sclass TripleIndex extends VirtualNodeIndex {
  SyncListMultiMap<S, TripleRef<S>> index = caseInsensitiveSyncListMultiMap();
  Map<GlobalID, TripleWeb> websByID = synchroHashMap();
  bool activated; // are we the main index (see tripleIndex())

  int numWebs() {
    ret l(websByID);
  }
  
  L<WebNode> get(S query) {
    ret ai_tripleRefsToWebNodes_lazyList(index.get(query));
  }
  
  Web getWeb(GlobalID id) {
    ret webFromTriple(websByID.get(id));
  }
  
  void addWeb(Web web) {
    if (web == null) ret;
    TripleWeb w = ai_webToTripleWeb(web);
    if (w == null)
      //ret with print("Skipping non-tripelizable web");
      fail("Skipping non-tripelizable web: " + webToStringShort(web));
    index.put(w.a, TripleA(w));
    index.put(w.b, TripleB(w));
    index.put(w.c, TripleC(w));
    websByID.put(w.globalID, w);
  }
  
  void clear() {
    index.clear();
    websByID.clear();
  }
  
  activate {
    if (!activated) {
      activated = true;
      ai_onNewOrRemovedWeb(voidfunc(Web web) {
        addWeb(web)
      }, voidfunc(Web web) {
        removeWeb(web)
      });
    }
  }
}