sclass ConceptsShadowLogger {
  Concepts cc;
  L<ConceptShadow> shadows;
  new LinkedHashSet<Long> changedIDs;
  bool fullChange;
  Writer writer;
  
  IVF1<ConceptsChange> changeHandler = change -> {
    if (change cast ConceptChange)
      changedIDs.add(change.c.id);
    else if (change cast ConceptDelete)
      changedIDs.add(change.id);
    else if (change cast FullChange)
      fullChange = true;
  };
  
  *() {}
  *(Concepts *cc) {}
  
  void install {
    makeShadows();
    cc.onChange(changeHandler);
  }
  
  void uninstall {
    cc.removeChangeListener(changeHandler);
  }
  
  void makeShadows {
    shadows = allConceptShadows(cc);
  }
  
  void flush {
  }
}