val file = TextIO.openIn "day_2.txt";
val input = TextIO.inputAll file;
TextIO.closeIn file;

fun equals a b = a = b
fun non f x = not (f x)

val maxRed = 12
val maxGreen = 13
val maxBlue = 14

val possibleGames =
  let val lines = String.tokens (equals #"\n") input
  in
    List.filter
      (fn line =>
        let
          val game = List.last (String.tokens (equals #":") line)
          val rounds = String.tokens (equals #";") game
          val rounds = map
            (fn round => String.extract (round, 1, NONE))
            rounds
        in
          List.all
            (fn round =>
              let
                val reveals = String.tokens (non Char.isAlphaNum) round
                val revealPairs = ListPair.zip (
                  (List.filter (fn elem => (Int.fromString elem) = NONE) reveals),
                  (List.mapPartial Int.fromString reveals)
                )
              in
                List.all
                  (fn revealPair =>
                    (#2 revealPair) <= (case #1 revealPair of
                        "red" => maxRed
                      | "green" => maxGreen
                      | "blue" => maxBlue
                  ))
                  revealPairs
              end
            )
            rounds
        end
      )
      lines
  end

val result = List.foldl
  (fn (game, acc) =>
    let
      val title = List.hd (String.tokens (equals #":") game)
      val id = Option.valOf (Int.fromString (String.extract (title, 5, NONE)))
    in
      acc + id
    end
  )
  0
  possibleGames