Merge branch 'master' of https://github.com/lonkaars/crepe into wouter/events

38 files changed, 325 insertions, 208 deletions

diff --git a/src/crepe/api/Animator.cpp b/src/crepe/api/Animator.cpp
index 58fee2a..464b0fd 100644
--- a/src/crepe/api/Animator.cpp
+++ b/src/crepe/api/Animator.cpp
@@ -1,7 +1,5 @@
 
-#include <cstdint>
-
-#include "util/log.h"
+#include "util/Log.h"
 
 #include "Animator.h"
 #include "Component.h"
@@ -9,7 +7,7 @@
 
 using namespace crepe;
 
-Animator::Animator(uint32_t id, Sprite & ss, int row, int col, int col_animator)
+Animator::Animator(game_object_id_t id, Sprite & ss, int row, int col, int col_animator)
 	: Component(id),
 	  spritesheet(ss),
 	  row(row),
diff --git a/src/crepe/api/Animator.h b/src/crepe/api/Animator.h
index b5bb4c9..53f4b91 100644
--- a/src/crepe/api/Animator.h
+++ b/src/crepe/api/Animator.h
@@ -1,11 +1,10 @@
 #pragma once
 
-#include <cstdint>
-
 #include "Component.h"
 #include "Sprite.h"
 
 namespace crepe {
+
 class AnimatorSystem;
 class SDLContext;
 
diff --git a/src/crepe/api/AssetManager.cpp b/src/crepe/api/AssetManager.cpp
index b891760..3925758 100644
--- a/src/crepe/api/AssetManager.cpp
+++ b/src/crepe/api/AssetManager.cpp
@@ -1,4 +1,4 @@
-#include "util/log.h"
+#include "util/Log.h"
 
 #include "AssetManager.h"
 
diff --git a/src/crepe/api/AudioSource.cpp b/src/crepe/api/AudioSource.cpp
deleted file mode 100644
index 63fd0d7..0000000
--- a/src/crepe/api/AudioSource.cpp
+++ /dev/null
@@ -1,23 +0,0 @@
-#include <memory>
-
-#include "../facade/Sound.h"
-
-#include "AudioSource.h"
-
-using namespace crepe;
-
-AudioSource::AudioSource(std::unique_ptr<Asset> audio_clip) {
-	this->sound = std::make_unique<crepe::Sound>(std::move(audio_clip));
-}
-
-void AudioSource::play() { return this->play(false); }
-
-void AudioSource::play(bool looping) {
-	this->sound->set_looping(looping);
-	this->sound->play();
-}
-
-void AudioSource::stop() {
-	this->sound->pause();
-	this->sound->rewind();
-}
diff --git a/src/crepe/api/AudioSource.h b/src/crepe/api/AudioSource.h
deleted file mode 100644
index 1e24ae8..0000000
--- a/src/crepe/api/AudioSource.h
+++ /dev/null
@@ -1,39 +0,0 @@
-#pragma once
-
-#include <memory>
-
-#include "../Asset.h"
-#include "../Component.h"
-
-namespace crepe {
-
-class Sound;
-
-//! Audio source component
-class AudioSource : public Component {
-public:
-	AudioSource(std::unique_ptr<Asset> audio_clip);
-	virtual ~AudioSource() = default;
-
-public:
-	//! Start or resume this audio source
-	void play();
-	void play(bool looping);
-	//! Stop this audio source
-	void stop();
-
-public:
-	//! Sample file location
-	std::unique_ptr<Asset> audio_clip;
-	//! TODO: ?????
-	bool play_on_awake;
-	//! Repeat the current audio clip during playback
-	bool loop;
-	//! Normalized volume (0.0 - 1.0)
-	float volume;
-
-private:
-	std::unique_ptr<Sound> sound;
-};
-
-} // namespace crepe
diff --git a/src/crepe/api/BehaviorScript.cpp b/src/crepe/api/BehaviorScript.cpp
index e69de29..7bbace0 100644
--- a/src/crepe/api/BehaviorScript.cpp
+++ b/src/crepe/api/BehaviorScript.cpp
@@ -0,0 +1,15 @@
+#include "BehaviorScript.h"
+#include "Component.h"
+#include "GameObject.h"
+
+using namespace crepe;
+
+BehaviorScript::BehaviorScript(game_object_id_t id, ComponentManager & mgr)
+	: Component(id),
+	  component_manager(mgr) {}
+
+template <>
+BehaviorScript & GameObject::add_component<BehaviorScript>() {
+	ComponentManager & mgr = this->component_manager;
+	return mgr.add_component<BehaviorScript>(this->id, mgr);
+}
diff --git a/src/crepe/api/BehaviorScript.h b/src/crepe/api/BehaviorScript.h
index 6b1fec7..9d85d4c 100644
--- a/src/crepe/api/BehaviorScript.h
+++ b/src/crepe/api/BehaviorScript.h
@@ -4,29 +4,69 @@
 
 #include "../Component.h"
 
+#include "GameObject.h"
+
 namespace crepe {
 
 class ScriptSystem;
 class ComponentManager;
 class Script;
 
+/**
+ * \brief Script component
+ *
+ * This class acts as a (component) wrapper around an instance of (a class derivatived from) \c
+ * Script. \c BehaviorScript is the only ECS component that stores member function
+ * implementations as data.
+ */
 class BehaviorScript : public Component {
 protected:
-	friend class crepe::ComponentManager;
-	using Component::Component;
-
-public:
-	virtual ~BehaviorScript() = default;
+	/**
+	 * \param id Parent \c GameObject id
+	 * \param component_manager Reference to component manager (passed through to \c Script
+	 * instance)
+	 *
+	 * \note Calls to this constructor (should) always pass through \c GameObject::add_component,
+	 * which has an exception for this specific component type. This was done so the user does
+	 * not have to pass references used within \c Script to each \c BehaviorScript instance.
+	 */
+	BehaviorScript(game_object_id_t id, ComponentManager & component_manager);
+	//! Only ComponentManager is allowed to instantiate BehaviorScript
+	friend class ComponentManager;
 
 public:
+	/**
+	 * \brief Set the concrete script of this component
+	 *
+	 * \tparam T Concrete script type (derived from \c crepe::Script)
+	 *
+	 * \returns Reference to BehaviorScript component (`*this`)
+	 */
 	template <class T>
 	BehaviorScript & set_script();
 
 protected:
-	friend class crepe::ScriptSystem;
+	//! Script instance
 	std::unique_ptr<Script> script = nullptr;
+	//! ScriptSystem needs direct access to the script instance
+	friend class ScriptSystem;
+
+protected:
+	//! Reference to component manager (passed to Script)
+	ComponentManager & component_manager;
 };
 
+/**
+ * \brief Add a BehaviorScript component to this game object
+ *
+ * The \c BehaviorScript class is the only exception to the ECS harmony, and requires a
+ * reference to the component manager passed to its constructor in order to function normally.
+ * This is because the \c BehaviorScript (and \c Script) classes are the only component-related
+ * classes that store implemented member functions as data.
+ */
+template <>
+BehaviorScript & GameObject::add_component<BehaviorScript>();
+
 } // namespace crepe
 
 #include "BehaviorScript.hpp"
diff --git a/src/crepe/api/BehaviorScript.hpp b/src/crepe/api/BehaviorScript.hpp
index 4751607..d80321d 100644
--- a/src/crepe/api/BehaviorScript.hpp
+++ b/src/crepe/api/BehaviorScript.hpp
@@ -2,7 +2,7 @@
 
 #include <type_traits>
 
-#include "../util/log.h"
+#include "../util/Log.h"
 
 #include "BehaviorScript.h"
 #include "Script.h"
@@ -11,10 +11,11 @@ namespace crepe {
 
 template <class T>
 BehaviorScript & BehaviorScript::set_script() {
-	static_assert(std::is_base_of<Script, T>::value);
 	dbg_trace();
+	static_assert(std::is_base_of<Script, T>::value);
 	Script * s = new T();
-	s->parent = this;
+	s->game_object_id = this->game_object_id;
+	s->component_manager_ref = &this->component_manager;
 	this->script = std::unique_ptr<Script>(s);
 	return *this;
 }
diff --git a/src/crepe/api/CMakeLists.txt b/src/crepe/api/CMakeLists.txt
index edf4250..a185ca6 100644
--- a/src/crepe/api/CMakeLists.txt
+++ b/src/crepe/api/CMakeLists.txt
@@ -1,7 +1,6 @@
 target_sources(crepe PUBLIC
 	# AudioSource.cpp
 	BehaviorScript.cpp
-	Script.cpp
 	GameObject.cpp
 	Rigidbody.cpp
 	ParticleEmitter.cpp
diff --git a/src/crepe/api/Camera.cpp b/src/crepe/api/Camera.cpp
index d5df196..5835bdd 100644
--- a/src/crepe/api/Camera.cpp
+++ b/src/crepe/api/Camera.cpp
@@ -1,7 +1,4 @@
-
-#include <cstdint>
-
-#include "util/log.h"
+#include "util/Log.h"
 
 #include "Camera.h"
 #include "Color.h"
@@ -9,7 +6,9 @@
 
 using namespace crepe;
 
-Camera::Camera(uint32_t id, const Color & bg_color) : Component(id), bg_color(bg_color) {
+Camera::Camera(game_object_id_t id, const Color & bg_color)
+	: Component(id),
+	  bg_color(bg_color) {
 	dbg_trace();
 }
 
diff --git a/src/crepe/api/Camera.h b/src/crepe/api/Camera.h
index c7f9af5..e0cda34 100644
--- a/src/crepe/api/Camera.h
+++ b/src/crepe/api/Camera.h
@@ -1,7 +1,5 @@
 #pragma once
 
-#include <cstdint>
-
 #include "Color.h"
 #include "Component.h"
 
@@ -22,7 +20,7 @@ public:
 	 * \param id Unique identifier for the camera component.
 	 * \param bg_color Background color for the camera view.
 	 */
-	Camera(uint32_t id, const Color & bg_color);
+	Camera(game_object_id_t id, const Color & bg_color);
 	~Camera(); // dbg_trace only
 
 public:
diff --git a/src/crepe/api/Config.h b/src/crepe/api/Config.h
index 1cee668..3ab877a 100644
--- a/src/crepe/api/Config.h
+++ b/src/crepe/api/Config.h
@@ -1,19 +1,24 @@
 #pragma once
 
-#include "../util/log.h"
+#include "../util/Log.h"
 
 namespace crepe {
 
+/**
+ * \brief Global configuration interface
+ *
+ * This class stores engine default settings. Properties on this class are only supposed to be
+ * modified *before* execution is handed over from the game programmer to the engine (i.e. the
+ * main loop is started).
+ */
 class Config {
-private:
-	Config() = default;
-
-public:
-	~Config() = default;
-
 public:
 	//! Retrieve handle to global Config instance
 	static Config & get_instance();
+
+private:
+	Config() = default;
+
 	// singleton
 	Config(const Config &) = delete;
 	Config(Config &&) = delete;
@@ -28,7 +33,7 @@ public:
 		 *
 		 * Only messages with equal or higher priority than this value will be logged.
 		 */
-		LogLevel level = LogLevel::INFO;
+		Log::Level level = Log::Level::INFO;
 		/**
 		 * \brief Colored log output
 		 *
diff --git a/src/crepe/api/GameObject.cpp b/src/crepe/api/GameObject.cpp
index d470295..287e81d 100644
--- a/src/crepe/api/GameObject.cpp
+++ b/src/crepe/api/GameObject.cpp
@@ -1,22 +1,26 @@
 #include "api/Transform.h"
 
+#include "BehaviorScript.h"
 #include "GameObject.h"
 #include "Metadata.h"
 
 using namespace crepe;
 using namespace std;
 
-GameObject::GameObject(game_object_id_t id, const std::string & name, const std::string & tag,
+GameObject::GameObject(ComponentManager & component_manager, game_object_id_t id,
+					   const std::string & name, const std::string & tag,
 					   const Vector2 & position, double rotation, double scale)
-	: id(id) {
+	: id(id),
+	  component_manager(component_manager) {
+
 	// Add Transform and Metadata components
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	mgr.add_component<Transform>(this->id, position, rotation, scale);
 	mgr.add_component<Metadata>(this->id, name, tag);
 }
 
 void GameObject::set_parent(const GameObject & parent) {
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 
 	// Set parent on own Metadata component
 	vector<reference_wrapper<Metadata>> this_metadata
diff --git a/src/crepe/api/GameObject.h b/src/crepe/api/GameObject.h
index 75c164b..34ef8bb 100644
--- a/src/crepe/api/GameObject.h
+++ b/src/crepe/api/GameObject.h
@@ -2,11 +2,12 @@
 
 #include <string>
 
+#include "Vector2.h"
 #include "types.h"
 
 namespace crepe {
 
-class Vector2;
+class ComponentManager;
 
 /**
  * \brief Represents a GameObject
@@ -15,11 +16,12 @@ class Vector2;
  * the game programmer. The actual implementation is done in the ComponentManager.
  */
 class GameObject {
-public:
+private:
 	/**
 	 * This constructor creates a new GameObject. It creates a new Transform and Metadata
 	 * component and adds them to the ComponentManager.
 	 * 
+	 * \param component_manager Reference to component_manager
 	 * \param id The id of the GameObject
 	 * \param name The name of the GameObject
 	 * \param tag The tag of the GameObject
@@ -27,8 +29,13 @@ public:
 	 * \param rotation The rotation of the GameObject
 	 * \param scale The scale of the GameObject
 	 */
-	GameObject(game_object_id_t id, const std::string & name, const std::string & tag,
-			   const Vector2 & position, double rotation, double scale);
+	GameObject(ComponentManager & component_manager, game_object_id_t id,
+			   const std::string & name, const std::string & tag, const Vector2 & position,
+			   double rotation, double scale);
+	//! ComponentManager instances GameObject
+	friend class ComponentManager;
+
+public:
 	/**
 	 * \brief Set the parent of this GameObject
 	 * 
@@ -56,6 +63,9 @@ public:
 public:
 	//! The id of the GameObject
 	const game_object_id_t id;
+
+protected:
+	ComponentManager & component_manager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/GameObject.hpp b/src/crepe/api/GameObject.hpp
index bfba7fe..17b17d7 100644
--- a/src/crepe/api/GameObject.hpp
+++ b/src/crepe/api/GameObject.hpp
@@ -8,7 +8,7 @@ namespace crepe {
 
 template <typename T, typename... Args>
 T & GameObject::add_component(Args &&... args) {
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	return mgr.add_component<T>(this->id, std::forward<Args>(args)...);
 }
 
diff --git a/src/crepe/api/LoopManager.cpp b/src/crepe/api/LoopManager.cpp
index 2e9823f..a64366f 100644
--- a/src/crepe/api/LoopManager.cpp
+++ b/src/crepe/api/LoopManager.cpp
@@ -1,5 +1,9 @@
-
 #include "../facade/SDLContext.h"
+
+#include "../system/AnimatorSystem.h"
+#include "../system/CollisionSystem.h"
+#include "../system/ParticleSystem.h"
+#include "../system/PhysicsSystem.h"
 #include "../system/RenderSystem.h"
 #include "../system/ScriptSystem.h"
 
@@ -7,11 +11,21 @@
 #include "LoopTimer.h"
 
 using namespace crepe;
+using namespace std;
+
+LoopManager::LoopManager() {
+	this->load_system<AnimatorSystem>();
+	this->load_system<CollisionSystem>();
+	this->load_system<ParticleSystem>();
+	this->load_system<PhysicsSystem>();
+	this->load_system<RenderSystem>();
+	this->load_system<ScriptSystem>();
+}
 
-LoopManager::LoopManager() {}
 void LoopManager::process_input() {
 	SDLContext::get_instance().handle_events(this->game_running);
 }
+
 void LoopManager::start() {
 	this->setup();
 	this->loop();
@@ -48,7 +62,7 @@ void LoopManager::setup() {
 
 void LoopManager::render() {
 	if (this->game_running) {
-		RenderSystem::get_instance().update();
+		this->get_system<RenderSystem>().update();
 	}
 }
 
diff --git a/src/crepe/api/LoopManager.h b/src/crepe/api/LoopManager.h
index 2f03193..f6904be 100644
--- a/src/crepe/api/LoopManager.h
+++ b/src/crepe/api/LoopManager.h
@@ -2,15 +2,9 @@
 
 #include <memory>
 
-class RenderSystem;
-class SDLContext;
-class LoopTimer;
-class ScriptSystem;
-class SoundSystem;
-class ParticleSystem;
-class PhysicsSystem;
-class AnimatorSystem;
-class CollisionSystem;
+#include "../ComponentManager.h"
+#include "../system/System.h"
+
 namespace crepe {
 
 class LoopManager {
@@ -73,7 +67,35 @@ private:
 	void render();
 
 	bool game_running = false;
-	//#TODO add system instances
+
+private:
+	//! Component manager instance
+	ComponentManager component_manager{};
+
+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
+	 */
+	template <class T>
+	T & get_system();
 };
 
 } // namespace crepe
+
+#include "LoopManager.hpp"
diff --git a/src/crepe/api/LoopManager.hpp b/src/crepe/api/LoopManager.hpp
new file mode 100644
index 0000000..0b14fdb
--- /dev/null
+++ b/src/crepe/api/LoopManager.hpp
@@ -0,0 +1,40 @@
+#pragma once
+
+#include <cassert>
+#include <format>
+#include <memory>
+
+#include "../system/System.h"
+
+#include "LoopManager.h"
+
+namespace crepe {
+
+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");
+
+	System * system = new T(this->component_manager);
+	this->systems[typeid(T)] = unique_ptr<System>(system);
+}
+
+} // namespace crepe
diff --git a/src/crepe/api/LoopTimer.cpp b/src/crepe/api/LoopTimer.cpp
index 417da47..a9800b7 100644
--- a/src/crepe/api/LoopTimer.cpp
+++ b/src/crepe/api/LoopTimer.cpp
@@ -1,7 +1,7 @@
 #include <chrono>
 
 #include "../facade/SDLContext.h"
-#include "../util/log.h"
+#include "../util/Log.h"
 
 #include "LoopTimer.h"
 
diff --git a/src/crepe/api/LoopTimer.h b/src/crepe/api/LoopTimer.h
index c3c5631..f277d7b 100644
--- a/src/crepe/api/LoopTimer.h
+++ b/src/crepe/api/LoopTimer.h
@@ -1,7 +1,6 @@
 #pragma once
 
 #include <chrono>
-#include <cstdint>
 
 namespace crepe {
 
diff --git a/src/crepe/api/Rigidbody.cpp b/src/crepe/api/Rigidbody.cpp
index 3bf1c5b..6b87695 100644
--- a/src/crepe/api/Rigidbody.cpp
+++ b/src/crepe/api/Rigidbody.cpp
@@ -2,8 +2,8 @@
 
 using namespace crepe;
 
-crepe::Rigidbody::Rigidbody(uint32_t game_object_id, const Data & data)
-	: Component(game_object_id),
+crepe::Rigidbody::Rigidbody(game_object_id_t id, const Data & data)
+	: Component(id),
 	  data(data) {}
 
 void crepe::Rigidbody::add_force_linear(const Vector2 & force) {
diff --git a/src/crepe/api/Rigidbody.h b/src/crepe/api/Rigidbody.h
index c74fea8..3e5c7a3 100644
--- a/src/crepe/api/Rigidbody.h
+++ b/src/crepe/api/Rigidbody.h
@@ -1,7 +1,5 @@
 #pragma once
 
-#include <cstdint>
-
 #include "../Component.h"
 
 #include "Vector2.h"
@@ -82,7 +80,7 @@ public:
 	 * \param game_object_id id of the gameobject the rigibody is added to.
 	 * \param data struct to configure the rigidbody.
 	 */
-	Rigidbody(uint32_t game_object_id, const Data & data);
+	Rigidbody(game_object_id_t id, const Data & data);
 	//! struct to hold data of rigidbody
 	Data data;
 
diff --git a/src/crepe/api/SaveManager.cpp b/src/crepe/api/SaveManager.cpp
index a71ad83..c5f43ea 100644
--- a/src/crepe/api/SaveManager.cpp
+++ b/src/crepe/api/SaveManager.cpp
@@ -1,5 +1,5 @@
 #include "../facade/DB.h"
-#include "../util/log.h"
+#include "../util/Log.h"
 
 #include "Config.h"
 #include "SaveManager.h"
diff --git a/src/crepe/api/Scene.cpp b/src/crepe/api/Scene.cpp
index 933edf4..88aa82d 100644
--- a/src/crepe/api/Scene.cpp
+++ b/src/crepe/api/Scene.cpp
@@ -2,4 +2,6 @@
 
 using namespace crepe;
 
-Scene::Scene(const std::string & name) : name(name) {}
+Scene::Scene(ComponentManager & mgr, const std::string & name)
+	: component_manager(mgr),
+	  name(name) {}
diff --git a/src/crepe/api/Scene.h b/src/crepe/api/Scene.h
index f8bcc3d..0e516b6 100644
--- a/src/crepe/api/Scene.h
+++ b/src/crepe/api/Scene.h
@@ -4,14 +4,23 @@
 
 namespace crepe {
 
+class SceneManager;
+class ComponentManager;
+
 class Scene {
+protected:
+	Scene(ComponentManager & mgr, const std::string & name);
+	friend class SceneManager;
+
 public:
-	Scene(const std::string & name);
 	virtual ~Scene() = default;
-	virtual void load_scene() = 0;
 
 public:
-	std::string name;
+	virtual void load_scene() = 0;
+	const std::string name;
+
+protected:
+	ComponentManager & component_manager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/SceneManager.cpp b/src/crepe/api/SceneManager.cpp
index c0f8b23..7fb5cb0 100644
--- a/src/crepe/api/SceneManager.cpp
+++ b/src/crepe/api/SceneManager.cpp
@@ -8,10 +8,7 @@
 using namespace crepe;
 using namespace std;
 
-SceneManager & SceneManager::get_instance() {
-	static SceneManager instance;
-	return instance;
-}
+SceneManager::SceneManager(ComponentManager & mgr) : component_manager(mgr) {}
 
 void SceneManager::set_next_scene(const string & name) { next_scene = name; }
 
@@ -29,7 +26,7 @@ void SceneManager::load_next_scene() {
 	unique_ptr<Scene> & scene = *it;
 
 	// Delete all components of the current scene
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	mgr.delete_all_components();
 
 	// Load the new scene
diff --git a/src/crepe/api/SceneManager.h b/src/crepe/api/SceneManager.h
index 1e0e670..e854794 100644
--- a/src/crepe/api/SceneManager.h
+++ b/src/crepe/api/SceneManager.h
@@ -8,14 +8,11 @@
 
 namespace crepe {
 
+class ComponentManager;
+
 class SceneManager {
 public:
-	// Singleton
-	static SceneManager & get_instance();
-	SceneManager(const SceneManager &) = delete;
-	SceneManager(SceneManager &&) = delete;
-	SceneManager & operator=(const SceneManager &) = delete;
-	SceneManager & operator=(SceneManager &&) = delete;
+	SceneManager(ComponentManager & mgr);
 
 public:
 	/**
@@ -38,11 +35,9 @@ public:
 	void load_next_scene();
 
 private:
-	SceneManager() = default;
-
-private:
 	std::vector<std::unique_ptr<Scene>> scenes;
 	std::string next_scene;
+	ComponentManager & component_manager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/SceneManager.hpp b/src/crepe/api/SceneManager.hpp
index 61c33bf..714f690 100644
--- a/src/crepe/api/SceneManager.hpp
+++ b/src/crepe/api/SceneManager.hpp
@@ -1,12 +1,16 @@
+#pragma once
+
 #include "SceneManager.h"
 
 namespace crepe {
 
 template <typename T>
 void SceneManager::add_scene(const std::string & name) {
-	static_assert(std::is_base_of<Scene, T>::value, "T must be derived from Scene");
+	using namespace std;
+	static_assert(is_base_of<Scene, T>::value, "T must be derived from Scene");
 
-	scenes.emplace_back(make_unique<T>(name));
+	Scene * scene = new T(this->component_manager, name);
+	this->scenes.emplace_back(unique_ptr<Scene>(scene));
 
 	// The first scene added, is the one that will be loaded at the beginning
 	if (next_scene.empty()) {
diff --git a/src/crepe/api/Script.cpp b/src/crepe/api/Script.cpp
deleted file mode 100644
index 390cec7..0000000
--- a/src/crepe/api/Script.cpp
+++ /dev/null
@@ -1,3 +0,0 @@
-#include "Script.h"
-
-using namespace crepe;
diff --git a/src/crepe/api/Script.h b/src/crepe/api/Script.h
index bf43a49..2b70379 100644
--- a/src/crepe/api/Script.h
+++ b/src/crepe/api/Script.h
@@ -2,34 +2,85 @@
 
 #include <vector>
 
-namespace crepe {
-class ScriptSystem;
-}
+#include "../types.h"
 
 namespace crepe {
 
+class ScriptSystem;
 class BehaviorScript;
+class ComponentManager;
 
+/**
+ * \brief Script interface
+ *
+ * This class is used as a base class for user-defined scripts that can be added to game
+ * objects using the \c BehaviorScript component.
+ *
+ * \note Additional *events* (like Unity's OnDisable and OnEnable) should be implemented as
+ * member or lambda methods in derivative user script classes and registered in \c init().
+ */
 class Script {
-	friend class crepe::ScriptSystem;
-
 protected:
+	/**
+	 * \brief Script initialization function
+	 *
+	 * This function is called during the ScriptSystem::update() routine *before*
+	 * Script::update() if it (a) has not yet been called and (b) the \c BehaviorScript component
+	 * holding this script instance is active.
+	 */
 	virtual void init() {}
+	/**
+	 * \brief Script update function
+	 *
+	 * This function is called during the ScriptSystem::update() routine if the \c BehaviorScript
+	 * component holding this script instance is active.
+	 */
 	virtual void update() {}
-	// NOTE: additional *events* (like unity's OnDisable and OnEnable) should be implemented as
-	// member methods in derivative user script classes and registered in init(), otherwise this
-	// class will balloon in size with each added event.
+	//! ScriptSystem calls \c init() and \c update()
+	friend class crepe::ScriptSystem;
 
 protected:
+	/**
+	 * \brief Get single component of type \c T on this game object (utility)
+	 *
+	 * \tparam T Type of component
+	 *
+	 * \returns Reference to component
+	 *
+	 * \throws nullptr if this game object does not have a component matching type \c T
+	 */
 	template <typename T>
-	T & get_component();
+	T & get_component() const;
+	// TODO: make get_component calls for component types that can have more than 1 instance
+	// cause compile-time errors
 
+	/**
+	 * \brief Get all components of type \c T on this game object (utility)
+	 *
+	 * \tparam T Type of component
+	 *
+	 * \returns List of component references
+	 */
 	template <typename T>
-	std::vector<std::reference_wrapper<T>> get_components();
+	std::vector<std::reference_wrapper<T>> get_components() const;
+
+protected:
+	// NOTE: Script must have a constructor without arguments so the game programmer doesn't need
+	// to manually add `using Script::Script` to their concrete script class.
+	Script() = default;
+	//! Only \c BehaviorScript instantiates Script
+	friend class BehaviorScript;
+
+private:
+	// These references are set by BehaviorScript immediately after calling the constructor of
+	// Script.
+	game_object_id_t game_object_id = -1;
+	ComponentManager * component_manager_ref = nullptr;
+	// TODO: use OptionalRef instead of pointer
 
 private:
-	friend class crepe::BehaviorScript;
-	BehaviorScript * parent = nullptr;
+	//! Flag to indicate if \c init() has been called already
+	bool initialized = false;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/Script.hpp b/src/crepe/api/Script.hpp
index ce39331..a064a90 100644
--- a/src/crepe/api/Script.hpp
+++ b/src/crepe/api/Script.hpp
@@ -8,17 +8,21 @@
 namespace crepe {
 
 template <typename T>
-T & Script::get_component() {
-	std::vector<std::reference_wrapper<T>> all_components = this->get_components<T>();
-	if (all_components.size() < 1) throw nullptr; // TODO
+T & Script::get_component() const {
+	using namespace std;
+	vector<reference_wrapper<T>> all_components = this->get_components<T>();
+	if (all_components.size() < 1)
+		throw runtime_error(
+			format("Script: no component found with type = {}", typeid(T).name()));
 
 	return all_components.back().get();
 }
 
 template <typename T>
-std::vector<std::reference_wrapper<T>> Script::get_components() {
-	ComponentManager & mgr = ComponentManager::get_instance();
-	return mgr.get_components_by_id<T>(this->parent->game_object_id);
+std::vector<std::reference_wrapper<T>> Script::get_components() const {
+	auto & mgr = *this->component_manager_ref;
+
+	return mgr.get_components_by_id<T>(this->game_object_id);
 }
 
 } // namespace crepe
diff --git a/src/crepe/api/Sprite.cpp b/src/crepe/api/Sprite.cpp
index c4cd29e..bd2d5cf 100644
--- a/src/crepe/api/Sprite.cpp
+++ b/src/crepe/api/Sprite.cpp
@@ -1,6 +1,6 @@
 #include <memory>
 
-#include "../util/log.h"
+#include "../util/Log.h"
 #include "facade/SDLContext.h"
 
 #include "Component.h"
diff --git a/src/crepe/api/Sprite.h b/src/crepe/api/Sprite.h
index 50ea88e..0192793 100644
--- a/src/crepe/api/Sprite.h
+++ b/src/crepe/api/Sprite.h
@@ -1,6 +1,5 @@
 #pragma once
 
-#include <cstdint>
 #include <memory>
 
 #include "Color.h"
diff --git a/src/crepe/api/Texture.cpp b/src/crepe/api/Texture.cpp
index 5ebd23d..de0d0ea 100644
--- a/src/crepe/api/Texture.cpp
+++ b/src/crepe/api/Texture.cpp
@@ -1,7 +1,7 @@
 #include <SDL2/SDL_render.h>
 
 #include "../facade/SDLContext.h"
-#include "../util/log.h"
+#include "../util/Log.h"
 
 #include "Asset.h"
 #include "Texture.h"
@@ -26,7 +26,7 @@ Texture::~Texture() {
 
 void Texture::load(unique_ptr<Asset> res) {
 	SDLContext & ctx = SDLContext::get_instance();
-	this->texture = std::move(ctx.texture_from_path(res->canonical()));
+	this->texture = std::move(ctx.texture_from_path(res->get_canonical()));
 }
 
 int Texture::get_width() const {
diff --git a/src/crepe/api/Transform.cpp b/src/crepe/api/Transform.cpp
index 8eeec41..cd944bd 100644
--- a/src/crepe/api/Transform.cpp
+++ b/src/crepe/api/Transform.cpp
@@ -1,4 +1,4 @@
-#include "util/log.h"
+#include "../util/Log.h"
 
 #include "Transform.h"
 
diff --git a/src/crepe/api/Transform.h b/src/crepe/api/Transform.h
index 51b0daa..18aa293 100644
--- a/src/crepe/api/Transform.h
+++ b/src/crepe/api/Transform.h
@@ -14,6 +14,14 @@ namespace crepe {
  */
 class Transform : public Component {
 public:
+	//! Translation (shift)
+	Vector2 position = {0, 0};
+	//! Rotation, in degrees
+	double rotation = 0;
+	//! Multiplication factor
+	double scale = 0;
+
+protected:
 	/**
 	 * \param id The id of the GameObject this component belongs to
 	 * \param point The position of the GameObject
@@ -22,19 +30,12 @@ public:
 	 */
 	Transform(game_object_id_t id, const Vector2 & point, double rotation, double scale);
 	/**
-	 * \brief Get the maximum number of instances for this component
-	 *
-	 * \return The maximum number of instances for this component
+	 * There is always exactly one transform component per entity
+	 * \return 1
 	 */
 	virtual int get_instances_max() const { return 1; }
-
-public:
-	//! Translation (shift)
-	Vector2 position;
-	//! Rotation, in degrees
-	double rotation;
-	//! Multiplication factor
-	double scale;
+	//! ComponentManager instantiates all components
+	friend class ComponentManager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/Vector2.cpp b/src/crepe/api/Vector2.cpp
index 437d1d8..30b968e 100644
--- a/src/crepe/api/Vector2.cpp
+++ b/src/crepe/api/Vector2.cpp
@@ -1,47 +1,33 @@
 #include "Vector2.h"
 
-namespace crepe {
+using namespace crepe;
 
-// Constructor with initial values
-Vector2::Vector2(double x, double y) : x(x), y(y) {}
-
-// Subtracts another vector from this vector and returns the result.
 Vector2 Vector2::operator-(const Vector2 & other) const { return {x - other.x, y - other.y}; }
 
-// Adds another vector to this vector and returns the result.
 Vector2 Vector2::operator+(const Vector2 & other) const { return {x + other.x, y + other.y}; }
 
-// Multiplies this vector by a scalar and returns the result.
 Vector2 Vector2::operator*(double scalar) const { return {x * scalar, y * scalar}; }
 
-// Multiplies this vector by another vector element-wise and updates this vector.
 Vector2 & Vector2::operator*=(const Vector2 & other) {
 	x *= other.x;
 	y *= other.y;
 	return *this;
 }
 
-// Adds another vector to this vector and updates this vector.
 Vector2 & Vector2::operator+=(const Vector2 & other) {
 	x += other.x;
 	y += other.y;
 	return *this;
 }
 
-// Adds a scalar value to both components of this vector and updates this vector.
 Vector2 & Vector2::operator+=(double other) {
 	x += other;
 	y += other;
 	return *this;
 }
 
-// Returns the negation of this vector.
 Vector2 Vector2::operator-() const { return {-x, -y}; }
 
-// Checks if this vector is equal to another vector.
 bool Vector2::operator==(const Vector2 & other) const { return x == other.x && y == other.y; }
 
-// Checks if this vector is not equal to another vector.
 bool Vector2::operator!=(const Vector2 & other) const { return !(*this == other); }
-
-} // namespace crepe
diff --git a/src/crepe/api/Vector2.h b/src/crepe/api/Vector2.h
index 5a57484..2fb6136 100644
--- a/src/crepe/api/Vector2.h
+++ b/src/crepe/api/Vector2.h
@@ -2,19 +2,12 @@
 
 namespace crepe {
 
-//! Vector2 class
-class Vector2 {
-public:
+//! 2D vector
+struct Vector2 {
 	//! X component of the vector
-	double x;
+	double x = 0;
 	//! Y component of the vector
-	double y;
-
-	//! Default constructor
-	Vector2() = default;
-
-	//! Constructor with initial values
-	Vector2(double x, double y);
+	double y = 0;
 
 	//! Subtracts another vector from this vector and returns the result.
 	Vector2 operator-(const Vector2 & other) const;