import Data.List
import Data.Maybe

type Path = ([String], [(Int, Int)])

main :: IO ()
main = do
  input <- lines <$> readFile "testinput"
  let s = findLetter 'S' input
  print $ walkTo 'E' (input, []) s

findLetter :: Char -> [String] -> (Int, Int)
findLetter c = f <*> fromJust . findIndex (/= Nothing) <$> map (elemIndex c)
  where
    f x y = (head $ catMaybes x, y)

walkTo :: Char -> Path -> (Int, Int) -> Int
walkTo c (field, visited) (x, y)
  | field !! y !! x == c = 0
  | null newCoords = (maxBound :: Int) `div` 2
  | otherwise =
    if length visited > lenX * lenY
      then (maxBound :: Int) `div` 2
      else succ $
           minimum $
           map (walkTo c (field, (x, y) : visited)) newCoords
  where
    lenX = length $ head field
    lenY = length field
    char = field !! y !! x
    current =
      if char == 'S'
        then pred 'a'
        else char
    newCoords =
      [ (x + x', y + y')
      | x' <- [-1 .. 1]
      , x' + x >= 0
      , x' + x < lenX
      , y' <- [-1 .. 1]
      , y' + y >= 0
      , y + y' < lenY
      , abs x' /= abs y'
      , let a = field !! (y + y') !! (x + x')
         in (a `elem` ['a' .. succ current] || (a == 'E' && current == 'z'))
      , (x + x', y + y') `notElem` visited
      ]