import 'dart:isolate';
import 'dart:math';

// 模拟一个 CPU 密集型计算：计算第 N 个斐波那契数
// 这个函数必须是顶级函数或静态函数，才能作为 Isolate 的入口点
int fibonacci(int n) {
  if (n <= 0) return 0;
  if (n == 1) return 1;
  int a = 0;
  int b = 1;
  for (int i = 2; i <= n; i++) {
    int temp = a + b;
    a = b;
    b = temp;
  }
  return b;
}

// 新 Isolate 的入口点函数
void isolateEntry(SendPort sendPort) {
  ReceivePort receivePort = ReceivePort();
  sendPort.send(receivePort.sendPort); // 将自己的 SendPort 发送给主 Isolate

  receivePort.listen((message) {
    if (message is int) {
      int result = fibonacci(message);
      sendPort.send(result); // 将计算结果发送回主 Isolate
    } else if (message == 'exit') {
      receivePort.close();
      Isolate.current.kill(); // 退出 Isolate
    }
  });
}

void main() async {
  print('Main Isolate: Starting heavy computation...');

  ReceivePort mainReceivePort = ReceivePort();
  Isolate newIsolate = await Isolate.spawn(isolateEntry, mainReceivePort.sendPort);

  SendPort? isolateSendPort;
  mainReceivePort.listen((message) {
    if (message is SendPort) {
      isolateSendPort = message; // 接收新 Isolate 的 SendPort
      isolateSendPort!.send(40); // 发送要计算的斐波那契数 (例如第40个)
    } else if (message is int) {
      print('Main Isolate: Received result: $message');
      isolateSendPort!.send('exit'); // 通知 Isolate 退出
      mainReceivePort.close();
    }
  });

  print('Main Isolate: UI remains responsive.');
}
// 预期输出：
// Main Isolate: Starting heavy computation...
// Main Isolate: UI remains responsive.
// (一段时间后)
// Main Isolate: Received result: 102334155

import 'package:flutter/foundation.dart'; // 包含 compute 函数

// 模拟一个 CPU 密集型计算：计算第 N 个斐波那契数
// 这个函数必须是顶级函数或静态函数
int fibonacciCompute(int n) {
  if (n <= 0) return 0;
  if (n == 1) return 1;
  int a = 0;
  int b = 1;
  for (int i = 2; i <= n; i++) {
    int temp = a + b;
    a = b;
    b = temp;
  }
  return b;
}

void main() async {
  print('Main Isolate: Starting heavy computation with compute...');

  // 使用 compute 在另一个 Isolate 中运行 fibonacciCompute
  int result = await compute(fibonacciCompute, 40);

  print('Main Isolate: Received result: $result');
  print('Main Isolate: UI remains responsive.');
}
// 预期输出：
// Main Isolate: Starting heavy computation with compute...
// Main Isolate: UI remains responsive.
// (一段时间后)
// Main Isolate: Received result: 102334155

import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart'; // 包含 compute 函数
import 'dart:convert'; // 用于 JSON 解析

// 模拟一个大型 JSON 字符串
String largeJsonString = '''
[
  {
    


    "id": 1,
    "name": "Product 1",
    "price": 10.99
  },
  {
    "id": 2,
    "name": "Product 2",
    "price": 25.50
  },
  // ... 假设这里有成千上万个产品 ...
  {
    "id": 10000,
    "name": "Product 10000",
    "price": 99.99
  }
]
""";

// 解析 JSON 的函数，必须是顶级函数或静态函数
List<Map<String, dynamic>> parseJson(String jsonString) {
  // 模拟耗时操作
  final stopwatch = Stopwatch()..start();
  final List<dynamic> parsedJson = jsonDecode(jsonString);
  print("JSON parsing took ${stopwatch.elapsedMilliseconds}ms in isolate.");
  return parsedJson.cast<Map<String, dynamic>>();
}

class IsolateExampleScreen extends StatefulWidget {
  const IsolateExampleScreen({super.key});

  @override
  State<IsolateExampleScreen> createState() => _IsolateExampleScreenState();
}

class _IsolateExampleScreenState extends State<IsolateExampleScreen> {
  List<Map<String, dynamic>>? _products;
  bool _isLoading = false;

  Future<void> _parseJsonInIsolate() async {
    setState(() {
      _isLoading = true;
      _products = null;
    });

    // 使用 compute 在后台 Isolate 中解析 JSON
    final List<Map<String, dynamic>> result = await compute(parseJson, largeJsonString);

    setState(() {
      _products = result;
      _isLoading = false;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("Isolate 解析 JSON 示例"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            ElevatedButton(
              onPressed: _isLoading ? null : _parseJsonInIsolate,
              child: const Text("在 Isolate 中解析 JSON"),
            ),
            const SizedBox(height: 20),
            if (_isLoading)
              const CircularProgressIndicator(),
            if (_products != null)
              Expanded(
                child: ListView.builder(
                  itemCount: _products!.length,
                  itemBuilder: (context, index) {
                    final product = _products![index];
                    return ListTile(
                      title: Text(product["name"] as String),
                      subtitle: Text("Price: \$${product["price"]}"),
                    );
                  },
                ),
              ),
          ],
        ),
      ),
    );
  }
}

void main() {
  runApp(const MaterialApp(home: IsolateExampleScreen()));
}