//===----------------------------------------------------------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++03, c++11, c++14, c++17
// UNSUPPORTED: no-localization
// UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME

// TODO FMT This test should not require std::to_chars(floating-point)
// XFAIL: availability-fp_to_chars-missing

// TODO FMT Investigate Windows issues.
// XFAIL: msvc

// REQUIRES: locale.fr_FR.UTF-8
// REQUIRES: locale.ja_JP.UTF-8

// <chrono>

// template<class charT> struct formatter<chrono::weekday_index, charT>;

#include <chrono>
#include <format>

#include <cassert>
#include <concepts>
#include <locale>
#include <iostream>
#include <type_traits>

#include "formatter_tests.h"
#include "make_string.h"
#include "platform_support.h" // locale name macros
#include "test_macros.h"

template <class CharT>
static void test_no_chrono_specs() {
  using namespace std::literals::chrono_literals;

  // Valid weekday valid index
  check(SV("Sun[1]"), SV("{}"), std::chrono::weekday_indexed{std::chrono::weekday(0), 1});

  // Invalid weekday valid index
  check(SV("8 is not a valid weekday[1]"), SV("{}"), std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
  check(SV("255 is not a valid weekday[1]"), SV("{}"), std::chrono::weekday_indexed{std::chrono::weekday(255), 1});

  // Valid weekday invalid index
  check(SV("Sun[0 is not a valid index]"), SV("{}"), std::chrono::weekday_indexed{std::chrono::weekday(0), 0});
  check(SV("Sun[6 is not a valid index]"), SV("{}"), std::chrono::weekday_indexed{std::chrono::weekday(0), 6});
  check(SV("Sun[255 is not a valid index]"), SV("{}"), std::chrono::weekday_indexed{std::chrono::weekday(0), 255});

  // Invalid weekday invalid index
  check(SV("8 is not a valid weekday[0 is not a valid index]"),
        SV("{}"),
        std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
  check(SV("127 is not a valid weekday[6 is not a valid index]"),
        SV("{}"),
        std::chrono::weekday_indexed{std::chrono::weekday(127), 6});
  check(SV("255 is not a valid weekday[255 is not a valid index]"),
        SV("{}"),
        std::chrono::weekday_indexed{std::chrono::weekday(255), 255});
}

template <class CharT>
static void test_valid_values() {
  constexpr std::basic_string_view<CharT> fmt =
      SV("{:%%u='%u'%t%%Ou='%Ou'%t%%w='%w'%t%%Ow='%Ow'%t%%a='%a'%t%%A='%A'%n}");
  constexpr std::basic_string_view<CharT> lfmt =
      SV("{:L%%u='%u'%t%%Ou='%Ou'%t%%w='%w'%t%%Ow='%Ow'%t%%a='%a'%t%%A='%A'%n}");

  const std::locale loc(LOCALE_ja_JP_UTF_8);
  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));

  // Non localized output using C-locale
  check(SV("%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\t%a='Sun'\t%A='Sunday'\n"),
        fmt,
        std::chrono::weekday_indexed{std::chrono::weekday(0), 0});
  check(SV("%u='1'\t%Ou='1'\t%w='1'\t%Ow='1'\t%a='Mon'\t%A='Monday'\n"),
        fmt,
        std::chrono::weekday_indexed{std::chrono::weekday(1), 1});
  check(SV("%u='2'\t%Ou='2'\t%w='2'\t%Ow='2'\t%a='Tue'\t%A='Tuesday'\n"),
        fmt,
        std::chrono::weekday_indexed{std::chrono::weekday(2), 2});
  check(SV("%u='3'\t%Ou='3'\t%w='3'\t%Ow='3'\t%a='Wed'\t%A='Wednesday'\n"),
        fmt,
        std::chrono::weekday_indexed{std::chrono::weekday(3), 3});
  check(SV("%u='4'\t%Ou='4'\t%w='4'\t%Ow='4'\t%a='Thu'\t%A='Thursday'\n"),
        fmt,
        std::chrono::weekday_indexed{std::chrono::weekday(4), 4});
  check(SV("%u='5'\t%Ou='5'\t%w='5'\t%Ow='5'\t%a='Fri'\t%A='Friday'\n"),
        fmt,
        std::chrono::weekday_indexed{std::chrono::weekday(5), 5});
  check(SV("%u='6'\t%Ou='6'\t%w='6'\t%Ow='6'\t%a='Sat'\t%A='Saturday'\n"),
        fmt,
        std::chrono::weekday_indexed{std::chrono::weekday(6), 6});
  check(SV("%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\t%a='Sun'\t%A='Sunday'\n"),
        fmt,
        std::chrono::weekday_indexed{std::chrono::weekday(7), 7});

  // Use the global locale (fr_FR)
#if defined(__APPLE__)
  check(SV("%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\t%a='Dim'\t%A='Dimanche'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(0), 0});
  check(SV("%u='1'\t%Ou='1'\t%w='1'\t%Ow='1'\t%a='Lun'\t%A='Lundi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(1), 1});
  check(SV("%u='2'\t%Ou='2'\t%w='2'\t%Ow='2'\t%a='Mar'\t%A='Mardi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(2), 2});
  check(SV("%u='3'\t%Ou='3'\t%w='3'\t%Ow='3'\t%a='Mer'\t%A='Mercredi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(3), 3});
  check(SV("%u='4'\t%Ou='4'\t%w='4'\t%Ow='4'\t%a='Jeu'\t%A='Jeudi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(4), 4});
  check(SV("%u='5'\t%Ou='5'\t%w='5'\t%Ow='5'\t%a='Ven'\t%A='Vendredi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(5), 5});
  check(SV("%u='6'\t%Ou='6'\t%w='6'\t%Ow='6'\t%a='Sam'\t%A='Samedi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(6), 6});
  check(SV("%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\t%a='Dim'\t%A='Dimanche'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(7), 7});
#else  // defined(__APPLE__)
  check(SV("%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\t%a='dim.'\t%A='dimanche'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(0), 0});
  check(SV("%u='1'\t%Ou='1'\t%w='1'\t%Ow='1'\t%a='lun.'\t%A='lundi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(1), 1});
  check(SV("%u='2'\t%Ou='2'\t%w='2'\t%Ow='2'\t%a='mar.'\t%A='mardi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(2), 2});
  check(SV("%u='3'\t%Ou='3'\t%w='3'\t%Ow='3'\t%a='mer.'\t%A='mercredi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(3), 3});
  check(SV("%u='4'\t%Ou='4'\t%w='4'\t%Ow='4'\t%a='jeu.'\t%A='jeudi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(4), 4});
  check(SV("%u='5'\t%Ou='5'\t%w='5'\t%Ow='5'\t%a='ven.'\t%A='vendredi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(5), 5});
  check(SV("%u='6'\t%Ou='6'\t%w='6'\t%Ow='6'\t%a='sam.'\t%A='samedi'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(6), 6});
  check(SV("%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\t%a='dim.'\t%A='dimanche'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(7), 7});
#endif // defined(__APPLE__)

  // Use supplied locale (ja_JP).
  // This locale has a different alternate, but not on all platforms
#if defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
  check(loc,
        SV("%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\t%a='日'\t%A='日曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(0), 0});
  check(loc,
        SV("%u='1'\t%Ou='1'\t%w='1'\t%Ow='1'\t%a='月'\t%A='月曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(1), 1});
  check(loc,
        SV("%u='2'\t%Ou='2'\t%w='2'\t%Ow='2'\t%a='火'\t%A='火曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(2), 2});
  check(loc,
        SV("%u='3'\t%Ou='3'\t%w='3'\t%Ow='3'\t%a='水'\t%A='水曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(3), 3});
  check(loc,
        SV("%u='4'\t%Ou='4'\t%w='4'\t%Ow='4'\t%a='木'\t%A='木曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(4), 4});
  check(loc,
        SV("%u='5'\t%Ou='5'\t%w='5'\t%Ow='5'\t%a='金'\t%A='金曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(5), 5});
  check(loc,
        SV("%u='6'\t%Ou='6'\t%w='6'\t%Ow='6'\t%a='土'\t%A='土曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(6), 6});
  check(loc,
        SV("%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\t%a='日'\t%A='日曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(7), 7});
#else  // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
  check(loc,
        SV("%u='7'\t%Ou='七'\t%w='0'\t%Ow='〇'\t%a='日'\t%A='日曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(0), 0});
  check(loc,
        SV("%u='1'\t%Ou='一'\t%w='1'\t%Ow='一'\t%a='月'\t%A='月曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(1), 1});
  check(loc,
        SV("%u='2'\t%Ou='二'\t%w='2'\t%Ow='二'\t%a='火'\t%A='火曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(2), 2});
  check(loc,
        SV("%u='3'\t%Ou='三'\t%w='3'\t%Ow='三'\t%a='水'\t%A='水曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(3), 3});
  check(loc,
        SV("%u='4'\t%Ou='四'\t%w='4'\t%Ow='四'\t%a='木'\t%A='木曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(4), 4});
  check(loc,
        SV("%u='5'\t%Ou='五'\t%w='5'\t%Ow='五'\t%a='金'\t%A='金曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(5), 5});
  check(loc,
        SV("%u='6'\t%Ou='六'\t%w='6'\t%Ow='六'\t%a='土'\t%A='土曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(6), 6});
  check(loc,
        SV("%u='7'\t%Ou='七'\t%w='0'\t%Ow='〇'\t%a='日'\t%A='日曜日'\n"),
        lfmt,
        std::chrono::weekday_indexed{std::chrono::weekday(7), 7});
#endif // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)

  std::locale::global(std::locale::classic());
}

template <class CharT>
static void test_invalid_values() {
  // Test that %a and %A throw an exception.
  check_exception("Formatting a weekday name needs a valid weekday",
                  SV("{:%a}"),
                  std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
  check_exception("Formatting a weekday name needs a valid weekday",
                  SV("{:%a}"),
                  std::chrono::weekday_indexed{std::chrono::weekday(255), 1});
  check_exception("Formatting a weekday name needs a valid weekday",
                  SV("{:%A}"),
                  std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
  check_exception("Formatting a weekday name needs a valid weekday",
                  SV("{:%A}"),
                  std::chrono::weekday_indexed{std::chrono::weekday(255), 1});

  const std::locale loc(LOCALE_ja_JP_UTF_8);
  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));

  { // Invalid weekday, can't test %a and %A
    constexpr std::basic_string_view<CharT> fmt  = SV("{:%%u='%u'%t%%Ou='%Ou'%t%%w='%w'%t%%Ow='%Ow'%n}");
    constexpr std::basic_string_view<CharT> lfmt = SV("{:L%%u='%u'%t%%Ou='%Ou'%t%%w='%w'%t%%Ow='%Ow'%n}");
#if defined(__APPLE__) || defined(__FreeBSD__)
    // Non localized output using C-locale
    check(SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(SV("%u='255'\t%Ou='255'\t%w='255'\t%Ow='255'\n"),
          fmt,
          std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(SV("%u='255'\t%Ou='255'\t%w='255'\t%Ow='255'\n"),
          fmt,
          std::chrono::weekday_indexed{std::chrono::weekday(255), 1});

    // Use the global locale (fr_FR)
    check(SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(SV("%u='255'\t%Ou='255'\t%w='255'\t%Ow='255'\n"),
          lfmt,
          std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(SV("%u='255'\t%Ou='255'\t%w='255'\t%Ow='255'\n"),
          lfmt,
          std::chrono::weekday_indexed{std::chrono::weekday(255), 1});

    // Use supplied locale (ja_JP). This locale has a different alternate.
    check(
        loc, SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(
        loc, SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(loc,
          SV("%u='255'\t%Ou='255'\t%w='255'\t%Ow='255'\n"),
          lfmt,
          std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(loc,
          SV("%u='255'\t%Ou='255'\t%w='255'\t%Ow='255'\n"),
          lfmt,
          std::chrono::weekday_indexed{std::chrono::weekday(255), 1});
#elif defined(_WIN32) //  defined(__APPLE__) || defined(__FreeBSD__)
    // Non localized output using C-locale
    check(SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 1});

    // Use the global locale (fr_FR)
    check(SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 1});

    // Use supplied locale (ja_JP). This locale has a different alternate.
    check(loc, SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(loc, SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(loc, SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(loc, SV("%u=''\t%Ou=''\t%w=''\t%Ow=''\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 1});
#elif defined(_AIX)   //  defined(__APPLE__) || defined(__FreeBSD__)
    // Non localized output using C-locale
    check(SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(SV("%u='5'\t%Ou='5'\t%w='5'\t%Ow='5'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(SV("%u='5'\t%Ou='5'\t%w='5'\t%Ow='5'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 1});

    // Use the global locale (fr_FR)
    check(SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(SV("%u='5'\t%Ou='5'\t%w='5'\t%Ow='5'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(SV("%u='5'\t%Ou='5'\t%w='5'\t%Ow='5'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 1});

    // Use supplied locale (ja_JP). This locale has a different alternate.
    check(
        loc, SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(
        loc, SV("%u='8'\t%Ou='8'\t%w='8'\t%Ow='8'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(loc,
          SV("%u='5'\t%Ou='5'\t%w='5'\t%Ow='5'\n"),
          lfmt,
          std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(loc,
          SV("%u='5'\t%Ou='5'\t%w='5'\t%Ow='5'\n"),
          lfmt,
          std::chrono::weekday_indexed{std::chrono::weekday(255), 1});
#else                 // defined(__APPLE__) || defined(__FreeBSD__)
    // Non localized output using C-locale
    check(SV("%u='1'\t%Ou='1'\t%w='8'\t%Ow='8'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(SV("%u='1'\t%Ou='1'\t%w='8'\t%Ow='8'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(
        SV("%u='3'\t%Ou='3'\t%w='255'\t%Ow='255'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(
        SV("%u='3'\t%Ou='3'\t%w='255'\t%Ow='255'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 1});

    // Use the global locale (fr_FR)
    check(SV("%u='1'\t%Ou='1'\t%w='8'\t%Ow='8'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(SV("%u='1'\t%Ou='1'\t%w='8'\t%Ow='8'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(
        SV("%u='3'\t%Ou='3'\t%w='255'\t%Ow='255'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(
        SV("%u='3'\t%Ou='3'\t%w='255'\t%Ow='255'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(255), 1});

    // Use supplied locale (ja_JP). This locale has a different alternate.
    check(loc,
          SV("%u='1'\t%Ou='一'\t%w='8'\t%Ow='八'\n"),
          lfmt,
          std::chrono::weekday_indexed{std::chrono::weekday(8), 0});
    check(loc,
          SV("%u='1'\t%Ou='一'\t%w='8'\t%Ow='八'\n"),
          lfmt,
          std::chrono::weekday_indexed{std::chrono::weekday(8), 1});
    check(loc,
          SV("%u='3'\t%Ou='三'\t%w='255'\t%Ow='255'\n"),
          lfmt,
          std::chrono::weekday_indexed{std::chrono::weekday(255), 0});
    check(loc,
          SV("%u='3'\t%Ou='三'\t%w='255'\t%Ow='255'\n"),
          lfmt,
          std::chrono::weekday_indexed{std::chrono::weekday(255), 1});
#endif                // defined(__APPLE__) || defined(__FreeBSD__)
  }

  { // Valid weekday, tests %a and %A
    constexpr std::basic_string_view<CharT> fmt  = SV("{:%%a='%a'%t%%A='%A'%n}");
    constexpr std::basic_string_view<CharT> lfmt = SV("{:L%%a='%a'%t%%A='%A'%n}");

    // Non localized output using C-locale
    check(SV("%a='Sun'\t%A='Sunday'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(0), 0});
    check(SV("%a='Sun'\t%A='Sunday'\n"), fmt, std::chrono::weekday_indexed{std::chrono::weekday(0), 6});

    // Use the global locale (fr_FR)
#if defined(__APPLE__)
    check(SV("%a='Dim'\t%A='Dimanche'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(0), 0});
    check(SV("%a='Dim'\t%A='Dimanche'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(0), 6});
#else  // defined(__APPLE__)
    check(SV("%a='dim.'\t%A='dimanche'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(0), 0});
    check(SV("%a='dim.'\t%A='dimanche'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(0), 6});
#endif // defined(__APPLE__)

    // Use supplied locale (ja_JP)
    check(loc, SV("%a='日'\t%A='日曜日'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(0), 0});
    check(loc, SV("%a='日'\t%A='日曜日'\n"), lfmt, std::chrono::weekday_indexed{std::chrono::weekday(0), 6});
  }

  std::locale::global(std::locale::classic());
}

template <class CharT>
static void test() {
  test_no_chrono_specs<CharT>();
  test_valid_values<CharT>();
  test_invalid_values<CharT>();
  check_invalid_types<CharT>({SV("a"), SV("A"), SV("t"), SV("u"), SV("w"), SV("Ou"), SV("Ow")},
                             std::chrono::weekday_indexed{std::chrono::weekday(0), 1});

  check_exception("The format specifier expects a '%' or a '}'",
                  SV("{:A"),
                  std::chrono::weekday_indexed{std::chrono::weekday(0), 1});
  check_exception(
      "The chrono specifiers contain a '{'", SV("{:%%{"), std::chrono::weekday_indexed{std::chrono::weekday(0), 1});
  check_exception("End of input while parsing a conversion specifier",
                  SV("{:%"),
                  std::chrono::weekday_indexed{std::chrono::weekday(0), 1});
  check_exception("End of input while parsing the modifier E",
                  SV("{:%E"),
                  std::chrono::weekday_indexed{std::chrono::weekday(0), 1});
  check_exception("End of input while parsing the modifier O",
                  SV("{:%O"),
                  std::chrono::weekday_indexed{std::chrono::weekday(0), 1});

  // Precision not allowed
  check_exception("The format specifier expects a '%' or a '}'",
                  SV("{:.3}"),
                  std::chrono::weekday_indexed{std::chrono::weekday(0), 1});
}

int main(int, char**) {
  test<char>();

#ifndef TEST_HAS_NO_WIDE_CHARACTERS
  test<wchar_t>();
#endif

  return 0;
}