//===----------------------------------------------------------------------===//
//
// 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 _Fp>
// _Fp midpoint(_Fp __a, _Fp __b) noexcept

#include <cassert>
#include <limits>
#include <numeric>

#include "test_macros.h"
#include "fp_compare.h"

//  Totally arbitrary picks for precision
template <typename T>
constexpr T fp_error_pct();

template <>
constexpr float fp_error_pct<float>() {
  return 1.0e-4f;
}

template <>
constexpr double fp_error_pct<double>() {
  return 1.0e-12;
}

template <>
constexpr long double fp_error_pct<long double>() {
  return 1.0e-13l;
}

template <typename T>
void fp_test() {
  ASSERT_SAME_TYPE(T, decltype(std::midpoint(T(), T())));
  ASSERT_NOEXCEPT(std::midpoint(T(), T()));

  constexpr T maxV = std::numeric_limits<T>::max();
  constexpr T minV = std::numeric_limits<T>::min();

  //  Things that can be compared exactly
  static_assert((std::midpoint(T(0), T(0)) == T(0)), "");
  static_assert((std::midpoint(T(2), T(4)) == T(3)), "");
  static_assert((std::midpoint(T(4), T(2)) == T(3)), "");
  static_assert((std::midpoint(T(3), T(4)) == T(3.5)), "");
  static_assert((std::midpoint(T(0), T(0.4)) == T(0.2)), "");

  //  Things that can't be compared exactly
  constexpr T pct = fp_error_pct<T>();
  assert((fptest_close_pct(std::midpoint(T(1.3), T(11.4)), T(6.35), pct)));
  assert((fptest_close_pct(std::midpoint(T(11.33), T(31.45)), T(21.39), pct)));
  assert((fptest_close_pct(std::midpoint(T(-1.3), T(11.4)), T(5.05), pct)));
  assert((fptest_close_pct(std::midpoint(T(11.4), T(-1.3)), T(5.05), pct)));
  assert((fptest_close_pct(std::midpoint(T(0.1), T(0.4)), T(0.25), pct)));

  assert((fptest_close_pct(std::midpoint(T(11.2345), T(14.5432)), T(12.88885), pct)));

  //  From e to pi
  assert((fptest_close_pct(
      std::midpoint(T(2.71828182845904523536028747135266249775724709369995),
                    T(3.14159265358979323846264338327950288419716939937510)),
      T(2.92993724102441923691146542731608269097720824653752),
      pct)));

  assert((fptest_close_pct(std::midpoint(maxV, T(0)), maxV / 2, pct)));
  assert((fptest_close_pct(std::midpoint(T(0), maxV), maxV / 2, pct)));
  assert((fptest_close_pct(std::midpoint(minV, T(0)), minV / 2, pct)));
  assert((fptest_close_pct(std::midpoint(T(0), minV), minV / 2, pct)));
  assert((fptest_close_pct(std::midpoint(maxV, maxV), maxV, pct)));
  assert((fptest_close_pct(std::midpoint(minV, minV), minV, pct)));
  assert((fptest_close_pct(std::midpoint(maxV, minV), maxV / 2, pct)));
  assert((fptest_close_pct(std::midpoint(minV, maxV), maxV / 2, pct)));

  //  Near the min and the max
  assert((fptest_close_pct(std::midpoint(maxV * T(0.75), maxV * T(0.50)), maxV * T(0.625), pct)));
  assert((fptest_close_pct(std::midpoint(maxV * T(0.50), maxV * T(0.75)), maxV * T(0.625), pct)));
  assert((fptest_close_pct(std::midpoint(minV * T(2), minV * T(8)), minV * T(5), pct)));

  //  Big numbers of different signs
  assert((fptest_close_pct(std::midpoint(maxV * T(0.75), maxV * T(-0.5)), maxV * T(0.125), pct)));
  assert((fptest_close_pct(std::midpoint(maxV * T(-0.75), maxV * T(0.5)), maxV * T(-0.125), pct)));

  //  Denormalized values
  //  TODO

  //  Check two values "close to each other"
  T d1 = T(3.14);
  T d0 = std::nextafter(d1, T(2));
  T d2 = std::nextafter(d1, T(5));
  assert(d0 < d1); // sanity checking
  assert(d1 < d2); // sanity checking

#if defined(__PPC__) && (defined(__LONG_DOUBLE_128__) && __LONG_DOUBLE_128__) &&                                       \
    !(defined(__LONG_DOUBLE_IEEE128__) && __LONG_DOUBLE_IEEE128__)
  //  For 128 bit long double implemented as 2 doubles on PowerPC,
  //  nextafterl() of libm gives imprecise results which fails the
  //  midpoint() tests below. So skip the test for this case.
  if constexpr (sizeof(T) != 16)
#endif
  {
    //  Since there's nothing in between, the midpoint has to be one or the other
    T res;
    res = std::midpoint(d0, d1);
    assert(res == d0 || res == d1);
    assert(d0 <= res);
    assert(res <= d1);
    res = std::midpoint(d1, d0);
    assert(res == d0 || res == d1);
    assert(d0 <= res);
    assert(res <= d1);

    res = std::midpoint(d1, d2);
    assert(res == d1 || res == d2);
    assert(d1 <= res);
    assert(res <= d2);
    res = std::midpoint(d2, d1);
    assert(res == d1 || res == d2);
    assert(d1 <= res);
    assert(res <= d2);
  }
}

int main(int, char**) {
  fp_test<float>();
  fp_test<double>();
  fp_test<long double>();

  return 0;
}