Add dungeon level generation

Add a dungeon level generator, which:

1. generates an infinite sequence of rectangular rooms within the
   dimensions of the level
2. removes any duplicates from that sequence
3. Generates a graph from the delaunay triangulation of the centerpoints
   of those rooms
4. Generates the minimum-spanning-tree of that delaunay triangulation,
   with weights given by line length in points
5. Adds back a subset (default 10-15%) of edges from the delaunay
   triangulation to the graph
6. Uses the resulting graph to draw corridors between the rooms, using a
   random point on the near edge of each room to pick the points of the
   corridors

1 files changed, 21 insertions, 0 deletions

diff --git a/src/Xanthous/Util/Optparse.hs b/src/Xanthous/Util/Optparse.hs
new file mode 100644
index 000000000000..dfa65372351d
--- /dev/null
+++ b/src/Xanthous/Util/Optparse.hs
@@ -0,0 +1,21 @@
+--------------------------------------------------------------------------------
+module Xanthous.Util.Optparse
+  ( readWithGuard
+  ) where
+--------------------------------------------------------------------------------
+import Xanthous.Prelude
+--------------------------------------------------------------------------------
+import qualified Options.Applicative as Opt
+--------------------------------------------------------------------------------
+
+readWithGuard
+  :: Read b
+  => (b -> Bool)
+  -> (b -> String)
+  -> Opt.ReadM b
+readWithGuard predicate errmsg = do
+  res <- Opt.auto
+  unless (predicate res)
+    $ Opt.readerError
+    $ errmsg res
+  pure res