// SPDX-FileCopyrightText: Copyright (c) 2024, NVIDIA CORPORATION. All rights reserved.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#pragma once

#include <thrust/detail/config.h>

#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
#  pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
#  pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
#  pragma system_header
#endif // no system header

#include <thrust/detail/config.h>

#include <thrust/iterator/counting_iterator.h>
#include <thrust/iterator/iterator_adaptor.h>
#include <thrust/iterator/tabulate_output_iterator.h>

THRUST_NAMESPACE_BEGIN

template <typename BinaryFunction, typename System, typename DifferenceT>
class tabulate_output_iterator;

namespace detail
{
// Proxy reference that invokes a BinaryFunction with the index of the dereferenced iterator and the assigned value
template <typename BinaryFunction, typename DifferenceT>
class tabulate_output_iterator_proxy
{
public:
  _CCCL_HOST_DEVICE tabulate_output_iterator_proxy(BinaryFunction fun, DifferenceT index)
      : fun(fun)
      , index(index)
  {}

  _CCCL_EXEC_CHECK_DISABLE
  template <typename T>
  _CCCL_HOST_DEVICE tabulate_output_iterator_proxy operator=(const T& x)
  {
    fun(index, x);
    return *this;
  }

private:
  BinaryFunction fun;
  DifferenceT index;
};

// Alias template for the iterator_adaptor instantiation to be used for tabulate_output_iterator
template <typename BinaryFunction, typename System, typename DifferenceT>
using make_tabulate_output_iterator_base =
  iterator_adaptor<tabulate_output_iterator<BinaryFunction, System, DifferenceT>,
                   counting_iterator<DifferenceT>,
                   void,
                   System,
                   use_default,
                   tabulate_output_iterator_proxy<BinaryFunction, DifferenceT>>;

// Register tabulate_output_iterator_proxy with 'is_proxy_reference' from
// type_traits to enable its use with algorithms.
template <class BinaryFunction, class OutputIterator>
struct is_proxy_reference<tabulate_output_iterator_proxy<BinaryFunction, OutputIterator>> : true_type
{};
} // namespace detail

//! \addtogroup iterators
//! \{

//! \addtogroup fancyiterator Fancy Iterators
//! \ingroup iterators
//! \{

//! \p tabulate_output_iterator is a special kind of output iterator which, whenever a value is assigned to a
//! dereferenced iterator, calls the given callable with the index that corresponds to the offset of the dereferenced
//! iterator and the assigned value.
//!
//! The following code snippet demonstrated how to create a \p tabulate_output_iterator which prints the index and the
//! assigned value.
//!
//! \code
//! #include <thrust/iterator/tabulate_output_iterator.h>
//!
//! // note: functor inherits form binary function
//! struct print_op
//! {
//!   __host__ __device__
//!   void operator()(int index, float value) const
//!   {
//!     printf("%d: %f\n", index, value);
//!   }
//! };
//!
//! int main()
//! {
//!   auto tabulate_it = thrust::make_tabulate_output_iterator(print_op{});
//!
//!   tabulate_it[0] =  1.0f;    // prints: 0: 1.0
//!   tabulate_it[1] =  3.0f;    // prints: 1: 3.0
//!   tabulate_it[9] =  5.0f;    // prints: 9: 5.0
//! }
//! \endcode
//!
//! \see make_tabulate_output_iterator
template <typename BinaryFunction, typename System = use_default, typename DifferenceT = ptrdiff_t>
class tabulate_output_iterator : public detail::make_tabulate_output_iterator_base<BinaryFunction, System, DifferenceT>
{
public:
  //! \cond
  using super_t = detail::make_tabulate_output_iterator_base<BinaryFunction, System, DifferenceT>;

  friend class iterator_core_access;
  //! \endcond

  tabulate_output_iterator() = default;

  //!  This constructor takes as argument a \c BinaryFunction and copies it to a new \p tabulate_output_iterator
  //!
  //! \param fun A \c BinaryFunction called whenever a value is assigned to this \p tabulate_output_iterator.
  _CCCL_HOST_DEVICE tabulate_output_iterator(BinaryFunction fun)
      : fun(fun)
  {}

private:
  //! \cond
  _CCCL_HOST_DEVICE typename super_t::reference dereference() const
  {
    return detail::tabulate_output_iterator_proxy<BinaryFunction, DifferenceT>{fun, *this->base()};
  }

  BinaryFunction fun;
  //! \endcond
};

//! \p make_tabulate_output_iterator creates a \p tabulate_output_iterator from a \c BinaryFunction.
//!
//! \param fun The \c BinaryFunction invoked whenever assigning to a dereferenced \p tabulate_output_iterator
//! \see tabulate_output_iterator
template <typename BinaryFunction>
tabulate_output_iterator<BinaryFunction> _CCCL_HOST_DEVICE make_tabulate_output_iterator(BinaryFunction fun)
{
  return tabulate_output_iterator<BinaryFunction>(fun);
}

//! \} // end fancyiterators
//! \} // end iterators

THRUST_NAMESPACE_END
