/**
 * @file mcp_thread_pool.h
 * @brief Simple thread pool implementation
 */

#ifndef MCP_THREAD_POOL_H
#define MCP_THREAD_POOL_H

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

namespace mcp {

class thread_pool {
public:
    /**
     * @brief Constructor
     * @param num_threads Number of threads in the thread pool
     */
    explicit thread_pool(size_t num_threads = std::thread::hardware_concurrency()) : stop_(false) {
        for (size_t i = 0; i < num_threads; ++i) {
            workers_.emplace_back([this] {
                while (true) {
                    std::function<void()> task;
                    
                    {
                        std::unique_lock<std::mutex> lock(queue_mutex_);
                        condition_.wait(lock, [this] { 
                            return stop_ || !tasks_.empty(); 
                        });
                        
                        if (stop_ && tasks_.empty()) {
                            return;
                        }
                        
                        task = std::move(tasks_.front());
                        tasks_.pop();
                    }
                    
                    task();
                }
            });
        }
    }
    
    /**
     * @brief Destructor
     */
    ~thread_pool() {
        {
            std::unique_lock<std::mutex> lock(queue_mutex_);
            stop_ = true;
        }
        
        condition_.notify_all();
        
        for (std::thread& worker : workers_) {
            if (worker.joinable()) {
                worker.join();
            }
        }
    }
    
    /**
     * @brief Submit task to thread pool
     * @param f Task function
     * @param args Task parameters
     * @return Task future
     */
    template<class F, class... Args>
    auto enqueue(F&& f, Args&&... args) -> std::future<typename std::invoke_result<F, Args...>::type> {
        using return_type = typename std::invoke_result<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> result = task->get_future();
        
        {
            std::unique_lock<std::mutex> lock(queue_mutex_);
            
            if (stop_) {
                throw std::runtime_error("Thread pool stopped, cannot add task");
            }
            
            tasks_.emplace([task]() { (*task)(); });
        }
        
        condition_.notify_one();
        return result;
    }
    
private:
    // Worker threads
    std::vector<std::thread> workers_;
    
    // Task queue
    std::queue<std::function<void()>> tasks_;
    
    // Mutex and condition variable
    std::mutex queue_mutex_;
    std::condition_variable condition_;
    
    // Stop flag
    std::atomic<bool> stop_;
};

} // namespace mcp

#endif // MCP_THREAD_POOL_H