//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

// REQUIRES: std-at-least-c++20

// <numeric>

// template <class _Tp>
// _Tp midpoint(_Tp __a, _Tp __b) noexcept
// Constraints:
//   - T is an arithmetic type other than bool.

#include <cassert>
#include <cstddef>
#include <cstdint>
#include <limits>
#include <numeric>
#include <stdint.h>

#include "test_macros.h"

template <typename T>
void signed_test() {
  constexpr T zero{0};
  constexpr T one{1};
  constexpr T two{2};
  constexpr T three{3};
  constexpr T four{4};

  ASSERT_SAME_TYPE(decltype(std::midpoint(T(), T())), T);
  ASSERT_NOEXCEPT(std::midpoint(T(), T()));
  using limits = std::numeric_limits<T>;

  static_assert(std::midpoint(one, three) == two, "");
  static_assert(std::midpoint(three, one) == two, "");

  assert(std::midpoint(zero, zero) == zero);
  assert(std::midpoint(zero, two) == one);
  assert(std::midpoint(two, zero) == one);
  assert(std::midpoint(two, two) == two);

  assert(std::midpoint(one, four) == two);
  assert(std::midpoint(four, one) == three);
  assert(std::midpoint(three, four) == three);
  assert(std::midpoint(four, three) == four);

  assert(std::midpoint(T(3), T(4)) == T(3));
  assert(std::midpoint(T(4), T(3)) == T(4));
  assert(std::midpoint(T(-3), T(4)) == T(0));
  assert(std::midpoint(T(-4), T(3)) == T(-1));
  assert(std::midpoint(T(3), T(-4)) == T(0));
  assert(std::midpoint(T(4), T(-3)) == T(1));
  assert(std::midpoint(T(-3), T(-4)) == T(-3));
  assert(std::midpoint(T(-4), T(-3)) == T(-4));

  static_assert(std::midpoint(limits::min(), limits::max()) == T(-1), "");
  static_assert(std::midpoint(limits::max(), limits::min()) == T(0), "");

  static_assert(std::midpoint(limits::min(), T(6)) == limits::min() / 2 + 3, "");
  assert(std::midpoint(T(6), limits::min()) == limits::min() / 2 + 3);
  assert(std::midpoint(limits::max(), T(6)) == limits::max() / 2 + 4);
  static_assert(std::midpoint(T(6), limits::max()) == limits::max() / 2 + 3, "");

  assert(std::midpoint(limits::min(), T(-6)) == limits::min() / 2 - 3);
  static_assert(std::midpoint(T(-6), limits::min()) == limits::min() / 2 - 3, "");
  static_assert(std::midpoint(limits::max(), T(-6)) == limits::max() / 2 - 2, "");
  assert(std::midpoint(T(-6), limits::max()) == limits::max() / 2 - 3);
}

template <typename T>
void unsigned_test() {
  constexpr T zero{0};
  constexpr T one{1};
  constexpr T two{2};
  constexpr T three{3};
  constexpr T four{4};

  ASSERT_SAME_TYPE(decltype(std::midpoint(T(), T())), T);
  ASSERT_NOEXCEPT(std::midpoint(T(), T()));
  using limits     = std::numeric_limits<T>;
  const T half_way = (limits::max() - limits::min()) / 2;

  static_assert(std::midpoint(one, three) == two, "");
  static_assert(std::midpoint(three, one) == two, "");

  assert(std::midpoint(zero, zero) == zero);
  assert(std::midpoint(zero, two) == one);
  assert(std::midpoint(two, zero) == one);
  assert(std::midpoint(two, two) == two);

  assert(std::midpoint(one, four) == two);
  assert(std::midpoint(four, one) == three);
  assert(std::midpoint(three, four) == three);
  assert(std::midpoint(four, three) == four);

  assert(std::midpoint(limits::min(), limits::max()) == T(half_way));
  assert(std::midpoint(limits::max(), limits::min()) == T(half_way + 1));

  static_assert(std::midpoint(limits::min(), T(6)) == limits::min() / 2 + 3, "");
  assert(std::midpoint(T(6), limits::min()) == limits::min() / 2 + 3);
  assert(std::midpoint(limits::max(), T(6)) == half_way + 4);
  static_assert(std::midpoint(T(6), limits::max()) == half_way + 3, "");
}

int main(int, char**) {
  signed_test<signed char>();
  signed_test<short>();
  signed_test<int>();
  signed_test<long>();
  signed_test<long long>();

  signed_test<std::int8_t>();
  signed_test<std::int16_t>();
  signed_test<std::int32_t>();
  signed_test<std::int64_t>();

  unsigned_test<unsigned char>();
  unsigned_test<unsigned short>();
  unsigned_test<unsigned int>();
  unsigned_test<unsigned long>();
  unsigned_test<unsigned long long>();

  unsigned_test<std::uint8_t>();
  unsigned_test<std::uint16_t>();
  unsigned_test<std::uint32_t>();
  unsigned_test<std::uint64_t>();

#ifndef TEST_HAS_NO_INT128
  unsigned_test<__uint128_t>();
  signed_test<__int128_t>();
#endif

  //     int_test<char>();
  signed_test<std::ptrdiff_t>();
  unsigned_test<std::size_t>();

  return 0;
}