module Part1 where

import Commons
import Data.Array ((!))


getDistanceToStart :: (Int, Int) -> Direction -> Grid -> Int
getDistanceToStart (y, x) South grid =
  case grid ! (y, x) of
       Pipe (North, South) -> 1 + getDistanceToStart (y + 1, x) South grid
       Pipe (North, East) -> 1 + getDistanceToStart (y, x + 1) East grid
       Pipe (North, West) -> 1 + getDistanceToStart (y, x - 1) West grid
       Start -> 0
getDistanceToStart (y, x) West grid =
  case grid ! (y, x) of
       Pipe (East, West) -> 1 + getDistanceToStart (y, x - 1) West grid
       Pipe (North, East) -> 1 + getDistanceToStart (y - 1, x) North grid
       Pipe (South, East) -> 1 + getDistanceToStart (y + 1, x) South grid
       Start -> 0
getDistanceToStart (y, x) North grid =
  case grid ! (y, x) of
       Pipe (North, South) -> 1 + getDistanceToStart (y - 1, x) North grid
       Pipe (South, East) -> 1 + getDistanceToStart (y, x + 1) East grid
       Pipe (South, West) -> 1 + getDistanceToStart (y, x - 1) West grid
       Start -> 0
getDistanceToStart (y, x) East grid =
  case grid ! (y, x) of
       Pipe (East, West) -> 1 + getDistanceToStart (y, x + 1) East grid
       Pipe (North, West) -> 1 + getDistanceToStart (y - 1, x) North grid
       Pipe (South, West) -> 1 + getDistanceToStart (y + 1, x) South grid
       Start -> 0

getCycleLength :: Grid -> Int
getCycleLength grid = let (dir, startCoords) = getStartDirection (getStartCoordinates grid) grid
                    in 1 + getDistanceToStart startCoords dir grid