entity tag system

src/Rev2/Compatibility/EntityComponentReader.cs

@@ -2,7 +2,7 @@
 
 public abstract class EntityComponentReader
 {
-	protected World World;
+	protected readonly World World;
 	public FilterBuilder FilterBuilder => World.FilterBuilder;
 
 	protected EntityComponentReader(World world)
@@ -10,6 +10,8 @@ public abstract class EntityComponentReader
 		World = world;
 	}
 
+	protected string GetTag(in EntityId entity) => World.GetTag(entity);
+
 	protected bool Has<T>(in EntityId entityId) where T : unmanaged => World.Has<T>(entityId);
 	protected bool Some<T>() where T : unmanaged => World.Some<T>();
 	protected ref T Get<T>(in EntityId entityId) where T : unmanaged => ref World.Get<T>(entityId);

src/Rev2/Compatibility/Manipulator.cs

@@ -5,6 +5,7 @@ public class Manipulator : EntityComponentReader
 	public Manipulator(World world) : base(world) { }
 
 	protected EntityId CreateEntity(string tag = "") => World.CreateEntity(tag);
+	protected void Tag(in EntityId entity, string tag) => World.Tag(entity, tag);
 	protected void Set<TComponent>(in EntityId entity, in TComponent component) where TComponent : unmanaged => World.Set<TComponent>(entity, component);
 	protected void Remove<TComponent>(in EntityId entity) where TComponent : unmanaged => World.Remove<TComponent>(entity);
 

src/Rev2/Snapshot.cs

@@ -4,6 +4,7 @@ using MoonTools.ECS.Collections;
 
 namespace MoonTools.ECS.Rev2;
 
+// TODO: we should implement a NativeDictionary that can be memcopied
 public class Snapshot
 {
 	private Dictionary<ArchetypeSignature, ArchetypeSnapshot> ArchetypeSnapshots =
@@ -17,6 +18,8 @@ public class Snapshot
 	private Dictionary<EntityId, IndexableSet<TypeId>> EntityRelationIndex =
 		new Dictionary<EntityId, IndexableSet<TypeId>>();
 
+	private Dictionary<EntityId, string> EntityTags = new Dictionary<EntityId, string>();
+
 	private IdAssigner EntityIdAssigner = new IdAssigner();
 
 	public int Count
@@ -71,6 +74,11 @@ public class Snapshot
 				world.EntityRelationIndex[id].Add(typeId);
 			}
 		}
+
+		foreach (var (id, s) in EntityTags)
+		{
+			world.EntityTags[id] = s;
+		}
 	}
 
 	public void Take(World world)
@@ -113,6 +121,11 @@ public class Snapshot
 				EntityRelationIndex[id].Add(typeId);
 			}
 		}
+
+		foreach (var (id, s) in world.EntityTags)
+		{
+			EntityTags[id] = s;
+		}
 	}
 
 	private void TakeArchetypeSnapshot(Archetype archetype)

src/Rev2/World.cs

@@ -27,6 +27,9 @@ public class World : IDisposable
 	// Going from EntityId to Archetype and storage row
 	internal Dictionary<EntityId, Record> EntityIndex = new Dictionary<EntityId, Record>();
 
+	// TODO: can we make the tag an inline array of chars at some point?
+	internal Dictionary<EntityId, string> EntityTags = new Dictionary<EntityId, string>();
+
 	// Relation Storages
 	internal Dictionary<TypeId, RelationStorage> RelationIndex =
 		new Dictionary<TypeId, RelationStorage>();
@@ -87,9 +90,21 @@ public class World : IDisposable
 			EntityRelationIndex.Add(entityId, new IndexableSet<TypeId>());
 		}
 
+		EntityTags[entityId] = tag;
+
 		return entityId;
 	}
 
+	public void Tag(in EntityId entityId, string tag)
+	{
+		EntityTags[entityId] = tag;
+	}
+
+	public string GetTag(in EntityId entityId)
+	{
+		return EntityTags[entityId];
+	}
+
 	internal TypeId GetTypeId<T>() where T : unmanaged
 	{
 		if (TypeToId.ContainsKey(typeof(T)))