AoC day 2

import scala.io.Source
import scala.annotation.tailrec

object day2 extends App {

  def nextDigit(d: Int, dir: Char): Int = dir match {
    case 'D' => if (d + 3 > 9) d else d + 3
    case 'R' => if (d % 3 == 0) d else d + 1
    case 'U' => if (d - 3 < 1) d else d - 3
    case 'L' => if ((d + 2) % 3 == 0) d else d - 1
  }

  def nextDigit2(d: Int, dir: Char): Int = dir match {
    case 'D' => d match {
      case 5 | 9 | 10 | 12 | 13 => d
      case 2 | 3 | 4 | 6 | 7 | 8 => d + 4
      case 1 | 11 => d + 2
    }
    case 'U' => d match {
      case 1 | 2 | 4 | 5 | 9 => d
      case 6 | 7 | 8 | 10 | 11 | 12 => d - 4
      case 3 | 13 => d - 2
    }
    case 'R' => d match {
      case 1 | 4 | 9 | 12 | 13 => d
      case _ => d + 1
    }
    case 'L' => d match {
      case 1 | 2 | 5 | 10 | 13 => d
      case _ => d - 1
    }
  }

  def getDigit(xs: List[Char], d: Int)(f: (Int, Char) => Int): Int = {

    @tailrec
    def enterDigit(s: List[Char], digit: Int): Int = s match {
      case Nil => digit
      case h :: t => {
        enterDigit(t, f(digit, h))
      }
    }

    enterDigit(xs, d)
  }

  val source = Source.fromFile("day2.txt").getLines.toList
  val passages = source map (l => l.toList)
  val sequence = passages.scanLeft(5)((a, b) => getDigit(b, a)(nextDigit))
  println((sequence drop 1).mkString)
  val sequence2 = passages.scanLeft(5)((a, b) => getDigit(b, a)(nextDigit2))
  println((sequence2 drop 1).map ("%x".format(_)).mkString)

}