Split Target.Recalculate into methods with and without invalidation.

TargetExtensions is moved into its own file.

OpenRA.Mods.Common/TargetExtensions.cs

@@ -0,0 +1,79 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2019 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common
+{
+	public static class TargetExtensions
+	{
+		/// <summary>
+		/// Update (Frozen)Actor targets to account for visibility changes or actor replacement.
+		/// If the target actor becomes hidden without a FrozenActor, the target is invalidated.
+		/// /// </summary>
+		public static Target RecalculateInvalidatingHiddenTargets(this Target t, Player viewer)
+		{
+			bool targetIsHiddenActor;
+			var updated = t.Recalculate(viewer, out targetIsHiddenActor);
+			return targetIsHiddenActor ? Target.Invalid : updated;
+		}
+
+		/// <summary>
+		/// Update (Frozen)Actor targets to account for visibility changes or actor replacement.
+		/// If the target actor becomes hidden without a FrozenActor, the target actor is kept
+		/// and the actorHidden flag is set to true.
+		/// </summary>
+		public static Target Recalculate(this Target t, Player viewer, out bool targetIsHiddenActor)
+		{
+			targetIsHiddenActor = false;
+
+			// Check whether the target has transformed into something else
+			// HACK: This relies on knowing the internal implementation details of Target
+			if (t.Type == TargetType.Invalid && t.Actor != null && t.Actor.ReplacedByActor != null)
+				t = Target.FromActor(t.Actor.ReplacedByActor);
+
+			// Bot-controlled units aren't yet capable of understanding visibility changes
+			if (viewer.IsBot)
+				return t;
+
+			if (t.Type == TargetType.Actor)
+			{
+				// Actor has been hidden under the fog
+				if (!t.Actor.CanBeViewedByPlayer(viewer))
+				{
+					// Replace with FrozenActor if applicable, otherwise return target unmodified
+					var frozen = viewer.FrozenActorLayer.FromID(t.Actor.ActorID);
+					if (frozen != null)
+						return Target.FromFrozenActor(frozen);
+
+					targetIsHiddenActor = true;
+					return t;
+				}
+			}
+			else if (t.Type == TargetType.FrozenActor)
+			{
+				// Frozen actor has been revealed
+				if (!t.FrozenActor.Visible || !t.FrozenActor.IsValid)
+				{
+					// Original actor is still alive
+					if (t.FrozenActor.Actor != null && t.FrozenActor.Actor.CanBeViewedByPlayer(viewer))
+						return Target.FromActor(t.FrozenActor.Actor);
+
+					// Original actor was killed while hidden
+					if (t.Actor == null)
+						return Target.Invalid;
+				}
+			}
+
+			return t;
+		}
+	}
+}