// TODO: run dbBot()

sclass ConceptsLoadedOnDemand {

  new Map<S, Concepts> loaded; // key = just the case ID. value can be null in case of error

  L onCaseLoaded; // L<voidfunc(S caseID, O extraInfo, Concepts concepts)>

  L onUnloadingCase; // L<voidfunc(S caseID, Concepts concepts)>

  Lock lock = lock();

  Concepts get(S caseID, O extraInfo) { ret conceptsForCase(caseID, extraInfo); }

  Concepts getIfLoaded(S caseID) {

    lock lock;

    ret loaded.get(unnull(caseID));

  }

  // caseID may be empty, then you get the program's main DB

  Concepts conceptsForCase(S caseID, O extraInfo) {

    lock lock;

    //assertNempty(+caseID);

    caseID = unnull(caseID);

    if (loaded.containsKey(caseID))

      ret assertNotNull("Concepts load error", loaded.get(caseID));

    S id = dbID(caseID);

    print("Loading concepts for case " + id);

    Concepts cc = new Concepts(id);

    cc.persist();

    loaded.put(caseID, cc);

    pcallFAll(onCaseLoaded, caseID, extraInfo, cc);

    ret cc;

  }

  S dbID(S caseID) {

    ret combineWithSlash(getDBProgramID(), caseID);

  }

  void cleanMeUp {

    cleanUpAndClear(loaded);

  }

  void onCaseLoaded(VF3<S, O, Concepts> f) {

    onCaseLoaded = listCreateAndAdd(onCaseLoaded, f);

  }

  void onUnloadingCase(VF2<S, Concepts> f) {

    onUnloadingCase = listCreateAndAdd(onUnloadingCase, f);

  }

  void unloadCase(S caseID) {

    lock lock;

    caseID = unnull(caseID);

    Concepts cc = loaded.get(caseID);

    if (cc != null) {

      pcallFAll(onUnloadingCase, caseID, cc);

      cleanUp(cc);

      loaded.remove(caseID);

    }

  }

}