import 'dart:isolate';

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

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

void _isolateEntryPoint(Map<String, Object?> message) {
  final sendPort = message['sendPort'] as SendPort;
  Isolate.exit(sendPort, null);
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Isolates bug',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Isolates bug'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final _receivePort = ReceivePort();
  var _receivePortIsListening = false;

  void _spawnIsolate() {
    if (!_receivePortIsListening) {
      _receivePort.listen(_onIsolateData);
      _receivePortIsListening = true;
    }

    Isolate.spawn(_isolateEntryPoint, {'sendPort': _receivePort.sendPort});
  }

  void _onIsolateData(message) {
    debugPrint('Isolate has completed.');

    setState(() {});

    // Run this line (break points won't work):
    _compute();

    // Or

    // Run this line (break points will work):
    // WidgetsBinding.instance.addPostFrameCallback((_) => _compute());
  }

  void _compute() {
    compute(
      (message) => debugPrint(message['key']),
      {'key': 'Compute function has completed.'},
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _spawnIsolate,
        child: const Icon(Icons.play_arrow_outlined),
      ),
    );
  }
}