// 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 <atomic>

#include <condition_variable>

#include <cstdint>

#include <iosfwd>

#include <memory>

#include <utility>

#include <vector>

#include "common/status.h"

#include "load/memtable/memtable.h"

#include "util/threadpool.h"

namespace doris {

class DataDir;

class MemTable;

class RowsetWriter;

class WorkloadGroup;

// the statistic of a certain flush handler.

// use atomic because it may be updated by multi threads

struct FlushStatistic {

    std::atomic_uint64_t flush_time_ns = 0;

    std::atomic_uint64_t flush_submit_count = 0;

    std::atomic_int64_t flush_running_count = 0;

    std::atomic_uint64_t flush_finish_count = 0;

    std::atomic_uint64_t flush_size_bytes = 0;

    std::atomic_uint64_t flush_disk_size_bytes = 0;

    std::atomic_uint64_t flush_wait_time_ns = 0;

};

std::ostream& operator<<(std::ostream& os, const FlushStatistic& stat);

// A thin wrapper of ThreadPoolToken to submit task.

// For a tablet, there may be multiple memtables, which will be flushed to disk

// one by one in the order of generation.

// If a memtable flush fails, then:

// 1. Immediately disallow submission of any subsequent memtable

// 2. For the memtables that have already been submitted, there is no need to flush,

//    because the entire job will definitely fail;

class FlushToken : public std::enable_shared_from_this<FlushToken> {

    ENABLE_FACTORY_CREATOR(FlushToken);

public:

    FlushToken(ThreadPool* thread_pool, std::shared_ptr<WorkloadGroup> wg_sptr)

            : _flush_status(Status::OK()), _thread_pool(thread_pool), _wg_wptr(wg_sptr) {}

    Status submit(std::shared_ptr<MemTable> mem_table);

    // error has happens, so we cancel this token

    // And remove all tasks in the queue.

    void cancel();

    // wait all tasks in token to be completed.

    Status wait();

    // get flush operations' statistics

    const FlushStatistic& get_stats() const { return _stats; }

    void set_rowset_writer(std::shared_ptr<RowsetWriter> rowset_writer) {

        _rowset_writer = rowset_writer;

    }

    const MemTableStat& memtable_stat() { return _memtable_stat; }

private:

    void _shutdown_flush_token() { _shutdown.store(true); }

    bool _is_shutdown() { return _shutdown.load(); }

    void _wait_submit_task_finish();

    void _wait_running_task_finish();

private:

    friend class MemtableFlushTask;

    void _flush_memtable(std::shared_ptr<MemTable> memtable_ptr, int32_t segment_id,

                         int64_t submit_task_time);

    Status _do_flush_memtable(MemTable* memtable, int32_t segment_id, int64_t* flush_size);

    Status _try_reserve_memory(const std::shared_ptr<ResourceContext>& resource_context,

                               int64_t size);

    // Records the current flush status of the tablet.

    // Note: Once its value is set to Failed, it cannot return to SUCCESS.

    std::shared_mutex _flush_status_lock;

    Status _flush_status;

    FlushStatistic _stats;

    std::shared_ptr<RowsetWriter> _rowset_writer = nullptr;

    MemTableStat _memtable_stat;

    std::atomic<bool> _shutdown = false;

    ThreadPool* _thread_pool = nullptr;

    std::mutex _mutex;

    std::condition_variable _submit_task_finish_cond;

    std::condition_variable _running_task_finish_cond;

    std::weak_ptr<WorkloadGroup> _wg_wptr;

};

// MemTableFlushExecutor is responsible for flushing memtables to disk.

// It encapsulate a ThreadPool to handle all tasks.

// Usage Example:

//      ...

//      std::shared_ptr<FlushHandler> flush_handler;

//      memTableFlushExecutor.create_flush_token(&flush_handler);

//      ...

//      flush_token->submit(memtable)

//      ...

class MemTableFlushExecutor {

public:

    MemTableFlushExecutor() = default;

    ~MemTableFlushExecutor() {

        _flush_pool->shutdown();

        _high_prio_flush_pool->shutdown();

    }

    // init should be called after storage engine is opened,

    // because it needs path hash of each data dir.

    void init(int num_disk);

    Status create_flush_token(std::shared_ptr<FlushToken>& flush_token,

                              std::shared_ptr<RowsetWriter> rowset_writer, bool is_high_priority,

                              std::shared_ptr<WorkloadGroup> wg_sptr);

    // return true if it already has any flushing task

    bool check_and_inc_has_any_flushing_task() {

        // need to use CAS instead of only `if (0 == _flushing_task_count)` statement,

        // to avoid concurrent entries both pass the if statement

        int expected_count = 0;

        if (!_flushing_task_count.compare_exchange_strong(expected_count, 1)) {

            return true;

        }

        DCHECK(expected_count == 0 && _flushing_task_count == 1);

        return false;

    }

    void inc_flushing_task() { _flushing_task_count++; }

    void dec_flushing_task() { _flushing_task_count--; }

    ThreadPool* flush_pool() { return _flush_pool.get(); }

    void update_memtable_flush_threads();

private:

    std::unique_ptr<ThreadPool> _flush_pool;

    std::unique_ptr<ThreadPool> _high_prio_flush_pool;

    std::atomic<int> _flushing_task_count = 0;

    int _num_disk = 0;

};

} // namespace doris