/*
 * ThreadPool.h
 *
 * open source  From:https://github.com/progschj/ThreadPool
 */

#ifndef COMMON_SOURCE_CPP_THREADPOOL_H_
#define COMMON_SOURCE_CPP_THREADPOOL_H_

#include <vector>
#include <queue>
#include <memory>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <future>
#include <functional>
#include <stdexcept>
namespace gdface{
class ThreadPool {
public:
	const size_t concurrency;
    ThreadPool(size_t);
    // add new work item to the pool
    template<class F, class... Args>
    auto enqueue(F&& f, Args&&... args)
        -> std::future<typename std::result_of<F(Args...)>::type>{
        using return_type = typename std::result_of<F(Args...)>::type;

        auto task = std::make_shared< std::packaged_task<return_type()> >(
                std::bind(std::forward<F>(f), std::forward<Args>(args)...)
            );

        std::future<return_type> res = task->get_future();
        {
            std::unique_lock<std::mutex> lock(queue_mutex);

            // don't allow enqueueing after stopping the pool
            if(stop)
                throw std::runtime_error("enqueue on stopped ThreadPool");

            tasks.emplace([task](){ (*task)(); });
        }
        condition.notify_one();
        return res;
    }
    ~ThreadPool();
private:
    // need to keep track of threads so we can join them
    std::vector< std::thread > workers;
    // the task queue
    std::queue< std::function<void()> > tasks;

    // synchronization
    std::mutex queue_mutex;
    std::condition_variable condition;
    bool stop;
};


} /* namespace gdface */

#endif /* COMMON_SOURCE_CPP_THREADPOOL_H_ */