module Main (main) where

import Data.List (delete)
import Text.Printf (printf)

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

  -- print $ filter safe columns
  printf "safe w damper: %d\n" $ length $ filter safe columns

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

distance :: (Ord a, Num a) => [a] -> [a] -> [a] -> Bool
distance full arr (x : y : xs)
  | length arr < length full - 1 = False
  | abs (x - y) <= 3 && abs (x - y) >= 1 = distance full arr (y : xs)
  | otherwise = distance full (delete y arr) (x : xs)
distance full arr [_] = length arr >= length full - 1
distance _ _ _ = False

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

asc :: (Ord a, Num a) => [a] -> [a] -> [a] -> Bool
asc full arr (x : y : xs)
  | length arr < length full - 1 = False
  | x < y = asc full arr (y : xs)
  | x >= y = asc full (delete y arr) (x : xs)
asc full arr [_] = length arr >= length full - 1
asc _ _ _ = False

desc :: (Ord a, Num a) => [a] -> [a] -> [a] -> Bool
desc full arr (x : y : xs)
  | length arr < length full - 1 = False
  | x > y = desc full arr (y : xs)
  | x <= y = desc full (delete y arr) (x : xs)
desc full arr [_] = length arr >= length full - 1
desc _ _ _ = False