From 13a86a76c82b0328d772fbc8391bd6e72b28f6f6 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Sat, 3 Feb 2024 15:22:33 +0300
Subject: [PATCH] Add ecs::dispatcher - an event-based ECS system launcher

---
 libs/ecs/include/psemek/ecs/dispatcher.hpp | 93 ++++++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 libs/ecs/include/psemek/ecs/dispatcher.hpp

diff --git a/libs/ecs/include/psemek/ecs/dispatcher.hpp b/libs/ecs/include/psemek/ecs/dispatcher.hpp
new file mode 100644
index 00000000..c2b351f9
--- /dev/null
+++ b/libs/ecs/include/psemek/ecs/dispatcher.hpp
@@ -0,0 +1,93 @@
+#pragma once
+
+#include <psemek/ecs/container.hpp>
+#include <psemek/util/hash_table.hpp>
+#include <psemek/util/function.hpp>
+
+#include <concepts>
+
+namespace psemek::ecs
+{
+
+	struct dispatcher
+	{
+		dispatcher() = default;
+
+		dispatcher(ecs::container & container)
+			: container_(&container)
+		{}
+
+		explicit operator bool() const
+		{
+			return container_ != nullptr;
+		}
+
+		ecs::container & container()
+		{
+			return *container_;
+		}
+
+		template <typename Event, typename Handler>
+		void handler(Handler handler)
+		{
+			handlers_[Event::uuid()].push_back([handler = std::move(handler), this](void const * event_ptr){
+				auto const & event = *reinterpret_cast<Event const *>(event_ptr);
+
+				if constexpr (std::invocable<Handler, Event const &, ecs::container &>)
+				{
+					handler(event, *container_);
+				}
+				else
+				{
+					handler(event);
+				}
+			});
+		}
+
+		template <typename Event, typename ... Components, typename System>
+		void system(System system)
+		{
+			handlers_[Event::uuid()].push_back([system = std::move(system), this, cache = container_->cache<Components...>()](void const * event_ptr){
+				auto const & event = *reinterpret_cast<Event const *>(event_ptr);
+
+				if constexpr (std::invocable<System, Event const &, ecs::container &, handle, Components & ...>)
+				{
+					container_->apply<Components...>([&](ecs::container & container, ecs::handle handle, Components & ... components){
+						system(event, container, handle, components...);
+					});
+				}
+				else if constexpr (std::invocable<System, Event const &, ecs::container &, Components & ...>)
+				{
+					container_->apply<Components...>([&](ecs::container & container, Components & ... components){
+						system(event, container, components...);
+					});
+				}
+				else if constexpr (std::invocable<System, Event const &, handle, Components & ...>)
+				{
+					container_->apply<Components...>([&](ecs::handle handle, Components & ... components){
+						system(event, handle, components...);
+					});
+				}
+				else
+				{
+					container_->apply<Components...>([&](Components & ... components){
+						system(event, components...);
+					});
+				}
+			});
+		}
+
+		template <typename Event>
+		void dispatch(Event const & event)
+		{
+			for (auto & handler : handlers_[event.uuid()])
+				handler(&event);
+		}
+
+	private:
+		ecs::container * container_;
+
+		util::hash_map<util::uuid, std::vector<util::function<void(void const *)>>> handlers_;
+	};
+
+}