1);
#elif defined(_MSC_VER)
    const auto split = func_name.substr(0, func_name.size() - 7);
    return split.substr(split.rfind("->") + 2);
#else
    static_assert(
        false,
        "You are using an unsupported compiler. Please use GCC, Clang "
        "or MSVC or switch to the rfl::Field-syntax."
    );
#endif
  }

  template <class T, auto ptr>
  consteval auto get_field_name_str_lit() {
    constexpr auto name       = get_field_name_str_view<T, ptr>();
    const auto     to_str_lit = [&]<auto... Ns>(std::index_sequence<Ns...>) {
      return StringLiteral<sizeof...(Ns) + 1> {name[Ns]...};
    };
    return to_str_lit(std::make_index_sequence<name.size()> {});
  }

  template <class T>
  auto get_field_names();

  template <class T, auto ptr>
  auto get_field_name() {
#if defined(__clang__)
    using Type = std::remove_cvref_t<std::remove_pointer_t<
        typename std::remove_pointer_t<decltype(ptr)>::Type>>;
#else
    using Type = std::remove_cvref_t<std::remove_pointer_t<decltype(ptr)>>;
#endif
    if constexpr (is_rename_v<Type>) {
      using Name = typename Type::Name;
      return Name();
    } else if constexpr (is_flatten_field_v<Type>) {
      return get_field_names<std::remove_cvref_t<typename Type::Type>>();
    } else {
      return rfl::Literal<get_field_name_str_lit<T, ptr>()>();
    }
  }

  template <StringLiteral... _names1, StringLiteral... _names2>
  auto concat_two_literals(
      const rfl::Literal<_names1...>& _lit1,
      const rfl::Literal<_names2...>& _lit2
  ) {
    return rfl::Literal<_names1..., _names2...>::template from_value<0>();
  }

  template <class Head, class... Tail>
  auto concat_literals(const Head& _head, const Tail&... _tail) {
    if constexpr (sizeof...(_tail) == 0) {
      return _head;
    } else {
      return concat_two_literals(_head, concat_literals(_tail...));
    }
  }

  inline auto concat_literals() { return rfl::Literal<>(); }

#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wundefined-var-template"
#pragma clang diagnostic ignored "-Wundefined-inline"
#endif

  template <class T>
#if __GNUC__
#ifndef __clang__
  [[gnu::no_sanitize_undefined]]
#endif
#endif
  auto get_field_names() {
    using Type = std::remove_cvref_t<T>;
    if constexpr (std::is_pointer_v<Type>) {
      return get_field_names<std::remove_pointer_t<T>>();
    } else {
#if defined(__clang__)
      const auto get = []<std::size_t... Is>(std::index_sequence<Is...>) {
        return concat_literals(
            get_field_name<
                Type,
                wrap(std::get<Is>(bind_fake_object_to_tuple<T>()))>()...
        );
      };
#else
      const auto get = []<std::size_t... Is>(std::index_sequence<Is...>) {
        return concat_literals(
            get_field_name<Type, std::get<Is>(bind_fake_object_to_tuple<T>())>(
            )...
        );
      };
#endif
      return get(std::make_index_sequence<num_fields<T>>());
    }
  }

#ifdef __clang__
#pragma clang diagnostic pop
#endif

} // namespace rfl::internal

#endif