From bda4a156e745efda17903ea6666f1ea13cbc8343 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Sun, 17 Dec 2023 15:44:38 +0300
Subject: [PATCH] Support registering components in ecs::container

---
 libs/ecs/include/psemek/ecs/container.hpp     | 29 ++++++++++++++++-
 .../psemek/ecs/detail/component_registry.hpp  | 32 +++++++++++++++++++
 2 files changed, 60 insertions(+), 1 deletion(-)
 create mode 100644 libs/ecs/include/psemek/ecs/detail/component_registry.hpp

diff --git a/libs/ecs/include/psemek/ecs/container.hpp b/libs/ecs/include/psemek/ecs/container.hpp
index 89aa1e3e..bc5e44c6 100644
--- a/libs/ecs/include/psemek/ecs/container.hpp
+++ b/libs/ecs/include/psemek/ecs/container.hpp
@@ -7,6 +7,7 @@
 #include <psemek/ecs/detail/all_different_types.hpp>
 #include <psemek/ecs/detail/component_uuid_helper.hpp>
 #include <psemek/ecs/detail/without.hpp>
+#include <psemek/ecs/detail/component_registry.hpp>
 #include <psemek/ecs/accessor.hpp>
 #include <psemek/ecs/exceptions.hpp>
 #include <psemek/util/range.hpp>
@@ -24,7 +25,6 @@ namespace psemek::ecs
 	// - Fully document which functions can be called from which callbacks
 	// - Constructors & destructors implementation (const-only)
 	// - Modification callbacks implementation (const-only)
-	// - Registering components
 	// - Tables serialization
 	// - Refactor query caches
 	// - Index API
@@ -32,6 +32,18 @@ namespace psemek::ecs
 
 	struct container
 	{
+		/** Register a component type within this container. This is used to properly deserialize
+		 *    a serialized container, otherwise it wouldn't know how to create entity tables from
+		 *    serialized data.
+		 *
+		 *  Note that creating entities or attaching components to them automatically registers all
+		 *    referenced components.
+		 *
+		 *  @tparam Component The component type to register
+		 */
+		template <typename Component>
+		void register_component();
+
 		/** Create an entity with the specified components. It is faster to create an entity
 		 *    with all the components at once than to create it with no components and `attach()`
 		 *    them one-by-one.
@@ -41,6 +53,8 @@ namespace psemek::ecs
 		 *  If the entity is created during iteration (inside an `apply()` call), it is unspecified
 		 *    whether the created entity will be visited by iteration or not.
 		 *
+		 *  This function automatically registers all the entity's component types by calling `register_component()`.
+		 *
 		 *  @param components The components to initialize the entity with
 		 *  @return A unique handle to the created entity
 		 *  @warning If any two of the passed component types are equal, the call fails with
@@ -124,6 +138,8 @@ namespace psemek::ecs
 		 *  For the purposes of `apply()` semantics, attaching behaves as if
 		 *    the entity was destroyed and then recreated with the same handle.
 		 *
+		 *  This function automatically registers all the new component types by calling `register_component()`.
+		 *
 		 *  @param entity A handle to the entity to attach components to
 		 *  @param components The components to attach to the entity
 		 *  @pre The entity was previously obtained by a `create()` call and is `alive()`
@@ -366,6 +382,7 @@ namespace psemek::ecs
 		detail::entity_list entity_list_;
 		detail::table_container table_container_;
 		detail::query_cache_container query_cache_container_;
+		detail::component_registry component_registry_;
 
 		std::vector<util::uuid> uuid_helper_;
 		util::hash_set<util::uuid> uuid_set_helper_;
@@ -375,11 +392,19 @@ namespace psemek::ecs
 		void remove_row(detail::table & table, std::uint32_t row, util::span<detail::entity_data> entities);
 	};
 
+	template <typename Component>
+	void container::register_component()
+	{
+		component_registry_.register_component<Component>();
+	}
+
 	template <typename ... Components>
 	handle container::create(Components && ... components)
 	{
 		static_assert(detail::all_different_types_v<std::remove_cvref_t<Components>...>, "all component types must be different");
 
+		(register_component<Components>(), ...);
+
 		detail::component_uuid_helper<std::remove_cvref_t<Components>...> uuids;
 
 		auto table = table_container_.get(uuids.get());
@@ -410,6 +435,8 @@ namespace psemek::ecs
 	{
 		static_assert(detail::all_different_types_v<std::remove_cvref_t<Components>...>, "all component types must be different");
 
+		(register_component<Components>(), ...);
+
 		auto & data = entity_list_.get_entities()[entity.id];
 		for (auto const & column : data.table->columns())
 			uuid_helper_.push_back(column->uuid());
diff --git a/libs/ecs/include/psemek/ecs/detail/component_registry.hpp b/libs/ecs/include/psemek/ecs/detail/component_registry.hpp
new file mode 100644
index 00000000..49cc9fa1
--- /dev/null
+++ b/libs/ecs/include/psemek/ecs/detail/component_registry.hpp
@@ -0,0 +1,32 @@
+#pragma once
+
+#include <psemek/ecs/detail/column.hpp>
+#include <psemek/util/uuid.hpp>
+#include <psemek/util/hash_table.hpp>
+#include <psemek/util/function.hpp>
+
+namespace psemek::ecs::detail
+{
+
+	struct component_registry
+	{
+		template <typename Component>
+		void register_component()
+		{
+			column_factories_.insert({Component::uuid(), []{
+				return std::make_unique<column_impl<Component>>();
+			}});
+		}
+
+		std::unique_ptr<column> create_column(util::uuid const & uuid) const
+		{
+			if (auto it = column_factories_.find(uuid); it != column_factories_.end())
+				return it->second();
+			return nullptr;
+		}
+
+	private:
+		util::hash_map<util::uuid, util::function<std::unique_ptr<column>()>> column_factories_;
+	};
+
+}