#3 Restrict player going places

lib/RPGEngine/Input/Level.hs

@@ -0,0 +1,27 @@
+module RPGEngine.Input.Level
+( putCoords
+, findFirst
+, whatIsAt
+) where
+import RPGEngine.Data (Level (..), Y, X, Physical(..))
+
+-- Map all Physicals onto coordinates
+putCoords :: Level -> [(X, Y, Physical)]
+putCoords l@Level{ layout = lay } = concatMap (\(a, bs) -> map (\(b, c) -> (b, a, c)) bs) numberedList
+    where numberedStrips = zip [0::Int .. ] lay
+          numberedList   = map (\(x, strip) -> (x, zip [0::Int ..] strip)) numberedStrips
+
+-- Find first position of a Physical
+-- Graceful exit by giving Nothing if there is nothing found.
+findFirst :: Level -> Physical -> Maybe (X, Y)
+findFirst l@Level{ coordlayout = lay } physical = try
+    where matches   = filter (\(x, y, v) -> v == physical) lay
+          try | not (null matches) = Just $ (\(x, y, _) -> (x, y)) $ head matches
+              | otherwise          = Nothing
+
+-- What is located at a given position in the level?
+whatIsAt :: (X, Y) -> Level -> Physical
+whatIsAt pos lvl@Level{ coordlayout = lay } = try
+    where matches = map (\(_, _, v) -> v) $ filter (\(x, y, v) -> (x, y) == pos) lay
+          try | not (null matches) = head matches
+              | otherwise          = Void