ThreadPool.hpp

#pragma once

#define WIN32_LEAN_AND_MEAN
#define NOMINMAX
#include <Windows.h>

#include <vector>
#include <queue>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <atomic>
#include <functional>
#include <future>
#include <type_traits>

class ThreadPool {
public:
    ThreadPool(size_t numThreads = std::thread::hardware_concurrency())
        : stop(false) {

        for (size_t i = 0; i < numThreads; ++i) {
            workers.emplace_back([this] {
                while (true) {
                    std::function<void()> task;

                    {
                        std::unique_lock<std::mutex> lock(queueMutex);
                        condition.wait(lock, [this] {
                            return stop || !tasks.empty();
                            });

                        if (stop && tasks.empty()) {
                            return;
                        }

                        task = std::move(tasks.front());
                        tasks.pop();
                    }

                    task();
                }
                });
        }
    }

    ~ThreadPool() {
        {
            std::unique_lock<std::mutex> lock(queueMutex);
            stop = true;
        }
        condition.notify_all();

        for (std::thread& worker : workers) {
            if (worker.joinable()) {
                worker.join();
            }
        }
    }

    template<typename F, typename... Args>
    auto Enqueue(F&& f, Args&&... args)
        -> std::future<typename std::invoke_result_t<F, Args...>> {

        using return_type = typename std::invoke_result_t<F, Args...>;

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

        std::future<return_type> result = task->get_future();

        {
            std::unique_lock<std::mutex> lock(queueMutex);
            if (stop) {
                throw std::runtime_error("enqueue on stopped ThreadPool");
            }

            tasks.emplace([task]() { (*task)(); });
        }

        condition.notify_one();
        return result;
    }

    size_t GetThreadCount() const {
        return workers.size();
    }

    size_t GetJobCount() const {
        std::unique_lock<std::mutex> lock(queueMutex);
        return tasks.size();
    }

    bool IsBusy() const {
        std::unique_lock<std::mutex> lock(queueMutex);
        return !tasks.empty();
    }

    void WaitForCompletion() {
        while (GetJobCount() > 0) {
            std::this_thread::sleep_for(std::chrono::milliseconds(10));
        }
    }

private:
    std::vector<std::thread> workers;
    std::queue<std::function<void()>> tasks;

    mutable std::mutex queueMutex;
    std::condition_variable condition;
    std::atomic<bool> stop;
};