// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// SPDX-FileCopyrightText: Copyright Contributors to the Kokkos project

#ifndef KOKKOS_STD_ALGORITHMS_REPLACE_IMPL_HPP
#define KOKKOS_STD_ALGORITHMS_REPLACE_IMPL_HPP

#include <Kokkos_Macros.hpp>
#ifdef KOKKOS_ENABLE_EXPERIMENTAL_CXX20_MODULES
import kokkos.core;
#else
#include <Kokkos_Core.hpp>
#endif
#include "Kokkos_Constraints.hpp"
#include "Kokkos_HelperPredicates.hpp"
#include <string>

namespace Kokkos {
namespace Experimental {
namespace Impl {

template <class InputIterator, class ValueType>
struct StdReplaceFunctor {
  using index_type = typename InputIterator::difference_type;
  InputIterator m_first;
  ValueType m_old_value;
  ValueType m_new_value;

  KOKKOS_FUNCTION
  void operator()(index_type i) const {
    if (m_first[i] == m_old_value) {
      m_first[i] = m_new_value;
    }
  }

  KOKKOS_FUNCTION
  StdReplaceFunctor(InputIterator first, ValueType old_value,
                    ValueType new_value)
      : m_first(std::move(first)),
        m_old_value(std::move(old_value)),
        m_new_value(std::move(new_value)) {}
};

template <class ExecutionSpace, class IteratorType, class ValueType>
void replace_exespace_impl(const std::string& label, const ExecutionSpace& ex,
                           IteratorType first, IteratorType last,
                           const ValueType& old_value,
                           const ValueType& new_value) {
  // checks
  Impl::static_assert_random_access_and_accessible(ex, first);
  Impl::expect_valid_range(first, last);

  // run
  const auto num_elements = Kokkos::Experimental::distance(first, last);
  ::Kokkos::parallel_for(label,
                         RangePolicy<ExecutionSpace>(ex, 0, num_elements),
                         StdReplaceFunctor(first, old_value, new_value));
  ex.fence("Kokkos::replace: fence after operation");
}

template <class TeamHandleType, class IteratorType, class ValueType>
KOKKOS_FUNCTION void replace_team_impl(const TeamHandleType& teamHandle,
                                       IteratorType first, IteratorType last,
                                       const ValueType& old_value,
                                       const ValueType& new_value) {
  // checks
  Impl::static_assert_random_access_and_accessible(teamHandle, first);
  Impl::expect_valid_range(first, last);

  // run
  const auto num_elements = Kokkos::Experimental::distance(first, last);
  ::Kokkos::parallel_for(TeamThreadRange(teamHandle, 0, num_elements),
                         StdReplaceFunctor(first, old_value, new_value));
  teamHandle.team_barrier();
}

}  // namespace Impl
}  // namespace Experimental
}  // namespace Kokkos

#endif
