/**
 * Copyright 2020-2024 by XGBoost contributors
 */
#include <gtest/gtest.h>

#include <oneapi/dpl/random>

#include "../../../plugin/sycl/tree/hist_updater.h"
#include "../../../plugin/sycl/device_manager.h"

#include "../helpers.h"

namespace xgboost::sycl::tree {

// Use this class to test the protected methods of HistUpdater
template <typename GradientSumT>
class TestHistUpdater : public HistUpdater<GradientSumT> {
 public:
  TestHistUpdater(::sycl::queue qu,
                  const xgboost::tree::TrainParam& param,
                  std::unique_ptr<TreeUpdater> pruner,
                  FeatureInteractionConstraintHost int_constraints_,
                  DMatrix const* fmat) : HistUpdater<GradientSumT>(qu, param, std::move(pruner),
                                                                   int_constraints_, fmat) {}

  void TestInitSampling(const USMVector<GradientPair, MemoryType::on_device> &gpair,
                        USMVector<size_t, MemoryType::on_device>* row_indices) {
    HistUpdater<GradientSumT>::InitSampling(gpair, row_indices);
  }

  const auto* TestInitData(Context const * ctx,
                    const common::GHistIndexMatrix& gmat,
                    const USMVector<GradientPair, MemoryType::on_device> &gpair,
                    const DMatrix& fmat,
                    const RegTree& tree) {
    HistUpdater<GradientSumT>::InitData(ctx, gmat, gpair, fmat, tree);
    return &(HistUpdater<GradientSumT>::row_set_collection_.Data());
  }
};

template <typename GradientSumT>
void TestHistUpdaterSampling(const xgboost::tree::TrainParam& param) {
  const size_t num_rows = 1u << 12;
  const size_t num_columns = 1;

  Context ctx;
  ctx.UpdateAllowUnknown(Args{{"device", "sycl"}});

  DeviceManager device_manager;
  auto qu = device_manager.GetQueue(ctx.Device());
  ObjInfo task{ObjInfo::kRegression};

  auto p_fmat = RandomDataGenerator{num_rows, num_columns, 0.0}.GenerateDMatrix();

  FeatureInteractionConstraintHost int_constraints;
  std::unique_ptr<TreeUpdater> pruner{TreeUpdater::Create("prune", &ctx, &task)};

  TestHistUpdater<GradientSumT> updater(qu, param, std::move(pruner), int_constraints, p_fmat.get());

  USMVector<size_t, MemoryType::on_device> row_indices_0(&qu, num_rows);
  USMVector<size_t, MemoryType::on_device> row_indices_1(&qu, num_rows);
  USMVector<GradientPair, MemoryType::on_device> gpair(&qu, num_rows);
  auto* gpair_ptr = gpair.Data();
  qu.submit([&](::sycl::handler& cgh) {
    cgh.parallel_for<>(::sycl::range<1>(::sycl::range<1>(num_rows)),
                                        [=](::sycl::item<1> pid) {
      uint64_t i = pid.get_linear_id();

      constexpr uint32_t seed = 777;
      oneapi::dpl::minstd_rand engine(seed, i);
      oneapi::dpl::uniform_real_distribution<GradientPair::ValueT> distr(-1., 1.);
      gpair_ptr[i] = {distr(engine), distr(engine)};
    });
  }).wait();

  updater.TestInitSampling(gpair, &row_indices_0);
  
  size_t n_samples = row_indices_0.Size();
  // Half of gpairs have neg hess
  ASSERT_LT(n_samples, num_rows * 0.5 * param.subsample * 1.2);
  ASSERT_GT(n_samples, num_rows * 0.5 * param.subsample / 1.2);

  // Check if two lanunches generate different realisations:
  updater.TestInitSampling(gpair, &row_indices_1);
  if (row_indices_1.Size() == n_samples) {
    std::vector<size_t> row_indices_0_host(n_samples);
    std::vector<size_t> row_indices_1_host(n_samples);
    qu.memcpy(row_indices_0_host.data(), row_indices_0.Data(), n_samples * sizeof(size_t)).wait();
    qu.memcpy(row_indices_1_host.data(), row_indices_1.Data(), n_samples * sizeof(size_t)).wait();

    // The order in row_indices_0 and row_indices_1 can be different
    std::set<size_t> rows;
    for (auto row : row_indices_0_host) {
      rows.insert(row);
    }

    size_t num_diffs = 0;
    for (auto row : row_indices_1_host) {
      if (rows.count(row) == 0) num_diffs++;
    }

    ASSERT_NE(num_diffs, 0);
  }

}

template <typename GradientSumT>
void TestHistUpdaterInitData(const xgboost::tree::TrainParam& param, bool has_neg_hess) {
  const size_t num_rows = 1u << 8;
  const size_t num_columns = 1;
  const size_t n_bins = 32;

  Context ctx;
  ctx.UpdateAllowUnknown(Args{{"device", "sycl"}});

  DeviceManager device_manager;
  auto qu = device_manager.GetQueue(ctx.Device());
  ObjInfo task{ObjInfo::kRegression};

  auto p_fmat = RandomDataGenerator{num_rows, num_columns, 0.0}.GenerateDMatrix();

  FeatureInteractionConstraintHost int_constraints;
  std::unique_ptr<TreeUpdater> pruner{TreeUpdater::Create("prune", &ctx, &task)};

  TestHistUpdater<GradientSumT> updater(qu, param, std::move(pruner), int_constraints, p_fmat.get());

  USMVector<GradientPair, MemoryType::on_device> gpair(&qu, num_rows);
  auto* gpair_ptr = gpair.Data();
  qu.submit([&](::sycl::handler& cgh) {
    cgh.parallel_for<>(::sycl::range<1>(::sycl::range<1>(num_rows)),
                                        [=](::sycl::item<1> pid) {
      uint64_t i = pid.get_linear_id();

      constexpr uint32_t seed = 777;
      oneapi::dpl::minstd_rand engine(seed, i);
      GradientPair::ValueT smallest_hess_val = has_neg_hess ? -1. : 0.;
      oneapi::dpl::uniform_real_distribution<GradientPair::ValueT> distr(smallest_hess_val, 1.);
      gpair_ptr[i] = {distr(engine), distr(engine)};
    });
  }).wait();

  DeviceMatrix dmat;
  dmat.Init(qu, p_fmat.get());
  common::GHistIndexMatrix gmat;
  gmat.Init(qu, &ctx, dmat, n_bins);
  RegTree tree;

  const auto* row_indices = updater.TestInitData(&ctx, gmat, gpair, *p_fmat, tree);

  std::vector<size_t> row_indices_host(row_indices->Size());
  qu.memcpy(row_indices_host.data(), row_indices->DataConst(), row_indices->Size()*sizeof(size_t)).wait();

  if (!has_neg_hess) {
    for (size_t i = 0; i < num_rows; ++i) {
      ASSERT_EQ(row_indices_host[i], i);
    }
  } else {
    std::vector<GradientPair> gpair_host(num_rows);
    qu.memcpy(gpair_host.data(), gpair.Data(), num_rows*sizeof(GradientPair)).wait();

    std::set<size_t> rows;
    for (size_t i = 0; i < num_rows; ++i) {
      if (gpair_host[i].GetHess() >= 0.0f) {
        rows.insert(i);
      }
    }
    ASSERT_EQ(rows.size(), row_indices_host.size());
    for (size_t row_idx : row_indices_host) {
      ASSERT_EQ(rows.count(row_idx), 1);
    }
  }
}

TEST(SyclHistUpdater, Sampling) {
  xgboost::tree::TrainParam param;
  param.UpdateAllowUnknown(Args{{"subsample", "0.7"}});

  TestHistUpdaterSampling<float>(param);
  TestHistUpdaterSampling<double>(param);
}

TEST(SyclHistUpdater, InitData) {
  xgboost::tree::TrainParam param;
  param.UpdateAllowUnknown(Args{{"subsample", "1"}});

  TestHistUpdaterInitData<float>(param, true);
  TestHistUpdaterInitData<float>(param, false);

  TestHistUpdaterInitData<double>(param, true);
  TestHistUpdaterInitData<double>(param, false);
}

}  // namespace xgboost::sycl::tree