#ifndef stack_h
#define stack_h 1

#include <memory>
#include <optional>

template <class T> class stack
{
public:
    ~stack() { while (pop()); } // ~stack() = default // STACK OVERFLOW!!!

    void push(T t)
    {
        head = std::make_unique<node>(std::move(head), std::move(t));
    }

    std::optional<T> pop()
    {
        if (head)
        {
            auto data = head->data;
            head = std::move(head->next);
            return data;
        }
        else
        {
            return std::nullopt;
        }
    }

private:
    struct node
    {
        std::unique_ptr<node> next;
        T data;
    };

    std::unique_ptr<node> head;
};

#endif // stack_h