//  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).

#include "db/trim_history_scheduler.h"

#include <cassert>

#include "db/column_family.h"

namespace ROCKSDB_NAMESPACE {

void TrimHistoryScheduler::ScheduleWork(ColumnFamilyData* cfd) {

  std::lock_guard<std::mutex> lock(checking_mutex_);

  cfd->Ref();

  cfds_.push_back(cfd);

  is_empty_.store(false, std::memory_order_relaxed);

}

ColumnFamilyData* TrimHistoryScheduler::TakeNextColumnFamily() {

  std::lock_guard<std::mutex> lock(checking_mutex_);

  while (true) {

    if (cfds_.empty()) {

      return nullptr;

    }

    ColumnFamilyData* cfd = cfds_.back();

    cfds_.pop_back();

    if (cfds_.empty()) {

      is_empty_.store(true, std::memory_order_relaxed);

    }

    if (!cfd->IsDropped()) {

      // success

      return cfd;

    }

    cfd->UnrefAndTryDelete();

  }

}

bool TrimHistoryScheduler::Empty() {

  bool is_empty = is_empty_.load(std::memory_order_relaxed);

  return is_empty;

}

void TrimHistoryScheduler::Clear() {

  ColumnFamilyData* cfd;

  while ((cfd = TakeNextColumnFamily()) != nullptr) {

    cfd->UnrefAndTryDelete();

  }

  assert(Empty());

}

}  // namespace ROCKSDB_NAMESPACE