//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.

//  This source code is licensed under both the GPLv2 (found in the

//  COPYING file in the root directory) and Apache 2.0 License

//  (found in the LICENSE.Apache file in the root directory).

//

#pragma once

#include "monitoring/perf_level_imp.h"

#include "monitoring/statistics_impl.h"

#include "rocksdb/system_clock.h"

namespace ROCKSDB_NAMESPACE {

class PerfStepTimer {

 public:

  explicit PerfStepTimer(

      uint64_t* metric, SystemClock* clock = nullptr, bool use_cpu_time = false,

      PerfLevel enable_level = PerfLevel::kEnableTimeExceptForMutex,

      Statistics* statistics = nullptr, uint32_t ticker_type = 0)

      : perf_counter_enabled_(perf_level >= enable_level),

        use_cpu_time_(use_cpu_time),

        ticker_type_(ticker_type),

        clock_((perf_counter_enabled_ || statistics != nullptr)

                   ? (clock ? clock : SystemClock::Default().get())

                   : nullptr),

        start_(0),

        metric_(metric),

        statistics_(statistics) {}

  ~PerfStepTimer() { Stop(); }

  void Start() {

    if (perf_counter_enabled_ || statistics_ != nullptr) {

      start_ = time_now();

    }

  }

  void Measure() {

    if (start_) {

      uint64_t now = time_now();

      *metric_ += now - start_;

      start_ = now;

    }

  }

  void Stop() {

    if (start_) {

      uint64_t duration = time_now() - start_;

      if (perf_counter_enabled_) {

        *metric_ += duration;

      }

      if (statistics_ != nullptr) {

        RecordTick(statistics_, ticker_type_, duration);

      }

      start_ = 0;

    }

  }

 private:

  uint64_t time_now() {

    if (!use_cpu_time_) {

      return clock_->NowNanos();

    } else {

      return clock_->CPUNanos();

    }

  }

  const bool perf_counter_enabled_;

  const bool use_cpu_time_;

  uint32_t ticker_type_;

  SystemClock* const clock_;

  uint64_t start_;

  uint64_t* metric_;

  Statistics* statistics_;

};

}  // namespace ROCKSDB_NAMESPACE