CallableTraits.hpp

#pragma once
#include <tuple>
 
namespace RavEngine {
    // adapted from answers on https://stackoverflow.com/questions/28509273/get-types-of-c-function-parameters
 
    template<typename Sig>
    struct signature;
    template<typename Ret, typename...Args>
    struct signature<Ret(Args...)> {
        using type = std::tuple<Args...>;
    };
 
    template<typename Ret, typename Obj, typename...Args>
    struct signature<Ret(Obj::*)(Args...)> {
        using type = std::tuple<Args...>;
    };
    template<typename Ret, typename Obj, typename...Args>
    struct signature<Ret(Obj::*)(Args...)const> {
        using type = std::tuple<Args...>;
    };
    template<typename Fun>
    concept is_fun = std::is_function_v<Fun>;
 
    template<typename Fun>
    concept is_mem_fun = std::is_member_function_pointer_v<std::decay_t<Fun>>;
 
    template<typename Fun>
    concept is_functor = std::is_class_v<std::decay_t<Fun>> && requires(Fun && t) {
        &std::decay_t<Fun>::operator();
    };
 
    template<is_functor T>
    using functor_args_t = typename signature<decltype(&std::decay_t<T>::operator())>::type;
 
    template<is_functor T>
    auto arguments(T&& t) -> typename signature<decltype(&std::decay_t<T>::operator())>::type;
 
    template<is_functor T>
    auto arguments(const T& t) -> typename signature<decltype(&std::decay_t<T>::operator())>::type;
 
    // template<is_fun T>
    // auto arguments(T&& t)->signature<T>::type;
 
    template<is_fun T>
    auto arguments(const T& t) -> typename signature<T>::type;
 
    template<is_mem_fun T>
    auto arguments(T&& t) -> typename signature<std::decay_t<T>>::type;
    
    template<is_mem_fun T>
    auto arguments(const T& t) -> typename signature<std::decay_t<T>>::type;
}