main.dart

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';

final class SwitchState {
  static const on = 1;
  static const enabled = 2;
  final int state;

  const SwitchState(this.state);

  bool isEnabled() {
    return 0 != state & SwitchState.enabled;
  }

  bool isOn() {
    return 0 != state & SwitchState.on;
  }

  bool isOff() {
    return !isOn();
  }

  bool isDisabled() {
    return !isEnabled();
  }

  SwitchState setOnOff(bool value) {
    if (value) return setOn();
    return setOff();
  }

  SwitchState setOn() {
    return SwitchState(state | SwitchState.on);
  }

  SwitchState setEnabled() {
    return SwitchState(state | SwitchState.enabled);
  }

  SwitchState setOff() {
    return SwitchState(state & ~SwitchState.on);
  }

  SwitchState setDisabled() {
    return SwitchState(state & ~SwitchState.enabled);
  }

  SwitchState.onEnabled() : state = SwitchState.on | SwitchState.enabled;

  SwitchState.onDisabled() : state = SwitchState.on;

  SwitchState.offEnabled() : state = SwitchState.enabled;

  SwitchState.offDisabled() : state = 0;
}

class SwitchEvent {
  SwitchState state;
  bool isPrimary;

  SwitchEvent({required this.state, this.isPrimary = false});
}

class TwoSwitches {
  SwitchState primary;
  SwitchState secondary;

  TwoSwitches(this.primary, this.secondary);
}

class SwitchesBloc extends Bloc<SwitchEvent, TwoSwitches> {
  SwitchesBloc()
      : super(TwoSwitches(SwitchState.onEnabled(), SwitchState.onEnabled())) {
    on<SwitchEvent>(_onSwitchEvent);
  }

  Future<void> _onSwitchEvent(SwitchEvent e, Emitter<TwoSwitches> emit) async {
    if (e.state.isOff() && e.isPrimary) {
      emit(TwoSwitches(state.primary.setOff(), state.secondary.setDisabled()));
    } else if (e.state.isOn() && e.isPrimary) {
      emit(TwoSwitches(state.primary.setOn(), state.secondary.setEnabled()));
    } else if (e.state.isOff()) {
      emit(TwoSwitches(state.primary, state.secondary.setOff()));
    } else if (e.state.isOn()) {
      emit(TwoSwitches(state.primary, state.secondary.setOn()));
    }
  }
}



void main() {
  runApp(MultiBlocProvider(
      //
      providers: [
        BlocProvider(create: (BuildContext context) => SwitchesBloc()) //
      ], //
      child: MaterialApp(home: MyApp()) //
      ));
}

class MyApp extends StatelessWidget {
  MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return BlocBuilder<SwitchesBloc, TwoSwitches>(builder: (context, state) {
      var swBloc = BlocProvider.of<SwitchesBloc>(context);
      return Scaffold(
          appBar: AppBar(
            leading: const IconButton(
              icon: Icon(Icons.menu),
              tooltip: 'Navigation menu',
              onPressed: null,
            ),
            title: const Text('Example title'),
            actions: const [
              IconButton(
                icon: Icon(Icons.search),
                tooltip: 'Search',
                onPressed: null,
              ),
            ],
          ),
          // body is the majority of the screen.
          body:
              Row(crossAxisAlignment: CrossAxisAlignment.center, children: [
            Column(mainAxisAlignment: MainAxisAlignment.start, children: [
              Switch(
                activeColor: Colors.red,
                value: swBloc.state.primary.isOn(),
                onChanged: (bool value) {
                  swBloc.add(SwitchEvent(
                      state: swBloc.state.primary.setOnOff(value),
                      isPrimary: true));
                },
              ),
              Switch(
                activeColor: Colors.red,
                value: swBloc.state.secondary.isOn(),
                onChanged: swBloc.state.secondary.isDisabled()? null : (bool value) {
                  swBloc.add(SwitchEvent(
                      state: swBloc.state.secondary.setOnOff(value),
                      isPrimary: false));
                },
              )
            ])
          ]));
    });
  }
}