module Main where

import           Control.Monad
import           Data.Map      (Map)
import qualified Data.Map      as Map
import           Data.Maybe
import           Utils

type Pos = (Int, Int, Int, Int)

toBool '#' = True
toBool '.' = False

gridMap :: String -> Map Pos Bool
gridMap s = Map.fromList
          [((x,y,0,0), toBool a)
          | (y, row) <- zip [0..] rows
          , (x, a) <- zip [0..] row
          ]
    where rows = lines s

around :: Pos -> [Pos]
around (x,y,z,w) =
    [(x+x', y+y', z+z', w+w')
    | x' <- [-1..1]
    , y' <- [-1..1]
    , z' <- [-1..1]
    , w' <- [-1..1]
    , (x',y',z',w') /= (0,0,0,0)
    ]

convert True 2  = True
convert True 3  = True
convert False 3 = True
convert _ _     = False

doStep :: Map Pos Bool -> Map Pos Bool
doStep m = Map.mapWithKey fn $ m <> Map.fromList [(p, False) | p <- concatMap around (Map.keys m)]
    where fn pos v = convert v n
            where n = howMany id $ map (fromMaybe False . flip Map.lookup m) $ around pos

main :: IO ()
main = do
    n <- readFile "input/17"
    let grid = gridMap n
    print $ Map.size $ Map.filter id (iterate doStep grid !! 6)