import Data.List
import Data.List.Split
import Data.Maybe

data Dir = Up | Down

safe :: [Int] -> Int -> Dir -> Bool
safe [] _ _ =
  True
safe (x:xs) last Up
  | x - last < 1 = False
  | x - last > 3 = False
  | otherwise = safe xs x Up
safe (x:xs) last Down
  | last - x < 1 = False
  | last - x > 3 = False
  | otherwise = safe xs x Down

isSafe (x:y:rest)
  | y > x = safe (y:rest) x Up
  | x > y = safe (y:rest) x Down
  | otherwise = False

deleteAt x list =
  let (h, t) = splitAt x list in
    h ++ (drop 1 t)

isSafeDamped Nothing rep
  | isSafe rep = True
  | otherwise = isSafeDamped (Just 0) rep
isSafeDamped (Just x) rep
  | x >= length rep = False
  | isSafe $ deleteAt x rep = True
  | otherwise = isSafeDamped (Just (x + 1)) rep

part1 reps = 
  length $ filter (isSafe) reps

part2 reps = 
  length $ filter (isSafeDamped Nothing) reps

main = do
  file <- readFile "day02.input"
  let lns = map (splitOn " ") $ lines file
  let reps = map (map (read::String->Int)) $ lns
  putStrLn ("Part 1: " ++ (show $ part1 reps))
  putStrLn ("Part 2: " ++ (show $ part2 reps))