From ec9552b1d6ab303d54a8bbb8c93418f32fa29654 Mon Sep 17 00:00:00 2001
From: stuebinm
Date: Wed, 8 Dec 2021 00:56:31 +0100
Subject: rudimentary linting for overlapping layers

---
 lib/LayerData.hs | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 lib/LayerData.hs

(limited to 'lib/LayerData.hs')

diff --git a/lib/LayerData.hs b/lib/LayerData.hs
new file mode 100644
index 0000000..1a07982
--- /dev/null
+++ b/lib/LayerData.hs
@@ -0,0 +1,42 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module LayerData where
+
+
+import           Control.Monad.Zip (mzipWith)
+import           Data.Set          (Set, insert)
+import           Data.Text         (Text)
+import qualified Data.Text         as T
+import           Data.Vector       (Vector, uncons)
+import           Tiled             (GlobalId (unGlobalId), Layer (..))
+import           Util              (PrettyPrint (..))
+
+-- | A collision between two layers of the given names.
+-- Wrapped in a newtype so that Eq can ignore the order of the two
+newtype Collision = Collision { fromCollision ::  (Text, Text) }
+  deriving Ord
+
+instance Eq Collision where
+  (Collision (a,b)) == (Collision (a',b')) = ((a,b) == (a',b')) || ((a,b) == (b',a'))
+
+instance PrettyPrint Collision where
+  prettyprint (Collision (a,b)) = a <> " and " <> b
+
+instance Show Collision where
+  show c = T.unpack $ prettyprint c
+
+-- | Finds pairwise tile collisions between the given layers.
+layerOverlaps :: Vector Layer -> Set Collision
+layerOverlaps layers = case uncons layers of
+  Nothing -> mempty
+  Just (l, ls) ->
+   fst . foldr overlapBetween (mempty, l) $ ls
+   where overlapBetween :: Layer -> (Set Collision, Layer) -> (Set Collision, Layer)
+         overlapBetween layer (acc, oldlayer) =
+          (if collides then insert collision acc else acc, layer)
+          where
+           collision = Collision (layerName layer, layerName oldlayer)
+           collides = case (layerData layer, layerData oldlayer) of
+             (Just d1, Just d2) ->
+               0 /= maximum (mzipWith (\a b -> unGlobalId a * unGlobalId b) d1 d2)
+             _ -> False
-- 
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