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

void main() {
  runApp(const MyApp());
}

class Counter1 extends ChangeNotifier {
  int _counter = 0;

  int get counter {
    return _counter;
  }

  void increment() {
    _counter = _counter + 1;
    notifyListeners();
  }

  void reset() {
    _counter = 0;
    notifyListeners();
  }
}

class Counter2 extends ChangeNotifier {
  int _counter = 0;

  int get counter {
    return _counter;
  }

  void increment() {
    _counter = _counter + 1;
    notifyListeners();
  }
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: MultiProvider(providers: [
        ChangeNotifierProvider(
          create: (context) {
            return Counter2();
          },
        ),
        ChangeNotifierProxyProvider<Counter2, Counter1>(
          create: (context) {
            return Counter1();
          },
          update: (BuildContext context, Counter2 value, Counter1? previous) {
            if (previous == null) {
              throw StateError("Counter1 is null");
            }
            value.removeListener(previous.reset); // To avoid multiple listener
            value.addListener(previous.reset);
            return previous;
          },
        ),
      ], child: const MyHomePage()),
    );
  }
}

class MyHomePage extends StatelessWidget {
  const MyHomePage({super.key});

  @override
  Widget build(BuildContext context) {
    var counter1 = Provider.of<Counter1>(context);
    var counter2 = Provider.of<Counter2>(context);
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title:
            const Text("Let's try to reset counter 1 when counter 2 increment"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              'Counter 1:',
            ),
            Text(
              '${counter1.counter}',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
            ElevatedButton(
                onPressed: counter1.increment,
                child: const Text("Increment counter 1")),
            const Text(
              'Counter 2:',
            ),
            Text(
              '${counter2.counter}',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
            ElevatedButton(
                onPressed: counter2.increment,
                child: const Text("Increment counter 2")),
          ],
        ),
      ),
    );
  }
}