module Part2 where

import Commons
import Data.Array ((!), bounds)


getAreaToStart :: (Int, Int) -> (Int, Int) -> Direction -> Direction -> Grid -> Int
getAreaToStart (y, x) (yMax, xMax) South sdir grid =
  case grid ! (y, x) of
       Pipe (North, South) -> xMax - x + getAreaToStart (y + 1, x) (yMax, xMax) South sdir grid
       Pipe (North, East) -> getAreaToStart (y, x + 1) (yMax, xMax) East sdir grid
       Pipe (North, West) -> xMax - x + getAreaToStart (y, x - 1) (yMax, xMax) West sdir grid
       Start -> if sdir == South then xMax - x else 0
getAreaToStart (y, x) (yMax, xMax) West sdir grid =
  case grid ! (y, x) of
       Pipe (East, West) -> getAreaToStart (y, x - 1) (yMax, xMax) West sdir grid
       Pipe (North, East) -> x - xMax - 1 + getAreaToStart (y - 1, x) (yMax, xMax) North sdir grid
       Pipe (South, East) -> getAreaToStart (y + 1, x) (yMax, xMax) South sdir grid
       Start -> 0
getAreaToStart (y, x) (yMax, xMax) North sdir grid =
  case grid ! (y, x) of
       Pipe (North, South) -> x - xMax - 1 + getAreaToStart (y - 1, x) (yMax, xMax) North sdir grid
       Pipe (South, East) -> x - xMax - 1 + getAreaToStart (y, x + 1) (yMax, xMax) East sdir grid
       Pipe (South, West) -> getAreaToStart (y, x - 1) (yMax, xMax) West sdir grid
       Start -> if sdir == East then x - xMax - 1 else 0
getAreaToStart (y, x) (yMax, xMax) East sdir grid =
  case grid ! (y, x) of
       Pipe (East, West) -> getAreaToStart (y, x + 1) (yMax, xMax) East sdir grid
       Pipe (North, West) -> getAreaToStart (y - 1, x) (yMax, xMax) North sdir grid
       Pipe (South, West) -> xMax - x + getAreaToStart (y + 1, x) (yMax, xMax) South sdir grid
       Start -> if sdir == South then xMax - x else 0

getCycleArea :: Grid -> Int
getCycleArea grid = let (dir, startCoords) = getStartDirection (getStartCoordinates grid) grid
                        ((_, _), (yMax, xMax)) = bounds grid
                    in getAreaToStart startCoords (yMax, xMax) dir dir grid