// 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 <Storages/KVStore/Decode/DecodingStorageSchemaSnapshot.h>
#include <Storages/KVStore/Decode/RegionDataRead.h>

namespace DB
{
class Block;

/// The Reader to read the region data in `data_list` and decode based on the given table_info and columns, as a block.
class RegionBlockReader : private boost::noncopyable
{
public:
    explicit RegionBlockReader(DecodingStorageSchemaSnapshotConstPtr schema_snapshot_);

    /// Read `data_list` as a block.
    ///
    /// On decode error, i.e. column number/type mismatch, caller should trigger a schema-sync and retry with `force_decode=True`,
    /// i.e. add/remove/cast unknown/missing/type-mismatch column if force_decode is true, otherwise return empty block and false.
    /// Moreover, exception will be thrown if we see fatal decode error meanwhile `force_decode` is true.
    ///
    /// `RegionBlockReader::read` is the common routine used by both 'flush' and 'read' processes of Delta-Tree engine,
    /// which will use carefully adjusted 'force_decode' with appropriate error handling/retry to get what they want.
    template <typename ReadList>
    bool read(Block & block, const ReadList & data_list, bool force_decode);

private:
    template <TMTPKType pk_type, typename ReadList>
    bool readImpl(Block & block, const ReadList & data_list, bool force_decode);

private:
    DecodingStorageSchemaSnapshotConstPtr schema_snapshot;
};

} // namespace DB