{-# LANGUAGE LambdaCase #-}
module Main where

import Data.Functor

data D = D { target :: Int, parts :: [Int]}

parse :: String -> [D]
parse = ((\(a:as) -> D (read $ takeWhile (/= ':') a) (read <$> as)) . words <$>) . lines

canBeTarget :: Int -> [Int] -> Bool
canBeTarget _ [] = False
canBeTarget t [x] = t == x
canBeTarget t (x:y:xs) = any (canBeTarget t) [x+y:xs, x*y:xs]

solve1 :: [D] -> Int
solve1 = sum . (target <$>) . filter (\(D t p) -> canBeTarget t p)

canBeTarget' :: Int -> [Int] -> Bool
canBeTarget' _ [] = False
canBeTarget' t [x] = t == x
canBeTarget' t (x:y:xs) = any (canBeTarget' t) [x+y:xs, x*y:xs, read (show x ++ show y):xs]

solve2 :: [D] -> Int
solve2 =  sum . (target <$>) . filter (\(D t p) -> canBeTarget' t p)

main :: IO ()
main = readFile "inputs/7" <&> parse >>= \i ->
       print (solve1 i)
       >> print (solve2 i)