day05.sc

import common.loadPackets

val initialState: Map[Int, String] = Map(
  1 -> "VRHBGDW",
  2 -> "FRCGNJ",
  3 -> "JNDHFSL",
  4 -> "VSDJ",
  5 -> "VNWQRDHS",
  6 -> "MCHGP",
  7 -> "CHZLGBJF",
  8 -> "RJS",
  9 -> "MVNBRSGL"
)

val regex = """move (\d+) from (\d+) to (\d+)""".r

case class Instruction(amount: Int, from: Int, to: Int)

val input: List[Instruction] = loadPackets(List("day05.txt")).map({
  case regex(amount, from, to) => Instruction(amount.toInt, from.toInt, to.toInt)
})

val part1 = input.foldLeft(initialState)((state, instruction) => instruction match {
  case Instruction(amount, from, to) =>
    state.updated(from, state(from).substring(amount))
      .updated(to, state(from).substring(0, amount).reverse + state(to))
}).toList.sortBy(_._1).map(_._2(0)).mkString

val part2 = input.foldLeft(initialState)((state, instruction) => instruction match {
  case Instruction(amount, from, to) =>
    state.updated(from, state(from).substring(amount))
      .updated(to, state(from).substring(0, amount) + state(to))
}).toList.sortBy(_._1).map(_._2(0)).mkString