package pattern
 
class Activity(val name : String) {
  protected var nested : List[Activity] = Nil
  var parent : Option[Activity] = None
  
  def subActivities = nested.reverse
  def level : Int = {
    var i = 0
    for (p <- parent) { i = p.level + 1 }
    i
  }
  override def toString = {
    var prefix = " "
    for (i <- 0 to level) {
      prefix = prefix + " " 
    }
    val nestedString = subActivities.foldLeft("") {_+_.toString}
    prefix + name + "\n" + nestedString
  }
}
 
class CompositeActivity(name : String) extends Activity(name) {
  def add[B <: Activity](a : B) = {
    nested = a :: nested
    a.parent = Some(this)
    a
  }
}
 
class ProjectPlan(name : String) extends CompositeActivity(name)
class SummaryTask(name : String) extends CompositeActivity(name) 
class Task(name : String) extends Activity(name) 
 
object Composite {
  def main(args : Array[String]) {
   val plan = new ProjectPlan("MyGreatPlan")
   val s = plan.add (new SummaryTask("Get it all together"))
   s.add (new Task("Put the kettle on"))
   s.add (new Task("Relax with a cuppa"))
   s.add (new Task("Now think ..."))
   println(plan)
  }
}