event_dispatcher.hpp

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#ifndef CODEX_EVENT_DISPATCHER_EVENT_DISPATCHER_HPP
#define CODEX_EVENT_DISPATCHER_EVENT_DISPATCHER_HPP
 
#include <concepts>
#include <cstdio>
#include <functional>
#include <vector>
 
namespace codex {
 
struct BaseEvent {};
struct OnClick : BaseEvent { int button; };
struct OnKey : BaseEvent { int key; };
 
template<typename T> concept Event = std::derived_from<T, BaseEvent>;
template<typename T, typename E>
concept EventListener = Event<E> && std::invocable<T, E>;
 
namespace detail {
 
template<Event E> struct EventListenerVec
    { protected: std::vector<std::function<void(E)>> v; };
 
}
 
template<Event ...Es>
class EventDispatcher : detail::EventListenerVec<Es>... {
public:
    template<Event E, EventListener<E> L>
    void add_listener(L l) { this->vec<E>().emplace_back(std::move(l)); }
    template<Event E> void trigger(E e) { for(auto &x: this->vec<E>()) x(e); }
private:
    template<Event E>
    requires std::is_base_of_v<
        detail::EventListenerVec<E>, EventDispatcher<Es...>>
    decltype(auto) vec() { return (detail::EventListenerVec<E>::v); }
};
 
}
 
#endif