backend support for selling

OpenRa.Game/OpenRa.Game.csproj

@@ -146,6 +146,7 @@
     <Compile Include="Traits\Activities\Rearm.cs" />
     <Compile Include="Traits\Activities\Repair.cs" />
     <Compile Include="Traits\Activities\ReturnToBase.cs" />
+    <Compile Include="Traits\Activities\Sell.cs" />
     <Compile Include="Traits\Activities\Teleport.cs" />
     <Compile Include="BuildingInfluenceMap.cs" />
     <Compile Include="IOrderGenerator.cs" />

OpenRa.Game/Traits/Activities/Sell.cs

@@ -0,0 +1,41 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace OpenRa.Game.Traits.Activities
+{
+	class Sell : IActivity
+	{
+		public IActivity NextActivity { get; set; }
+
+		bool started;
+
+		void DoSell(Actor self)
+		{
+			var refund = Rules.General.RefundPercent 
+				* self.Health * self.Info.Cost / self.Info.Strength;
+
+			self.Owner.GiveCash((int)refund);
+			self.Health = 0;
+			Game.world.Remove(self);
+		}
+
+		public IActivity Tick(Actor self)
+		{
+			if (!started)
+			{
+				var rb = self.traits.Get<RenderBuilding>();
+				rb.PlayCustomAnimBackwards(self, "make",
+					() => Game.world.AddFrameEndTask(w => DoSell(self)));
+
+				Sound.Play("cashturn.aud");
+				started = true;
+			}
+
+			return this;
+		}
+
+		public void Cancel(Actor self) { /* never gonna give you up.. */ }
+	}
+}

OpenRa.Game/Traits/RenderBuilding.cs

@@ -62,6 +62,12 @@ namespace OpenRa.Game.Traits
 				() => anim.PlayRepeating(GetPrefix(self) + "idle"));
 		}
 
+		public void PlayCustomAnimBackwards(Actor self, string name, Action a)
+		{
+			anim.PlayBackwardsThen(GetPrefix(self) + name,
+				() => { anim.PlayRepeating(GetPrefix(self) + "idle"); a(); });
+		}
+
 		public virtual void Damaged(Actor self, AttackInfo e)
 		{
 			if (!e.DamageStateChanged)