module Day6_1 where
import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
import Data.Text (splitOn, unpack, pack)
import Prelude hiding (splitAt)
import Data.List (group, sort)
import Data.Map.Strict (toList, fromListWith)

splitAt :: String -> String -> [String]
splitAt delimiter str = map unpack $ splitOn (pack delimiter) $ pack str

count :: [Int] -> [(Int, Int)]
count fish = map (\x -> (head x, length x)) $ group $ sort fish

grow :: (Int, Int) -> [(Int, Int)]
grow fish
    | fst fish > 0 = [(fst fish - 1, snd fish)]
    | otherwise = [(6, snd fish), (8, snd fish)]

sumFishes :: [(Int, Int)] -> [(Int, Int)]
sumFishes = toList . fromListWith (+)

main :: IO ()
main = do
    input <- openFile "inputs/6.txt" ReadMode
    contents <- hGetContents input

    let fishies = map read $ splitAt "," contents :: [Int]
    print . sum . map snd . (!! 256) . iterate (sumFishes . concatMap grow) $ count fishies

    hClose input