factory.hpp

#ifndef ENTT_META_FACTORY_HPP
#define ENTT_META_FACTORY_HPP
 
#include <cstddef>
#include <functional>
#include <memory>
#include <tuple>
#include <type_traits>
#include <utility>
#include "../config/config.h"
#include "../core/fwd.hpp"
#include "../core/type_info.hpp"
#include "../core/type_traits.hpp"
#include "../locator/locator.hpp"
#include "context.hpp"
#include "meta.hpp"
#include "node.hpp"
#include "policy.hpp"
#include "range.hpp"
#include "resolve.hpp"
#include "utility.hpp"
 
namespace entt {
 
namespace internal {
 
[[nodiscard]] inline decltype(auto) owner(meta_ctx &ctx, const type_info &info) {
    auto &&context = internal::meta_context::from(ctx);
    ENTT_ASSERT(context.value.contains(info.hash()), "Type not available");
    return context.value[info.hash()];
}
 
inline meta_data_node &meta_extend(internal::meta_type_node &parent, const id_type id, meta_data_node node) {
    return parent.details->data.insert_or_assign(id, std::move(node)).first->second;
}
 
inline meta_func_node &meta_extend(internal::meta_type_node &parent, const id_type id, meta_func_node node) {
    if(auto it = parent.details->func.find(id); it != parent.details->func.end()) {
        for(auto *curr = &it->second; curr; curr = curr->next.get()) {
            if(curr->invoke == node.invoke) {
                node.next = std::move(curr->next);
                *curr = std::move(node);
                return *curr;
            }
        }
 
        // locally overloaded function
        node.next = std::make_shared<meta_func_node>(std::move(parent.details->func[id]));
    }
 
    return parent.details->func.insert_or_assign(id, std::move(node)).first->second;
}
 
} // namespace internal
template<typename Type>
class meta_factory {
    template<typename Setter, auto Getter, typename Policy, std::size_t... Index>
    void data(const id_type id, std::index_sequence<Index...>) noexcept {
        using data_type = std::invoke_result_t<decltype(Getter), Type &>;
        using args_type = type_list<typename meta_function_helper_t<Type, decltype(value_list_element_v<Index, Setter>)>::args_type...>;
        static_assert(Policy::template value<data_type>, "Invalid return type for the given policy");
 
        auto &&elem = internal::meta_extend(
            internal::owner(*ctx, *info),
            id,
            internal::meta_data_node{
                /* this is never static */
                (std::is_member_object_pointer_v<decltype(value_list_element_v<Index, Setter>)> && ... && std::is_const_v<std::remove_reference_t<data_type>>) ? internal::meta_traits::is_const : internal::meta_traits::is_none,
                Setter::size,
                &internal::resolve<std::remove_cv_t<std::remove_reference_t<data_type>>>,
                &meta_arg<type_list<type_list_element_t<type_list_element_t<Index, args_type>::size != 1u, type_list_element_t<Index, args_type>>...>>,
                +[](meta_handle instance, meta_any value) { return (meta_setter<Type, value_list_element_v<Index, Setter>>(*instance.operator->(), value.as_ref()) || ...); },
                &meta_getter<Type, Getter, Policy>});
 
        bucket = &elem.prop;
    }
 
public:
    meta_factory() noexcept
        : meta_factory{locator<meta_ctx>::value_or()} {}
 
    meta_factory(meta_ctx &area) noexcept
        : ctx{&area},
          bucket{},
          info{&type_id<Type>()} {
        auto &&elem = internal::owner(*ctx, *info);
 
        if(!elem.details) {
            elem.details = std::make_shared<internal::meta_type_descriptor>();
        }
 
        bucket = &elem.details->prop;
    }
 
    auto type(const id_type id) noexcept {
        auto &&elem = internal::owner(*ctx, *info);
        ENTT_ASSERT(elem.id == id || !resolve(*ctx, id), "Duplicate identifier");
        bucket = &elem.details->prop;
        elem.id = id;
        return *this;
    }
 
    template<typename Base>
    auto base() noexcept {
        static_assert(!std::is_same_v<Type, Base> && std::is_base_of_v<Base, Type>, "Invalid base type");
        auto *const op = +[](const void *instance) noexcept { return static_cast<const void *>(static_cast<const Base *>(static_cast<const Type *>(instance))); };
        internal::owner(*ctx, *info).details->base.insert_or_assign(type_id<Base>().hash(), internal::meta_base_node{&internal::resolve<Base>, op});
        bucket = nullptr;
        return *this;
    }
 
    template<auto Candidate>
    auto conv() noexcept {
        using conv_type = std::remove_cv_t<std::remove_reference_t<std::invoke_result_t<decltype(Candidate), Type &>>>;
        auto *const op = +[](const meta_ctx &area, const void *instance) { return forward_as_meta(area, std::invoke(Candidate, *static_cast<const Type *>(instance))); };
        internal::owner(*ctx, *info).details->conv.insert_or_assign(type_id<conv_type>().hash(), internal::meta_conv_node{op});
        bucket = nullptr;
        return *this;
    }
 
    template<typename To>
    auto conv() noexcept {
        using conv_type = std::remove_cv_t<std::remove_reference_t<To>>;
        auto *const op = +[](const meta_ctx &area, const void *instance) { return forward_as_meta(area, static_cast<To>(*static_cast<const Type *>(instance))); };
        internal::owner(*ctx, *info).details->conv.insert_or_assign(type_id<conv_type>().hash(), internal::meta_conv_node{op});
        bucket = nullptr;
        return *this;
    }
 
    template<auto Candidate, typename Policy = as_is_t>
    auto ctor() noexcept {
        using descriptor = meta_function_helper_t<Type, decltype(Candidate)>;
        static_assert(Policy::template value<typename descriptor::return_type>, "Invalid return type for the given policy");
        static_assert(std::is_same_v<std::remove_cv_t<std::remove_reference_t<typename descriptor::return_type>>, Type>, "The function doesn't return an object of the required type");
        internal::owner(*ctx, *info).details->ctor.insert_or_assign(type_id<typename descriptor::args_type>().hash(), internal::meta_ctor_node{descriptor::args_type::size, &meta_arg<typename descriptor::args_type>, &meta_construct<Type, Candidate, Policy>});
        bucket = nullptr;
        return *this;
    }
 
    template<typename... Args>
    auto ctor() noexcept {
        // default constructor is already implicitly generated, no need for redundancy
        if constexpr(sizeof...(Args) != 0u) {
            using descriptor = meta_function_helper_t<Type, Type (*)(Args...)>;
            internal::owner(*ctx, *info).details->ctor.insert_or_assign(type_id<typename descriptor::args_type>().hash(), internal::meta_ctor_node{descriptor::args_type::size, &meta_arg<typename descriptor::args_type>, &meta_construct<Type, Args...>});
        }
 
        bucket = nullptr;
        return *this;
    }
 
    template<auto Func>
    auto dtor() noexcept {
        static_assert(std::is_invocable_v<decltype(Func), Type &>, "The function doesn't accept an object of the type provided");
        auto *const op = +[](void *instance) { std::invoke(Func, *static_cast<Type *>(instance)); };
        internal::owner(*ctx, *info).dtor = internal::meta_dtor_node{op};
        bucket = nullptr;
        return *this;
    }
 
    template<auto Data, typename Policy = as_is_t>
    auto data(const id_type id) noexcept {
        if constexpr(std::is_member_object_pointer_v<decltype(Data)>) {
            using data_type = std::invoke_result_t<decltype(Data), Type &>;
            static_assert(Policy::template value<data_type>, "Invalid return type for the given policy");
 
            auto &&elem = internal::meta_extend(
                internal::owner(*ctx, *info),
                id,
                internal::meta_data_node{
                    /* this is never static */
                    std::is_const_v<std::remove_reference_t<data_type>> ? internal::meta_traits::is_const : internal::meta_traits::is_none,
                    1u,
                    &internal::resolve<std::remove_cv_t<std::remove_reference_t<data_type>>>,
                    &meta_arg<type_list<std::remove_cv_t<std::remove_reference_t<data_type>>>>,
                    &meta_setter<Type, Data>,
                    &meta_getter<Type, Data, Policy>});
 
            bucket = &elem.prop;
        } else {
            using data_type = std::remove_pointer_t<decltype(Data)>;
 
            if constexpr(std::is_pointer_v<decltype(Data)>) {
                static_assert(Policy::template value<decltype(*Data)>, "Invalid return type for the given policy");
            } else {
                static_assert(Policy::template value<data_type>, "Invalid return type for the given policy");
            }
 
            auto &&elem = internal::meta_extend(
                internal::owner(*ctx, *info),
                id,
                internal::meta_data_node{
                    ((std::is_same_v<Type, std::remove_cv_t<std::remove_reference_t<data_type>>> || std::is_const_v<std::remove_reference_t<data_type>>) ? internal::meta_traits::is_const : internal::meta_traits::is_none) | internal::meta_traits::is_static,
                    1u,
                    &internal::resolve<std::remove_cv_t<std::remove_reference_t<data_type>>>,
                    &meta_arg<type_list<std::remove_cv_t<std::remove_reference_t<data_type>>>>,
                    &meta_setter<Type, Data>,
                    &meta_getter<Type, Data, Policy>});
 
            bucket = &elem.prop;
        }
 
        return *this;
    }
 
    template<auto Setter, auto Getter, typename Policy = as_is_t>
    auto data(const id_type id) noexcept {
        using data_type = std::invoke_result_t<decltype(Getter), Type &>;
        static_assert(Policy::template value<data_type>, "Invalid return type for the given policy");
 
        if constexpr(std::is_same_v<decltype(Setter), std::nullptr_t>) {
            auto &&elem = internal::meta_extend(
                internal::owner(*ctx, *info),
                id,
                internal::meta_data_node{
                    /* this is never static */
                    internal::meta_traits::is_const,
                    0u,
                    &internal::resolve<std::remove_cv_t<std::remove_reference_t<data_type>>>,
                    &meta_arg<type_list<>>,
                    &meta_setter<Type, Setter>,
                    &meta_getter<Type, Getter, Policy>});
 
            bucket = &elem.prop;
        } else {
            using args_type = typename meta_function_helper_t<Type, decltype(Setter)>::args_type;
 
            auto &&elem = internal::meta_extend(
                internal::owner(*ctx, *info),
                id,
                internal::meta_data_node{
                    /* this is never static nor const */
                    internal::meta_traits::is_none,
                    1u,
                    &internal::resolve<std::remove_cv_t<std::remove_reference_t<data_type>>>,
                    &meta_arg<type_list<type_list_element_t<args_type::size != 1u, args_type>>>,
                    &meta_setter<Type, Setter>,
                    &meta_getter<Type, Getter, Policy>});
 
            bucket = &elem.prop;
        }
 
        return *this;
    }
 
    template<typename Setter, auto Getter, typename Policy = as_is_t>
    auto data(const id_type id) noexcept {
        data<Setter, Getter, Policy>(id, std::make_index_sequence<Setter::size>{});
        return *this;
    }
 
    template<auto Candidate, typename Policy = as_is_t>
    auto func(const id_type id) noexcept {
        using descriptor = meta_function_helper_t<Type, decltype(Candidate)>;
        static_assert(Policy::template value<typename descriptor::return_type>, "Invalid return type for the given policy");
 
        auto &&elem = internal::meta_extend(
            internal::owner(*ctx, *info),
            id,
            internal::meta_func_node{
                (descriptor::is_const ? internal::meta_traits::is_const : internal::meta_traits::is_none) | (descriptor::is_static ? internal::meta_traits::is_static : internal::meta_traits::is_none),
                descriptor::args_type::size,
                &internal::resolve<std::conditional_t<std::is_same_v<Policy, as_void_t>, void, std::remove_cv_t<std::remove_reference_t<typename descriptor::return_type>>>>,
                &meta_arg<typename descriptor::args_type>,
                &meta_invoke<Type, Candidate, Policy>});
 
        bucket = &elem.prop;
        return *this;
    }
 
    template<typename... Value>
    meta_factory prop(id_type id, [[maybe_unused]] Value &&...value) {
        ENTT_ASSERT(bucket != nullptr, "Meta object does not support properties");
 
        if constexpr(sizeof...(Value) == 0u) {
            (*bucket)[id] = internal::meta_prop_node{&internal::resolve<void>};
        } else {
            (*bucket)[id] = internal::meta_prop_node{
                &internal::resolve<std::decay_t<Value>>...,
                std::make_shared<std::decay_t<Value>>(std::forward<Value>(value))...};
        }
 
        return *this;
    }
 
private:
    meta_ctx *ctx;
    dense_map<id_type, internal::meta_prop_node, identity> *bucket;
    const type_info *info;
};
 
template<typename Type>
[[nodiscard]] auto meta(meta_ctx &ctx) noexcept {
    auto &&context = internal::meta_context::from(ctx);
    // make sure the type exists in the context before returning a factory
    context.value.try_emplace(type_id<Type>().hash(), internal::resolve<Type>(context));
    return meta_factory<Type>{ctx};
}
 
template<typename Type>
[[nodiscard]] auto meta() noexcept {
    return meta<Type>(locator<meta_ctx>::value_or());
}
 
inline void meta_reset(meta_ctx &ctx, const id_type id) noexcept {
    auto &&context = internal::meta_context::from(ctx);
 
    for(auto it = context.value.begin(); it != context.value.end();) {
        if(it->second.id == id) {
            it = context.value.erase(it);
        } else {
            ++it;
        }
    }
}
 
inline void meta_reset(const id_type id) noexcept {
    meta_reset(locator<meta_ctx>::value_or(), id);
}
 
template<typename Type>
void meta_reset(meta_ctx &ctx) noexcept {
    internal::meta_context::from(ctx).value.erase(type_id<Type>().hash());
}
 
template<typename Type>
void meta_reset() noexcept {
    meta_reset<Type>(locator<meta_ctx>::value_or());
}
 
inline void meta_reset(meta_ctx &ctx) noexcept {
    internal::meta_context::from(ctx).value.clear();
}
 
inline void meta_reset() noexcept {
    meta_reset(locator<meta_ctx>::value_or());
}
 
} // namespace entt
 
#endif