sclass Schedule<A extends Runnable> extends Meta {

  sclass Entry {}

  srecord Action<A>(A action) extends Entry {}

  srecord Jump (Seconds dest) extends Entry {}

  new TreeMultiMap<Seconds, Entry> entries;

  Timestamp start;

  TreeMultiMap<Seconds, Entry> currentEntries;

  void add(double seconds, A a) {

    entries.put(Seconds(seconds), new Action<A>(a));

  }

  void jumpFromTo(double from, double to) {

    entries.put(Seconds(from), new Jump(Seconds(to)));

  }

  void speedUp(double factor) {

    entries = (TreeMultiMap) mapMultiMapKeys(entries, seconds -> seconds.div(factor));

  }

  run {

    start = tsNow();

    reschedule(Seconds(0));

    while ping (nempty(currentEntries))

      fire(first(currentEntries));

  }

  void reschedule(Seconds startInSchedule) {

    currentEntries = (TreeMultiMap) cloneTailMultiMap(entries, startInSchedule, true);

    /*if (scaffoldActive(this))

      printStruct(this);*/

  }

  scaffolded void fire(Pair<Seconds, Entry> p) {

    if (p == null) ret;

    currentEntries.removePair(p);

    sleepUntil(start.plus(p.a));

    var e = p.b;

    if (e cast Action<A>)

      pcallF(e.action);

    else if (e cast Jump) {

      start = start.plus(p.a.minus(e.dest));

      reschedule(e.dest);

    } else

      fail(e);

  }

}