module Main (main) where

import Text.Printf (printf)

main :: IO ()
main = do
  inputs <- readFile "./inputs/day2"
  let columns = map (map (read :: String -> Int) . words) (lines inputs)

  printf "safe: %d\n" $ length $ filter safe columns

safe :: (Ord a, Num a) => [a] -> Bool
safe x = distance x && ascOrDesc x

distance :: (Ord a, Num a) => [a] -> Bool
distance [] = True
distance [_] = True
distance (x : y : xs) = abs (x - y) <= 3 && abs (x - y) >= 1 && distance (y : xs)

ascOrDesc :: (Ord a, Num a) => [a] -> Bool
ascOrDesc [] = False
ascOrDesc [_] = False
ascOrDesc (x : y : xs) = (x < y && asc (x : y : xs)) || (x > y && desc (x : y : xs))

asc :: (Ord a, Num a) => [a] -> Bool
asc [] = True
asc [_] = True
asc (x : y : xs) = x < y && asc (y : xs)

desc :: (Ord a, Num a) => [a] -> Bool
desc [] = True
desc [_] = True
desc (x : y : xs) = x > y && desc (y : xs)