// Copyright 2023 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#pragma once
#include <common/types.h>

namespace DB
{

enum class WALRecoveryMode : UInt8
{
    // Original levelDB recovery
    //
    // We tolerate the last record in any log to be incomplete due to a crash
    // while writing it. Zeroed bytes from preallocation are also tolerated in the
    // trailing data of any log.
    //
    // Use case: Applications for which updates, once applied, must not be rolled
    // back even after a crash-recovery. In this recovery mode, RocksDB guarantees
    // this as long as `WritableFile::Append()` writes are durable. In case the
    // user needs the guarantee in more situations (e.g., when
    // `WritableFile::Append()` writes to page cache, but the user desires this
    // guarantee in face of power-loss crash-recovery), RocksDB offers various
    // mechanisms to additionally invoke `WritableFile::Sync()` in order to
    // strengthen the guarantee.
    //
    // This differs from `kPointInTimeRecovery` in that, in case a corruption is
    // detected during recovery, this mode will refuse to open the DB. Whereas,
    // `kPointInTimeRecovery` will stop recovery just before the corruption since
    // that is a valid point-in-time to which to recover.
    TolerateCorruptedTailRecords = 0x00,
    // Recover from clean shutdown
    // We don't expect to find any corruption in the WAL
    // Use case : This is ideal for unit tests and rare applications that
    // can require high consistency guarantee
    AbsoluteConsistency = 0x01,
    // Recover to point-in-time consistency (default)
    // We stop the WAL playback on discovering WAL inconsistency
    // Use case : Ideal for systems that have disk controller cache like
    // hard disk, SSD without super capacitor that store related data
    PointInTimeRecovery = 0x02,
    // Recovery after a disaster
    // We ignore any corruption in the WAL and try to salvage as much data as
    // possible
    // Use case : Ideal for last ditch effort to recover data or systems that
    // operate with low grade unrelated data
    SkipAnyCorruptedRecords = 0x03,
};

} // namespace DB