// 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 <Columns/countBytesInFilter.h>
#include <Storages/DeltaMerge/ColumnFile/ColumnFileSetSnapshot.h>
#include <Storages/DeltaMerge/DMContext_fwd.h>
#include <Storages/DeltaMerge/SkippableBlockInputStream.h>

namespace DB::DM
{

class ColumnFileSetReader
{
    friend class ColumnFileSetInputStream;
    friend class VectorIndexColumnFileSetInputStream;

private:
    const DMContext & context;
    ColumnFileSetSnapshotPtr snapshot;

    // The columns expected to read. Note that we will do reading exactly in this column order.
    ColumnDefinesPtr col_defs;
    RowKeyRange segment_range;

    // The row count of each column file. Cache here to speed up checking.
    std::vector<size_t> column_file_rows;
    // The cumulative rows of column files. Used to fast locate specific column files according to rows offset by binary search.
    std::vector<size_t> column_file_rows_end;

    std::vector<ColumnFileReaderPtr> column_file_readers;

private:
    explicit ColumnFileSetReader(const DMContext & context_);

    Block readPKVersion(size_t offset, size_t limit);

public:
    ColumnFileSetReader(
        const DMContext & context_,
        const ColumnFileSetSnapshotPtr & snapshot_,
        const ColumnDefinesPtr & col_defs_,
        const RowKeyRange & segment_range_,
        ReadTag read_tag_);

    // If we need to read columns besides pk and version, a ColumnFileSetReader can NOT be used more than once.
    // This method create a new reader based on the current one. It will reuse some caches in the current reader.
    ColumnFileSetReaderPtr createNewReader(const ColumnDefinesPtr & new_col_defs, ReadTag read_tag);

    // Use for DeltaMergeBlockInputStream to read rows from MemTableSet to do full compaction with other layer.
    // This method will check whether offset and limit are valid. It only return those valid rows.
    // The returned rows is not continuous, since records may be filtered by `range`. When `row_ids` is not null,
    // this function will fill corresponding offset of each row into `*row_ids`.
    size_t readRows(
        MutableColumns & output_columns,
        size_t offset,
        size_t limit,
        const RowKeyRange * range,
        std::vector<UInt32> * row_ids = nullptr);

    void getPlaceItems(
        BlockOrDeletes & place_items,
        size_t rows_begin,
        size_t deletes_begin,
        size_t rows_end,
        size_t deletes_end,
        size_t place_rows_offset = 0);

    bool shouldPlace(
        const DMContext & context,
        const RowKeyRange & relevant_range,
        UInt64 start_ts,
        size_t placed_rows);
};

} // namespace DB::DM