#include <condition_variable>
#include <cstdio>
#include <iostream>
#include <memory>
#include <mutex>
#include <queue>
#include <thread>

template <typename T>
class queue {
private:
  mutable std::mutex mut;
  std::queue<T> data_queue;
  std::condition_variable data_cond;

public:
  queue() {}

  queue(const queue& other)
  {
    std::lock_guard<std::mutex> lk(other.mut);
    data_queue = other.data_queue;
  }

  void push(T new_value)
  {
    std::lock_guard<std::mutex> lk(mut);
    data_queue.push(new_value);
    data_cond.notify_one();
  }

  void wait_and_pop(T& value)
  {
    std::unique_lock<std::mutex> lk(mut);
    data_cond.wait(lk, [this] { return !data_queue.empty(); });
    value = data_queue.front();
    data_queue.pop();
  }

  std::shared_ptr<T> wait_and_pop()
  {
    std::unique_lock<std::mutex> lk(mut);
    data_cond.wait(lk, [this] { return !data_queue.empty(); });
    std::shared_ptr<T> res(std::make_shared<T>(data_queue.front()));
    data_queue.pop();
    return res;
  }

  bool try_pop(T& value)
  {
    std::lock_guard<std::mutex> lk(mut);
    if (data_queue.empty()) {
      return false;
    }
    value = data_queue.front();
    data_queue.pop();
    return true;
  }

  std::shared_ptr<T> try_pop()
  {
    std::lock_guard<std::mutex> lk(mut);
    if (data_queue.empty()) {
      return std::shared_ptr<T>();
    }
    std::shared_ptr<T> res(std::make_shared<T>(data_queue.front()));
    data_queue.pop();
    return res;
  }

  bool empty() const
  {
    std::lock_guard<std::mutex> lk(mut);
    return data_queue.empty();
  }
};

void
push(queue<int>* q)
{
  for (int i = 0; i < 10; ++i) {
    // std::cout << "pushing " << i << std::endl;
    printf("pushing %d\n", i);
    q->push(i);
  }
}

void
pop(queue<int>* q)
{
  for (int i = 0; i < 10; ++i) {
    printf("poping %d\n", *q->wait_and_pop());
  }
}

int
main()
{
  queue<int> q;
  std::thread t1(push, &q);
  std::thread t2(pop, &q);
  t1.join();
  t2.join();
  return 0;
}