import Control.Monad
import Data.List
import qualified Data.Map.Strict as Map
import Data.Maybe


repSplitAt :: Int -> [a] -> [[a]]
repSplitAt _ [] = []
repSplitAt n l = let (pre, post) = splitAt n l in pre : repSplitAt n post

data Pattern = Pattern Int [Bool]
  deriving (Show, Eq, Ord)

parse :: String -> (Pattern, Pattern)
parse str =
    let [p1, "=>", p2] = words str
    in (parsePat p1, parsePat p2)

parsePat :: String -> Pattern
parsePat str =
    let n = length (takeWhile (/= '/') str)
        bin = [c == '#' | c <- str, c /= '/']
    in Pattern n bin

sp :: Pattern -> String
sp (Pattern n pat) = intercalate "\n" (go pat)
  where go [] = []
        go p = let (pre, post) = splitAt n p in map ((".#" !!) . fromEnum) pre : go post

genequiv :: Pattern -> [Pattern]
genequiv pat =
    let r = take 4 (iterate rotate pat)
    in r ++ map mirror r
  where
    transform f (Pattern n p) = Pattern n [p !! f n x y | y <- [0..n-1], x <- [0..n-1]]
    rotate = transform $ \n x y -> n * x + n - 1 - y
    mirror = transform $ \n x y -> n * y + (n - 1 - x)

getimg :: Map.Map Pattern Pattern -> Pattern -> Pattern
getimg mp pat = fromJust $ msum $ map (flip Map.lookup mp) (genequiv pat)

adjoin :: [[Bool]] -> [[Bool]] -> [[Bool]]
adjoin a b = map (uncurry (++)) (zip a b)

blocks :: [[Bool]] -> [[[[Bool]]]]
blocks grid =
    let n = if length grid `mod` 2 == 0 then 2 else 3
    in map transpose $ map (map (repSplitAt n)) $ repSplitAt n grid

pblocks :: [[Bool]] -> [[Pattern]]
pblocks grid =
    let n = if length grid `mod` 2 == 0 then 2 else 3
    in map (map (Pattern n . concat)) (blocks grid)

unpblocks :: [[Pattern]] -> [[[[Bool]]]]
unpblocks = map $ map $ \(Pattern n p) -> repSplitAt n p

joinblocks :: [[[[Bool]]]] -> [[Bool]]
joinblocks = concatMap (foldl1 adjoin)

main :: IO ()
main = do
    mp <- liftM (Map.fromList . map parse . lines) (readFile "21.in")
    let orig = [[False, True, False], [False, False, True], [True, True, True]]
        iters = iterate (joinblocks . unpblocks . map (map (getimg mp)) . pblocks) orig
    -- mapM_ (print . sum . map fromEnum . concat . (iters !!)) [0..]
    print (sum $ map fromEnum $ concat $ iters !! 5)
    print (sum $ map fromEnum $ concat $ iters !! 18)