{-# LANGUAGE TupleSections #-}
module Day5_1 where
import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
import Data.Text (splitOn, unpack, pack)
import Prelude hiding (splitAt)
import Data.List (sort, intersect)
import Data.Bifunctor (bimap)

type Coordinate = (Int, Int)
type Range = ([Int], [Int])

toCoord :: String -> Coordinate
toCoord str = (x, y)
    where
        xy = splitAt "," str
        x = read $ head xy
        y = read $ xy !! 1

isStraight :: Coordinate -> Coordinate -> Bool
isStraight c1 c2 = fst c1 == fst c2 || snd c1 == snd c2

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

range :: (Num a, Enum a, Eq a) => a -> a -> [a]
range a b
    | a == b = [a]
    | otherwise = [a, a + signum (b - a) .. b]

coordsToRange :: (Coordinate, Coordinate) -> Range
coordsToRange (a, b) = bimap (range (fst a)) (range (snd a)) b

points :: (Range, Bool) -> [Coordinate]
points (range, diag)
        | diag = uncurry zip range
        | otherwise = [ (i,j) | i <- fst range, j <- snd range ]

intersections :: [(Range, Bool)] -> [[Coordinate]]
intersections [] = []
intersections (x:xs) = map (\y -> points x `intersect` points y) xs ++ intersections xs

dedup :: Eq a => [(a, a)] -> [(a, a)]
dedup [] = []
dedup (x:xs) = x : dedup (filter (x /=) xs)

main :: IO ()
main = do
    input <- openFile "inputs/5.txt" ReadMode
    contents <- hGetContents input

    let coords = map toCoord . splitAt " -> " <$> lines contents
    -- remove lines that aren't horizontal/vertical and sort them
    let straight' = map sort $ filter (\(x:y:_) -> isStraight x y) coords
    let gay' = filter (\(x:y:_) -> not $ isStraight x y) coords
    let straight = map ((, False) . coordsToRange . (\x -> (head x, x !! 1))) straight'
    let gay = map ((, True) . coordsToRange . (\x -> (head x, x !! 1))) gay'

    print . length . dedup . concat $ intersections $ straight ++ gay

    hClose input