From 8fcaef4ba1d15944e48e515e904b98041c244eb3 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Wed, 10 Jan 2024 00:12:55 +0300
Subject: [PATCH] ECS index API wip: support creating & storing indices

---
 libs/ecs/include/psemek/ecs/container.hpp     | 11 +++++
 .../psemek/ecs/detail/index_container.hpp     | 45 +++++++++++++++++++
 2 files changed, 56 insertions(+)
 create mode 100644 libs/ecs/include/psemek/ecs/detail/index_container.hpp

diff --git a/libs/ecs/include/psemek/ecs/container.hpp b/libs/ecs/include/psemek/ecs/container.hpp
index eb854a53..296f6415 100644
--- a/libs/ecs/include/psemek/ecs/container.hpp
+++ b/libs/ecs/include/psemek/ecs/container.hpp
@@ -8,6 +8,7 @@
 #include <psemek/ecs/detail/component_uuid_helper.hpp>
 #include <psemek/ecs/detail/without.hpp>
 #include <psemek/ecs/detail/component_registry.hpp>
+#include <psemek/ecs/detail/index_container.hpp>
 #include <psemek/ecs/accessor.hpp>
 #include <psemek/ecs/exceptions.hpp>
 #include <psemek/util/range.hpp>
@@ -375,11 +376,15 @@ namespace psemek::ecs
 		template <typename ... Components, typename Function>
 		void watch(Function && function);
 
+		template <typename Index, typename ... Args>
+		Index & index(Args && ... args);
+
 	private:
 		detail::entity_list entity_list_;
 		detail::table_container table_container_;
 		detail::query_cache_container query_cache_container_;
 		detail::component_registry component_registry_;
+		detail::index_container index_container_;
 
 		std::vector<util::uuid> uuid_helper_;
 		util::hash_set<util::uuid> uuid_set_helper_;
@@ -656,4 +661,10 @@ namespace psemek::ecs
 		callback_caches_.push_back(cache);
 	}
 
+	template <typename Index, typename ... Args>
+	Index & container::index(Args && ... args)
+	{
+		return index_container_.get<Index>(*this, std::forward<Args>(args)...);
+	}
+
 }
diff --git a/libs/ecs/include/psemek/ecs/detail/index_container.hpp b/libs/ecs/include/psemek/ecs/detail/index_container.hpp
new file mode 100644
index 00000000..3b9c4e86
--- /dev/null
+++ b/libs/ecs/include/psemek/ecs/detail/index_container.hpp
@@ -0,0 +1,45 @@
+#pragma once
+
+#include <psemek/util/uuid.hpp>
+#include <psemek/util/hash_table.hpp>
+#include <psemek/util/type_name.hpp>
+#include <psemek/util/exception.hpp>
+
+#include <memory>
+
+namespace psemek::ecs
+{
+
+	struct container;
+
+}
+
+namespace psemek::ecs::detail
+{
+
+	struct index_container
+	{
+		template <typename Index, typename ... Args>
+		Index & get(container & container, Args && ... args)
+		{
+			auto uuid = Index::uuid();
+			if (auto it = storage_.find(uuid); it != storage_.end())
+				return *reinterpret_cast<Index *>(it->second.get());
+
+			if constexpr (std::is_constructible_v<Index, ecs::container &, Args && ...>)
+			{
+				auto ptr = std::make_shared<Index>(container, std::forward<Args>(args)...);
+				storage_.insert({uuid, ptr});
+				return *ptr;
+			}
+			else
+			{
+				throw util::exception("Index " + util::type_name<Index>() + " is neither present nor constructible");
+			}
+		}
+
+	private:
+		util::hash_map<util::uuid, std::shared_ptr<void>> storage_;
+	};
+
+}