split various flying behaviors into own files

OpenRa.Game/Traits/ProductionSurround.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using OpenRa.Game.GameRules;
+
+namespace OpenRa.Game.Traits
+{
+	class ProductionSurround : Production
+	{
+		public ProductionSurround(Actor self) : base(self) { }
+
+		static int2? FindAdjacentTile(Actor a, UnitMovementType umt)
+		{
+			var tiles = Footprint.Tiles(a, a.traits.Get<Traits.Building>());
+			var min = tiles.Aggregate(int2.Min) - new int2(1, 1);
+			var max = tiles.Aggregate(int2.Max) + new int2(1, 1);
+
+			for (var j = min.Y; j <= max.Y; j++)
+				for (var i = min.X; i <= max.X; i++)
+					if (Game.IsCellBuildable(new int2(i, j), umt))
+						return new int2(i, j);
+
+			return null;
+		}
+
+		public override int2? CreationLocation(Actor self, UnitInfo producee)
+		{
+			return FindAdjacentTile(self, producee.WaterBound ?
+					UnitMovementType.Float : UnitMovementType.Wheel);	/* hackety hack */
+		}
+
+		public override int CreationFacing(Actor self, Actor newUnit)
+		{
+			return Util.GetFacing(newUnit.CenterLocation - self.CenterLocation, 128);
+		}
+	}
+}