import System.IO
import Data.List (intersect)
-- import Data.Array ((!), listArray)
import Debug.Trace (traceShow)

main = do file <- openFile "input/04.txt" ReadMode
          input <- hGetContents' file
          hClose file

          let ans1 = part1 input
          let ans2 = part2 input
          putStr "Part 1 answer: "
          putStr . show $ ans1
          putStr "\nPart 2 answer: "
          putStr . show $ ans2
          putStr "\n"

test = "Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53\n\
\Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19\n\
\Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1\n\
\Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83\n\
\Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36\n\
\Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11"

part1 :: String -> Int
part1 = foldr valueWin 0 . parseInput
  where valueWin 0 acc = acc
        valueWin x acc = acc + 2^(x-1)

-- part2 :: String -> Int
part2 input =  foldr go initialCards (zip [1..3] wins)
  where wins = parseInput input
        initialCards = zip [1..] $ replicate (length wins) 1
        go (i,win) acc = map (\(i',copies) -> if i' `elem` [i+1 .. i+win] then (i', copies+multiplier) else (i', copies)) acc
          where multiplier = snd $ acc!!i

parseInput :: String -> [Int] -- returns wins array
parseInput input = map (\(m,w) -> length $ intersect m w) (zip myNumbers winningNumbers)
  where allNumbers = map (drop 2 . words) . lines $ input
        myNumbers = map (takeWhile (/="|")) allNumbers
        winningNumbers = map (drop 1 . dropWhile (/="|")) allNumbers