//===----------------------------------------------------------------------===//
//
// 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 OtherIndexType, size_t... OtherExtents>
//   friend constexpr bool operator==(const extents& lhs,
//                                    const extents<OtherIndexType, OtherExtents...>& rhs) noexcept;
//
// Returns: true if lhs.rank() equals rhs.rank() and
// if lhs.extent(r) equals rhs.extent(r) for every rank index r of rhs, otherwise false.
//

#include <cassert>
#include <cstddef>
#include <mdspan>
#include <span> // dynamic_extent

#include "test_macros.h"

template <class To, class From>
constexpr void test_comparison(bool equal, To dest, From src) {
  ASSERT_NOEXCEPT(dest == src);
  assert((dest == src) == equal);
  assert((dest != src) == !equal);
}

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

  test_comparison(false, std::extents<T1>(), std::extents<T2, D>(1));
  test_comparison(false, std::extents<T1>(), std::extents<T2, 1>());

  test_comparison(false, std::extents<T1, D>(1), std::extents<T2>());
  test_comparison(false, std::extents<T1, 1>(), std::extents<T2>());

  test_comparison(false, std::extents<T1, D>(5), std::extents<T2, D, D>(5, 5));
  test_comparison(false, std::extents<T1, 5>(), std::extents<T2, 5, D>(5));
  test_comparison(false, std::extents<T1, 5>(), std::extents<T2, 5, 1>());

  test_comparison(false, std::extents<T1, D, D>(5, 5), std::extents<T2, D>(5));
  test_comparison(false, std::extents<T1, 5, D>(5), std::extents<T2, D>(5));
  test_comparison(false, std::extents<T1, 5, 5>(), std::extents<T2, 5>());
}

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

  test_comparison(true, std::extents<T1>(), std::extents<T2>());

  test_comparison(true, std::extents<T1, D>(5), std::extents<T2, D>(5));
  test_comparison(true, std::extents<T1, 5>(), std::extents<T2, D>(5));
  test_comparison(true, std::extents<T1, D>(5), std::extents<T2, 5>());
  test_comparison(true, std::extents<T1, 5>(), std::extents< T2, 5>());
  test_comparison(false, std::extents<T1, D>(5), std::extents<T2, D>(7));
  test_comparison(false, std::extents<T1, 5>(), std::extents<T2, D>(7));
  test_comparison(false, std::extents<T1, D>(5), std::extents<T2, 7>());
  test_comparison(false, std::extents<T1, 5>(), std::extents<T2, 7>());

  test_comparison(true, std::extents<T1, D, D, D, D, D>(5, 6, 7, 8, 9), std::extents<T2, D, D, D, D, D>(5, 6, 7, 8, 9));
  test_comparison(true, std::extents<T1, D, 6, D, 8, D>(5, 7, 9), std::extents<T2, 5, D, D, 8, 9>(6, 7));
  test_comparison(true, std::extents<T1, 5, 6, 7, 8, 9>(5, 6, 7, 8, 9), std::extents<T2, 5, 6, 7, 8, 9>());
  test_comparison(
      false, std::extents<T1, D, D, D, D, D>(5, 6, 7, 8, 9), std::extents<T2, D, D, D, D, D>(5, 6, 3, 8, 9));
  test_comparison(false, std::extents<T1, D, 6, D, 8, D>(5, 7, 9), std::extents<T2, 5, D, D, 3, 9>(6, 7));
  test_comparison(false, std::extents<T1, 5, 6, 7, 8, 9>(5, 6, 7, 8, 9), std::extents<T2, 5, 6, 7, 3, 9>());
}

template <class T1, class T2>
constexpr void test_comparison() {
  test_comparison_same_rank<T1, T2>();
  test_comparison_different_rank<T1, T2>();
}

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

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