3 files changed, 70 insertions, 20 deletions

diff --git a/src/crepe/api/LoopManager.cpp b/src/crepe/api/LoopManager.cpp
index 637fbe1..ff428fd 100644
--- a/src/crepe/api/LoopManager.cpp
+++ b/src/crepe/api/LoopManager.cpp
@@ -13,18 +13,17 @@
 using namespace crepe;
 using namespace std;
 
-LoopManager::LoopManager()
-	: systems({
-		ScriptSystem{this->mediator},
-		PhysicsSystem{this->mediator},
-		CollisionSystem{this->mediator},
-		AnimatorSystem{this->mediator},
-		ParticleSystem{this->mediator},
-		RenderSystem{this->mediator},
-		InputSystem{this->mediator},
-		EventSystem{this->mediator},
-		AudioSystem{this->mediator},
-	}) { }
+LoopManager::LoopManager() {
+	this->load_system<ScriptSystem>();
+	this->load_system<PhysicsSystem>();
+	this->load_system<CollisionSystem>();
+	this->load_system<AnimatorSystem>();
+	this->load_system<ParticleSystem>();
+	this->load_system<RenderSystem>();
+	this->load_system<InputSystem>();
+	this->load_system<EventSystem>();
+	this->load_system<AudioSystem>();
+}
 
 void LoopManager::start() {
 	this->setup();
@@ -32,16 +31,16 @@ void LoopManager::start() {
 }
 
 void LoopManager::fixed_update() {
-	for (System & system : this->systems) {
-		if (!system.active) continue;
-		system.fixed_update();
+	for (auto & [type, system] : this->systems) {
+		if (!system->active) continue;
+		system->fixed_update();
 	}
 }
 
 void LoopManager::frame_update() {
-	for (System & system : this->systems) {
-		if (!system.active) continue;
-		system.frame_update();
+	for (auto & [type, system] : this->systems) {
+		if (!system->active) continue;
+		system->frame_update();
 	}
 }
 
diff --git a/src/crepe/api/LoopManager.h b/src/crepe/api/LoopManager.h
index 1183a4d..4b1fc1e 100644
--- a/src/crepe/api/LoopManager.h
+++ b/src/crepe/api/LoopManager.h
@@ -73,15 +73,32 @@ private:
 	SaveManager save_manager{mediator};
 
 	//! SDL context \todo no more singletons!
-	SDLContext & sdl_context = SDLContext::get_instance();
+	SDLContext & sdl_context = mediator.sdl_context;
 	//! Loop timer \todo no more singletons!
 	LoopTimer & loop_timer = LoopTimer::get_instance();
 
 private:
 	/**
 	 * \brief Collection of System instances
+	 *
+	 * This map holds System instances indexed by the system's class typeid. It is filled in the
+	 * constructor of \c LoopManager using LoopManager::load_system.
+	 */
+	std::unordered_map<std::type_index, std::unique_ptr<System>> systems;
+	/**
+	 * \brief Initialize a system
+	 * \tparam T System type (must be derivative of \c System)
+	 */
+	template <class T>
+	void load_system();
+	/**
+	 * \brief Retrieve a reference to ECS system
+	 * \tparam T System type
+	 * \returns Reference to system instance
+	 * \throws std::runtime_error if the System is not initialized
 	 */
-	std::vector<System> systems;
+	template <class T>
+	T & get_system();
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/LoopManager.hpp b/src/crepe/api/LoopManager.hpp
index 51afa70..627b281 100644
--- a/src/crepe/api/LoopManager.hpp
+++ b/src/crepe/api/LoopManager.hpp
@@ -1,5 +1,10 @@
 #pragma once
 
+#include <memory>
+#include <cassert>
+#include <format>
+
+#include "../system/System.h"
 #include "LoopManager.h"
 
 namespace crepe {
@@ -9,4 +14,33 @@ void LoopManager::add_scene() {
 	this->scene_manager.add_scene<T>();
 }
 
+template <class T>
+T & LoopManager::get_system() {
+	using namespace std;
+	static_assert(is_base_of<System, T>::value, "get_system must recieve a derivative class of System");
+
+	const type_info & type = typeid(T);
+	if (!this->systems.contains(type))
+		throw runtime_error(format("LoopManager: {} is not initialized", type.name()));
+
+	System * system = this->systems.at(type).get();
+	T * concrete_system = dynamic_cast<T *>(system);
+	assert(concrete_system != nullptr);
+
+	return *concrete_system;
+}
+
+template <class T>
+void LoopManager::load_system() {
+	using namespace std;
+	static_assert(is_base_of<System, T>::value,
+			"load_system must recieve a derivative class of System");
+
+	const type_info & type = typeid(T);
+	if (this->systems.contains(type))
+		throw runtime_error(format("LoopManager: {} is already initialized", type.name()));
+	System * system = new T(this->mediator);
+	this->systems[type] = unique_ptr<System>(system);
+}
+
 } // namespace crepe