import Control.Arrow
import Data.Function
import Data.List
import Data.List.Split
import Data.Maybe
import Text.Read

type HASH = (String, Maybe Int)

main :: IO ()
main = interact $ show . genBuckets . parse . init

parse :: String -> [HASH]
parse = map (second (readMaybe . tail) . break (`elem` "=-")) . splitOn ","

day15a :: String -> Int
day15a = sum . map (foldl' hashAlg 0) . splitOn ","

hashAlg :: Int -> Char -> Int
hashAlg x y = (17 * (fromEnum y + x)) `mod` 256

removeHashes :: [String] -> [HASH] -> [HASH]
removeHashes _ [] = []
removeHashes rs ((label, Nothing):xs) = removeHashes (label : rs) xs
removeHashes rs ((label, Just x):xs)
  | label `elem` rs = removeHashes (delete label rs) xs
  | otherwise = (label, Just x) : removeHashes rs xs

genBuckets :: [HASH] -> Int
genBuckets input =
  sum
    [ sum $ zipWith (*) [1 ..] $ map ((* (succ x)) . fromJust . snd) (sorted x)
    | x <- [0 .. 255]
    ]
  where
    filterBucket x f =
      nubBy ((==) `on` fst) $
      f $ removeHashes [] (reverse $ filter (f1 x) input)
    sorted x =
      sortOn
        (\y -> fst y `elemIndex` (map fst (filterBucket x reverse)))
        (filterBucket x id)
    f1 n (x, _) = foldl hashAlg 0 x == n