/*!
 * Copyright (c) 2016-2026 Microsoft Corporation. All rights reserved.
 * Copyright (c) 2016-2026 The LightGBM developers. All rights reserved.
 * Licensed under the MIT License. See LICENSE file in the project root for license information.
 */
#include <LightGBM/dataset.h>
#include <LightGBM/utils/common.h>

#include <set>
#include <string>
#include <unordered_map>
#include <vector>

#ifndef LGB_R_BUILD
#include "../arrow/array.hpp"
#endif  // LGB_R_BUILD

namespace LightGBM {

Metadata::Metadata() {
  num_weights_ = 0;
  num_init_score_ = 0;
  num_data_ = 0;
  num_queries_ = 0;
  num_positions_ = 0;
  weight_load_from_file_ = false;
  position_load_from_file_ = false;
  query_load_from_file_ = false;
  init_score_load_from_file_ = false;
  #ifdef USE_CUDA
  cuda_metadata_ = nullptr;
  #endif  // USE_CUDA
}

void Metadata::Init(const char* data_filename) {
  data_filename_ = data_filename;
  // for lambdarank, it needs query data for partition data in distributed learning
  LoadQueryBoundaries();
  LoadWeights();
  LoadPositions();
  CalculateQueryWeights();
  LoadInitialScore(data_filename_);
}

Metadata::~Metadata() {
}

void Metadata::Init(data_size_t num_data, int weight_idx, int query_idx) {
  num_data_ = num_data;
  label_ = std::vector<label_t>(num_data_);
  if (weight_idx >= 0) {
    if (!weights_.empty()) {
      Log::Info("Using weights in data file, ignoring the additional weights file");
      weights_.clear();
    }
    weights_ = std::vector<label_t>(num_data_, 0.0f);
    num_weights_ = num_data_;
    weight_load_from_file_ = false;
  }
  if (query_idx >= 0) {
    if (!query_boundaries_.empty()) {
      Log::Info("Using query id in data file, ignoring the additional query file");
      query_boundaries_.clear();
    }
    if (!query_weights_.empty()) {
      query_weights_.clear();
    }
    queries_ = std::vector<data_size_t>(num_data_, 0);
    query_load_from_file_ = false;
  }
}

void Metadata::InitByReference(data_size_t num_data, const Metadata* reference) {
  int has_weights = reference->num_weights_ > 0;
  int has_init_scores = reference->num_init_score_ > 0;
  int has_queries = reference->num_queries_ > 0;
  int nclasses = reference->num_init_score_classes();
  Init(num_data, has_weights, has_init_scores, has_queries, nclasses);
}

void Metadata::Init(data_size_t num_data, int32_t has_weights, int32_t has_init_scores, int32_t has_queries, int32_t nclasses) {
  num_data_ = num_data;
  label_ = std::vector<label_t>(num_data_);
  if (has_weights) {
    if (!weights_.empty()) {
      Log::Fatal("Calling Init() on Metadata weights that have already been initialized");
    }
    weights_.resize(num_data_, 0.0f);
    num_weights_ = num_data_;
    weight_load_from_file_ = false;
  }
  if (has_init_scores) {
    if (!init_score_.empty()) {
      Log::Fatal("Calling Init() on Metadata initial scores that have already been initialized");
    }
    num_init_score_ = static_cast<int64_t>(num_data) * nclasses;
    init_score_.resize(num_init_score_, 0);
  }
  if (has_queries) {
    if (!query_weights_.empty()) {
      Log::Fatal("Calling Init() on Metadata queries that have already been initialized");
    }
    queries_.resize(num_data_, 0);
    query_load_from_file_ = false;
  }
}

void Metadata::Init(const Metadata& fullset, const data_size_t* used_indices, data_size_t num_used_indices) {
  num_data_ = num_used_indices;

  label_.resize(num_used_indices);
#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (num_used_indices >= 1024)
  for (data_size_t i = 0; i < num_used_indices; ++i) {
    label_[i] = fullset.label_[used_indices[i]];
  }

  if (!fullset.weights_.empty()) {
    weights_ = std::vector<label_t>(num_used_indices);
    num_weights_ = num_used_indices;
#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (num_used_indices >= 1024)
    for (data_size_t i = 0; i < num_used_indices; ++i) {
      weights_[i] = fullset.weights_[used_indices[i]];
    }
  } else {
    num_weights_ = 0;
  }

  if (!fullset.init_score_.empty()) {
    int num_class = static_cast<int>(fullset.num_init_score_ / fullset.num_data_);
    init_score_ = std::vector<double>(static_cast<size_t>(num_used_indices) * num_class);
    num_init_score_ = static_cast<int64_t>(num_used_indices) * num_class;
    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
    for (int k = 0; k < num_class; ++k) {
      const size_t offset_dest = static_cast<size_t>(k) * num_data_;
      const size_t offset_src = static_cast<size_t>(k) * fullset.num_data_;
      for (data_size_t i = 0; i < num_used_indices; ++i) {
        init_score_[offset_dest + i] = fullset.init_score_[offset_src + used_indices[i]];
      }
    }
  } else {
    num_init_score_ = 0;
  }

  if (!fullset.query_boundaries_.empty()) {
    std::vector<data_size_t> used_query;
    data_size_t data_idx = 0;
    for (data_size_t qid = 0; qid < num_queries_ && data_idx < num_used_indices; ++qid) {
      data_size_t start = fullset.query_boundaries_[qid];
      data_size_t end = fullset.query_boundaries_[qid + 1];
      data_size_t len = end - start;
      if (used_indices[data_idx] > start) {
        continue;
      } else if (used_indices[data_idx] == start) {
        if (num_used_indices >= data_idx + len && used_indices[data_idx + len - 1] == end - 1) {
          used_query.push_back(qid);
          data_idx += len;
        } else {
          Log::Fatal("Data partition error, data didn't match queries");
        }
      } else {
        Log::Fatal("Data partition error, data didn't match queries");
      }
    }
    query_boundaries_ = std::vector<data_size_t>(used_query.size() + 1);
    num_queries_ = static_cast<data_size_t>(used_query.size());
    query_boundaries_[0] = 0;
    for (data_size_t i = 0; i < num_queries_; ++i) {
      data_size_t qid = used_query[i];
      data_size_t len = fullset.query_boundaries_[qid + 1] - fullset.query_boundaries_[qid];
      query_boundaries_[i + 1] = query_boundaries_[i] + len;
    }
  } else {
    num_queries_ = 0;
  }
}

void Metadata::PartitionLabel(const std::vector<data_size_t>& used_indices) {
  if (used_indices.empty()) {
    return;
  }
  auto old_label = label_;
  num_data_ = static_cast<data_size_t>(used_indices.size());
  label_ = std::vector<label_t>(num_data_);
#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (num_data_ >= 1024)
  for (data_size_t i = 0; i < num_data_; ++i) {
    label_[i] = old_label[used_indices[i]];
  }
  old_label.clear();
}

void Metadata::CalculateQueryBoundaries() {
  if (!queries_.empty()) {
    // need convert query_id to boundaries
    std::vector<data_size_t> tmp_buffer;
    data_size_t last_qid = -1;
    data_size_t cur_cnt = 0;
    for (data_size_t i = 0; i < num_data_; ++i) {
      if (last_qid != queries_[i]) {
        if (cur_cnt > 0) {
          tmp_buffer.push_back(cur_cnt);
        }
        cur_cnt = 0;
        last_qid = queries_[i];
      }
      ++cur_cnt;
    }
    tmp_buffer.push_back(cur_cnt);
    query_boundaries_ = std::vector<data_size_t>(tmp_buffer.size() + 1);
    num_queries_ = static_cast<data_size_t>(tmp_buffer.size());
    query_boundaries_[0] = 0;
    for (size_t i = 0; i < tmp_buffer.size(); ++i) {
      query_boundaries_[i + 1] = query_boundaries_[i] + tmp_buffer[i];
    }
    CalculateQueryWeights();
    queries_.clear();
  }
}

void Metadata::CheckOrPartition(data_size_t num_all_data, const std::vector<data_size_t>& used_data_indices) {
  if (used_data_indices.empty()) {
     CalculateQueryBoundaries();
    // check weights
    if (!weights_.empty() && num_weights_ != num_data_) {
      weights_.clear();
      num_weights_ = 0;
      Log::Fatal("Weights size doesn't match data size");
    }

    // check positions
    if (!positions_.empty() && num_positions_ != num_data_) {
      Log::Fatal("Positions size (%i) doesn't match data size (%i)", num_positions_, num_data_);
      positions_.clear();
      num_positions_ = 0;
    }

    // check query boundaries
    if (!query_boundaries_.empty() && query_boundaries_[num_queries_] != num_data_) {
      query_boundaries_.clear();
      num_queries_ = 0;
      Log::Fatal("Query size doesn't match data size");
    }

    // contain initial score file
    if (!init_score_.empty() && (num_init_score_ % num_data_) != 0) {
      init_score_.clear();
      num_init_score_ = 0;
      Log::Fatal("Initial score size doesn't match data size");
    }
  } else {
    if (!queries_.empty()) {
      Log::Fatal("Cannot used query_id for distributed training");
    }
    data_size_t num_used_data = static_cast<data_size_t>(used_data_indices.size());
    // check weights
    if (weight_load_from_file_) {
      if (weights_.size() > 0 && num_weights_ != num_all_data) {
        weights_.clear();
        num_weights_ = 0;
        Log::Fatal("Weights size doesn't match data size");
      }
      // get local weights
      if (!weights_.empty()) {
        auto old_weights = weights_;
        num_weights_ = num_data_;
        weights_ = std::vector<label_t>(num_data_);
#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512)
        for (int i = 0; i < static_cast<int>(used_data_indices.size()); ++i) {
          weights_[i] = old_weights[used_data_indices[i]];
        }
        old_weights.clear();
      }
    }
    // check positions
    if (position_load_from_file_) {
      if (positions_.size() > 0 && num_positions_ != num_all_data) {
        positions_.clear();
        num_positions_ = 0;
        Log::Fatal("Positions size (%i) doesn't match data size (%i)", num_positions_, num_data_);
      }
      // get local positions
      if (!positions_.empty()) {
        auto old_positions = positions_;
        num_positions_ = num_data_;
        positions_ = std::vector<data_size_t>(num_data_);
        #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512)
        for (int i = 0; i < static_cast<int>(used_data_indices.size()); ++i) {
          positions_[i] = old_positions[used_data_indices[i]];
        }
        old_positions.clear();
      }
    }
    if (query_load_from_file_) {
      // check query boundaries
      if (!query_boundaries_.empty() && query_boundaries_[num_queries_] != num_all_data) {
        query_boundaries_.clear();
        num_queries_ = 0;
        Log::Fatal("Query size doesn't match data size");
      }
      // get local query boundaries
      if (!query_boundaries_.empty()) {
        std::vector<data_size_t> used_query;
        data_size_t data_idx = 0;
        for (data_size_t qid = 0; qid < num_queries_ && data_idx < num_used_data; ++qid) {
          data_size_t start = query_boundaries_[qid];
          data_size_t end = query_boundaries_[qid + 1];
          data_size_t len = end - start;
          if (used_data_indices[data_idx] > start) {
            continue;
          } else if (used_data_indices[data_idx] == start) {
            if (num_used_data >= data_idx + len && used_data_indices[data_idx + len - 1] == end - 1) {
              used_query.push_back(qid);
              data_idx += len;
            } else {
              Log::Fatal("Data partition error, data didn't match queries");
            }
          } else {
            Log::Fatal("Data partition error, data didn't match queries");
          }
        }
        auto old_query_boundaries = query_boundaries_;
        query_boundaries_ = std::vector<data_size_t>(used_query.size() + 1);
        num_queries_ = static_cast<data_size_t>(used_query.size());
        query_boundaries_[0] = 0;
        for (data_size_t i = 0; i < num_queries_; ++i) {
          data_size_t qid = used_query[i];
          data_size_t len = old_query_boundaries[qid + 1] - old_query_boundaries[qid];
          query_boundaries_[i + 1] = query_boundaries_[i] + len;
        }
        old_query_boundaries.clear();
      }
    }
    if (init_score_load_from_file_) {
      // contain initial score file
      if (!init_score_.empty() && (num_init_score_ % num_all_data) != 0) {
        init_score_.clear();
        num_init_score_ = 0;
        Log::Fatal("Initial score size doesn't match data size");
      }

      // get local initial scores
      if (!init_score_.empty()) {
        auto old_scores = init_score_;
        int num_class = static_cast<int>(num_init_score_ / num_all_data);
        num_init_score_ = static_cast<int64_t>(num_data_) * num_class;
        init_score_ = std::vector<double>(num_init_score_);
#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
        for (int k = 0; k < num_class; ++k) {
          const size_t offset_dest = static_cast<size_t>(k) * num_data_;
          const size_t offset_src = static_cast<size_t>(k) * num_all_data;
          for (size_t i = 0; i < used_data_indices.size(); ++i) {
            init_score_[offset_dest + i] = old_scores[offset_src + used_data_indices[i]];
          }
        }
        old_scores.clear();
      }
    }
    // re-calculate query weight
    CalculateQueryWeights();
  }
  if (num_queries_ > 0) {
    Log::Debug("Number of queries in %s: %i. Average number of rows per query: %f.",
      data_filename_.c_str(), static_cast<int>(num_queries_), static_cast<double>(num_data_) / num_queries_);
  }
}

template <typename It>
void Metadata::SetInitScoresFromIterator(It first, It last) {
  std::lock_guard<std::mutex> lock(mutex_);
  // Clear init scores on empty input
  if (last - first == 0) {
    init_score_.clear();
    num_init_score_ = 0;
    return;
  }
  if (((last - first) % num_data_) != 0) {
    Log::Fatal("Initial score size doesn't match data size");
  }
  if (init_score_.empty()) {
    init_score_.resize(last - first);
  }
  num_init_score_ = last - first;

  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (num_init_score_ >= 1024)
  for (int64_t i = 0; i < num_init_score_; ++i) {
    init_score_[i] = Common::AvoidInf(first[i]);
  }
  init_score_load_from_file_ = false;

  #ifdef USE_CUDA
  if (cuda_metadata_ != nullptr) {
    cuda_metadata_->SetInitScore(init_score_.data(), init_score_.size());
  }
  #endif  // USE_CUDA
}

void Metadata::SetInitScore(const double* init_score, data_size_t len) {
  SetInitScoresFromIterator(init_score, init_score + len);
}

#ifndef LGB_R_BUILD
ArrowChunkedArray::View InitScoreView(const ArrowChunkedArray& chunked_array) {
  auto view = chunked_array.view();
  // For multiclass classification, the init scores are provided in multiple columns. In this
  // case, we must concatenate all fields of the chunked array.
  if (chunked_array.is_struct()) {
    std::vector<ArrowChunkedArray::View> concat_views;
    concat_views.reserve(chunked_array.get_num_fields());
    for (int64_t i = 0; i < chunked_array.get_num_fields(); ++i) {
      concat_views.push_back(view.field(i));
    }
    view = ArrowChunkedArray::View(concat_views);
  }
  return view;
}

void Metadata::SetInitScore(struct ArrowArrayStream* stream) {
  ArrowChunkedArray chunked_array(stream);
  auto view = InitScoreView(chunked_array);
  view.visit<double>([&](auto&& visitor) {
    SetInitScoresFromIterator(visitor.begin(), visitor.end());
  });
}

void Metadata::SetInitScore(int64_t n_chunks, struct ArrowArray* chunks,
                            struct ArrowSchema* schema) {
  ArrowChunkedArray chunked_array(n_chunks, chunks, schema);
  auto view = InitScoreView(chunked_array);
  view.visit<double>([&](auto&& visitor) {
    SetInitScoresFromIterator(visitor.begin(), visitor.end());
  });
}
#endif  // LGB_R_BUILD

void Metadata::InsertInitScores(const double* init_scores, data_size_t start_index, data_size_t len, data_size_t source_size) {
  if (num_init_score_ <= 0) {
    Log::Fatal("Inserting initial score data into dataset with no initial scores");
  }
  if (start_index + len > num_data_) {
    // Note that len here is row count, not num_init_score, so we compare against num_data
    Log::Fatal("Inserted initial score data is too large for dataset");
  }
  if (init_score_.empty()) {
    init_score_.resize(num_init_score_);
  }

  int nclasses = num_init_score_classes();

  for (int32_t col = 0; col < nclasses; ++col) {
    int32_t dest_offset = num_data_ * col + start_index;
    // We need to use source_size here, because len might not equal size (due to a partially loaded dataset)
    int32_t source_offset = source_size * col;
    memcpy(init_score_.data() + dest_offset, init_scores + source_offset, sizeof(double) * len);
  }
  init_score_load_from_file_ = false;
  // CUDA is handled after all insertions are complete
}

template <typename It>
void Metadata::SetLabelsFromIterator(It first, It last) {
  std::lock_guard<std::mutex> lock(mutex_);
  if (num_data_ != last - first) {
    Log::Fatal("Length of labels differs from the length of #data");
  }
  if (label_.empty()) {
    label_.resize(num_data_);
  }

  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (num_data_ >= 1024)
  for (data_size_t i = 0; i < num_data_; ++i) {
    label_[i] = Common::AvoidInf(first[i]);
  }

  #ifdef USE_CUDA
  if (cuda_metadata_ != nullptr) {
    cuda_metadata_->SetLabel(label_.data(), label_.size());
  }
  #endif  // USE_CUDA
}

void Metadata::SetLabel(const label_t* label, data_size_t len) {
  if (label == nullptr) {
    Log::Fatal("label cannot be nullptr");
  }
  SetLabelsFromIterator(label, label + len);
}

#ifndef LGB_R_BUILD
void Metadata::SetLabel(struct ArrowArrayStream* stream) {
  ArrowChunkedArray chunked_array(stream);
  chunked_array.view().visit<label_t>([&](auto&& visitor) {
    SetLabelsFromIterator(visitor.begin(), visitor.end());
  });
}

void Metadata::SetLabel(int64_t n_chunks, struct ArrowArray* chunks,
                        struct ArrowSchema* schema) {
  ArrowChunkedArray chunked_array(n_chunks, chunks, schema);
  chunked_array.view().visit<label_t>([&](auto&& visitor) {
    SetLabelsFromIterator(visitor.begin(), visitor.end());
  });
}
#endif  // LGB_R_BUILD

void Metadata::InsertLabels(const label_t* labels, data_size_t start_index, data_size_t len) {
  if (labels == nullptr) {
    Log::Fatal("label cannot be nullptr");
  }
  if (start_index + len > num_data_) {
    Log::Fatal("Inserted label data is too large for dataset");
  }
  if (label_.empty()) {
    label_.resize(num_data_);
  }

  memcpy(label_.data() + start_index, labels, sizeof(label_t) * len);

  // CUDA is handled after all insertions are complete
}

template <typename It>
void Metadata::SetWeightsFromIterator(It first, It last) {
  std::lock_guard<std::mutex> lock(mutex_);
  // Clear weights on empty input
  if (last - first == 0) {
    weights_.clear();
    num_weights_ = 0;
    return;
  }
  if (num_data_ != last - first) {
    Log::Fatal("Length of weights differs from the length of #data");
  }
  if (weights_.empty()) {
    weights_.resize(num_data_);
  }
  num_weights_ = num_data_;

  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (num_weights_ >= 1024)
  for (data_size_t i = 0; i < num_weights_; ++i) {
    weights_[i] = Common::AvoidInf(first[i]);
  }
  CalculateQueryWeights();
  weight_load_from_file_ = false;

  #ifdef USE_CUDA
  if (cuda_metadata_ != nullptr) {
    cuda_metadata_->SetWeights(weights_.data(), weights_.size());
  }
  #endif  // USE_CUDA
}

void Metadata::SetWeights(const label_t* weights, data_size_t len) {
  SetWeightsFromIterator(weights, weights + len);
}

#ifndef LGB_R_BUILD
void Metadata::SetWeights(struct ArrowArrayStream* stream) {
  ArrowChunkedArray chunked_array(stream);
  chunked_array.view().visit<label_t>([&](auto&& visitor) {
    SetWeightsFromIterator(visitor.begin(), visitor.end());
  });
}

void Metadata::SetWeights(int64_t n_chunks, struct ArrowArray* chunks,
                          struct ArrowSchema* schema) {
  ArrowChunkedArray chunked_array(n_chunks, chunks, schema);
  chunked_array.view().visit<label_t>([&](auto&& visitor) {
    SetWeightsFromIterator(visitor.begin(), visitor.end());
  });
}
#endif  // LGB_R_BUILD

void Metadata::InsertWeights(const label_t* weights, data_size_t start_index, data_size_t len) {
  if (!weights) {
    Log::Fatal("Passed null weights");
  }
  if (num_weights_ <= 0) {
    Log::Fatal("Inserting weight data into dataset with no weights");
  }
  if (start_index + len > num_weights_) {
    Log::Fatal("Inserted weight data is too large for dataset");
  }
  if (weights_.empty()) {
    weights_.resize(num_weights_);
  }

  memcpy(weights_.data() + start_index, weights, sizeof(label_t) * len);

  weight_load_from_file_ = false;
  // CUDA is handled after all insertions are complete
}

template <typename It>
void Metadata::SetQueriesFromIterator(It first, It last) {
  std::lock_guard<std::mutex> lock(mutex_);
  // Clear query boundaries on empty input
  if (last - first == 0) {
    query_boundaries_.clear();
    num_queries_ = 0;
    return;
  }

  data_size_t sum = 0;
  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static) reduction(+:sum)
  for (data_size_t i = 0; i < static_cast<data_size_t>(last - first); ++i) {
    sum += first[i];
  }
  if (num_data_ != sum) {
    Log::Fatal("Sum of query counts (%i) differs from the length of #data (%i)", num_data_, sum);
  }
  num_queries_ = last - first;

  query_boundaries_.resize(num_queries_ + 1);
  query_boundaries_[0] = 0;
  for (data_size_t i = 0; i < num_queries_; ++i) {
    query_boundaries_[i + 1] = query_boundaries_[i] + first[i];
  }
  CalculateQueryWeights();
  query_load_from_file_ = false;

  #ifdef USE_CUDA
  if (cuda_metadata_ != nullptr) {
    if (query_weights_.size() > 0) {
      CHECK_EQ(query_weights_.size(), static_cast<size_t>(num_queries_));
      cuda_metadata_->SetQuery(query_boundaries_.data(), query_weights_.data(), num_queries_);
    } else {
      cuda_metadata_->SetQuery(query_boundaries_.data(), nullptr, num_queries_);
    }
  }
  #endif  // USE_CUDA
}

void Metadata::SetQuery(const data_size_t* query, data_size_t len) {
  SetQueriesFromIterator(query, query + len);
}

#ifndef LGB_R_BUILD
void Metadata::SetQuery(struct ArrowArrayStream* stream) {
  ArrowChunkedArray chunked_array(stream);
  chunked_array.view().visit<data_size_t>([&](auto&& visitor) {
    SetQueriesFromIterator(visitor.begin(), visitor.end());
  });
}

void Metadata::SetQuery(int64_t n_chunks, struct ArrowArray* chunks,
                        struct ArrowSchema* schema) {
  ArrowChunkedArray chunked_array(n_chunks, chunks, schema);
  chunked_array.view().visit<data_size_t>([&](auto&& visitor) {
    SetQueriesFromIterator(visitor.begin(), visitor.end());
  });
}
#endif  // LGB_R_BUILD

void Metadata::SetPosition(const data_size_t* positions, data_size_t len) {
  std::lock_guard<std::mutex> lock(mutex_);
  // save to nullptr
  if (positions == nullptr || len == 0) {
    positions_.clear();
    num_positions_ = 0;
    return;
  }
  #ifdef USE_CUDA
  Log::Fatal("Positions in learning to rank is not supported in CUDA version yet.");
  #endif  // USE_CUDA
  if (num_data_ != len) {
    Log::Fatal("Positions size (%i) doesn't match data size (%i)", len, num_data_);
  }
  if (positions_.empty()) {
    positions_.resize(num_data_);
  } else {
    Log::Warning("Overwriting positions in dataset.");
  }
  num_positions_ = num_data_;

  position_load_from_file_ = false;

  position_ids_.clear();
  std::unordered_map<data_size_t, int> map_id2pos;
  for (data_size_t i = 0; i < num_positions_; ++i) {
    if (map_id2pos.count(positions[i]) == 0) {
      int pos = static_cast<int>(map_id2pos.size());
      map_id2pos[positions[i]] = pos;
      position_ids_.push_back(std::to_string(positions[i]));
    }
  }

  Log::Debug("number of unique positions found = %ld", position_ids_.size());

  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (num_positions_ >= 1024)
  for (data_size_t i = 0; i < num_positions_; ++i) {
    positions_[i] = map_id2pos.at(positions[i]);
  }
}

#ifndef LGB_R_BUILD
void Metadata::SetPosition(struct ArrowArrayStream* stream) {
  ArrowChunkedArray chunked_array(stream);
  chunked_array.view().visit<data_size_t>([&](auto&& visitor) {
    std::vector<data_size_t> positions;
    positions.reserve(visitor.end() - visitor.begin());
    for (auto it = visitor.begin(); it != visitor.end(); ++it) {
      positions.push_back(*it);
    }
    SetPosition(positions.data(), static_cast<data_size_t>(positions.size()));
  });
}

void Metadata::SetPosition(int64_t n_chunks, struct ArrowArray* chunks,
                           struct ArrowSchema* schema) {
  ArrowChunkedArray chunked_array(n_chunks, chunks, schema);
  chunked_array.view().visit<data_size_t>([&](auto&& visitor) {
    std::vector<data_size_t> positions;
    positions.reserve(visitor.end() - visitor.begin());
    for (auto it = visitor.begin(); it != visitor.end(); ++it) {
      positions.push_back(*it);
    }
    SetPosition(positions.data(), static_cast<data_size_t>(positions.size()));
  });
}
#endif  // LGB_R_BUILD

void Metadata::InsertQueries(const data_size_t* queries, data_size_t start_index, data_size_t len) {
  if (!queries) {
    Log::Fatal("Passed null queries");
  }
  if (queries_.size() <= 0) {
    Log::Fatal("Inserting query data into dataset with no queries");
  }
  if (static_cast<size_t>(start_index + len) > queries_.size()) {
    Log::Fatal("Inserted query data is too large for dataset");
  }

  memcpy(queries_.data() + start_index, queries, sizeof(data_size_t) * len);

  query_load_from_file_ = false;
  // CUDA is handled after all insertions are complete
}

void Metadata::LoadWeights() {
  num_weights_ = 0;
  std::string weight_filename(data_filename_);
  // default weight file name
  weight_filename.append(".weight");
  TextReader<size_t> reader(weight_filename.c_str(), false);
  reader.ReadAllLines();
  if (reader.Lines().empty()) {
    return;
  }
  Log::Info("Loading weights...");
  num_weights_ = static_cast<data_size_t>(reader.Lines().size());
  weights_ = std::vector<label_t>(num_weights_);
  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
  for (data_size_t i = 0; i < num_weights_; ++i) {
    double tmp_weight = 0.0f;
    Common::Atof(reader.Lines()[i].c_str(), &tmp_weight);
    weights_[i] = Common::AvoidInf(static_cast<label_t>(tmp_weight));
  }
  weight_load_from_file_ = true;
}

void Metadata::LoadPositions() {
  num_positions_ = 0;
  std::string position_filename(data_filename_);
  // default position file name
  position_filename.append(".position");
  TextReader<size_t> reader(position_filename.c_str(), false);
  reader.ReadAllLines();
  if (reader.Lines().empty()) {
    return;
  }
  Log::Info("Loading positions from %s ...", position_filename.c_str());
  num_positions_ = static_cast<data_size_t>(reader.Lines().size());
  positions_ = std::vector<data_size_t>(num_positions_);
  position_ids_ = std::vector<std::string>();
  std::unordered_map<std::string, data_size_t> map_id2pos;
  for (data_size_t i = 0; i < num_positions_; ++i) {
    std::string& line = reader.Lines()[i];
    if (map_id2pos.count(line) == 0) {
      map_id2pos[line] = static_cast<data_size_t>(position_ids_.size());
      position_ids_.push_back(line);
    }
    positions_[i] = map_id2pos.at(line);
  }
  position_load_from_file_ = true;
}

void Metadata::LoadInitialScore(const std::string& data_filename) {
  num_init_score_ = 0;
  std::string init_score_filename(data_filename);
  init_score_filename = std::string(data_filename);
  // default init_score file name
  init_score_filename.append(".init");
  TextReader<size_t> reader(init_score_filename.c_str(), false);
  reader.ReadAllLines();
  if (reader.Lines().empty()) {
    return;
  }
  Log::Info("Loading initial scores...");

  // use first line to count number class
  int num_class = static_cast<int>(Common::Split(reader.Lines()[0].c_str(), '\t').size());
  data_size_t num_line = static_cast<data_size_t>(reader.Lines().size());
  num_init_score_ = static_cast<int64_t>(num_line) * num_class;

  init_score_ = std::vector<double>(num_init_score_);
  if (num_class == 1) {
    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
    for (data_size_t i = 0; i < num_line; ++i) {
      double tmp = 0.0f;
      Common::Atof(reader.Lines()[i].c_str(), &tmp);
      init_score_[i] = Common::AvoidInf(static_cast<double>(tmp));
    }
  } else {
    std::vector<std::string> oneline_init_score;
    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
    for (data_size_t i = 0; i < num_line; ++i) {
      double tmp = 0.0f;
      oneline_init_score = Common::Split(reader.Lines()[i].c_str(), '\t');
      if (static_cast<int>(oneline_init_score.size()) != num_class) {
        Log::Fatal("Invalid initial score file. Redundant or insufficient columns");
      }
      for (int k = 0; k < num_class; ++k) {
        Common::Atof(oneline_init_score[k].c_str(), &tmp);
        init_score_[static_cast<size_t>(k) * num_line + i] = Common::AvoidInf(static_cast<double>(tmp));
      }
    }
  }
  init_score_load_from_file_ = true;
}

void Metadata::LoadQueryBoundaries() {
  num_queries_ = 0;
  std::string query_filename(data_filename_);
  // default query file name
  query_filename.append(".query");
  TextReader<size_t> reader(query_filename.c_str(), false);
  reader.ReadAllLines();
  if (reader.Lines().empty()) {
    return;
  }
  Log::Info("Calculating query boundaries...");
  query_boundaries_ = std::vector<data_size_t>(reader.Lines().size() + 1);
  num_queries_ = static_cast<data_size_t>(reader.Lines().size());
  query_boundaries_[0] = 0;
  for (size_t i = 0; i < reader.Lines().size(); ++i) {
    int tmp_cnt;
    Common::Atoi(reader.Lines()[i].c_str(), &tmp_cnt);
    query_boundaries_[i + 1] = query_boundaries_[i] + static_cast<data_size_t>(tmp_cnt);
  }
  query_load_from_file_ = true;
}

void Metadata::CalculateQueryWeights() {
  if (weights_.size() == 0 || query_boundaries_.size() == 0) {
    return;
  }
  query_weights_.clear();
  Log::Info("Calculating query weights...");
  query_weights_ = std::vector<label_t>(num_queries_);
  for (data_size_t i = 0; i < num_queries_; ++i) {
    query_weights_[i] = 0.0f;
    for (data_size_t j = query_boundaries_[i]; j < query_boundaries_[i + 1]; ++j) {
      query_weights_[i] += weights_[j];
    }
    query_weights_[i] /= (query_boundaries_[i + 1] - query_boundaries_[i]);
  }
}

void Metadata::InsertAt(data_size_t start_index,
  data_size_t count,
  const float* labels,
  const float* weights,
  const double* init_scores,
  const int32_t* queries) {
  if (num_data_ < count + start_index) {
    Log::Fatal("Length of metadata is too long to append #data");
  }
  InsertLabels(labels, start_index, count);
  if (weights) {
    InsertWeights(weights, start_index, count);
  }
  if (init_scores) {
    InsertInitScores(init_scores, start_index, count, count);
  }
  if (queries) {
    InsertQueries(queries, start_index, count);
  }
}

void Metadata::FinishLoad() {
  CalculateQueryBoundaries();
}

#ifdef USE_CUDA
void Metadata::CreateCUDAMetadata(const int gpu_device_id) {
  cuda_metadata_.reset(new CUDAMetadata(gpu_device_id));
  cuda_metadata_->Init(label_, weights_, query_boundaries_, query_weights_, init_score_);
}
#endif  // USE_CUDA

void Metadata::LoadFromMemory(const void* memory) {
  const char* mem_ptr = reinterpret_cast<const char*>(memory);

  num_data_ = *(reinterpret_cast<const data_size_t*>(mem_ptr));
  mem_ptr += VirtualFileWriter::AlignedSize(sizeof(num_data_));
  num_weights_ = *(reinterpret_cast<const data_size_t*>(mem_ptr));
  mem_ptr += VirtualFileWriter::AlignedSize(sizeof(num_weights_));
  num_queries_ = *(reinterpret_cast<const data_size_t*>(mem_ptr));
  mem_ptr += VirtualFileWriter::AlignedSize(sizeof(num_queries_));

  if (!label_.empty()) {
    label_.clear();
  }
  label_ = std::vector<label_t>(num_data_);
  std::memcpy(label_.data(), mem_ptr, sizeof(label_t) * num_data_);
  mem_ptr += VirtualFileWriter::AlignedSize(sizeof(label_t) * num_data_);

  if (num_weights_ > 0) {
    if (!weights_.empty()) {
      weights_.clear();
    }
    weights_ = std::vector<label_t>(num_weights_);
    std::memcpy(weights_.data(), mem_ptr, sizeof(label_t) * num_weights_);
    mem_ptr += VirtualFileWriter::AlignedSize(sizeof(label_t) * num_weights_);
    weight_load_from_file_ = true;
  }
  if (num_queries_ > 0) {
    if (!query_boundaries_.empty()) {
      query_boundaries_.clear();
    }
    query_boundaries_ = std::vector<data_size_t>(num_queries_ + 1);
    std::memcpy(query_boundaries_.data(), mem_ptr, sizeof(data_size_t) * (num_queries_ + 1));
    mem_ptr += VirtualFileWriter::AlignedSize(sizeof(data_size_t) *
                                              (num_queries_ + 1));
    query_load_from_file_ = true;
  }
  CalculateQueryWeights();
}

void Metadata::SaveBinaryToFile(BinaryWriter* writer) const {
  writer->AlignedWrite(&num_data_, sizeof(num_data_));
  writer->AlignedWrite(&num_weights_, sizeof(num_weights_));
  writer->AlignedWrite(&num_queries_, sizeof(num_queries_));
  writer->AlignedWrite(label_.data(), sizeof(label_t) * num_data_);
  if (!weights_.empty()) {
    writer->AlignedWrite(weights_.data(), sizeof(label_t) * num_weights_);
  }
  if (!query_boundaries_.empty()) {
    writer->AlignedWrite(query_boundaries_.data(),
                         sizeof(data_size_t) * (num_queries_ + 1));
  }
  if (num_init_score_ > 0) {
    Log::Warning("Please note that `init_score` is not saved in binary file.\n"
      "If you need it, please set it again after loading Dataset.");
  }
}

size_t Metadata::SizesInByte() const {
  size_t size = VirtualFileWriter::AlignedSize(sizeof(num_data_)) +
                VirtualFileWriter::AlignedSize(sizeof(num_weights_)) +
                VirtualFileWriter::AlignedSize(sizeof(num_queries_));
  size += VirtualFileWriter::AlignedSize(sizeof(label_t) * num_data_);
  if (!weights_.empty()) {
    size += VirtualFileWriter::AlignedSize(sizeof(label_t) * num_weights_);
  }
  if (!query_boundaries_.empty()) {
    size += VirtualFileWriter::AlignedSize(sizeof(data_size_t) *
                                           (num_queries_ + 1));
  }
  return size;
}


}  // namespace LightGBM