refactor(xan): Switch to V2 over tuples most places

These are generally rather nicer to work due to some typeclass instances,
and integrate better with other ecosystems for things like linear
algebra etc.

Change-Id: I546c8da7b17234648f3d612b28741c1fded25447
Reviewed-on: https://cl.tvl.fyi/c/depot/+/910
Tested-by: BuildkiteCI
Reviewed-by: glittershark <grfn@gws.fyi>

users/glittershark/xanthous/src/Xanthous/Generators/LevelContents.hs

@@ -14,13 +14,15 @@ import           Control.Monad.Random
 import           Data.Array.IArray (amap, bounds, rangeSize, (!))
 import qualified Data.Array.IArray as Arr
 import           Data.Foldable (any, toList)
+import           Linear.V2
 --------------------------------------------------------------------------------
 import           Xanthous.Generators.Util
 import           Xanthous.Random
-import           Xanthous.Data ( Position, _Position, positionFromPair
-                               , rotations, arrayNeighbors, Neighbors(..)
-                               , neighborPositions
-                               )
+import           Xanthous.Data
+                 ( positionFromV2,  Position, _Position
+                 , rotations, arrayNeighbors, Neighbors(..)
+                 , neighborPositions
+                 )
 import           Xanthous.Data.EntityMap (EntityMap, _EntityMap)
 import           Xanthous.Entities.Raws (rawsWithType, RawType)
 import qualified Xanthous.Entities.Item as Item
@@ -49,7 +51,7 @@ randomDoors cells = do
   doorRatio <- getRandomR subsetRange
   let numDoors = floor $ doorRatio * fromIntegral (length candidateCells)
       doorPositions =
-        removeAdjacent . fmap positionFromPair . take numDoors $ candidateCells
+        removeAdjacent . fmap positionFromV2 . take numDoors $ candidateCells
       doors = zip doorPositions $ repeat unlockedDoor
   pure $ _EntityMap # doors
   where
@@ -92,8 +94,9 @@ tutorialMessage cells characterPosition = do
     accessiblePositionsWithin :: Int -> Cells -> Position -> [Position]
     accessiblePositionsWithin dist valid pos =
       review _Position
-      <$> filter (\(px, py) -> not $ valid ! (fromIntegral px, fromIntegral py))
-          (circle (pos ^. _Position) dist)
+      <$> filter
+            (\pt -> not $ valid ! (fromIntegral <$> pt))
+            (circle (pos ^. _Position) dist)
 
 randomEntities
   :: forall entity raw m. (MonadRandom m, RawType raw)
@@ -116,10 +119,10 @@ randomEntities newWithType sizeRange cells =
       pure $ _EntityMap # entities
 
 randomPosition :: MonadRandom m => Cells -> m Position
-randomPosition = fmap positionFromPair . choose . impureNonNull . cellCandidates
+randomPosition = fmap positionFromV2 . choose . impureNonNull . cellCandidates
 
 -- cellCandidates :: Cells -> Cells
-cellCandidates :: Cells -> Set (Word, Word)
+cellCandidates :: Cells -> Set (V2 Word)
 cellCandidates
   -- find the largest contiguous region of cells in the cave.
   = maximumBy (compare `on` length)