//===----------------------------------------------------------------------===//
//
// 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, c++20

// <mdspan>

// template<class OtherExtents>
//   constexpr explicit(extents_type::rank() > 0)
//     mapping(const layout_stride::mapping<OtherExtents>& other);
//
// Constraints: is_constructible_v<extents_type, OtherExtents> is true.
//
// Preconditions:
//   - If extents_type::rank() > 0 is true, then for all r in the range [0, extents_type::rank()),
//     other.stride(r) equals other.extents().fwd-prod-of-extents(r), and
//   - other.required_span_size() is representable as a value of type index_type ([basic.fundamental]).
//
// Effects: Direct-non-list-initializes extents_ with other.extents().

#include <array>
#include <cassert>
#include <cstddef>
#include <mdspan>
#include <type_traits>

#include "test_macros.h"

template <bool implicit, class ToE, class FromE>
constexpr void test_conversion(FromE src_exts) {
  using To   = std::layout_left::mapping<ToE>;
  using From = std::layout_stride::mapping<FromE>;
  std::array<typename FromE::index_type, FromE::rank()> strides;
  if constexpr (FromE::rank() > 0) {
    strides[0] = 1;
    for (size_t r = 1; r < FromE::rank(); r++)
      strides[r] = src_exts.extent(r - 1) * strides[r - 1];
  }
  From src(src_exts, strides);

  ASSERT_NOEXCEPT(To(src));
  To dest(src);
  assert(dest == src);

  if constexpr (implicit) {
    To dest_implicit = src;
    assert(dest_implicit == src);
  } else {
    assert((!std::is_convertible_v<From, To>));
  }
}

template <class T1, class T2>
constexpr void test_conversion() {
  constexpr size_t D = std::dynamic_extent;

  // clang-format off
  test_conversion<true,  std::extents<T1>>(std::extents<T2>());
  test_conversion<false, std::extents<T1, D>>(std::extents<T2, D>(5));
  test_conversion<false, std::extents<T1, 5>>(std::extents<T2, D>(5));
  test_conversion<false, std::extents<T1, 5>>(std::extents<T2, 5>());
  test_conversion<false, std::extents<T1, 5, D>>(std::extents<T2, D, D>(5, 5));
  test_conversion<false, std::extents<T1, D, D>>(std::extents<T2, D, D>(5, 5));
  test_conversion<false, std::extents<T1, D, D>>(std::extents<T2, D, 7>(5));
  test_conversion<false, std::extents<T1, 5, 7>>(std::extents<T2, 5, 7>());
  test_conversion<false, std::extents<T1, 5, D, 8, D, D>>(std::extents<T2, D, D, 8, 9, 1>(5, 7));
  test_conversion<false, std::extents<T1, D, D, D, D, D>>(
                         std::extents<T2, D, D, D, D, D>(5, 7, 8, 9, 1));
  test_conversion<false, std::extents<T1, D, D, 8, 9, D>>(std::extents<T2, D, 7, 8, 9, 1>(5));
  test_conversion<false, std::extents<T1, 5, 7, 8, 9, 1>>(std::extents<T2, 5, 7, 8, 9, 1>());
  // clang-format on
}

template <class IdxT, size_t... Extents>
using lr_mapping_t = std::layout_right::mapping<std::extents<IdxT, Extents...>>;
template <class IdxT, size_t... Extents>
using ls_mapping_t = std::layout_stride::mapping<std::extents<IdxT, Extents...>>;

constexpr void test_rank_mismatch() {
  constexpr size_t D = std::dynamic_extent;

  static_assert(!std::is_constructible_v<lr_mapping_t<int, D>, ls_mapping_t<int>>);
  static_assert(!std::is_constructible_v<lr_mapping_t<int>, ls_mapping_t<int, D, D>>);
  static_assert(!std::is_constructible_v<lr_mapping_t<int, D>, ls_mapping_t<int, D, D>>);
  static_assert(!std::is_constructible_v<lr_mapping_t<int, D, D, D>, ls_mapping_t<int, D, D>>);
}

constexpr void test_static_extent_mismatch() {
  constexpr size_t D = std::dynamic_extent;

  static_assert(!std::is_constructible_v<lr_mapping_t<int, D, 5>, ls_mapping_t<int, D, 4>>);
  static_assert(!std::is_constructible_v<lr_mapping_t<int, 5>, ls_mapping_t<int, 4>>);
  static_assert(!std::is_constructible_v<lr_mapping_t<int, 5, D>, ls_mapping_t<int, 4, D>>);
}

constexpr bool test() {
  test_conversion<int, int>();
  test_conversion<int, size_t>();
  test_conversion<size_t, int>();
  test_conversion<size_t, long>();
  test_rank_mismatch();
  test_static_extent_mismatch();
  return true;
}

int main(int, char**) {
  test();
  static_assert(test());
  return 0;
}
