import Data.Function
import Data.Ix
import Control.Lens
import Data.List
import Data.Ord
import Linear.V2

main :: IO ()
main = interact $ show . day11 . parse . lines

day11 :: [V2 Int] -> Int
day11 = (`div` 2) . sum . f . (expand =<< findEmptyRows)
    where f xs = [sum $ abs $ x-y | x<- xs, y<- xs]

parse :: [String] -> [V2 Int]
parse = map fst . filter ((=='#') . snd) . concat . zipWith (map . f) [0..] . map (zip [0..])
    where f x (y,z) = (V2 y x, z)


expand :: [V2 Int] -> [V2 Int] -> [V2 Int]
expand [] input = input
expand (d:ds) input = expand (map (moveCoord d) ds) (map (moveCoord d) input)


findEmptyRows :: [V2 Int] -> [V2 Int]
findEmptyRows input = map flipV2 (findEmptyRows  $ map flipV2 input) ++ findEmptyRows input
    where findEmptyRows = deleteFirstsBy ((==) `on` view _x) b
          b = range (V2 0 0, set _y 0 maxP)
          maxP = maximumBy (comparing (view _x)) input
          flipV2 (V2 x y) = V2 y x

moveCoord :: V2 Int -> V2 Int -> V2 Int
moveCoord x y = if y^.p >= x ^.p then y + signum x else y
    where p = if x^._x == 0 then _y else _x