// 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.

// This file is copied from

// https://github.com/ClickHouse/ClickHouse/blob/master/src/Interpreters/Cache/FileCacheFactory.h

// and modified by Doris

#pragma once

#include <gen_cpp/internal_service.pb.h>

#include <glog/logging.h>

#include <atomic>

#include <chrono>

#include <condition_variable>

#include <deque>

#include <memory>

#include <thread>

#include <variant>

#include "cloud/cloud_storage_engine.h"

#include "io/fs/file_system.h"

namespace doris::io {

struct DownloadFileMeta {

    Path path;

    int64_t file_size {-1};

    int64_t offset {0};

    int64_t download_size {-1};

    io::FileSystemSPtr file_system;

    IOContext ctx;

    std::function<void(Status)> download_done;

    int64_t tablet_id {-1};

};

struct DownloadTask {

    std::chrono::steady_clock::time_point atime = std::chrono::steady_clock::now();

    using FileCacheBlockMetaVec =

            ::google::protobuf::RepeatedPtrField< ::doris::FileCacheBlockMeta>;

    std::variant<FileCacheBlockMetaVec, DownloadFileMeta> task_message;

    DownloadTask(FileCacheBlockMetaVec metas) : task_message(std::move(metas)) {}

    DownloadTask(DownloadFileMeta meta) : task_message(std::move(meta)) {}

    DownloadTask() = default;

};

class FileCacheBlockDownloader {

public:

    explicit FileCacheBlockDownloader(CloudStorageEngine& engine);

    ~FileCacheBlockDownloader();

    // download into cache block

    void download_blocks(DownloadTask& task);

    // submit the task to download queue

    void submit_download_task(DownloadTask task);

    // polling the queue, get the task to download

    void polling_download_task();

    // check whether the tasks about tables finish or not

    void check_download_task(const std::vector<int64_t>& tablets, std::map<int64_t, bool>* done);

private:

    void download_file_cache_block(const DownloadTask::FileCacheBlockMetaVec&);

    void download_segment_file(const DownloadFileMeta&);

    CloudStorageEngine& _engine;

    std::thread _poller;

    std::unique_ptr<ThreadPool> _workers;

    std::mutex _mtx;

    bool _closed {false};

    std::condition_variable _empty;

    std::deque<DownloadTask> _task_queue;

    std::mutex _inflight_mtx;

    // tablet id -> inflight block num of tablet

    std::unordered_map<int64_t, int64_t> _inflight_tablets;

    static inline constexpr size_t _max_size {102400};

};

} // namespace doris::io