import Control.Arrow
import Data.List
import Data.Map (Map)
import Data.Map qualified as Map
import Data.Set (Set)
import Data.Set qualified as Set

readInput :: String -> Map (Int, Int) Char
readInput s = Map.fromList [((i, j), c) | (i, l) <- zip [0 ..] (lines s), (j, c) <- zip [0 ..] l]

(i1, j1) .+. (i2, j2) = (i1 + i2, j1 + j2)

(i1, j1) .-. (i2, j2) = (i1 - i2, j1 - j2)

directions = [(0, 1), (1, 0), (0, -1), (-1, 0)] :: [(Int, Int)]

edges = zip ps (drop 1 ps) :: [((Int, Int), (Int, Int))]
  where
    ps = [(0, 1), (1, 1), (1, 0), (0, 0), (0, 1)]

regions :: Map (Int, Int) Char -> [Set (Int, Int)]
regions = unfoldr (fmap (uncurry removeRegion) . Map.minViewWithKey)
  where
    removeRegion (p, t) = go Set.empty (Set.singleton p)
      where
        go r ps plots
          | Set.null ps = (r, plots)
          | otherwise =
              let ps' =
                    Set.filter (\p -> plots Map.!? p == Just t) $
                      Set.fromList (concatMap adjacent ps) Set.\\ ps
               in go (Set.union r ps) ps' (Map.withoutKeys plots ps')
        adjacent = (`map` directions) . (.+.)

boundary :: Set (Int, Int) -> Set ((Int, Int), (Int, Int))
boundary region =
  Set.fromList $
    [ (p .+. e1, p .+. e2)
      | p <- Set.elems region,
        (d, (e1, e2)) <- zip directions edges,
        p .+. d `Set.notMember` region
    ]

perimeter :: Set (Int, Int) -> [[(Int, Int)]]
perimeter = unfoldr (fmap (uncurry removeChain) . Set.minView) . boundary
  where
    removeChain e@(e1, e2) es = first (e1 :) $ go [] e es
    go c e@(e1, e2) es =
      case find ((== e2) . fst) es of
        Nothing -> (e1 : c, es)
        Just e' -> go (e1 : c) e' (Set.delete e' es)

countSides :: [(Int, Int)] -> Int
countSides ps = length $ group $ zipWith (.-.) (drop 1 ps) ps

main = do
  input <- readInput <$> readFile "input12"
  let rs = map (Set.size &&& perimeter) $ regions input
  print . sum $ map (\(a, p) -> a * sum (map (subtract 1 . length) p)) rs
  print . sum $ map (\(a, p) -> a * sum (map countSides p)) rs