From 20401bee45ad13a11a3015d9b55dbd0c8f7b563a Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Fri, 28 Oct 2022 23:36:04 +0300
Subject: [PATCH] Implement ecs constructors & destructors

---
 libs/util/include/psemek/util/ecs.hpp | 117 +++++++++++++++++++++++++-
 1 file changed, 116 insertions(+), 1 deletion(-)

diff --git a/libs/util/include/psemek/util/ecs.hpp b/libs/util/include/psemek/util/ecs.hpp
index 8cf6ec17..a0debede 100644
--- a/libs/util/include/psemek/util/ecs.hpp
+++ b/libs/util/include/psemek/util/ecs.hpp
@@ -95,6 +95,14 @@ namespace psemek::util
 				apply_impl(behavior, static_cast<typename Behavior::component_types *>(nullptr), std::make_index_sequence<std::tuple_size_v<typename Behavior::component_types>>{}, args...);
 			}
 
+			template <typename Behavior, typename ... Args>
+			void apply_single(Behavior & behavior, entity_id entity, Args const & ... args)
+			{
+				if (!check_forbidden(behavior, 0))
+					return;
+				apply_single_impl(behavior, entity, static_cast<typename Behavior::component_types *>(nullptr), std::make_index_sequence<std::tuple_size_v<typename Behavior::component_types>>{}, args...);
+			}
+
 			virtual ~species_base() {}
 
 			virtual entity_id const * get_free_list() const = 0;
@@ -202,6 +210,44 @@ namespace psemek::util
 					}
 				}
 			}
+
+			template <typename Behavior, typename ... Components, std::size_t ... Is, typename ... Args>
+			void apply_single_impl(Behavior & behavior, entity_id entity, std::tuple<Components...> *, std::index_sequence<Is...>, Args const & ... args)
+			{
+				std::tuple<typename Components::data * ...> cptrs;
+
+				((std::get<Is>(cptrs) = get_entity_component<Components>()), ...);
+
+				auto all_nonzero = [](auto * ... ptrs)
+				{
+					return ((ptrs != nullptr) && ...);
+				};
+
+				if (!std::apply(all_nonzero, cptrs))
+					return;
+
+				((std::get<Is>(cptrs) += entity), ...);
+
+				typename Behavior::context ctx;
+
+				((std::get<Components *>(ctx.components) = get_species_component<Components>()), ...);
+
+				behavior.begin({id_}, *std::get<Components *>(ctx.components)...);
+
+				auto visit = [&](auto * ... ptrs)
+				{
+					if constexpr (std::is_invocable_v<Behavior, typename Components::data & ..., typename Behavior::context const &, Args const & ...>)
+					{
+						behavior(*ptrs..., ctx, args...);
+					}
+					else
+					{
+						behavior(*ptrs..., args...);
+					}
+				};
+
+				std::apply(visit, cptrs);
+			}
 		};
 
 		template <typename ... Components>
@@ -539,6 +585,9 @@ namespace psemek::util
 		template <typename Behavior, typename ... Args>
 		void apply(Behavior && behavior, species_handle species, Args const & ... args);
 
+		template <typename Behavior, typename ... Args>
+		void apply(Behavior && behavior, entity_handle entity, Args const & ... args);
+
 		template <typename Event, typename Processor>
 		void register_processor(Processor && processor);
 
@@ -548,6 +597,18 @@ namespace psemek::util
 		template <typename Event, typename Behavior>
 		void register_behavior(Behavior && behavior, species_handle species);
 
+		template <typename Behavior>
+		void register_constructor(Behavior && behavior);
+
+		template <typename Behavior>
+		void register_constructor(Behavior && behavior, species_handle species);
+
+		template <typename Behavior>
+		void register_destructor(Behavior && behavior);
+
+		template <typename Behavior>
+		void register_destructor(Behavior && behavior, species_handle species);
+
 		template <typename Event>
 		void event(Event const & event);
 
@@ -555,6 +616,12 @@ namespace psemek::util
 		std::vector<std::unique_ptr<ecs_detail::species_base>> species_;
 
 		std::unordered_map<std::type_index, std::vector<util::function<void(void const *)>>> event_subscribers_;
+
+		std::vector<util::function<void(entity_handle)>> constructors_;
+		std::unordered_map<ecs_detail::species_handle, std::vector<util::function<void(entity_handle)>>> species_constructors_;
+
+		std::vector<util::function<void(entity_handle)>> destructors_;
+		std::unordered_map<ecs_detail::species_handle, std::vector<util::function<void(entity_handle)>>> species_destructors_;
 	};
 
 	template <typename ... Components>
@@ -570,7 +637,12 @@ namespace psemek::util
 
 	inline ecs::entity_handle ecs::add_entity(species_handle species)
 	{
-		return {species_[species.value]->add_entity()};
+		entity_handle entity{species_[species.value]->add_entity()};
+		for (auto const & ctor : constructors_)
+			ctor(entity);
+		for (auto const & ctor : species_constructors_[species.value])
+			ctor(entity);
+		return entity;
 	}
 
 	inline ecs_detail::entity_id ecs::entity_count(species_handle species) const
@@ -580,6 +652,10 @@ namespace psemek::util
 
 	inline void ecs::remove_entity(entity_handle entity)
 	{
+		for (auto const & dtor : destructors_)
+			dtor(entity);
+		for (auto const & dtor : species_destructors_[ecs_detail::unpack(entity.value).species])
+			dtor(entity);
 		species_[ecs_detail::unpack(entity.value).species]->remove_entity(entity.value);
 	}
 
@@ -660,6 +736,13 @@ namespace psemek::util
 		species_[species.value]->apply(behavior, args...);
 	}
 
+	template <typename Behavior, typename ... Args>
+	void ecs::apply(Behavior && behavior, entity_handle entity, Args const & ... args)
+	{
+		auto id = ecs_detail::unpack(entity.value);
+		species_[id.species]->apply_single(behavior, id.entity, args...);
+	}
+
 	template <typename Event, typename Processor>
 	void ecs::register_processor(Processor && processor)
 	{
@@ -684,6 +767,38 @@ namespace psemek::util
 		});
 	}
 
+	template <typename Behavior>
+	void ecs::register_constructor(Behavior && behavior)
+	{
+		constructors_.push_back([this, behavior = std::move(behavior)](entity_handle entity) mutable {
+			apply(behavior, entity);
+		});
+	}
+
+	template <typename Behavior>
+	void ecs::register_constructor(Behavior && behavior, species_handle species)
+	{
+		species_constructors_[species.value].push_back([this, behavior = std::move(behavior)](entity_handle entity) mutable {
+			apply(behavior, entity);
+		});
+	}
+
+	template <typename Behavior>
+	void ecs::register_destructor(Behavior && behavior)
+	{
+		destructors_.push_back([this, behavior = std::move(behavior)](entity_handle entity) mutable {
+			apply(behavior, entity);
+		});
+	}
+
+	template <typename Behavior>
+	void ecs::register_destructor(Behavior && behavior, species_handle species)
+	{
+		species_destructors_[species.value].push_back([this, behavior = std::move(behavior)](entity_handle entity) mutable {
+			apply(behavior, entity);
+		});
+	}
+
 	template <typename Event>
 	void ecs::event(Event const & event)
 	{