sclass FormInFlight {
  Conversation conversation;
  S hashTag;
  new L<FormStep> steps;
  int stepIndex; // in steps list
  
  S handleInput(S s) { null; }
  
  FormStep currentStep() {
    ret get(steps, stepIndex);
  }
  
  void update(Runnable onChange) {
    if (currentStep() != null) currentStep().update(onChange);
  }
  
  S complete() { ret "Form complete"; }
  S cancel() { ret "Request cancelled"; }

  FormStep byKey(S key) {
    ret objectWhere(steps, +key);
  }
  
  S getValue(S key) {
    FormStep step = byKey(key);
    ret step?.value;
  }
  
  SS allValues() {
    SS map = litorderedmap();
    for (FormStep step : steps)
      map.put(step.key, step.value);
    ret map;
  }
  
  bool allowGeneralOverride() { false; }

  Conversation cancelMe() {
    Conversation conv = conversation;
    print("cancelMe called");
    // TODO: conversation.cancelForm();
    ret conv;
  }
  
  void change {
    if (conversation != null) conversation.change();
  }
}

abstract concept BotShowForm > BotStep {
  abstract FormInFlight makeForm();
  
  bool run(Conversation conv) {
    Form form = makeForm();
    true;
  }