CallableWrapper.hpp

#pragma once

#include <functional>
#include <memory>
#include <iostream>

template<int Ind, typename R, typename... Args>
struct Wrapper;

template <int Ind, typename Callable, typename R, typename... Args>
R wrapper(Args... args);

template<int Ind, typename Callable>
struct CallableStorage
{
    static void store(Callable callable_)
    {
        callable = std::make_unique<Callable>(callable_);
    }

    template <typename R, typename... Args>
    static R invoke(Args... args)
    {
        return (*callable)(args...);
    }

private:
    static std::unique_ptr<Callable> callable;
};

template <int Ind, typename Callable>
std::unique_ptr<Callable> CallableStorage<Ind, Callable>::callable;

template<int Ind, typename R, typename... Args>
struct Wrapper<Ind, R(Args...)>
{
    using RawType = R(*)(Args...);

    template<typename Callable>
    static RawType wrap(Callable callable)
    {
        CallableStorage<Ind, Callable>::store(callable);
        return wrapper<Ind, Callable, R, Args...>;
    }
};

template <int Ind, typename Callable, typename R, typename... Args>
R wrapper(Args... args)
{
    return CallableStorage<Ind, Callable>::template invoke<R>(args...);
}