Partial Implementation of Doors in Mazes

Made progress on implementing the placement of doors in mazes. Still
incomplete.

src/main/java/StevenDimDoors/experimental/LinkPlan.java

@@ -0,0 +1,87 @@
+package StevenDimDoors.experimental;
+
+public class LinkPlan
+{
+	private RoomData source;
+	private RoomData destination;
+	private boolean entrance;
+	
+	private LinkPlan(RoomData source, RoomData destination, boolean entrance)
+	{
+		this.source = source;
+		this.destination = destination;
+		this.entrance = entrance;
+	}
+	
+	public static LinkPlan createInternalLink(RoomData source, RoomData destination)
+	{
+		if (source == null)
+		{
+			throw new IllegalArgumentException("source cannot be null.");
+		}
+		if (destination == null)
+		{
+			throw new IllegalArgumentException("destination cannot be null.");
+		}
+		LinkPlan plan = new LinkPlan(source, destination, false);
+		source.getOutboundLinks().add(plan);
+		destination.getInboundLinks().add(plan);
+		return plan;
+	}
+	
+	public static LinkPlan createEntranceLink(RoomData source)
+	{
+		if (source == null)
+		{
+			throw new IllegalArgumentException("source cannot be null.");
+		}
+		LinkPlan plan = new LinkPlan(source, null, true);
+		source.getOutboundLinks().add(plan);
+		return plan;
+	}
+	
+	public static LinkPlan createDungeonLink(RoomData source)
+	{
+		if (source == null)
+		{
+			throw new IllegalArgumentException("source cannot be null.");
+		}
+		LinkPlan plan = new LinkPlan(source, null, false);
+		source.getOutboundLinks().add(plan);
+		return plan;
+	}
+	
+	public RoomData source()
+	{
+		return this.source;
+	}
+	
+	public RoomData destination()
+	{
+		return this.destination;
+	}
+	
+	public boolean isEntrance()
+	{
+		return entrance;
+	}
+	
+	public boolean isInternal()
+	{
+		return (destination != null);
+	}
+	
+	public void remove()
+	{
+		if (source != null)
+		{
+			source.getOutboundLinks().remove(this);
+			source = null;
+		}
+		if (destination != null)
+		{
+			destination.getInboundLinks().remove(this);
+			destination = null;
+		}
+	}
+}