sclass SimpleCRUD_v2<A extends Concept> extends JConceptsTable<A> {
  JPanel buttons, panel;
  Set<S> unshownFields; // not shown in table or form
  Set<S> excludeFieldsFromEditing;
  S modifiedField; // field to hold last-modified timestamp
  TableSearcher tableSearcher;
  Set<S> multiLineFields; // string fields that should be shown as text areas
  Set<S> dontDuplicateFields;
  int formFixer = 12; // stupid value to make submit button appear
  bool showBackRefs;
  int maxRefsToShow = 3;
  bool showClassNameSelectors;
  bool allowNewFields;
  int newFieldsToShow = 3;
  bool emptyStringsToNull; // convert all empty string values to nulls (also means dropping the field if it's dynamic)
  int formLabelsWidth = 100; // just another bug fixer
  settable bool showSearchBar = true;
  settable bool showAddButton = true;
  settable bool showEditButton = true;

  *(Class<A> conceptClass) { super(conceptClass); }
  *(Concepts concepts, Class<A> conceptClass) { super(concepts, conceptClass); }
  
  SimpleCRUD_v2<A> show(S frameTitle) {
    make();
    showFrame(frameTitle, panel);
    this;
  }
  
  SimpleCRUD_v2<A> show() {
    ret show(plural(shortClassName(conceptClass)));
  }
  
  SimpleCRUD_v2<A> showMaximized() { show(); maximizeFrame(panel); ret this; }
  
  JPanel makePanel() { ret make(); }
  JPanel make() {
    db();
    framesBot();
    ret make_dontStartBots();
  }
  
  swappable MapSO itemToMap_inner(A a) {
    ret super.itemToMap_base(a);
  }
  
  MapSO itemToMap_base(A a) {
    MapSO map = itemToMap_inner(a);
    if (map == null) null;
    ret putAll(map, moreSpecialFieldsForItem(a));
  }
  
  // shown on the right (usually)
  swappable MapSO moreSpecialFieldsForItem(A a) {
    MapSO map = litorderedmap();
    if (showBackRefs) {
      Cl<Concept> refs = allBackRefs(a);
      if (nempty(refs)) {
        refs = sortedByConceptID(refs);
        int more = l(refs)-maxRefsToShow;
        map.put("Referenced by",
          joinWithComma(takeFirst(maxRefsToShow, refs))
        + (more > 0 ? ", " + more + " more" : ""));
      }
    }
    ret map;
  }
  
  JPanel make_dontStartBots() {
    dropFields = asList(unshownFields);
    makeTable();
    swing {
      buttons = jRightAlignedLine(flattenToList(
        !showAddButton ? null : jbutton("Add...", r { newConcept() }),
        !showEditButton ? null : tableDependButton(table, jbutton("Edit", r {
          editConcept(selectedConcept())
        })),
        !showEditButton ? null : tableDependButton(table, jbutton("Duplicate...", r {
          duplicateConcept(selectedConcept())
        })),
        tableDependButton(table, jbutton("Delete", r {
          final L<A> l = selectedConcepts();
          withDBLock(concepts, r { for (A c : l) c.delete() });
        })),
      ));
        
      if (showSearchBar) {
        tableSearcher = tableWithSearcher2(table, withMargin := true);
        panel = centerAndSouthWithMargin(tableSearcher.panel, buttons);
      } else
        panel = centerAndSouthWithMargin(table, buttons);
      
      O fEdit = voidfunc(int row) {
        editConcept(getItem(row))
      };
      tablePopupMenuItem(table, "Edit...", fEdit);
      onDoubleClick(table, fEdit);
      tablePopupMenuFirst(table, (menu, row) -> {
        Concept c = getItem(row);
        if (c != null)
          addMenuItem(menu, "Delete " + quote(shorten(str(c))), rThread {
            deleteConcept(c);
          });
      });
    } // end of swing
    ret panel;
  }
  
  void newConcept {
    duplicateConcept(null);
  }
    
  void duplicateConcept(A oldConcept) {
    new EditWindow ew;
    ew.item = (A) unlisted(oldConcept == null ? conceptClass : _getClass(oldConcept));
    ccopyFieldsExcept(oldConcept, ew.item, dontDuplicateFields);
    makeComponents(ew);
    
    // save action
    F0<Bool> r = func -> bool {
      try {
        concepts.register(ew.item);
        saveData(ew);
        setSelected(ew.item);
      } catch print e {
        infoBox(e);
        false;
      }
      true;
    };
    temp tempSetMCOpt(formLayouter1_fixer2 := formFixer);
    renameSubmitButton("Create", showAForm("New " + shortClassName(conceptClass),
      toObjectArray(listPlus(ew.matrix, r))));
  }

  void editConcept(A c) {
    if (c == null) ret;
    new EditWindow ew;
    ew.item = c;
    makeComponents(ew);
    F0<Bool> r = func -> bool {
      try {
        // concept class was changed, replace object
        if (ew.item != c) {
          print("Replacing object: " + c + " => " + ew.item);
          replaceConceptAndUpdateRefs(c, ew.item);
        }
        saveData(ew);
      } catch print e {
        infoBox(e);
        false;
      }
      true;
    };
    temp tempSetMCOpt(formLayouter1_fixer2 := formFixer);
    renameSubmitButton("Save", showAForm("Edit " + shortClassName(conceptClass) + " #" + c.id,
      toObjectArray(listPlus(ew.matrix, r))));
  }
  
  JComponent fieldComponent(A c, S field) {
    Class type = getFieldType(conceptClass, field);
    O value = cget(c, field);
    if (type == null) type = _getClass(value);
    print("Field type: " + field + " => " + type);
    if (type == bool.class)
      ret jCenteredCheckBox(isTrue(value));
    else if (contains(multiLineFields, field) || containsNewLines(optCast S(value)))
      ret typeWriterTextArea((S) value);
    else if (isSubtype(type, Concept))
      ret jcomboboxFromConcepts_str(concepts, type, (Concept) value);
    ifclass SecretValue
    else if (type == SecretValue.class)
      ret jpassword(strOrEmpty(getVar(value/SecretValue)));
    endif
    else if (isUneditableFieldType(type))
      ret jlabel(structureOrText_crud(value));
    else try {
      ret autoComboBox(structureOrText_crud(value), new TreeSet<S>(map structureOrText_crud(collect(list(concepts, conceptClass), field))));
    } catch e {
      printException(e);
      ret jTextField(structureOrText_crud(value));
    }
  }
  
  void saveComponent(A c, S field, JComponent comp) {
    comp = unwrap(comp);
    ifdef SimpleCRUD_v2_debug
      printVars_str("saveComponent", +field, +comp);
    endifdef
    Class type = fieldType(c, field);
    ifclass SecretValue
      if (type == SecretValue.class) {
        S text = getTextTrim((JPasswordField) comp);
        cset(c, field, empty(text) ? null : SecretValue(text));
      } else
    endif
    if (comp instanceof JTextComponent) {
      S text = trimIf(!comp instanceof JTextArea, getText((JTextComponent) comp));
      O value = postProcessValue(text);
      O converted = convertToField(value, conceptClass, field);
      ifdef SimpleCRUD_v2_debug
        printVars_str("saveComponent", +field, +text, +value, +converted);
      endifdef
      cset(c, field, converted);
    }
    else if (comp cast JComboBox) {
      S text = getTextTrim(comp);
      if (isSubtype(type, Concept))
        cset(c, field, getConcept(concepts, parseFirstLong(text)));
      else {
        O value = postProcessValue(text);
        cset(c, field, convertToField(value, conceptClass, field));
      }
    } else if (comp instanceof JCheckBox)
      cset(c, field, isChecked((JCheckBox) comp));
    ifclass ImageChooser
      else if (comp instanceof ImageChooser)
        cUpdatePNGFile(c, field, comp/ImageChooser.getImage(), false);
    endif
  }
  
  L<S> fieldsForItem(A c) {
    if (excludeFieldsFromEditing != null && modifiedField != null) excludeFieldsFromEditing.add(modifiedField);
    ret listWithoutSet([S field : conceptFields(c) | fieldType(conceptClass, field) != Concept.Ref.class],
      joinSets(excludeFieldsFromEditing, unshownFields));
  }
  
  void excludeFieldsFromEditing(S... fields) {
    excludeFieldsFromEditing = setPlus(excludeFieldsFromEditing, fields);
  }
  
  
  Cl<Class<? extends A>> possibleClasses() {
    ret (Cl) moveItemFirst(conceptClass, dropTypeParameter(sortClassesByNameIC(myNonAbstractClassesImplementing(conceptClass))));
  }
  
  JComboBox<Class<? extends A>> classSelectorComponent(A c) {
    ret setComboBoxRenderer(jTypedComboBox(possibleClasses(), _getClass(c)),
      customToStringListCellRenderer shortClassName());
  }
  
  class NewField {
    JTextField tfName = jtextfield();
    JTextField tfValue = jtextfield();
    JComboBox cbRef = jcomboboxFromConcepts_str(concepts, conceptClass);
    JComboBox cbType = jcombobox("String", "Reference");
    SingleComponentPanel scpValue = singleComponentPanel();
    
    JPanel panel() {
      onChangeAndNow(cbType, r updateSCP);
      ret jhgridWithSpacing(
        withToolTip("Name for new field", withLabel("Name", tfName)),
        withLabel("Value", westAndCenterWithMargin(cbType, scpValue)));
    }
    
    S typeStr() { ret getText(cbType); }
    
    void updateSCP {
      scpValue.setComponent(eqic(typeStr(), "Reference")
        ? cbRef
        : withToolTip("Contents of new field", tfValue));
    }
    
    S field() { ret gtt(tfName); }
    O value() {
      ret eqic(typeStr(), "Reference")
        ? getConcept(concepts, parseFirstLong(getText(cbRef)))
        : gtt(tfValue);
    }
  }
  
  class EditWindow {
    A item;
    Map<S, JComponent> componentsByField = litorderedmap();
    new L matrix; // label, component, label, component, ...
    JComboBox<Class<? extends A>> classSelector;
    new L<NewField> newFields;
  }
  
  // override the following two methods to customize edit window
  
  void makeComponents(EditWindow ew) {
    // class selector
    
    if (showClassNameSelectors) {
      addAll(ew.matrix, makeLabel("Java Class"), ew.classSelector = classSelectorComponent(ew.item));
      onChange(ew.classSelector, r {
        Class<? extends A> oldClass = _getClass(ew.item);
        Class<? extends A> newClass = getSelectedItem_typed(ew.classSelector);
        if (oldClass == newClass) ret;
        A oldItem = ew.item;
        ew.item = unlisted(newClass);
        ccopyFields(oldItem, ew.item);
      });
    }
      
    // regular fields
    
    for (S field : fieldsForItem(ew.item)) {
      JComponent c = fieldComponent(ew.item, field);
      ew.componentsByField.put(field, c);
      addAll(ew.matrix, makeLabel(field), c);
    }
      
    // new fields
    
    if (allowNewFields && newFieldsToShow > 0) {
      addAll(ew.matrix, " ", jlabel()); // spacing
      for i to newFieldsToShow: {
        new NewField nf;
        ew.newFields.add(nf);
        addAll(ew.matrix, makeLabel(""/*"New field"*/), nf.panel());
      }
    }
  }
  
  void saveData(EditWindow ew) {
    // save regular fields
    
    for (S field, JComponent component : ew.componentsByField)
      if (isIdentifier(field))
        saveComponent(ew.item, field, component);
        
    // save new fields
    
    for (NewField nf : ew.newFields) {
      S field = nf.field();
      O value = nf.value();
      if (nempty(field) && notNullOrEmptyString(value))
        cset(ew.item, field, value);
    }
        
    if (modifiedField != null) cset(ew.item, modifiedField, now());
  }
  
  O postProcessValue(O o) {
    if (emptyStringsToNull && eq(o, "")) null;
    ret o;
  }
  
  // labels on left hand side of form
  JComponent makeLabel(S label) {
    ret jMinWidthAtLeast(formLabelsWidth, jlabel(label));
  }
  
  swappable JComponent showAForm(S title, O... parts) {
    ret showFormTitled2(title, parts);
  }
  
  bool isUneditableFieldType(Class type) {
    ret isSubclassOfAny(type, Map, L, Pair);
  }
  
  void hideFields(S... fields) {
    unshownFields = createOrAddToSet(unshownFields, fields);
  }
} // end of SimpleCRUD_v2