Tree parsing with tailrec recursive method

Tailrec.scala

import scala.annotation.tailrec

class Item(name: String) {
  override def toString: String = name
}
class Group(name: String, items: List[Item]) extends Item(name) {
  def size: Int = items.size
  def get(i: Int): Item = items(i)
}

// Build up a tree:
//                      |
//                     g0
//                    /  \
//                  g1    g2------g3
//                 /     /  \    /  \
//                a     b   e   c    d
//
val a = new Item("a")
val b = new Item("b")
val c = new Item("c")
val d = new Item("d")
val e = new Item("e")

val g3 = new Group("3", List(c, d))
val g2 = new Group("2", List(g3, b, e))
val g1 = new Group("1", List(a))
val g0 = new Group("0", List(g1, g2))

def findItems(item: Item): List[Item] = {
  @tailrec
  def findItems(startItems: List[Item], resultCache: List[Item]): List[Item] = {
    startItems match {
      case List() =>
        resultCache
      case (head: Group) :: tail =>
        val list: List[Item] = (
          for (i <- 0 until head.size) yield head.get(i)
          ).toList
        findItems(list ::: tail, head :: resultCache)
      case (head: Item) :: tail =>
        findItems(tail, head :: resultCache)
    }
  }
  findItems(List(item), List.empty)
}

val result = findItems(g0)
result.foreach { item => println(s"- Item: $item") }