// 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 <cstdint>

#include <memory>

#include <vector>

namespace doris {

class BaseTablet;

// One entry of a per-dimension top-N list. Kept thrift-free on purpose so this header

// does not drag gen_cpp into the storage layer; conversion lives in task_worker_pool.cpp.

struct ActiveTabletCandidate {

    int64_t tablet_id = 0;

    int64_t delta = 0;

    int64_t window_ms = 1;

    int64_t last_time_ms = 0;

    // Rate, not raw delta. Raw deltas are not comparable: a dropped report round commits

    // no baseline, so the next delta covers several intervals, and backends report on

    // independent phases.

    double rate() const {

        return static_cast<double>(delta) * 1000.0 / static_cast<double>(window_ms);

    }

};

// Collected inside the EXISTING report-tablet walk (no extra traversal). Collection is

// strictly read-only on the tablet baselines; commit() is called only after

// handle_report() returned true, so a retried or dropped report loses nothing.

class ActiveTabletCollector {

public:

    // Called at the top of each build_all_report_tablets_info() pass.

    void start();

    // Called once per tablet during the walk.

    void collect(const std::shared_ptr<BaseTablet>& tablet);

    // Per-dimension nth_element by rate. No cross-dimension merging or weighting here:

    // query and load counts differ by one to two orders of magnitude, so ranking them

    // against each other drops load-heavy tablets as a class. FE owns that trade-off,

    // where the split is a mutable config instead of a be.conf restart.

    void take_top_n();

    // Advance the baselines. ONLY after handle_report() succeeded.

    void commit();

    // Reset everything; called on each retry of the report loop.

    void clear();

    const std::vector<ActiveTabletCandidate>& query_candidates() const { return _query_cands; }

    const std::vector<ActiveTabletCandidate>& load_candidates() const { return _load_cands; }

    bool truncated() const { return _truncated; }

private:

    struct Pending {

        std::weak_ptr<BaseTablet> tablet;

        int64_t scan_count = 0;

        int64_t flush_count = 0;

    };

    std::vector<ActiveTabletCandidate> _query_cands;

    std::vector<ActiveTabletCandidate> _load_cands;

    std::vector<Pending> _pending;

    int64_t _now_ms = 0;

    bool _truncated = false;

};

} // namespace doris