{-# LANGUAGE MultiParamTypeClasses, TypeSynonymInstances #-}
module CircularShifter where

import LineStorage
import qualified Data.IntMap as IntMap

class CircularShifter s t r where
  shift :: (s (t e)) -> (s (r (t e)))

rotate :: [a] -> [a]
rotate [] = []
rotate (x:xs) = xs ++ [x]

rotateAll :: [a] -> [[a]]
rotateAll xs = take (length xs) (iterate rotate xs)

instance CircularShifter StorageList StorageList StorageList where
  shift (ListStorage es) = ListStorage $ map shift_ es
    where shift_ (ListStorage es) = ListStorage $ map ListStorage $ rotateAll es

instance CircularShifter StorageMap StorageMap StorageMap where
  shift m = IntMap.map (toMap . map toMap . rotateAll . IntMap.elems) m
    where toMap = foldl add IntMap.empty