scala fun

gistfile1.scala

case class Item(cat: String, parent: Option[String], items: Seq[Map[String,String]])

val rows = Seq(
  Map("a1" -> "b1"),
  Map("a2" -> "b2"),
  Map("a3" -> "b3")
)

val items = List(
  Item("research", None, rows),
  Item("table", Some("research"), rows),
  Item("table-row", Some("table"), rows),
  Item("balancesheet", None, rows),
  Item("table-val", Some("table-cell"), rows),
  Item("table-cell", Some("table-row"), rows),
  Item("author", Some("research"), rows)
)


def process(parent: Item, children: Seq[Item]) {
  println(parent.cat)
  children.foreach(item => {
    process(item, items.filter(_.parent.getOrElse(None).equals(item.cat)))
  })
}

items.filter(_.parent == None).foreach(item => {
  process(item, items.filter(i => i.parent.getOrElse(None).equals(item.cat)))
})

output:

research
table
table-row
table-cell
table-val
author
balancesheet