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

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 );
+		}
+	}
+}