#include <array>
#include <charconv>
#include <stdfloat>
#include <iostream>
#include <string_view>
#include <system_error>

template<typename T>
void
test(std::chars_format fmt = std::chars_format{})
{
  std::array<char, 64> str1, str2;
  union U { unsigned short s; T f; } u, v;
  for (int i = 0; i <= (unsigned short) ~0; ++i)
    {
      u.s = i;
      auto [ptr1, ec1] = std::to_chars(str1.data(), str1.data() + str1.size(), u.f, fmt);
      auto [ptr2, ec2] = std::to_chars(str2.data(), str2.data() + str2.size(), std::float32_t(u.f), fmt);
      if (ec1 != std::errc())
	{
	  std::cout << std::make_error_code(ec1).message() << '\n';
	  continue;
	}
      else if (ec2 != std::errc())
	{
	  std::cout << std::make_error_code(ec2).message() << '\n';
	  continue;
	}
      std::cout << i << ' ' << std::string_view (str1.data(), ptr1) << '\t' << std::string_view (str2.data(), ptr2) << '\n';
      if (fmt == std::chars_format::fixed)
	{
	  auto [ptr3, ec3] = std::to_chars(str1.data(), ptr1, u.f, fmt);
	  if (ec3 != std::errc() || ptr3 != ptr1)
	    throw "Consistency failure";
	  else
	    {
	      auto [ptr4, ec4] = std::to_chars(str1.data(), ptr1 - 1, u.f, fmt);
	      if (ec4 == std::errc())
		throw "Consistency failure";
	    }
	}
      auto [ptr5, ec5] = std::to_chars(str1.data(), str1.data() + str1.size(), u.f, fmt);
      std::float32_t f;
      auto [ptr6, ec6] = std::from_chars(str1.data(), ptr5, f, fmt == std::chars_format{} ? std::chars_format::general : fmt);
      if (ec6 != std::errc())
	{
	  std::cout << std::make_error_code(ec6).message() << '\n';
	  continue;
	}
      v.f = T(f);
      if (u.s != v.s)
	{
	  auto [ptr7, ec7] = std::to_chars(str2.data(), str2.data() + str1.size(), v.f, fmt);
	  if (ec7 != std::errc())
	    {
	      std::cout << std::make_error_code(ec7).message() << '\n';
	      continue;
	    }
	  std::cout << "Difference on " << i << ' ' << u.s << ' ' << v.s << ' ' << std::string_view (str1.data(), ptr5) << '\t' << std::string_view (str2.data(), ptr7) << '\n';;
	}
    }
}

int
main()
{
#ifdef __STDCPP_FLOAT16_T__
  std::cout << "float16_t" << '\n';
  test<std::float16_t>();
  std::cout << "float16_t fixed" << '\n';
  test<std::float16_t>(std::chars_format::fixed);
  std::cout << "float16_t scientific" << '\n';
  test<std::float16_t>(std::chars_format::scientific);
  std::cout << "float16_t general" << '\n';
  test<std::float16_t>(std::chars_format::general);
  std::cout << "float16_t hex" << '\n';
  test<std::float16_t>(std::chars_format::hex);
#endif
#ifdef __STDCPP_BFLOAT16_T__
  std::cout << "bfloat16_t" << '\n';
  test<std::bfloat16_t>();
  std::cout << "bfloat16_t fixed" << '\n';
  test<std::bfloat16_t>(std::chars_format::fixed);
  std::cout << "bfloat16_t scientific" << '\n';
  test<std::bfloat16_t>(std::chars_format::scientific);
  std::cout << "bfloat16_t general" << '\n';
  test<std::bfloat16_t>(std::chars_format::general);
  std::cout << "bfloat16_t hex" << '\n';
  test<std::bfloat16_t>(std::chars_format::hex);
#endif
}