//  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 <atomic>

#include <cstdint>

#include <mutex>

#include <set>

#include "util/autovector.h"

namespace ROCKSDB_NAMESPACE {

class ColumnFamilyData;

// FlushScheduler keeps track of all column families whose memtable may

// be full and require flushing. Unless otherwise noted, all methods on

// FlushScheduler should be called only with the DB mutex held or from

// a single-threaded recovery context.

class FlushScheduler {

 public:

  FlushScheduler() : head_(nullptr) {}

  // May be called from multiple threads at once, but not concurrent with

  // any other method calls on this instance

  void ScheduleWork(ColumnFamilyData* cfd);

  // Removes and returns Ref()-ed column family. Client needs to Unref().

  // Filters column families that have been dropped.

  ColumnFamilyData* TakeNextColumnFamily();

  // This can be called concurrently with ScheduleWork but it would miss all

  // the scheduled flushes after the last synchronization. This would result

  // into less precise enforcement of memtable sizes but should not matter much.

  bool Empty();

  void Clear();

 private:

  struct Node {

    ColumnFamilyData* column_family;

    Node* next;

  };

  std::atomic<Node*> head_;

#ifndef NDEBUG

  std::mutex checking_mutex_;

  std::set<ColumnFamilyData*> checking_set_;

#endif  // NDEBUG

};

}  // namespace ROCKSDB_NAMESPACE