helis return to base after finishing an attack

OpenRa.Game/OpenRa.Game.csproj

@@ -117,6 +117,7 @@
     <Compile Include="Traits\Activities\HeliAttack.cs" />
     <Compile Include="Traits\Activities\HeliFly.cs" />
     <Compile Include="Traits\Activities\HeliLand.cs" />
+    <Compile Include="Traits\Activities\HeliReturn.cs" />
     <Compile Include="Traits\Activities\IActivity.cs" />
     <Compile Include="Traits\Activities\DeliverOre.cs" />
     <Compile Include="Traits\Activities\DeployMcv.cs" />

OpenRa.Game/Traits/Activities/HeliReturn.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using OpenRa.Game.GameRules;
+
+namespace OpenRa.Game.Traits.Activities
+{
+	class HeliReturn : IActivity
+	{
+		public IActivity NextActivity { get; set; }
+		bool isCanceled;
+
+		static Actor ChooseHelipad(Actor self)
+		{
+			return Game.world.Actors.FirstOrDefault(
+				a => a.Info == Rules.UnitInfo["HPAD"] &&
+					a.Owner == self.Owner &&
+					!Reservable.IsReserved(a));
+		}
+
+		public IActivity Tick(Actor self)
+		{
+			if (isCanceled) return NextActivity;
+			var dest = ChooseHelipad(self);
+
+			if (dest == null)
+				return Util.SequenceActivities(
+					new Turn(self.Info.InitialFacing), 
+					new HeliLand(true),
+					NextActivity);
+
+			var res = dest.traits.GetOrDefault<Reservable>();
+			if (res != null)
+				self.traits.Get<Helicopter>().reservation = res.Reserve(self);
+
+			var offset = (dest.Info as BuildingInfo).SpawnOffset;
+			var offsetVec = new float2(offset[0], offset[1]);
+
+			return Util.SequenceActivities(
+				new HeliFly(dest.CenterLocation + offsetVec),
+				new Turn(self.Info.InitialFacing),
+				new HeliLand(false),
+				new Rearm(),
+				NextActivity);
+		}
+
+		public void Cancel(Actor self) { isCanceled = true; NextActivity = null; }
+	}
+}

OpenRa.Game/Traits/AttackHeli.cs

@@ -10,7 +10,7 @@ namespace OpenRa.Game.Traits
 		{
 			target = order.TargetActor;
 			self.QueueActivity(new HeliAttack(order.TargetActor));
-			// todo: fly home
+			self.QueueActivity(new HeliReturn());
 		}
 	}
 }