#include <thrust/adjacent_difference.h>
#include <thrust/device_free.h>
#include <thrust/device_malloc.h>
#include <thrust/execution_policy.h>

#include <unittest/unittest.h>

struct detect_wrong_difference
{
  using difference_type   = void;
  using value_type        = long long;
  using pointer           = void;
  using reference         = detect_wrong_difference;
  using iterator_category = ::cuda::std::output_iterator_tag;

  bool* flag;

  _CCCL_HOST_DEVICE detect_wrong_difference operator++() const
  {
    return *this;
  }
  _CCCL_HOST_DEVICE detect_wrong_difference operator*() const
  {
    return *this;
  }
  template <typename Difference>
  _CCCL_HOST_DEVICE detect_wrong_difference operator+(Difference) const
  {
    return *this;
  }
  template <typename Index>
  _CCCL_HOST_DEVICE detect_wrong_difference operator[](Index) const
  {
    return *this;
  }

  _CCCL_DEVICE void operator=(long long difference) const
  {
    if (difference != 1)
    {
      *flag = false;
    }
  }
};

void TestAdjacentDifferenceWithBigIndexesHelper(int magnitude)
{
  thrust::counting_iterator<long long> begin(1);
  thrust::counting_iterator<long long> end = begin + (1ll << magnitude);
  ASSERT_EQUAL(::cuda::std::distance(begin, end), 1ll << magnitude);

  thrust::device_ptr<bool> all_differences_correct = thrust::device_malloc<bool>(1);
  *all_differences_correct                         = true;

  detect_wrong_difference out = {thrust::raw_pointer_cast(all_differences_correct)};

  thrust::adjacent_difference(thrust::device, begin, end, out);

  bool all_differences_correct_h = *all_differences_correct;
  thrust::device_free(all_differences_correct);

  ASSERT_EQUAL(all_differences_correct_h, true);
}

void TestAdjacentDifferenceWithBigIndexes()
{
  TestAdjacentDifferenceWithBigIndexesHelper(30);
  TestAdjacentDifferenceWithBigIndexesHelper(31);
  TestAdjacentDifferenceWithBigIndexesHelper(32);
  TestAdjacentDifferenceWithBigIndexesHelper(33);
}
DECLARE_UNITTEST(TestAdjacentDifferenceWithBigIndexes);