//  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 <algorithm>

#include <atomic>

#include <chrono>

#include <deque>

#include "port/port.h"

#include "rocksdb/env.h"

#include "rocksdb/rate_limiter.h"

#include "rocksdb/status.h"

#include "rocksdb/system_clock.h"

#include "util/mutexlock.h"

#include "util/random.h"

namespace ROCKSDB_NAMESPACE {

class GenericRateLimiter : public RateLimiter {

 public:

  GenericRateLimiter(int64_t refill_bytes, int64_t refill_period_us,

                     int32_t fairness, RateLimiter::Mode mode,

                     const std::shared_ptr<SystemClock>& clock, bool auto_tuned,

                     int64_t single_burst_bytes);

  virtual ~GenericRateLimiter();

  // This API allows user to dynamically change rate limiter's bytes per second.

  void SetBytesPerSecond(int64_t bytes_per_second) override;

  Status SetSingleBurstBytes(int64_t single_burst_bytes) override;

  // Request for token to write bytes. If this request can not be satisfied,

  // the call is blocked. Caller is responsible to make sure

  // bytes <= GetSingleBurstBytes() and bytes >= 0. Negative bytes

  // passed in will be rounded up to 0.

  using RateLimiter::Request;

  void Request(const int64_t bytes, const Env::IOPriority pri,

               Statistics* stats) override;

  int64_t GetSingleBurstBytes() const override {

    int64_t raw_single_burst_bytes =

        raw_single_burst_bytes_.load(std::memory_order_relaxed);

    if (raw_single_burst_bytes == 0) {

      return refill_bytes_per_period_.load(std::memory_order_relaxed);

    }

    return raw_single_burst_bytes;

  }

  int64_t GetTotalBytesThrough(

      const Env::IOPriority pri = Env::IO_TOTAL) const override {

    MutexLock g(&request_mutex_);

    if (pri == Env::IO_TOTAL) {

      int64_t total_bytes_through_sum = 0;

      for (int i = Env::IO_LOW; i < Env::IO_TOTAL; ++i) {

        total_bytes_through_sum += total_bytes_through_[i];

      }

      return total_bytes_through_sum;

    }

    return total_bytes_through_[pri];

  }

  int64_t GetTotalRequests(

      const Env::IOPriority pri = Env::IO_TOTAL) const override {

    MutexLock g(&request_mutex_);

    if (pri == Env::IO_TOTAL) {

      int64_t total_requests_sum = 0;

      for (int i = Env::IO_LOW; i < Env::IO_TOTAL; ++i) {

        total_requests_sum += total_requests_[i];

      }

      return total_requests_sum;

    }

    return total_requests_[pri];

  }

  Status GetTotalPendingRequests(

      int64_t* total_pending_requests,

      const Env::IOPriority pri = Env::IO_TOTAL) const override {

    assert(total_pending_requests != nullptr);

    MutexLock g(&request_mutex_);

    if (pri == Env::IO_TOTAL) {

      int64_t total_pending_requests_sum = 0;

      for (int i = Env::IO_LOW; i < Env::IO_TOTAL; ++i) {

        total_pending_requests_sum += static_cast<int64_t>(queue_[i].size());

      }

      *total_pending_requests = total_pending_requests_sum;

    } else {

      *total_pending_requests = static_cast<int64_t>(queue_[pri].size());

    }

    return Status::OK();

  }

  int64_t GetBytesPerSecond() const override {

    return rate_bytes_per_sec_.load(std::memory_order_relaxed);

  }

  virtual void TEST_SetClock(std::shared_ptr<SystemClock> clock) {

    MutexLock g(&request_mutex_);

    clock_ = std::move(clock);

    next_refill_us_ = NowMicrosMonotonicLocked();

  }

 private:

  static constexpr int kMicrosecondsPerSecond = 1000000;

  void RefillBytesAndGrantRequestsLocked();

  std::vector<Env::IOPriority> GeneratePriorityIterationOrderLocked();

  int64_t CalculateRefillBytesPerPeriodLocked(int64_t rate_bytes_per_sec);

  Status TuneLocked();

  void SetBytesPerSecondLocked(int64_t bytes_per_second);

  uint64_t NowMicrosMonotonicLocked() {

    return clock_->NowNanos() / std::milli::den;

  }

  // This mutex guard all internal states

  mutable port::Mutex request_mutex_;

  const int64_t refill_period_us_;

  std::atomic<int64_t> rate_bytes_per_sec_;

  std::atomic<int64_t> refill_bytes_per_period_;

  // This value is validated but unsanitized (may be zero).

  std::atomic<int64_t> raw_single_burst_bytes_;

  std::shared_ptr<SystemClock> clock_;

  bool stop_;

  port::CondVar exit_cv_;

  int32_t requests_to_wait_;

  int64_t total_requests_[Env::IO_TOTAL];

  int64_t total_bytes_through_[Env::IO_TOTAL];

  int64_t available_bytes_;

  int64_t next_refill_us_;

  int32_t fairness_;

  Random rnd_;

  struct Req;

  std::deque<Req*> queue_[Env::IO_TOTAL];

  bool wait_until_refill_pending_;

  bool auto_tuned_;

  int64_t num_drains_;

  const int64_t max_bytes_per_sec_;

  std::chrono::microseconds tuned_time_;

};

}  // namespace ROCKSDB_NAMESPACE