{-# LANGUAGE LambdaCase #-}
module Main where

import Data.List as L
import Data.Bifunctor
import Data.Char
import Data.Maybe
import Data.List.Extra
import Safe

data InputOptions = SumPrios
                  | SumGroups
                  | Quit


getInput :: IO InputOptions
getInput = do
  putStrLn "Sum Prios or Quit? (s/g/q)"
  getLine >>= \case
       "s" -> return SumPrios
       "g" -> return SumGroups
       "q" -> return Quit
       _   -> putStrLn "not understood" >> getInput

main :: IO ()
main = getInput >>= \case
    Quit -> putStrLn "bye!"
    SumPrios -> interact $
          (<>"\n")
        . show
        . sum
        . fmap turnIntoPrios
        . lines
    SumGroups -> interact $
          (<>"\n")
        . show
        . sum
        . fmap turnIntoGroup
        . chunksOf 3
        . lines

turnIntoPrios :: String -> Integer
turnIntoPrios l = maximum . fmap toPrio . uncurry intersect . bimap sort sort . splitAt (length l `div` 2) $ l

turnIntoGroup :: [String] -> Integer
turnIntoGroup [a,b,c] = maximum . fmap toPrio $ intersect a (b `intersect` c)

toPrio :: Char -> Integer
toPrio x
  | isAsciiLower x = toInteger $ ord x - ord 'a' + 1
  | isAsciiUpper x = toInteger $ ord x - ord 'A' + 27
  | otherwise      = error "malformed input"