// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you 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 <memory>

#include <string>

#include <unordered_map>

#include <utility>

#include "exec/scan/olap_scanner.h"

#include "storage/rowset/rowset_fwd.h"

#include "storage/segment/row_ranges.h"

#include "storage/segment/segment_loader.h"

#include "storage/tablet/base_tablet.h"

#include "storage/tablet/tablet.h"

namespace doris {

class OlapScanLocalState;

class Scanner;

using ScannerSPtr = std::shared_ptr<Scanner>;

class ParallelScannerBuilder {

public:

    ParallelScannerBuilder(OlapScanLocalState* parent,

                           const std::vector<TabletWithVersion>& tablets,

                           std::vector<TabletReadSource>& read_sources,

                           const std::shared_ptr<RuntimeProfile>& profile,

                           const std::vector<OlapScanRange*>& key_ranges, RuntimeState* state,

                           int64_t limit, bool is_dup_mow_key, bool is_preaggregation)

            : _parent(parent),

              _scanner_profile(profile),

              _state(state),

              _limit(limit),

              _is_dup_mow_key(is_dup_mow_key),

              _is_preaggregation(is_preaggregation),

              _tablets(tablets.cbegin(), tablets.cend()),

              _key_ranges(key_ranges.cbegin(), key_ranges.cend()),

              _read_sources(read_sources) {}

    Status build_scanners(std::list<ScannerSPtr>& scanners);

    void set_max_scanners_count(size_t count) { _max_scanners_count = count; }

    void set_min_rows_per_scanner(int64_t size) { _min_rows_per_scanner = size; }

    void set_scan_parallelism_by_per_segment(bool v) { _scan_parallelism_by_per_segment = v; }

    const OlapReaderStatistics* builder_stats() const { return &_builder_stats; }

private:

    Status _load();

    Status _build_scanners_by_rowid(std::list<ScannerSPtr>& scanners);

    // Build scanners so that each segment is handled by its own scanner.

    Status _build_scanners_by_per_segment(std::list<ScannerSPtr>& scanners);

    std::shared_ptr<OlapScanner> _build_scanner(BaseTabletSPtr tablet, int64_t version,

                                                const std::vector<OlapScanRange*>& key_ranges,

                                                TabletReadSource&& read_source);

    OlapScanLocalState* _parent;

    /// Max scanners count limit to build

    size_t _max_scanners_count {16};

    /// Min rows per scanner

    size_t _min_rows_per_scanner {2 * 1024 * 1024};

    size_t _total_rows {};

    size_t _rows_per_scanner {_min_rows_per_scanner};

    std::map<RowsetId, std::vector<size_t>> _all_segments_rows;

    // Force building one scanner per segment when true.

    bool _scan_parallelism_by_per_segment {false};

    std::shared_ptr<RuntimeProfile> _scanner_profile;

    OlapReaderStatistics _builder_stats;

    RuntimeState* _state;

    int64_t _limit;

    bool _is_dup_mow_key;

    // The flag of preagg's meaning is whether return pre agg data(or partial agg data)

    // PreAgg ON: The storage layer returns partially aggregated data without additional processing. (Fast data reading)

    // for example, if a table is select userid,count(*) from base table.

    // And the user send a query like select userid,count(*) from base table group by userid.

    // then the storage layer do not need do aggregation, it could just return the partial agg data, because the compute layer will do aggregation.

    // PreAgg OFF: The storage layer must complete pre-aggregation and return fully aggregated data. (Slow data reading)

    bool _is_preaggregation;

    std::vector<TabletWithVersion> _tablets;

    std::vector<OlapScanRange*> _key_ranges;

    std::unordered_map<int64_t, TabletReadSource> _all_read_sources;

    std::vector<TabletReadSource>& _read_sources;

};

} // namespace doris