ClickHouse/src/Storages/MergeTree/MergeTreeWriteAheadLog.h

#pragma once

#include <DataStreams/NativeBlockInputStream.h>
#include <DataStreams/NativeBlockOutputStream.h>
#include <Storages/MergeTree/IMergeTreeDataPart.h>
#include <Disks/IDisk.h>

namespace DB
{

// class WALBlockOutputStream : public NativeBlockOutputStream
// {
// public:
//     WALBlockOutputStream(WriteBuffer & out_, const Block & header_);
//     void write(const Block & block, const String & part_name);

// private:
//     WriteBuffer & out;
// };

// class WALBlockInputStream : public NativeBlockInputStream
// {
// };

class MergeTreeData;

class MergeTreeWriteAheadLog
{
public:
    constexpr static auto WAL_FILE_NAME = "wal";
    constexpr static auto WAL_FILE_EXTENSION = ".bin";
    constexpr static size_t MAX_WAL_BYTES = 1024;

    MergeTreeWriteAheadLog(const MergeTreeData & storage_, const DiskPtr & disk_,
        const String & name = String(WAL_FILE_NAME) + WAL_FILE_EXTENSION);

    void write(const Block & block, const String & part_name);
    std::vector<std::shared_ptr<IMergeTreeDataPart>> restore();

private:
    void rotate(const std::lock_guard<std::mutex> & write_lock);

    const MergeTreeData & storage;
    DiskPtr disk;
    String path;

    std::unique_ptr<WriteBuffer> out;
    std::unique_ptr<NativeBlockOutputStream> block_out;

    Int64 min_block_number = std::numeric_limits<Int64>::max();
    Int64 max_block_number = std::numeric_limits<Int64>::min();

    mutable std::mutex write_mutex;
};

}