//@HEADER
// ************************************************************************
//
//                        Kokkos v. 4.0
//       Copyright (2022) National Technology & Engineering
//               Solutions of Sandia, LLC (NTESS).
//
// Under the terms of Contract DE-NA0003525 with NTESS,
// the U.S. Government retains certain rights in this software.
//
// Part of Kokkos, under the Apache License v2.0 with LLVM Exceptions.
// See https://kokkos.org/LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//@HEADER

#include <TestStdAlgorithmsCommon.hpp>
#ifdef KOKKOS_ENABLE_EXPERIMENTAL_CXX20_MODULES
#include <std_algorithms/impl/Kokkos_FunctorsForExclusiveScan.hpp>
#endif
#include <utility>
#include <iomanip>

namespace Test {
namespace stdalgos {
namespace EScan {

namespace KE = Kokkos::Experimental;

template <class ValueType>
struct UnifDist;

template <>
struct UnifDist<double> {
  using dist_type = std::uniform_real_distribution<double>;
  std::mt19937 m_gen;
  dist_type m_dist;

  UnifDist() : m_dist(0.05, 1.2) { m_gen.seed(1034343); }

  double operator()() { return m_dist(m_gen); }
};

template <>
struct UnifDist<int> {
  using dist_type = std::uniform_int_distribution<int>;
  std::mt19937 m_gen;
  dist_type m_dist;

  UnifDist() : m_dist(1, 3) { m_gen.seed(1034343); }

  int operator()() { return m_dist(m_gen); }
};

template <>
struct UnifDist<CustomValueType> {
  using dist_type = std::uniform_real_distribution<double>;
  std::mt19937 m_gen;
  dist_type m_dist;

  UnifDist() : m_dist(0.05, 1.2) { m_gen.seed(1034343); }

  CustomValueType operator()() { return m_dist(m_gen); }
};

template <class ViewType>
void fill_view(ViewType dest_view, const std::string& name) {
  using value_type = typename ViewType::value_type;
  using exe_space  = typename ViewType::execution_space;

  const std::size_t ext = dest_view.extent(0);
  using aux_view_t      = Kokkos::View<value_type*, exe_space>;
  aux_view_t aux_view("aux_view", ext);
  auto v_h = create_mirror_view(Kokkos::HostSpace(), aux_view);

  UnifDist<value_type> randObj;

  if (name == "empty") {
    // no op
  }

  else if (name == "one-element") {
    v_h(0) = static_cast<value_type>(1);
  }

  else if (name == "two-elements-a") {
    v_h(0) = static_cast<value_type>(1);
    v_h(1) = static_cast<value_type>(2);
  }

  else if (name == "two-elements-b") {
    v_h(0) = static_cast<value_type>(2);
    v_h(1) = static_cast<value_type>(-1);
  }

  else if (name == "small-a") {
    for (std::size_t i = 0; i < ext; ++i) {
      v_h(i) = static_cast<value_type>(i + 1);
    }
  }

  else if (name == "small-b") {
    for (std::size_t i = 0; i < ext; ++i) {
      v_h(i) = randObj();
    }
    v_h(5) = static_cast<value_type>(-2);
  }

  else if (name == "medium" || name == "large") {
    for (std::size_t i = 0; i < ext; ++i) {
      v_h(i) = randObj();
    }
  }

  else {
    FAIL() << "invalid choice";
  }

  Kokkos::deep_copy(aux_view, v_h);
  CopyFunctor<aux_view_t, ViewType> F1(aux_view, dest_view);
  Kokkos::parallel_for("copy", dest_view.extent(0), F1);
}

// I had to write my own because std::exclusive_scan is ONLY found with
// std=c++17
template <class it1, class it2, class ValType, class BopType>
void my_host_exclusive_scan(it1 first, it1 last, it2 dest, ValType init,
                            BopType bop) {
  const auto num_elements = last - first;
  if (num_elements > 0) {
    while (first < last - 1) {
      *(dest++) = init;
      init      = bop(*first++, init);
    }
    *dest = init;
  }
}

template <class ValueType>
struct MultiplyFunctor {
  KOKKOS_INLINE_FUNCTION
  ValueType operator()(const ValueType& a, const ValueType& b) const {
    return (a * b);
  }
};

template <class ValueType>
struct SumFunctor {
  KOKKOS_INLINE_FUNCTION
  ValueType operator()(const ValueType& a, const ValueType& b) const {
    return (a + b);
  }
};

struct VerifyData {
  template <class ViewType1, class ViewType2, class ValueType, class BinaryOp>
  void operator()(ViewType1 data_view,  // contains data
                  ViewType2 test_view,  // the view to test
                  ValueType init_value, BinaryOp bop) {
    //! always careful because views might not be deep copyable

    auto data_view_dc = create_deep_copyable_compatible_clone(data_view);
    auto data_view_h =
        create_mirror_view_and_copy(Kokkos::HostSpace(), data_view_dc);

    using gold_view_value_type = typename ViewType2::value_type;
    Kokkos::View<gold_view_value_type*, Kokkos::HostSpace> gold_h(
        "goldh", data_view.extent(0));
    my_host_exclusive_scan(KE::cbegin(data_view_h), KE::cend(data_view_h),
                           KE::begin(gold_h), init_value, bop);

    auto test_view_dc = create_deep_copyable_compatible_clone(test_view);
    auto test_view_h =
        create_mirror_view_and_copy(Kokkos::HostSpace(), test_view_dc);
    if (test_view_h.extent(0) > 0) {
      for (std::size_t i = 0; i < test_view_h.extent(0); ++i) {
        if (std::is_same_v<gold_view_value_type, int>) {
          ASSERT_EQ(gold_h(i), test_view_h(i));
        } else {
          const auto error =
              std::abs(static_cast<double>(gold_h(i) - test_view_h(i)));
          ASSERT_LT(error, 1e-10) << i << " " << std::setprecision(15) << error
                                  << static_cast<double>(test_view_h(i)) << " "
                                  << static_cast<double>(gold_h(i));
        }
      }
    }
  }

  template <class ViewType1, class ViewType2, class ValueType>
  void operator()(ViewType1 data_view,  // contains data
                  ViewType2 test_view,  // the view to test
                  ValueType init_value) {
    (*this)(data_view, test_view, init_value, SumFunctor<ValueType>());
  }
};

std::string value_type_to_string(int) { return "int"; }

std::string value_type_to_string(double) { return "double"; }

template <class Tag, class ValueType, class InfoType, class... OpOrEmpty>
void run_single_scenario(const InfoType& scenario_info, ValueType init_value,
                         OpOrEmpty... empty_or_op) {
  const auto name            = std::get<0>(scenario_info);
  const std::size_t view_ext = std::get<1>(scenario_info);

  auto view_dest = create_view<ValueType>(Tag{}, view_ext, "exclusive_scan");
  auto view_from = create_view<ValueType>(Tag{}, view_ext, "exclusive_scan");
  fill_view(view_from, name);
  // view_dest is filled with zeros before calling the algorithm everytime to
  // ensure the algorithm does something meaningful

  {
    fill_zero(view_dest);
    auto r = KE::exclusive_scan(exespace(), KE::cbegin(view_from),
                                KE::cend(view_from), KE::begin(view_dest),
                                init_value, empty_or_op...);
    ASSERT_EQ(r, KE::end(view_dest));
    VerifyData()(view_from, view_dest, init_value, empty_or_op...);
  }

  {
    fill_zero(view_dest);
    auto r = KE::exclusive_scan("label", exespace(), KE::cbegin(view_from),
                                KE::cend(view_from), KE::begin(view_dest),
                                init_value, empty_or_op...);
    ASSERT_EQ(r, KE::end(view_dest));
    VerifyData()(view_from, view_dest, init_value, empty_or_op...);
  }

  {
    fill_zero(view_dest);
    auto r = KE::exclusive_scan(exespace(), view_from, view_dest, init_value,
                                empty_or_op...);
    ASSERT_EQ(r, KE::end(view_dest));
    VerifyData()(view_from, view_dest, init_value, empty_or_op...);
  }

  {
    fill_zero(view_dest);
    auto r = KE::exclusive_scan("label", exespace(), view_from, view_dest,
                                init_value, empty_or_op...);
    ASSERT_EQ(r, KE::end(view_dest));
    VerifyData()(view_from, view_dest, init_value, empty_or_op...);
  }

  Kokkos::fence();
}

template <class Tag, class ValueType, class InfoType, class... OpOrEmpty>
void run_single_scenario_inplace(const InfoType& scenario_info,
                                 ValueType init_value,
                                 OpOrEmpty... empty_or_op) {
  const auto name            = std::get<0>(scenario_info);
  const std::size_t view_ext = std::get<1>(scenario_info);

  // since here we call the in-place operation, we need to use two views:
  // view1: filled according to what the scenario asks for and is not modified
  // view2: filled according to what the scenario asks for and used for the
  // in-place op Therefore, after the op is done, view2 should contain the
  // result of doing exclusive scan NOTE: view2 is filled below every time
  // because the algorithm acts in place

  auto view1 =
      create_view<ValueType>(Tag{}, view_ext, "exclusive_scan_inplace_view1");
  fill_view(view1, name);

  auto view2 =
      create_view<ValueType>(Tag{}, view_ext, "exclusive_scan_inplace_view2");
  {
    fill_view(view2, name);
    auto r = KE::exclusive_scan(exespace(), KE::cbegin(view2), KE::cend(view2),
                                KE::begin(view2), init_value, empty_or_op...);
    ASSERT_EQ(r, KE::end(view2));
    VerifyData()(view1, view2, init_value, empty_or_op...);
  }

  {
    fill_view(view2, name);
    auto r = KE::exclusive_scan("label", exespace(), KE::cbegin(view2),
                                KE::cend(view2), KE::begin(view2), init_value,
                                empty_or_op...);
    ASSERT_EQ(r, KE::end(view2));
    VerifyData()(view1, view2, init_value, empty_or_op...);
  }

  {
    fill_view(view2, name);
    auto r = KE::exclusive_scan(exespace(), view2, view2, init_value,
                                empty_or_op...);
    ASSERT_EQ(r, KE::end(view2));
    VerifyData()(view1, view2, init_value, empty_or_op...);
  }

  {
    fill_view(view2, name);
    auto r = KE::exclusive_scan("label", exespace(), view2, view2, init_value,
                                empty_or_op...);
    ASSERT_EQ(r, KE::end(view2));
    VerifyData()(view1, view2, init_value, empty_or_op...);
  }

  Kokkos::fence();
}

template <class Tag, class ValueType>
void run_exclusive_scan_all_scenarios() {
  const std::map<std::string, std::size_t> scenarios = {
      {"empty", 0},          {"one-element", 1}, {"two-elements-a", 2},
      {"two-elements-b", 2}, {"small-a", 9},     {"small-b", 13},
      {"medium", 1103},      {"large", 10513}};

  for (const auto& it : scenarios) {
    run_single_scenario<Tag, ValueType>(it, ValueType{0});
    run_single_scenario<Tag, ValueType>(it, ValueType{1});
    run_single_scenario<Tag, ValueType>(it, ValueType{-2});
    run_single_scenario<Tag, ValueType>(it, ValueType{3});

    run_single_scenario_inplace<Tag, ValueType>(it, ValueType{0});
    run_single_scenario_inplace<Tag, ValueType>(it, ValueType{-2});

#if !defined KOKKOS_ENABLE_OPENMPTARGET
    // custom multiply op is only run for small views otherwise it overflows
    if (it.first == "small-a" || it.first == "small-b") {
      using custom_bop_t = MultiplyFunctor<ValueType>;
      run_single_scenario<Tag, ValueType>(it, ValueType{0}, custom_bop_t());
      run_single_scenario<Tag, ValueType>(it, ValueType{1}, custom_bop_t());
      run_single_scenario<Tag, ValueType>(it, ValueType{-2}, custom_bop_t());
      run_single_scenario<Tag, ValueType>(it, ValueType{3}, custom_bop_t());

      run_single_scenario_inplace<Tag, ValueType>(it, ValueType{0},
                                                  custom_bop_t());
      run_single_scenario_inplace<Tag, ValueType>(it, ValueType{-2},
                                                  custom_bop_t());
    }

    using custom_bop_t = SumFunctor<ValueType>;
    run_single_scenario<Tag, ValueType>(it, ValueType{0}, custom_bop_t());
    run_single_scenario<Tag, ValueType>(it, ValueType{1}, custom_bop_t());
    run_single_scenario<Tag, ValueType>(it, ValueType{-2}, custom_bop_t());
    run_single_scenario<Tag, ValueType>(it, ValueType{3}, custom_bop_t());

    run_single_scenario_inplace<Tag, ValueType>(it, ValueType{0},
                                                custom_bop_t());
    run_single_scenario_inplace<Tag, ValueType>(it, ValueType{-2},
                                                custom_bop_t());
#endif
  }
}

TEST(std_algorithms_numeric_ops_test, exclusive_scan) {
  run_exclusive_scan_all_scenarios<DynamicTag, double>();
  run_exclusive_scan_all_scenarios<StridedThreeTag, double>();
  run_exclusive_scan_all_scenarios<DynamicTag, int>();
  run_exclusive_scan_all_scenarios<StridedThreeTag, int>();
  run_exclusive_scan_all_scenarios<DynamicTag, CustomValueType>();
  run_exclusive_scan_all_scenarios<StridedThreeTag, CustomValueType>();
}

TEST(std_algorithms_numeric_ops_test, exclusive_scan_functor) {
  int dummy       = 0;
  using view_type = Kokkos::View<int*, exespace>;
  view_type dummy_view("dummy_view", 0);
  using functor_type =
      Kokkos::Experimental::Impl::ExclusiveScanDefaultFunctorWithValueWrapper<
          exespace, int, int, view_type, view_type>;
  functor_type functor(dummy, dummy_view, dummy_view);
  using value_type = functor_type::value_type;

  value_type value1;
  functor.init(value1);
  ASSERT_EQ(value1.val, 0);
  ASSERT_EQ(value1.is_initial, true);

  value_type value2;
  value2.val        = 1;
  value2.is_initial = false;
  functor.join(value1, value2);
  ASSERT_EQ(value1.val, 1);
  ASSERT_EQ(value1.is_initial, false);

  functor.init(value1);
  functor.join(value2, value1);
  ASSERT_EQ(value2.val, 1);
  ASSERT_EQ(value2.is_initial, false);

  functor.init(value2);
  functor.join(value2, value1);
  ASSERT_EQ(value2.val, 0);
  ASSERT_EQ(value2.is_initial, true);

  value1.val        = 1;
  value1.is_initial = false;
  value2.val        = 2;
  value2.is_initial = false;
  functor.join(value2, value1);
  ASSERT_EQ(value2.val, 3);
  ASSERT_EQ(value2.is_initial, false);
}

}  // namespace EScan
}  // namespace stdalgos
}  // namespace Test