module Day2

import Data.String


parseRow : String -> List Int
parseRow str = do
  num <- words str
  maybe [] pure (parseInteger num)

parseInp : String -> List (List Int)
parseInp inp = do
  numrow <- lines inp
  pure $ parseRow numrow
  
isSafe : List Int -> Bool
isSafe [] = False
isSafe (x :: xs) = fst up || fst down where
  up   = foldl (\(b, y) => \n => (b && y - n <= 3 && y - n > 0, n)) (True, x) xs
  down = foldl (\(b, y) => \n => (b && n - y <= 3 && n - y > 0, n)) (True, x) xs

btoi : Bool -> Int
btoi False = 0
btoi True = 1

part1 : List (List Int) -> Int
part1 iss = sum $ map (btoi . isSafe) iss

export sol1 : String -> String
sol1 = show . part1 . parseInp

joinLists : (List a, List a) -> List a
joinLists (x, []) = []
joinLists (x, (y :: xs)) = x ++ xs

subLists : List a -> List (List a)
subLists xs = do
  splitNum <- [0.. (length xs)]
  pure $ joinLists $ splitAt splitNum xs

isSafe' : List Int -> Bool
isSafe' xs = isSafe xs || (any isSafe $ subLists xs)

part2 : List (List Int) -> Int
part2 iss = sum $ map (btoi . isSafe') iss

export sol2 : String -> String
sol2 = show . part2 . parseInp

export out : String -> String
out = show . parseInp