module Day4.Main (main) where

import System.IO
import Data.List.Split

main :: IO ()
main = do
    putStrLn "Day 4"
    
    handle <- openFile "app/Day4/input" ReadMode
    contents <- hGetContents handle

    let r1 = part1 contents
    putStrLn $ "part 1: " ++ show r1

    let r2 = part2 contents
    putStrLn $ "part 2: " ++ show r2

listToPair :: [a] -> (a, a)
listToPair l = (l !! 0, l !! 1)

type Start = Int
type End = Int
type Section = (Start, End)

parseData :: String -> [(Section, Section)]
parseData contents = transformOuter
    where
        pairs = map (splitOn ",") (lines contents)
        ranges = (map . map) (splitOn "-") pairs
        toNumbers = (map . map . map) (read :: String -> Int) ranges
        transformInner = (map . map) listToPair toNumbers
        transformOuter = map listToPair transformInner
        

contained :: Section -> Section -> Bool
contained (as, ae) (bs, be) = as <= bs && ae >= be || bs <= as && be >= ae

overlap :: Section -> Section -> Bool
overlap (as, ae) (bs, be) = bs <= as && be >= as ||
                            bs <= ae && be >= ae ||
                            as <= bs && ae >= bs ||
                            as <= be && ae >= be

part1, part2 :: String -> Int
part1 contents = length $ filter (uncurry contained) $ parseData contents
part2 contents = length $ filter (uncurry overlap)   $ parseData contents