Ridiculously Simple FSM DSL in Scala

FsmDsl.scala

/**
  * A Ridiculously Simple FSM DSL in Scala, similar to AKKA Actor-based FSM syntax
  *
  * def MY_STATE(...args...) = state("MY_STATE") {
  *   ... do something on entry ...
  *   events {
  *     case MyEvent =>
  *       ... do something on event ...
  *       MY_OTHER_STATE(...)
  *   }
  * }
  *
  * ... then somewhere else ...
  * var state = MY_STATE
  * while (...) { state = state + event_queue.poll() }
  */
FsmDsl {
  type BehaviorPf = PartialFunction[Event, Behavior]
  sealed trait Behavior extends BehaviorPf {
    val name: String
    def +(event: Event): Behavior = applyOrElse(event, (_: Event) => this)
  }

  def state(name: String)(supplier: => BehaviorPf): Behavior = supplier match {
    case b: Behavior => b
    case pf          => behavior(name, pf)
  }

  def events(pf: BehaviorPf): BehaviorPf = pf

  val ignore_events: BehaviorPf = events(PartialFunction.empty)

  private def behavior(n: String, pf: BehaviorPf): Behavior = new Behavior {
    override val name: String                       = n
    override def isDefinedAt(event: Event): Boolean = pf.isDefinedAt(event)
    override def apply(event: Event): Behavior      = pf.apply(event)
  }
}