//
// SPDX-FileCopyrightText: Hadad <hadad@linuxmail.org>
// SPDX-License-Identifier: Apache-2.0
//

#ifndef POCKET_TTS_THREAD_POOL_HPP
#define POCKET_TTS_THREAD_POOL_HPP

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

namespace pocket_tts_accelerator {

class ThreadPool {
public:
    explicit ThreadPool(std::size_t number_of_threads);
    ~ThreadPool();

    ThreadPool(const ThreadPool&) = delete;
    ThreadPool& operator=(const ThreadPool&) = delete;
    ThreadPool(ThreadPool&&) = delete;
    ThreadPool& operator=(ThreadPool&&) = delete;

    template<typename FunctionType, typename... ArgumentTypes>
    auto submit_task(FunctionType&& function, ArgumentTypes&&... arguments)
        -> std::future<typename std::invoke_result<FunctionType, ArgumentTypes...>::type>;

    void shutdown();
    bool is_running() const;
    std::size_t get_pending_task_count() const;
    std::size_t get_thread_count() const;

private:
    void worker_thread_function();

    std::vector<std::thread> worker_threads;
    std::queue<std::function<void()>> task_queue;
    mutable std::mutex queue_mutex;
    std::condition_variable task_available_condition;
    std::atomic<bool> should_stop;
    std::atomic<bool> is_stopped;
    std::size_t thread_count;
};

template<typename FunctionType, typename... ArgumentTypes>
auto ThreadPool::submit_task(FunctionType&& function, ArgumentTypes&&... arguments)
    -> std::future<typename std::invoke_result<FunctionType, ArgumentTypes...>::type> {
    
    using ReturnType = typename std::invoke_result<FunctionType, ArgumentTypes...>::type;
    
    auto packaged_task = std::make_shared<std::packaged_task<ReturnType()>>(
        std::bind(std::forward<FunctionType>(function), std::forward<ArgumentTypes>(arguments)...)
    );
    
    std::future<ReturnType> result_future = packaged_task->get_future();
    
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        
        if (should_stop.load()) {
            throw std::runtime_error("Cannot submit task to stopped thread pool");
        }
        
        task_queue.emplace([packaged_task]() {
            (*packaged_task)();
        });
    }
    
    task_available_condition.notify_one();
    
    return result_future;
}

}

#endif