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