import Data.List
import Data.Maybe

type Position = (Int,Int)
type Entry = (Maybe Int, Int)
type MatrixMap = [(Position, Entry)]

parse :: Int -> Int -> String -> MatrixMap
parse x y []=[]
parse x y ('\n':xs)=parse 0(y+1)xs
parse x y ('S':xs)=((x,y),(Just 0,fromEnum 'a')):parse(x+1)y xs
parse x y ('E':xs)=((x,y),(Nothing,fromEnum 'z')):parse(x+1)y xs
parse x y (i:xs)=((x,y),(Nothing,fromEnum i)):parse(x+1)y xs

parse2 x y []=[]
parse2 x y ('\n':xs)=parse2 0(y+1)xs
parse2 x y ('S':xs)=((x,y),(Nothing,fromEnum 'a')):parse2(x+1)y xs
parse2 x y ('E':xs)=((x,y),(Just 0,fromEnum 'z')):parse2(x+1)y xs
parse2 x y (i:xs)=((x,y),(Nothing,fromEnum i)):parse2(x+1)y xs

s = f(0,0)'S'
e = f(0,0)'E'

f :: Position -> Char-> String -> Position
f(x,y)i(h:t)|h==i=(x,y)|'\n'==h=f(0,y+1)i t|let=f(x+1,y)i t

lookup2 i p = lookup i p >>= \x->pure(i, x)

valuesSurrounding :: Position -> MatrixMap -> [(Position, Entry)]
valuesSurrounding (x,y)pos|Just (Just d,h)<-lookup (x,y) pos 
  = map (\(p,(_,i))->(p,(Just (d+1), i))) $ filter((==Nothing).fst.snd) $ filter((<=h+1).snd.snd) $ catMaybes $ map(`lookup2`pos) [(x,y-1),(x,y+1),(x+1,y),(x-1,y)]

valuesSurrounding2 :: Position -> MatrixMap -> [(Position, Entry)]
valuesSurrounding2 (x,y)pos|Just (Just d,h)<-lookup (x,y) pos 
  = map (\(p,(_,i))->(p,(Just (d+1), i))) $ filter((==Nothing).fst.snd) $ filter((>=h-1).snd.snd) $ catMaybes $ map(`lookup2`pos) [(x,y-1),(x,y+1),(x+1,y),(x-1,y)]

doStuff :: MatrixMap -> [(Position, Entry)] -> MatrixMap
doStuff i [] = i
doStuff i (x:t)|n<-valuesSurrounding (fst x) i=doStuff (foldr update i n) (t++n)

doStuff2 :: MatrixMap -> [(Position, Entry)] -> MatrixMap
doStuff2 i [] = i
doStuff2 i (x:t)|n<-valuesSurrounding2 (fst x) i=doStuff2 (foldr update i n) (t++n)

update :: (Position, Entry) -> MatrixMap -> MatrixMap
update x m|Just entry<-lookup (fst x) m, Just idx<-elemIndex (fst x,entry) m,(h,c:t)<-splitAt idx m = h++x:t

p1 f = do
  x <- readFile f
  let m = parse 0 0 x
  let Just start = lookup2 (s x) m
  let d = doStuff m [start]
  let end = lookup2 (e x) d
  print end

p2 f = do
  x <- readFile f
  let m = parse2 0 0 x
  let Just start = lookup2 (e x) m
  let d = doStuff2 m [start]
  let (Just f, _) = head$sort$map snd$filter (\(p,(i,q))->q==97 && i /= Nothing) d
  print f


main=p1 "day12long" >> p2 "day12long"