#pragma once
#include <utility>
#include <mutex>
#include <queue>

template <typename T> class Queue {
 public:
  T Pop();
  size_t Size();

  template <typename U>
  void Push(U var);

  template <typename... U>
  void Emplace(U &&... args);
 private:
  std::queue<T> data;
  std::mutex access;
};

template <typename T>
inline T Queue<T>::Pop() {
  std::lock_guard<std::mutex> mutex_lock(access);
  T res = std::move(data.front());
  data.pop();
  return res;
}

template <typename T>
inline size_t Queue<T>::Size() {
  std::lock_guard<std::mutex> mutex_lock(access);
  return data.size();
}

template <typename T>
template <typename U>
inline void Queue<T>::Push(U value) {
  access.lock();
  data.push(std::move(value));
  access.unlock();
}

template <typename T>
template <typename... U>
inline void Queue<T>::Emplace(U &&... args) {
  access.lock();
  data.emplace(std::forward<U &&...>(args...));
  access.unlock();
}