KnobsNotifier that supports adding custom knobs

knobs_notifier.dart

// ignore_for_file: invalid_use_of_internal_member

import 'package:widgetbook/widgetbook.dart';
import 'package:widgetbook/src/repositories/selected_use_case_repository.dart';
import 'package:widgetbook/src/knobs/options_knob.dart';

class CustomKnobsNotifier extends KnobsNotifier {
  CustomKnobsNotifier(this.selectedStoryRepository)
      : super(selectedStoryRepository);

  final SelectedUseCaseRepository selectedStoryRepository;

  final Map<WidgetbookUseCaseData, Map<String, Knob<dynamic>>> customKnobs =
      <WidgetbookUseCaseData, Map<String, Knob<dynamic>>>{};

  @override
  List<Knob<dynamic>> all() {
    if (!selectedStoryRepository.isSet()) {
      return [];
    }

    final story = selectedStoryRepository.item;
    final knobs = customKnobs[story]?.values.toList() ?? [];

    return [...knobs, ...super.all()];
  }

  @override
  void update<T>(String label, T value) {
    if (!selectedStoryRepository.isSet()) {
      return;
    }

    if (customKnobs[selectedStoryRepository.item] != null &&
        customKnobs[selectedStoryRepository.item]![label] != null) {
      customKnobs[selectedStoryRepository.item]![label]!.value = value;
      notifyListeners();
      return;
    }

    super.update(label, value);
  }

  T addCustomKnob<T>(Knob<T> value) {
    final story = selectedStoryRepository.item!;
    final knobs = customKnobs.putIfAbsent(
      story,
      () => <String, Knob<dynamic>>{},
    );

    return (knobs.putIfAbsent(value.label, () {
      Future.microtask(notifyListeners);
      return value;
    }) as Knob<T>)
        .value;
  }

  T optionsWithDefault<T>({
    required String label,
    String? description,
    required List<T> options,
    T? initialValue,
    String Function(T)? labelBuilder,
  }) {
    assert(options.isNotEmpty, 'Must specify at least one option');
    return addCustomKnob(
      OptionsKnob(
        label: label,
        value: initialValue ?? options.first,
        description: description,
        options: options,
        labelBuilder: labelBuilder,
      ),
    );
  }
}