/************************************************************************
* file name         : thread_pool.h
* ----------------- :
* creation time     : 2018/01/28
* author            : Victor Zarubkin
* email             : v.s.zarubkin@gmail.com
* ----------------- :
* description       : The file contains declaration of ThreadPool.
* ----------------- :
* license           : Lightweight profiler library for c++
*                   : Copyright(C) 2016-2019  Sergey Yagovtsev, Victor Zarubkin
*                   :
*                   : Licensed under either of
*                   :     * MIT license (LICENSE.MIT or http://opensource.org/licenses/MIT)
*                   :     * Apache License, Version 2.0, (LICENSE.APACHE or http://www.apache.org/licenses/LICENSE-2.0)
*                   : at your option.
*                   :
*                   : The MIT License
*                   :
*                   : Permission is hereby granted, free of charge, to any person obtaining a copy
*                   : of this software and associated documentation files (the "Software"), to deal
*                   : in the Software without restriction, including without limitation the rights
*                   : to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
*                   : of the Software, and to permit persons to whom the Software is furnished
*                   : to do so, subject to the following conditions:
*                   :
*                   : The above copyright notice and this permission notice shall be included in all
*                   : copies or substantial portions of the Software.
*                   :
*                   : THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
*                   : INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
*                   : PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
*                   : LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
*                   : TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
*                   : USE OR OTHER DEALINGS IN THE SOFTWARE.
*                   :
*                   : 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.
************************************************************************/

#ifndef EASY_PROFILER_THREAD_POOL_H
#define EASY_PROFILER_THREAD_POOL_H

#include "thread_pool_task.h"
#include <vector>
#include <deque>
#include <condition_variable>
#include <thread>
#include <functional>

#if !defined(_WIN32) && !defined(__APPLE__)
// FIXME: Workaround for Qt on Linux
//
// There is a memory leak in Qt when creating Qt objects in several separate threads
// and removing them in one another (different) thread.
//
// But there is no memory leak when there is only one separate thread (apart from main thread)
// for creating Qt objects and one separate (different!) thread for removing them.
//
#define EASY_THREADPOOL_SEPARATE_QT_THREAD
#endif

class ThreadPool EASY_FINAL
{
    friend ThreadPoolTask;

    template <class T>
    struct Jobs
    {
        std::deque<T>        queue;
        std::mutex           mutex;
        std::condition_variable cv;
    };

    using TaskJobs = Jobs<std::reference_wrapper<ThreadPoolTask> >;
    using BackgroundJobs = Jobs<std::function<void()> >;

    TaskJobs m_tasks;
#ifdef EASY_THREADPOOL_SEPARATE_QT_THREAD
    TaskJobs m_qtasks;
#endif
    BackgroundJobs m_backgroundJobs;
    std::vector<std::thread> m_threads;
    std::atomic_bool m_interrupt;

    ThreadPool();

public:

    ~ThreadPool();

    static ThreadPool& instance();

    void backgroundJob(std::function<void()>&& func);

private:

    void enqueue(ThreadPoolTask& task);
    void dequeue(ThreadPoolTask& task);

    void enqueue(ThreadPoolTask& task, TaskJobs& tasks);
    void dequeue(ThreadPoolTask& task, TaskJobs& tasks);

    void tasksWorker(TaskJobs& tasks);
    void jobsWorker();

}; // end of class ThreadPool.

#endif //EASY_PROFILER_THREAD_POOL_H