{-# LANGUAGE LambdaCase #-}
module Main where

import Data.Functor
import Data.Matrix hiding (trace)
import Data.List
import Debug.Trace

parse :: String -> Matrix Char
parse = fromLists . lines

getGroup :: (Int,Int) -> Matrix Char -> [(Int,Int)] -> [(Int,Int)]
getGroup p@(i,j) s v
  | p `elem` v = v
  | otherwise = let e = getElem i j s in
      nub . (p:) $ filter((== Just e) . flip (uncurry safeGet) s) [(i,j+1),(i,j-1),(i+1,j),(i-1,j)] >>= \p' -> getGroup p' s (p:v)
  where

groups :: Matrix Char -> [[(Int,Int)]]
groups s = nub $ go [(i,j) | i <- [1 .. nrows s], j <- [1 .. ncols s]] []
  where go :: [(Int,Int)] -> [[(Int,Int)]] -> [[(Int,Int)]]
        go [] v = v
        go (x:xs) v
          | any (x `elem`) v = go xs v
          | otherwise = go xs (getGroup x s []:v)

perimeter :: [(Int,Int)] -> Int
perimeter s = length $ s >>= \(i,j) -> [(i,j+1),(i,j-1),(i+1,j),(i-1,j)] \\ s

solve1 :: Matrix Char -> Int
solve1 s = let g = groups s; p = perimeter <$> g in sum $ zipWith (*) (length <$> g) p

solve2 :: Matrix Char -> Int
solve2 = undefined

main :: IO ()
main = readFile "inputs/12.example" <&> parse >>= \i ->
       print (solve1 i) >>
       print (solve2 i)