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

// Modifications Copyright (c) 2025 Advanced Micro Devices, Inc.
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
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// furnished to do so, subject to the following conditions:
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// THE SOFTWARE.

// <numeric>

// template <class _Float>
// _Tp midpoint(_Float __a, _Float __b) noexcept
//

#include <cuda/std/cassert>
#include <cuda/std/cmath>
#include <cuda/std/numeric>

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

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

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

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

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

template <typename T>
__host__ __device__ void fp_test()
{
  static_assert(cuda::std::is_same_v<T, decltype(cuda::std::midpoint(T(), T()))>);
  static_assert(noexcept(cuda::std::midpoint(T(), T())));

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

  //  Things that can be compared exactly
  assert((cuda::std::midpoint(T(0), T(0)) == T(0)));
  assert((cuda::std::midpoint(T(2), T(4)) == T(3)));
  assert((cuda::std::midpoint(T(4), T(2)) == T(3)));
  assert((cuda::std::midpoint(T(3), T(4)) == T(3.5)));
  assert((cuda::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(cuda::std::midpoint(T(1.3), T(11.4)), T(6.35), pct)));
  assert((fptest_close_pct(cuda::std::midpoint(T(11.33), T(31.45)), T(21.39), pct)));
  assert((fptest_close_pct(cuda::std::midpoint(T(-1.3), T(11.4)), T(5.05), pct)));
  assert((fptest_close_pct(cuda::std::midpoint(T(11.4), T(-1.3)), T(5.05), pct)));
  assert((fptest_close_pct(cuda::std::midpoint(T(0.1), T(0.4)), T(0.25), pct)));

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

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

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

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

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

#if !TEST_COMPILER(NVRTC) && !defined(TEST_COMPILER_HIPRTC) // missing nextafter
  //  Check two values "close to each other"
  T d1 = T(3.14);
  T d0 = cuda::std::nextafter(d1, T(2));
  T d2 = cuda::std::nextafter(d1, T(5));
  assert(d0 < d1); // sanity checking
  assert(d1 < d2); // sanity checking

  //  Since there's nothing in between, the midpoint has to be one or the other
  T res;
  res = cuda::std::midpoint(d0, d1);
  assert(res == d0 || res == d1);
  assert(d0 <= res);
  assert(res <= d1);
  res = cuda::std::midpoint(d1, d0);
  assert(res == d0 || res == d1);
  assert(d0 <= res);
  assert(res <= d1);

  res = cuda::std::midpoint(d1, d2);
  assert(res == d1 || res == d2);
  assert(d1 <= res);
  assert(res <= d2);
  res = cuda::std::midpoint(d2, d1);
  assert(res == d1 || res == d2);
  assert(d1 <= res);
  assert(res <= d2);
#endif // !TEST_COMPILER(NVRTC)
}

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

  return 0;
}
