AoC day 1

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

object day1 extends App {

  def getRoute(xs: List[(Char, Int)]): List[(Int, Int)] = {

    def nextDir(dir: Char, turn: Char): Char = dir match {
      case 'E' => if (turn == 'R') 'S' else 'N'
      case 'N' => if (turn == 'R') 'E' else 'W'
      case 'W' => if (turn == 'R') 'N' else 'S'
      case 'S' => if (turn == 'R') 'W' else 'E'
    }

    def updateCoords(dir: Char, n: Int, c: (Int, Int)): List[(Int, Int)] = dir match {
      case 'E' => (1 to n).map(i => (c._1 + i, c._2)).toList
      case 'N' => (1 to n).map(i => (c._1, c._2 + i)).toList
      case 'W' => (1 to n).map(i => (c._1 - i, c._2)).toList
      case 'S' => (1 to n).map(i => (c._1, c._2 - i)).toList
    }

    @tailrec
    def drive(xs: List[(Char, Int)], dir: Char, acc: List[(Int, Int)]): List[(Int, Int)] = xs match {
      case Nil => acc
      case h :: t => {
        val newDir = nextDir(dir, h._1)
        val newCoords = updateCoords(newDir, h._2, acc.last)
        drive(t, newDir, acc ::: newCoords)
      }
    }
    drive(xs, 'N', List((0,0)))
  }

  def findRevisit(xs: List[(Int, Int)], acc: List[(Int, Int)]): (Int, Int) = xs match {
    case h :: t => if (acc.count(_ == h) == 1) h else findRevisit(t, acc :+ h)
  }

  val lines = Source.fromFile("day1.txt").mkString
  val blocks = lines.trim.split(", ") map (b => (b.head, b.drop(1).toInt))
  val route = getRoute(blocks.toList)

  println((math.abs(route.last._1) + math.abs(route.last._2)))
  val revisitedFirst = findRevisit(route, Nil)
  println((math.abs(revisitedFirst._1) + math.abs(revisitedFirst._2)))

}