module Day13_1 where
import System.IO (openFile)
import Data.Text (unpack, splitOn, pack)
import Prelude hiding (splitAt)
import Data.Char (digitToInt)
import Data.List (nub, transpose)

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

insert :: Int -> Char -> [Char] -> [Char]
insert 0 y xs = xs
insert n y [] = []
insert n y xs
    | length xs < n = xs
    | otherwise = take n xs ++ [y] ++ insert n y (drop n xs)


fold :: String -> (Int, Int) -> (Int, Int)
fold str (x, y)
    | head str == 'x' = (fold' x, y)
    | head str == 'y' = (x, fold' y)
    where coord = read . last $ splitAt "=" str
          fold' num
            | num > coord = coord - (num - coord)
            | otherwise = num

main :: IO ()
main = do
    input <- readFile "inputs/13.txt"

    let (coords', folds') = (\[a,b] -> (lines a, lines b)) $ splitAt "\n\n" input
    --
    let coords = (\[a,b] -> (read a, read b) :: (Int, Int)) <$> map (splitAt ",") coords'
        folds  = map (last . splitAt " ") folds'

    let result = map (\(a,b) -> (b,a)) 
                    $ nub 
                    $ foldl (\acc x -> map (fold x) acc) coords folds

    let width  = maximum $ snd <$> result
        height = maximum $ fst <$> result
        field  = (,) <$> [0..height] <*> [0..width]

    let display x
            | x `elem` result = '#'
            | otherwise = ' '
        in putStrLn $ insert (width+1) '\n' $ map display field