module Commons where

import GHC.IO.Handle (isEOF)
import Data.Array (Array, listArray, (!), Ix (inRange), bounds)


data Direction = North | South | West | East deriving (Eq, Ord, Show)
data Tile = Empty | Rock | Slope { direction :: Direction } deriving (Eq, Show)
type Trails = Array (Int, Int) Tile


parseLine :: String -> [Tile]
parseLine = map (\case
                  '.' -> Empty
                  '#' -> Rock
                  '>' -> Slope {direction = East}
                  'v' -> Slope {direction = South}
                  '<' -> Slope {direction = West}
                  '^' -> Slope {direction = North})

parseTrails :: IO [[Tile]]
parseTrails = do done <- isEOF
                 if done
                    then return []
                    else do line <- getLine
                            let trailsLine = parseLine line
                            trails <- parseTrails
                            return (trailsLine: trails)

parse :: IO Trails
parse = do trails <- parseTrails
           return $ listArray ((1, 1), (length trails, length $ head trails)) $ concat trails