//  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).

//

// Copyright (c) 2011 The LevelDB Authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file. See the AUTHORS file for names of contributors.

#pragma once

#include <atomic>

#include <string>

#include "rocksdb/status.h"

#include "rocksdb/system_clock.h"

namespace ROCKSDB_NAMESPACE {

// A SystemClock that can "mock" sleep and counts its operations.

class EmulatedSystemClock : public SystemClockWrapper {

 private:

  // Something to return when mocking current time

  const int64_t maybe_starting_time_;

  std::atomic<int> sleep_counter_{0};

  std::atomic<int> cpu_counter_{0};

  std::atomic<int64_t> addon_microseconds_{0};

  // Do not modify in the env of a running DB (could cause deadlock)

  std::atomic<bool> time_elapse_only_sleep_;

  bool no_slowdown_;

 public:

  explicit EmulatedSystemClock(const std::shared_ptr<SystemClock>& base,

                               bool time_elapse_only_sleep = false);

  static const char* kClassName() { return "TimeEmulatedSystemClock"; }

  const char* Name() const override { return kClassName(); }

  void SleepForMicroseconds(int micros) override {

    sleep_counter_++;

    if (no_slowdown_ || time_elapse_only_sleep_) {

      addon_microseconds_.fetch_add(micros);

    }

    if (!no_slowdown_) {

      SystemClockWrapper::SleepForMicroseconds(micros);

    }

  }

  void MockSleepForMicroseconds(int64_t micros) {

    sleep_counter_++;

    assert(no_slowdown_);

    addon_microseconds_.fetch_add(micros);

  }

  void MockSleepForSeconds(int64_t seconds) {

    sleep_counter_++;

    assert(no_slowdown_);

    addon_microseconds_.fetch_add(seconds * 1000000);

  }

  void SetTimeElapseOnlySleep(bool enabled) {

    // We cannot set these before destroying the last DB because they might

    // cause a deadlock or similar without the appropriate options set in

    // the DB.

    time_elapse_only_sleep_ = enabled;

    no_slowdown_ = enabled;

  }

  bool IsTimeElapseOnlySleep() const { return time_elapse_only_sleep_.load(); }

  void SetMockSleep(bool enabled = true) { no_slowdown_ = enabled; }

  bool IsMockSleepEnabled() const { return no_slowdown_; }

  int GetSleepCounter() const { return sleep_counter_.load(); }

  Status GetCurrentTime(int64_t* unix_time) override {

    Status s;

    if (time_elapse_only_sleep_) {

      *unix_time = maybe_starting_time_;

    } else {

      s = SystemClockWrapper::GetCurrentTime(unix_time);

    }

    if (s.ok()) {

      // mock microseconds elapsed to seconds of time

      *unix_time += addon_microseconds_.load() / 1000000;

    }

    return s;

  }

  uint64_t CPUNanos() override {

    cpu_counter_++;

    return SystemClockWrapper::CPUNanos();

  }

  uint64_t CPUMicros() override {

    cpu_counter_++;

    return SystemClockWrapper::CPUMicros();

  }

  uint64_t NowNanos() override {

    return (time_elapse_only_sleep_ ? 0 : SystemClockWrapper::NowNanos()) +

           addon_microseconds_.load() * 1000;

  }

  uint64_t NowMicros() override {

    return (time_elapse_only_sleep_ ? 0 : SystemClockWrapper::NowMicros()) +

           addon_microseconds_.load();

  }

  int GetCpuCounter() const { return cpu_counter_.load(); }

  void ResetCounters() {

    cpu_counter_.store(0);

    sleep_counter_.store(0);

  }

};

}  // namespace ROCKSDB_NAMESPACE