entity_mapping.h

#pragma once
 
#include <cstdint>
#include <type_traits>
 
#include "ecs/entity.h"
 
namespace Vkm::Engine {
 
template<typename Signature>
class EntityMapping;

template<typename R, typename A>
class EntityMapping<R(A)> {
    public:
        template<typename Fn, typename = std::enable_if_t<!std::is_same_v<std::decay_t<Fn>, EntityMapping>>>
        EntityMapping(Fn& fn) noexcept
            : m_carrier(&fn)
            , m_call([](void* c, A from) -> R { return (*static_cast<Fn*>(c))(from); })
        {}
        ~EntityMapping() = default;
 
        EntityMapping(const EntityMapping& other) = default;
        EntityMapping& operator=(const EntityMapping& other) = default;
 
        EntityMapping(EntityMapping && other) = default;
        EntityMapping& operator=(EntityMapping && other) = default;

        R operator()(A from) const {
            return from ? m_call(m_carrier, from) : R{};
        }
 
    private:
        void* m_carrier = nullptr;
        R (*m_call)(void*, A) = nullptr;
};

using EntityResolver = EntityMapping<EntityId(uint32_t)>;

using EntityNamer = EntityMapping<uint32_t(EntityId)>;
 
} // namespace Vkm::Engine