import Data.List.Split (splitOn)

split3Ways :: [Int] -> Int -> Int -> ([Int], [Int], [Int])
split3Ways xs from to
  | to >= from = (take from xs, take (to - from) (drop from xs), drop to xs)
  | otherwise = split3Ways xs to from

permute :: [Int] -> Int -> Int -> [Int]
permute xs from to 
  | to >= from = xs1 ++ reverse xs2 ++ xs3
  | otherwise = xs1' ++ xs2 ++ xs3'
      where (xs1, xs2, xs3) = split3Ways xs from to
            xs4 = reverse (xs3 ++ xs1)
            (xs3', xs1') = splitAt (length xs3) xs4

step :: ([Int], Int, Int) -> Int -> ([Int], Int, Int)
step (xs, skip, from) n = let m = length xs in 
  (permute xs from ((from + n) `mod` m), skip + 1, (from + n + skip) `mod` m)

solve1' :: [Int] -> Int
solve1' xs = let (ys, _, _) = foldl step ([0 .. 255], 0, 0) xs in
--solve1' xs = let (ys, _, _) = foldl step ([0 .. 4], 0, 0) xs in
  (head ys) * (head $ tail ys)

parseInput :: [Char] -> [Int]
parseInput = (fmap read) . (splitOn ",")

solve1 :: [Char] -> Int
solve1 = solve1' . parseInput

input = "120,93,0,90,5,80,129,74,1,165,204,255,254,2,50,113"