package aoc
package day04

import scala.collection.mutable

val dayNumber = "04"

@main def part1: Unit =
  println(part1(loadInput(dayNumber)))

@main def part2: Unit =
  println(part2(loadInput(dayNumber)))

def part1(input: String): String =
  input
    .split('\n')
    .map { case s"$_: $winning | $numbers" =>
      (
        winning.split(" ").flatMap(_.toIntOption),
        numbers.split(" ").flatMap(_.toIntOption)
      )
    }
    .map((w, n) => w.intersect(n).length)
    .filter(_ > 0)
    .map(l => Math.pow(2, l - 1).toInt)
    .sum
    .toString

def part2(input: String): String =

  final case class Card(
      matchingCards: List[Int],
      instances: Int = 1
  ):
    def addInstances(n: Int) = copy(instances = instances + n)

  val cards =
    input
      .split('\n')
      .map { case s"$_: $winning | $numbers" =>
        winning
          .split(" ")
          .flatMap(_.toIntOption)
          .intersect(numbers.split(" ").flatMap(_.toIntOption))
          .length
      }
      .zipWithIndex
      .map((count, index) => Card((1 to count).map(_ + index).toList))
      .to(mutable.ArraySeq)

  for card <- cards do
    for index <- card.matchingCards do
      cards.update(index, cards(index).addInstances(card.instances))

  cards
    .map(_.instances)
    .sum
    .toString