Reimplement iron curtain as a generic stat upgrade.

OpenRA.Mods.RA/InvulnerabilityUpgrade.cs

@@ -0,0 +1,51 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation. For more information,
+ * see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using OpenRA.GameRules;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.RA
+{
+	public class InvulnerabilityUpgradeInfo : ITraitInfo
+	{
+		public readonly string RequiresUpgrade = "invulnerability";
+
+		public object Create(ActorInitializer init) { return new InvulnerabilityUpgrade(this); }
+	}
+
+	public class InvulnerabilityUpgrade : IUpgradable, IDamageModifier
+	{
+		readonly InvulnerabilityUpgradeInfo info;
+		bool enabled;
+
+		public InvulnerabilityUpgrade(InvulnerabilityUpgradeInfo info)
+		{
+			this.info = info;
+		}
+
+		public bool AcceptsUpgrade(string type)
+		{
+			return type == info.RequiresUpgrade;
+		}
+
+		public void UpgradeAvailable(Actor self, string type, bool available)
+		{
+			if (type == info.RequiresUpgrade)
+				enabled = available;
+		}
+
+		public int GetDamageModifier(Actor attacker, DamageWarhead warhead)
+		{
+			return enabled ? 0 : 100;
+		}
+	}
+}