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import 'package:flutter/material.dart';
import 'package:vflutter_ffi/vflutter_ffi.dart' as v;

void main() => runApp(const ExampleApp());

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

  @override
  Widget build(BuildContext context) => MaterialApp(
        title: 'vflutter_ffi',
        theme: ThemeData(colorSchemeSeed: Colors.indigo, useMaterial3: true),
        home: const HomePage(),
      );
}

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

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  final _controller = TextEditingController(text: 'Flutter');

  // Synchronous results are cheap enough to compute in build(); the async one
  // is not, so it is held here and refreshed on demand.
  String _async = '(not run)';
  String _stress = '(not run)';

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  Future<void> _runAsync() async {
    final r = await v.greetAsync(_controller.text);
    setState(() => _async = r);
  }

  /// 20k round trips on the UI isolate. Fast enough not to jank, and proves
  /// the V side frees its temporaries under load.
  void _runStress() {
    final sw = Stopwatch()..start();
    for (var i = 0; i < 20000; i++) {
      v.greet('stress$i');
    }
    sw.stop();
    setState(() => _stress = '20k calls in ${sw.elapsedMilliseconds} ms');
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('V → Flutter over dart:ffi')),
      body: Center(
        child: ConstrainedBox(
          constraints: const BoxConstraints(maxWidth: 520),
          child: ListView(
            padding: const EdgeInsets.all(24),
            shrinkWrap: true,
            children: [
              _Row(label: 'v.add(20, 22)', value: '${v.add(20, 42 - 20)}'),
              const Divider(height: 32),
              TextField(
                controller: _controller,
                decoration: const InputDecoration(
                  labelText: 'name',
                  border: OutlineInputBorder(),
                ),
                onChanged: (_) => setState(() {}),
              ),
              const SizedBox(height: 16),
              _Row(label: 'v.greet(name)', value: v.greet(_controller.text)),
              const Divider(height: 32),
              _Row(label: 'v.greetAsync(name)', value: _async),
              const SizedBox(height: 8),
              FilledButton.tonal(
                onPressed: _runAsync,
                child: const Text('run on background isolate'),
              ),
              const Divider(height: 32),
              _Row(label: 'ownership stress', value: _stress),
              const SizedBox(height: 8),
              FilledButton.tonal(
                onPressed: _runStress,
                child: const Text('run 20k round trips'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

class _Row extends StatelessWidget {
  const _Row({required this.label, required this.value});

  final String label;
  final String value;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Text(label, style: theme.textTheme.labelMedium),
        const SizedBox(height: 4),
        SelectableText(
          value,
          style: theme.textTheme.titleMedium
              ?.copyWith(fontFamily: 'monospace', color: theme.colorScheme.primary),
        ),
      ],
    );
  }
}