From 0ddc89ddea19351980e7189872c999e54906d453 Mon Sep 17 00:00:00 2001
From: cosmonaut <evan@moonside.games>
Date: Mon, 21 Mar 2022 16:21:42 -0700
Subject: [PATCH] add singleton getter

---
 src/ComponentDepot.cs        | 10 ++++++++++
 src/ComponentStorage.cs      | 16 ++++++++++++++++
 src/EntityComponentReader.cs | 14 ++++++++++++--
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/src/ComponentDepot.cs b/src/ComponentDepot.cs
index 3afb8b6..02afb20 100644
--- a/src/ComponentDepot.cs
+++ b/src/ComponentDepot.cs
@@ -50,6 +50,11 @@ internal class ComponentDepot
 		return ref Lookup<TComponent>().Get(entityID);
 	}
 
+	public ref readonly TComponent Get<TComponent>() where TComponent : struct
+	{
+		return ref Lookup<TComponent>().Get();
+	}
+
 	public void Set<TComponent>(int entityID, in TComponent component) where TComponent : struct
 	{
 		Lookup<TComponent>().Set(entityID, component);
@@ -74,6 +79,11 @@ internal class ComponentDepot
 		}
 	}
 
+	public ref readonly Entity GetEntity<TComponent>() where TComponent : struct
+	{
+		return ref Lookup<TComponent>().FirstEntity();
+	}
+
 	public ReadOnlySpan<Entity> ReadEntities<TComponent>() where TComponent : struct
 	{
 		return Lookup<TComponent>().AllEntities();
diff --git a/src/ComponentStorage.cs b/src/ComponentStorage.cs
index fcbd3a5..54ca698 100644
--- a/src/ComponentStorage.cs
+++ b/src/ComponentStorage.cs
@@ -29,6 +29,17 @@ internal class ComponentStorage<TComponent> : ComponentStorage where TComponent
 		return ref components[entityIDToStorageIndex[entityID]];
 	}
 
+	public ref readonly TComponent Get()
+	{
+		#if DEBUG
+		if (nextID == 0)
+		{
+			throw new ArgumentOutOfRangeException("Component storage is empty!");
+		}
+		#endif
+		return ref components[0];
+	}
+
 	public void Set(int entityID, in TComponent component)
 	{
 		if (!entityIDToStorageIndex.ContainsKey(entityID))
@@ -87,4 +98,9 @@ internal class ComponentStorage<TComponent> : ComponentStorage where TComponent
 	{
 		return new ReadOnlySpan<TComponent>(components, 0, nextID);
 	}
+
+	public ref readonly Entity FirstEntity()
+	{
+		return ref storageIndexToEntities[0];
+	}
 }
diff --git a/src/EntityComponentReader.cs b/src/EntityComponentReader.cs
index 2531109..f547518 100644
--- a/src/EntityComponentReader.cs
+++ b/src/EntityComponentReader.cs
@@ -37,8 +37,18 @@ public abstract class EntityComponentReader
 		return ComponentDepot.Some<TComponent>();
 	}
 
-	protected TComponent Get<TComponent>(in Entity entity) where TComponent : struct
+	protected ref readonly TComponent Get<TComponent>(in Entity entity) where TComponent : struct
 	{
-		return ComponentDepot.Get<TComponent>(entity.ID);
+		return ref ComponentDepot.Get<TComponent>(entity.ID);
+	}
+
+	protected ref readonly TComponent Get<TComponent>() where TComponent : struct
+	{
+		return ref ComponentDepot.Get<TComponent>();
+	}
+
+	protected ref readonly Entity GetEntity<TComponent>() where TComponent : struct
+	{
+		return ref ComponentDepot.GetEntity<TComponent>();
 	}
 }