// 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 "rocksdb/types.h"

namespace ROCKSDB_NAMESPACE {

enum class SnapshotCheckerResult : int {

  kInSnapshot = 0,

  kNotInSnapshot = 1,

  // In case snapshot is released and the checker has no clue whether

  // the given sequence is visible to the snapshot.

  kSnapshotReleased = 2,

};

// Callback class that control GC of duplicate keys in flush/compaction.

class SnapshotChecker {

 public:

  virtual ~SnapshotChecker() {}

  virtual SnapshotCheckerResult CheckInSnapshot(

      SequenceNumber sequence, SequenceNumber snapshot_sequence) const = 0;

};

class DisableGCSnapshotChecker : public SnapshotChecker {

 public:

  virtual ~DisableGCSnapshotChecker() {}

  SnapshotCheckerResult CheckInSnapshot(

      SequenceNumber /*sequence*/,

      SequenceNumber /*snapshot_sequence*/) const override {

    // By returning kNotInSnapshot, we prevent all the values from being GCed

    return SnapshotCheckerResult::kNotInSnapshot;

  }

  static DisableGCSnapshotChecker* Instance();

 protected:

  explicit DisableGCSnapshotChecker() {}

};

class WritePreparedTxnDB;

// Callback class created by WritePreparedTxnDB to check if a key

// is visible by a snapshot.

class WritePreparedSnapshotChecker : public SnapshotChecker {

 public:

  explicit WritePreparedSnapshotChecker(WritePreparedTxnDB* txn_db);

  virtual ~WritePreparedSnapshotChecker() {}

  SnapshotCheckerResult CheckInSnapshot(

      SequenceNumber sequence, SequenceNumber snapshot_sequence) const override;

 private:

  const WritePreparedTxnDB* const txn_db_;

};

bool DataIsDefinitelyInSnapshot(SequenceNumber seqno, SequenceNumber snapshot,

                                const SnapshotChecker* snapshot_checker);

bool DataIsDefinitelyNotInSnapshot(SequenceNumber seqno,

                                   SequenceNumber snapshot,

                                   const SnapshotChecker* snapshot_checker);

}  // namespace ROCKSDB_NAMESPACE