sclass HCRUD_Concepts<A extends Concept> extends HCRUD_Data {
  Concepts cc = db_mainConcepts();
  Class<A> cClass;
  new L<IVF1<A>> onCreateOrUpdate;
  MapSO filters; // fields to filter by/add to new objects
  ValueConverterForField valueConverter;
  bool referencesBlockDeletion;
  bool trimAllSingleLineValues;
  
  *(Class<A> *cClass) {}
  
  // XXX - breaking change from just shortName()
  swappable S itemName() { ret humanizeShortName(cClass); }
  
  //LS fields() { ret conceptFields(cClass); }
  
  L<A> itemsForListing() {
    ret defaultSort(asList(listConcepts()));
  }
  
  @Override
  L<MapSO> list() {
    ret lambdaMap itemToMapForList(itemsForListing());
  }
  
  // more efficient version - convert items only after taking subList
  // TODO: this is never called by HCRUD; make lazy list instead?
  @Override
  L<MapSO> list(IntRange range) {
    ret lambdaMap itemToMapForList(subListOrFull(itemsForListing(), range));
  }
  
  Cl<A> listConcepts() {
    ret conceptsWhere(cc, cClass, mapToParams(filters));
  }
  
  L<A> defaultSort(L<A> l) { ret l; }
  
  MapSO emptyObject() {
    A c = unlisted(cClass);
    print("fieldOrder", getFieldOrder(c));
    ret printStruct("emptyObject", itemToMap(c));
  }
  
  MapSO itemToMap(A c) {
    if (c == null) null;
    ret putKeysFirst(getFieldOrder(c), conceptToMap_gen_withNullValues(c));
  }
  
  MapSO itemToMapForList(A c) {
    if (c == null) null;
    MapSO map = itemToMap(c);
    massageItemMapForList(c, map);
    ret map;
  }
  
  swappable void massageItemMapForList(A c, MapSO map) {
  }
  
  swappable void massageItemMapForUpdate(A c, MapSO map) {
    // Concepts.RefL magic
    
    for (Field f : nonStaticNonTransientFieldObjectsOfType(Concept.RefL.class, cClass)) {
      new TreeMap<Int, O> values;
      new Matches m;
      for (S key, O value : cloneMap(map))
        if (startsWith(key, f.getName() + "_", m) && isInteger(m.rest())) {
          long conceptID = parseFirstLong((S) value);
          Concept concept = getConcept(cc, conceptID);
          printVars_str("RefL magic", +key, +conceptID, +concept);
          mapPut(values, parseInt(m.rest()), concept);
          map.remove(key);
        }
      map.put(f.getName(), valuesAsList(values));
    }
    
    // Concepts.Ref magic (look up concept)
    
    for (Field f : nonStaticNonTransientFieldObjectsOfType(Concept.Ref.class, cClass)) {
      O value = map.get(f.getName());
      if (value cast S) {
        long conceptID = parseFirstLong(value);
        Concept concept = getConcept(cc, conceptID);
        map.put(f.getName(), concept);
      }
    }
    
    if (trimAllSingleLineValues)
      for (Map.Entry<S, O> e : map.entrySet()) {
        S val = optCastString(e.getValue());
        if (val != null && isSingleLine(val) && isUntrimmed(val))
          e.setValue(trim(val));
      }

  }
  
  MapSO getObject(O id) {
    ret itemToMap(conceptForID(id));
  }
  
  O createObject(SS map) {
    A c = cnew(cc, cClass);
    // make sure filters override
    setValues(c, mapMinusKeys(map, filteredFields()));
    cset(c, mapToParams(filters));
    pcallFAll(onCreateOrUpdate, c);
    ret c.id;
  }
  
  void setValues(A c, SS map) {
    MapSO map2 = (Map) cloneMap(map);
    massageItemMapForUpdate(c, map2);
    if (valueConverter == null)
      cSmartSet(c, mapToParams(map2));
    else
      cSmartSet_withConverter(valueConverter, c, mapToParams(map2));
  }
  
  A conceptForID(O id) {
    ret getConcept(cc, cClass, toLong(id));
  }
  
  S updateObject(O id, SS map) {
    A c = conceptForID(id);
    if (c == null) ret "Object " + id + " not found";
    try answer checkFilters(c);
    setValues(c, map);
    pcallFAll(onCreateOrUpdate, c);
    ret "Object " + id + " updated";
  }
  
  S deleteObject(O id) {
    A c = conceptForID(id);
    if (c == null) ret "Object " + id + " not found";
    try answer checkFilters(c);
    deleteConcept(c);
    ret "Object " + id + " deleted";
  }
  
  S checkFilters(A c) {
    ret checkConceptFields(c, mapToParams(filters)) ? "" : "Object " + c.id + " not in view";
  }
  
  HCRUD_Concepts<A> addFilters(MapSO map) {
    fOr (S field, O value : map)
      addFilter(field, value);
    this;
  }
  
  HCRUD_Concepts<A> addFilter(S field, O value) {
    filters = orderedMapPutOrCreate(filters, field, value);
    this;
  }
  
  Renderer getRenderer(S field) {
    Class type = fieldType(cClass, field);
    
    if (eq(type, bool.class))
      ret new CheckBox;
      
    if (eq(type, Bool.class))
      ret new ComboBox(ll("", "yes", "no"),
        b -> trueFalseNull((Bool) b, "yes", "no", ""));
    
    // show a Ref<> field as a combo box
    
    if (eq(type, Concept.Ref.class)) {
      Class<? extends Concept> c = getTypeArgumentAsClass(genericFieldType(cClass, field));
      ret makeConceptsComboBox(comboBoxItemsForConceptClass(c));
    }
    
    // show a RefL<> field as a list of combo boxes
    
    if (eq(type, Concept.RefL.class)) {
      Class<? extends Concept> c = getTypeArgumentAsClass(genericFieldType(cClass, field));
      LS items = comboBoxItemsForConceptClass(c);
      ret new FlexibleLengthList(makeConceptsComboBox(items));
    }
    
    ret super.getRenderer(field);
  }
  
  ComboBox makeConceptsComboBox(LS entries) {
    ComboBox cb = new(entries);
    cb.valueToEntry = value -> {
      value = deref(value);
      print("ComboBox: value type=" + _getClass(value);
      if (value cast Concept) {
        long id = conceptID(value);
        S entry = firstWhereFirstLongIs(entries, id);
        print("combobox selected: " + id + " / " + entry);
        ret entry;
      }
      null;
    };
    ret cb;
  }
  
  LS comboBoxItemsForConceptClass(Class<? extends Concept> c) {
    ret itemPlus("", map(cc.list(c), val -> shorten(val.id + ": " + val)));
  }
  
  bool objectCanBeDeleted(O id) {
    ret !referencesBlockDeletion || !hasBackRefs(conceptForID(id));
  }
  
  Set<S> filteredFields() { ret keys(filters); }
}