11 files changed, 80 insertions, 14 deletions
diff --git a/src/crepe/CMakeLists.txt b/src/crepe/CMakeLists.txt
index 8830e05..867329f 100644
--- a/src/crepe/CMakeLists.txt
+++ b/src/crepe/CMakeLists.txt
@@ -4,6 +4,7 @@ target_sources(crepe PUBLIC
 	ComponentManager.cpp
 	Component.cpp
 	Collider.cpp
+	Metadata.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
@@ -12,6 +13,7 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	ComponentManager.hpp
 	Component.h
 	Collider.h
+	Metadata.h
 )
 
 add_subdirectory(api)
diff --git a/src/crepe/Component.cpp b/src/crepe/Component.cpp
index 358ce31..78b47fa 100644
--- a/src/crepe/Component.cpp
+++ b/src/crepe/Component.cpp
@@ -3,3 +3,5 @@
 using namespace crepe;
 
 Component::Component(uint32_t id) : game_object_id(id), active(true) {}
+
+int Component::get_instances_max() const { return -1; }
diff --git a/src/crepe/Component.h b/src/crepe/Component.h
index bc44865..039836e 100644
--- a/src/crepe/Component.h
+++ b/src/crepe/Component.h
@@ -13,6 +13,7 @@ protected:
 
 public:
 	virtual ~Component() = default;
+	virtual int get_instances_max() const;
 
 public:
 	uint32_t game_object_id;
diff --git a/src/crepe/ComponentManager.hpp b/src/crepe/ComponentManager.hpp
index 9b07f13..f469d12 100644
--- a/src/crepe/ComponentManager.hpp
+++ b/src/crepe/ComponentManager.hpp
@@ -30,9 +30,18 @@ T & ComponentManager::add_component(uint32_t id, Args &&... args) {
 
 	// Create a new component of type T (arguments directly forwarded). The
 	// constructor must be called by ComponentManager.
-	T * instance = new T(id, forward<Args>(args)...);
+	T * instance_pointer = new T(id, forward<Args>(args)...);
+	unique_ptr<T> instance = unique_ptr<T>(instance_pointer);
+
+	// Check if the vector size is not greater than get_instances_max
+	if (instance->get_instances_max() != -1
+		&& components[type][id].size() >= instance->get_instances_max()) {
+		throw std::runtime_error(
+			"Exceeded maximum number of instances for this component type");
+	}
+
 	// store its unique_ptr in the vector<>
-	components[type][id].push_back(unique_ptr<T>(instance));
+	components[type][id].push_back(move(instance));
 
 	return *instance;
 }
diff --git a/src/crepe/Metadata.cpp b/src/crepe/Metadata.cpp
new file mode 100644
index 0000000..d362e0a
--- /dev/null
+++ b/src/crepe/Metadata.cpp
@@ -0,0 +1,9 @@
+#include "Metadata.h"
+
+using namespace crepe;
+using namespace std;
+
+Metadata::Metadata(uint32_t gameObjectId, string name, string tag)
+	: Component(gameObjectId), name(name), tag(tag) {}
+
+int Metadata::get_instances_max() const { return 1; }
diff --git a/src/crepe/Metadata.h b/src/crepe/Metadata.h
new file mode 100644
index 0000000..2f08476
--- /dev/null
+++ b/src/crepe/Metadata.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "Component.h"
+
+namespace crepe {
+
+class Metadata : public Component {
+public:
+	Metadata(uint32_t game_object_id, std::string name, std::string tag);
+	int get_instances_max() const;
+
+public:
+	std::string name;
+	std::string tag;
+	uint32_t parent = UINT32_MAX;
+	std::vector<uint32_t> children;
+};
+
+} // namespace crepe
diff --git a/src/crepe/api/GameObject.cpp b/src/crepe/api/GameObject.cpp
index 445a60d..2592d2d 100644
--- a/src/crepe/api/GameObject.cpp
+++ b/src/crepe/api/GameObject.cpp
@@ -1,7 +1,25 @@
+#include "api/Transform.h"
+
 #include "GameObject.h"
+#include "Metadata.h"
 
 using namespace crepe;
 using namespace std;
 
-GameObject::GameObject(uint32_t id, string name, string tag, int layer)
-	: id(id), name(name), tag(tag), active(true), layer(layer) {}
+GameObject::GameObject(uint32_t id, std::string name, std::string tag,
+					   Point position, double rotation, double scale)
+	: id(id) {
+	ComponentManager & mgr = ComponentManager::get_instance();
+	mgr.add_component<Transform>(this->id, position, rotation, scale);
+	mgr.add_component<Metadata>(this->id, name, tag);
+}
+
+void GameObject::set_parent(GameObject & parent) {
+	auto & mgr = ComponentManager::get_instance();
+	vector<reference_wrapper<Metadata>> thisMetadata
+		= mgr.get_components_by_id<Metadata>(this->id);
+	vector<reference_wrapper<Metadata>> parentMetadata
+		= mgr.get_components_by_id<Metadata>(parent.id);
+	thisMetadata.at(0).get().parent = parent.id;
+	parentMetadata.at(0).get().children.push_back(this->id);
+}
diff --git a/src/crepe/api/GameObject.h b/src/crepe/api/GameObject.h
index b5d6399..dcd33ad 100644
--- a/src/crepe/api/GameObject.h
+++ b/src/crepe/api/GameObject.h
@@ -3,20 +3,20 @@
 #include <cstdint>
 #include <string>
 
+#include "api/Point.h"
+
 namespace crepe {
 
 class GameObject {
 public:
-	GameObject(uint32_t id, std::string name, std::string tag, int layer);
+	GameObject(uint32_t id, std::string name, std::string tag, Point position,
+			   double rotation, double scale);
+	void set_parent(GameObject & parent);
 
 	template <typename T, typename... Args>
 	T & add_component(Args &&... args);
 
 	uint32_t id;
-	std::string name;
-	std::string tag;
-	bool active;
-	int layer;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/Transform.cpp b/src/crepe/api/Transform.cpp
index 70b16bd..a80aff3 100644
--- a/src/crepe/api/Transform.cpp
+++ b/src/crepe/api/Transform.cpp
@@ -8,9 +8,11 @@
 
 using namespace crepe;
 
-Transform::Transform(uint32_t game_id, const Point & point, double rot,
-					 double scale)
+Transform::Transform(uint32_t game_id, Point point, double rot, double scale)
 	: Component(game_id), position(point), rotation(rot), scale(scale) {
 	dbg_trace();
 }
+
 Transform::~Transform() { dbg_trace(); }
+
+int Transform::get_instances_max() const { return 1; }
diff --git a/src/crepe/api/Transform.h b/src/crepe/api/Transform.h
index d416088..f918115 100644
--- a/src/crepe/api/Transform.h
+++ b/src/crepe/api/Transform.h
@@ -14,8 +14,9 @@ class Transform : public Component {
 	// works similar (or the same) as those found in GLSL?
 
 public:
-	Transform(uint32_t id, const Point &, double, double);
+	Transform(uint32_t id, Point, double, double);
 	~Transform();
+	int get_instances_max() const;
 	//! Translation (shift)
 	Point position;
 	//! Rotation, in radians
diff --git a/src/crepe/system/System.h b/src/crepe/system/System.h
index ecbb7f5..8744920 100644
--- a/src/crepe/system/System.h
+++ b/src/crepe/system/System.h
@@ -8,8 +8,8 @@ public:
 	virtual void update() = 0;
 
 protected:
-	System() {};
-	virtual ~System() {};
+	System(){};
+	virtual ~System(){};
 
 private:
 	// singleton