#pragma once

#include <cstdint>

#include <string>

#include "envoy/config/metrics/v3/stats.pb.h"

#include "envoy/stats/histogram.h"

#include "envoy/stats/stats.h"

#include "envoy/stats/store.h"

#include "source/common/common/matchers.h"

#include "source/common/common/non_copyable.h"

#include "source/common/stats/metric_impl.h"

#include "circllhist.h"

namespace Envoy {

namespace Stats {

class HistogramSettingsImpl : public HistogramSettings {

public:

  HistogramSettingsImpl() = default;

  HistogramSettingsImpl(const envoy::config::metrics::v3::StatsConfig& config);

  // HistogramSettings

  const ConstSupportedBuckets& buckets(absl::string_view stat_name) const override;

  static ConstSupportedBuckets& defaultBuckets();

private:

  using Config = std::pair<Matchers::StringMatcherImpl<envoy::type::matcher::v3::StringMatcher>,

                           ConstSupportedBuckets>;

  const std::vector<Config> configs_{};

};

/**

 * Implementation of HistogramStatistics for circllhist.

 */

class HistogramStatisticsImpl final : public HistogramStatistics, NonCopyable {

public:

  HistogramStatisticsImpl();

  /**

   * HistogramStatisticsImpl object is constructed using the passed in histogram.

   * @param histogram_ptr pointer to the histogram for which stats will be calculated. This pointer

   * will not be retained.

   */

  HistogramStatisticsImpl(

      const histogram_t* histogram_ptr, Histogram::Unit unit = Histogram::Unit::Unspecified,

      ConstSupportedBuckets& supported_buckets = HistogramSettingsImpl::defaultBuckets());

  void refresh(const histogram_t* new_histogram_ptr);

  // HistogramStatistics

  std::string quantileSummary() const override;

  std::string bucketSummary() const override;

  const std::vector<double>& supportedQuantiles() const final;

  const std::vector<double>& computedQuantiles() const override { return computed_quantiles_; }

  ConstSupportedBuckets& supportedBuckets() const override { return supported_buckets_; }

  const std::vector<uint64_t>& computedBuckets() const override { return computed_buckets_; }

  std::vector<uint64_t> computeDisjointBuckets() const override;

  uint64_t sampleCount() const override { return sample_count_; }

  double sampleSum() const override { return sample_sum_; }

private:

  ConstSupportedBuckets& supported_buckets_;

  std::vector<double> computed_quantiles_;

  std::vector<uint64_t> computed_buckets_;

  uint64_t sample_count_{0};

  double sample_sum_{0};

  const Histogram::Unit unit_{Histogram::Unit::Unspecified};

};

class HistogramImplHelper : public MetricImpl<Histogram> {

public:

  HistogramImplHelper(StatName name, StatName tag_extracted_name,

                      const StatNameTagVector& stat_name_tags, SymbolTable& symbol_table)

      : MetricImpl<Histogram>(name, tag_extracted_name, stat_name_tags, symbol_table) {}

  HistogramImplHelper(SymbolTable& symbol_table) : MetricImpl<Histogram>(symbol_table) {}

  // RefcountInterface

  void incRefCount() override { refcount_helper_.incRefCount(); }

  bool decRefCount() override { return refcount_helper_.decRefCount(); }

  uint32_t use_count() const override { return refcount_helper_.use_count(); }

private:

  RefcountHelper refcount_helper_;

};

/**

 * Histogram implementation for the heap.

 */

class HistogramImpl : public HistogramImplHelper {

public:

  HistogramImpl(StatName name, Unit unit, Store& parent, StatName tag_extracted_name,

                const StatNameTagVector& stat_name_tags)

      : HistogramImplHelper(name, tag_extracted_name, stat_name_tags, parent.symbolTable()),

        unit_(unit), parent_(parent) {}

  ~HistogramImpl() override {

    // We must explicitly free the StatName here in order to supply the

    // SymbolTable reference. An RAII alternative would be to store a

    // reference to the SymbolTable in MetricImpl, which would cost 8 bytes

    // per stat.

    MetricImpl::clear(symbolTable());

  }

  // Stats::Histogram

  Unit unit() const override { return unit_; };

  void recordValue(uint64_t value) override { parent_.deliverHistogramToSinks(*this, value); }

  bool used() const override { return true; }

  bool hidden() const override { return false; }

  SymbolTable& symbolTable() final { return parent_.symbolTable(); }

private:

  Unit unit_;

  // This is used for delivering the histogram data to sinks.

  Store& parent_;

};

/**

 * Null histogram implementation.

 * No-ops on all calls and requires no underlying metric or data.

 */

class NullHistogramImpl : public HistogramImplHelper {

public:

  explicit NullHistogramImpl(SymbolTable& symbol_table)

      : HistogramImplHelper(symbol_table), symbol_table_(symbol_table) {}

  ~NullHistogramImpl() override { MetricImpl::clear(symbol_table_); }

  bool used() const override { return false; }

  bool hidden() const override { return false; }

  SymbolTable& symbolTable() override { return symbol_table_; }

  Unit unit() const override { return Unit::Null; };

  void recordValue(uint64_t) override {}

private:

  SymbolTable& symbol_table_;

};

} // namespace Stats

} // namespace Envoy