advent-of-code/2020/day07/Bag.hs

{-# LANGUAGE OverloadedStrings #-}
module Bag where

import Data.Bifunctor
import qualified Data.Text as T
import Data.Tuple

type Bag = (String, [(String, Int)])

bagSpec :: String -> Bag
bagSpec = bimap T.unpack contents . breakNoPrefix " bags contain " . T.pack

contents :: T.Text -> [(String, Int)]
contents c
    | c == "no other bags." = []
    | otherwise = map (bimap T.unpack (read . T.unpack) . swap . breakNoPrefix " " . T.strip . fst . T.breakOnEnd " ") . T.splitOn "," $ T.init c

breakNoPrefix :: T.Text -> T.Text -> (T.Text, T.Text)
breakNoPrefix prefix text = (a, T.drop (T.length prefix) b) where (a, b) = T.breakOn prefix text