WorldBuilder

src/System.cs

@@ -5,11 +5,6 @@ public abstract class System : EntityComponentReader
 	internal MessageDepot MessageDepot;
 	public FilterBuilder FilterBuilder => new FilterBuilder(ComponentDepot);
 
-	public System(World world)
-	{
-		world.AddSystem(this);
-	}
-
 	internal void RegisterMessageDepot(MessageDepot messageDepot)
 	{
 		MessageDepot = messageDepot;
@@ -42,6 +37,11 @@ public abstract class System : EntityComponentReader
 		return MessageDepot.Some<TMessage>();
 	}
 
+	protected void Send<TMessage>(in TMessage message) where TMessage : struct
+	{
+		MessageDepot.Add(message);
+	}
+
 	protected void Destroy(in Entity entity)
 	{
 		ComponentDepot.OnEntityDestroy(entity.ID);

src/World.cs

@@ -2,25 +2,25 @@
 
 public class World
 {
-	private readonly List<System> Systems = new List<System>();
+	private readonly List<System> Systems;
-	private readonly List<Renderer> Renderers = new List<Renderer>();
+	private readonly List<Renderer> Renderers;
-	private EntityStorage EntityStorage { get; } = new EntityStorage();
+	private readonly EntityStorage EntityStorage;
-	private ComponentDepot ComponentDepot { get; } = new ComponentDepot();
+	private readonly ComponentDepot ComponentDepot;
-	private MessageDepot MessageDepot { get; } = new MessageDepot();
+	private MessageDepot MessageDepot;
 
-	internal void AddSystem(System system)
+	internal World(
+		List<System> systems,
+		List<Renderer> renderers,
+		ComponentDepot componentDepot,
+		EntityStorage entityStorage,
+		MessageDepot messageDepot
+	)
 	{
-		system.RegisterEntityStorage(EntityStorage);
+		Systems = systems;
-		system.RegisterComponentDepot(ComponentDepot);
+		Renderers = renderers;
-		system.RegisterMessageDepot(MessageDepot);
+		ComponentDepot = componentDepot;
-		Systems.Add(system);
+		EntityStorage = entityStorage;
-	}
+		MessageDepot = messageDepot;
-
-	internal void AddRenderer(Renderer renderer)
-	{
-		renderer.RegisterEntityStorage(EntityStorage);
-		renderer.RegisterComponentDepot(ComponentDepot);
-		Renderers.Add(renderer);
 	}
 
 	public void Update(TimeSpan delta)

src/WorldBuilder.cs

@@ -0,0 +1,59 @@
+namespace MoonTools.ECS;
+
+public class WorldBuilder
+{
+	private ComponentDepot componentDepot;
+	private EntityStorage entityStorage;
+	private MessageDepot messageDepot;
+
+	private readonly List<System> systems = new List<System>();
+	private readonly List<Renderer> renderers = new List<Renderer>();
+
+	public WorldBuilder()
+	{
+		componentDepot = new ComponentDepot();
+		entityStorage = new EntityStorage();
+		messageDepot = new MessageDepot();
+	}
+
+	public void AddSystem(System system)
+	{
+		system.RegisterEntityStorage(entityStorage);
+		system.RegisterComponentDepot(componentDepot);
+		system.RegisterMessageDepot(messageDepot);
+		systems.Add(system);
+	}
+
+	public void AddRenderer(Renderer renderer)
+	{
+		renderer.RegisterEntityStorage(entityStorage);
+		renderer.RegisterComponentDepot(componentDepot);
+		renderers.Add(renderer);
+	}
+
+	public Entity CreateEntity()
+	{
+		return entityStorage.Create();
+	}
+
+	public void Set<TComponent>(Entity entity, in TComponent component) where TComponent : struct
+	{
+		componentDepot.Set(entity.ID, component);
+	}
+
+	public void Send<TMessage>(in TMessage message) where TMessage : struct
+	{
+		messageDepot.Add(message);
+	}
+
+	public World Build()
+	{
+		return new World(
+			systems,
+			renderers,
+			componentDepot,
+			entityStorage,
+			messageDepot
+		);
+	}
+}