Killed that fail TechTree, and added a new one to Rules.

OpenRa.Game/GameRules/FieldLoader.cs

@@ -29,7 +29,7 @@ namespace OpenRa.Game.GameRules
 				return x;
 
 			else if (fieldType.IsEnum)
-				return Enum.Parse(fieldType, x);
+				return Enum.Parse(fieldType, x, true);
 
 			else if (fieldType == typeof(bool))
 				return ParseYesNo(x);

OpenRa.Game/GameRules/Rules.cs

@@ -16,6 +16,7 @@ namespace OpenRa.Game
 		public static InfoLoader<WeaponInfo> WeaponInfo;
 		public static InfoLoader<WarheadInfo> WarheadInfo;
 		public static InfoLoader<ProjectileInfo> ProjectileInfo;
+		public static TechTree TechTree;
 
 		public static void LoadRules( string mapFileName )
 		{
@@ -52,6 +53,8 @@ namespace OpenRa.Game
 
 			ProjectileInfo = new InfoLoader<ProjectileInfo>(
 				Pair.New<string, Func<string, ProjectileInfo>>("Projectile", _ => new ProjectileInfo()));
+
+			TechTree = new TechTree();
 		}
 
 		static void LoadCategories( params string[] types )

OpenRa.Game/GameRules/TechTree.cs

@@ -0,0 +1,65 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using IjwFramework.Collections;
+
+namespace OpenRa.Game.GameRules
+{
+	class TechTree
+	{
+		readonly Cache<string, List<UnitInfo.BuildingInfo>> producesIndex = new Cache<string, List<UnitInfo.BuildingInfo>>( x => new List<UnitInfo.BuildingInfo>() );
+
+		public TechTree()
+		{
+			foreach( var b in Rules.Categories[ "Building" ] )
+			{
+				var info = (UnitInfo.BuildingInfo)Rules.UnitInfo[ b ];
+				foreach( var p in info.Produces )
+					producesIndex[ p ].Add( info );
+			}
+		}
+
+		public Cache<string, List<Actor>> GatherBuildings( Player player )
+		{
+			var ret = new Cache<string, List<Actor>>( x => new List<Actor>() );
+			foreach( var b in Game.world.Actors.Where( x => x.Owner == player && Rules.UnitCategory[ x.unitInfo.Name ] == "Building" ) )
+				ret[ b.unitInfo.Name ].Add( b );
+			return ret;
+		}
+
+		public bool CanBuild( UnitInfo unit, Player player, Cache<string, List<Actor>> playerBuildings )
+		{
+			if( unit.TechLevel == -1 )
+				return false;
+
+			if( !unit.Owner.Any( x => x == player.Race ) )
+				return false;
+
+			foreach( var p in unit.Prerequisite )
+				if( playerBuildings[ p ].Count == 0 )
+					return false;
+
+			if( producesIndex[ Rules.UnitCategory[ unit.Name ] ].All( x => playerBuildings[ x.Name ].Count == 0 ) )
+				return false;
+
+			return true;
+		}
+
+		public IEnumerable<string> BuildableItems( Player player, params string[] categories )
+		{
+			var playerBuildings = GatherBuildings( player );
+			foreach( var unit in categories.SelectMany( x => Rules.Categories[ x ] ).Select( x => Rules.UnitInfo[ x ] ) )
+				if( CanBuild( unit, player, playerBuildings ) )
+					yield return unit.Name;
+		}
+
+		public IEnumerable<string> UnitBuiltAt( UnitInfo info )
+		{
+			if( info.BuiltAt.Length != 0 )
+				return info.BuiltAt;
+			else
+				return producesIndex[ Rules.UnitCategory[ info.Name ] ].Select( x => x.Name );
+		}
+	}
+}

OpenRa.Game/GameRules/UnitInfo.cs

@@ -33,7 +33,7 @@ namespace OpenRa.Game.GameRules
 		public readonly int GuardRange = -1; // -1 = use weapon's range
 		public readonly string Image = null; // sprite-set to use when rendering
 		public readonly bool Invisible = false;
-		public readonly string[] Owner = { "allies", "soviet" };
+		public readonly Race[] Owner = { Race.Allies, Race.Soviet };
 		public readonly int Points = 0;
 		public readonly string[] Prerequisite = { };
 		public readonly string Primary = null;
@@ -81,6 +81,7 @@ namespace OpenRa.Game.GameRules
 		{
 			public readonly int2 Dimensions = new int2( 1, 1 );
 			public readonly string Footprint = "x";
+			public readonly string[] Produces = { };
 
 			public readonly bool BaseNormal = true;
 			public readonly int Adjacent = 1;