follow activity for turreted attacks

OpenRa.Game/Traits/Activities/Follow.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace OpenRa.Game.Traits.Activities
+{
+	class Follow : IActivity
+	{
+		Actor Target;
+		int Range;
+
+		public Follow(Actor target, int range)
+		{
+			Target = target;
+			Range = range;
+		}
+
+		public IActivity NextActivity { get; set; }
+
+		public void Tick(Actor self, Mobile mobile)
+		{
+			if (Target.IsDead)
+			{
+				mobile.InternalSetActivity(NextActivity);
+				return;
+			}
+
+			if ((Target.Location - self.Location).LengthSquared >= Range * Range)
+			{
+				mobile.InternalSetActivity(new Move(Target, Range));
+				mobile.QueueActivity(this);
+			}
+		}
+
+		public void Cancel(Actor self, Mobile mobile) { }
+	}
+}