Move held item scrolling into dedicated datatype

src/Dodge/HeldScroll.hs

@@ -0,0 +1,37 @@
+module Dodge.HeldScroll 
+    ( doHeldScroll
+    ) where
+import Dodge.Data
+import Dodge.Item.Weapon.ZoomScope
+import Control.Lens hiding ((|>),(<|))
+import Data.Sequence
+
+doHeldScroll :: HeldScroll -> Float -> Creature -> Item -> Item
+doHeldScroll hs = case hs of
+    HeldScrollDoNothing -> const . const id
+    HeldScrollZoom -> zoomLongGun
+    HeldScrollCharMode -> scrollCharMode
+scrollCharMode
+    :: Float    -- ^ Amount scrolled
+    -> Creature
+    -> Item
+    -> Item
+scrollCharMode x _ 
+    | x > 0 = incCharMode
+    | x < 0 = decCharMode
+    | otherwise = id
+
+incCharMode 
+    :: Item 
+    -> Item
+incCharMode = itAttachment . atCharMode %~ cycleL
+  where
+    cycleL (x :<| xs) = xs |> x
+    cycleL xs = xs
+decCharMode 
+    :: Item 
+    -> Item
+decCharMode = itAttachment . atCharMode %~ cycleR
+  where
+    cycleR (xs :|> x) = x <| xs
+    cycleR xs = xs