#include <thrust/functional.h>
#include <thrust/iterator/retag.h>
#include <thrust/partition.h>

#include <unittest/unittest.h>

template <typename T>
struct is_even
{
  _CCCL_HOST_DEVICE bool operator()(T x) const
  {
    return ((int) x % 2) == 0;
  }
};

template <typename Vector>
void TestIsPartitionedSimple()
{
  Vector v{1, 1, 1, 0};

  // empty partition
  ASSERT_EQUAL_QUIET(true, thrust::is_partitioned(v.begin(), v.begin(), ::cuda::std::identity{}));

  // one element true partition
  ASSERT_EQUAL_QUIET(true, thrust::is_partitioned(v.begin(), v.begin() + 1, ::cuda::std::identity{}));

  // just true partition
  ASSERT_EQUAL_QUIET(true, thrust::is_partitioned(v.begin(), v.begin() + 2, ::cuda::std::identity{}));

  // both true & false partitions
  ASSERT_EQUAL_QUIET(true, thrust::is_partitioned(v.begin(), v.end(), ::cuda::std::identity{}));

  // one element false partition
  ASSERT_EQUAL_QUIET(true, thrust::is_partitioned(v.begin() + 3, v.end(), ::cuda::std::identity{}));

  v = {1, 0, 1, 1};

  // not partitioned
  ASSERT_EQUAL_QUIET(false, thrust::is_partitioned(v.begin(), v.end(), ::cuda::std::identity{}));
}
DECLARE_VECTOR_UNITTEST(TestIsPartitionedSimple);

template <class Vector>
void TestIsPartitioned()
{
  using T = typename Vector::value_type;

  const size_t n = (1 << 16) + 13;

  Vector v = unittest::random_integers<T>(n);

  v[0] = 1;
  v[1] = 0;

  ASSERT_EQUAL(false, thrust::is_partitioned(v.begin(), v.end(), is_even<T>()));

  thrust::partition(v.begin(), v.end(), is_even<T>());

  ASSERT_EQUAL(true, thrust::is_partitioned(v.begin(), v.end(), is_even<T>()));
}
DECLARE_INTEGRAL_VECTOR_UNITTEST(TestIsPartitioned);

template <typename InputIterator, typename Predicate>
bool is_partitioned(my_system& system, InputIterator /*first*/, InputIterator, Predicate)
{
  system.validate_dispatch();
  return false;
}

void TestIsPartitionedDispatchExplicit()
{
  thrust::device_vector<int> vec(1);

  my_system sys(0);
  thrust::is_partitioned(sys, vec.begin(), vec.end(), 0);

  ASSERT_EQUAL(true, sys.is_valid());
}
DECLARE_UNITTEST(TestIsPartitionedDispatchExplicit);

template <typename InputIterator, typename Predicate>
bool is_partitioned(my_tag, InputIterator first, InputIterator, Predicate)
{
  *first = 13;
  return false;
}

void TestIsPartitionedDispatchImplicit()
{
  thrust::device_vector<int> vec(1);

  thrust::is_partitioned(thrust::retag<my_tag>(vec.begin()), thrust::retag<my_tag>(vec.end()), 0);

  ASSERT_EQUAL(13, vec.front());
}
DECLARE_UNITTEST(TestIsPartitionedDispatchImplicit);