// Copyright (c) the JPEG XL Project Authors. All rights reserved.

//

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

// Functions for clustering similar histograms together.

#ifndef LIB_JXL_ENC_CLUSTER_H_

#define LIB_JXL_ENC_CLUSTER_H_

#include <cstddef>

#include <cstdint>

#include <cstring>

#include <vector>

#include "lib/jxl/base/common.h"

#include "lib/jxl/base/status.h"

#include "lib/jxl/enc_ans_params.h"

namespace jxl {

struct Histogram {

  Histogram() {

    total_count_ = 0;

    entropy_ = 0.0;

  }

  void Clear() {

    data_.clear();

    total_count_ = 0;

  }

  void Add(size_t symbol) {

    if (data_.size() <= symbol) {

      data_.resize(DivCeil(symbol + 1, kRounding) * kRounding);

    }

    ++data_[symbol];

    ++total_count_;

  }

  void AddHistogram(const Histogram& other) {

    if (other.data_.size() > data_.size()) {

      data_.resize(other.data_.size());

    }

    for (size_t i = 0; i < other.data_.size(); ++i) {

      data_[i] += other.data_[i];

    }

    total_count_ += other.total_count_;

  }

  size_t alphabet_size() const {

    for (int i = data_.size() - 1; i >= 0; --i) {

      if (data_[i] > 0) {

        return i + 1;

      }

    }

    return 1;

  }

  StatusOr<float> PopulationCost() const;

  float ShannonEntropy() const;

  std::vector<ANSHistBin> data_;

  size_t total_count_;

  mutable float entropy_;  // WARNING: not kept up-to-date.

  static constexpr size_t kRounding = 8;

};

Status ClusterHistograms(const HistogramParams& params,

                         const std::vector<Histogram>& in,

                         size_t max_histograms, std::vector<Histogram>* out,

                         std::vector<uint32_t>* histogram_symbols);

}  // namespace jxl

#endif  // LIB_JXL_ENC_CLUSTER_H_