chanora/poc/flutter_rust_bridge_hello/lib/main.dart

// Chanora PoC — Flutter side of the flutter_rust_bridge hello spike.
//
// Demonstrates both halves of the PoC exit criterion
// (docs/architecture/proof-of-concept-plan.md §2):
//   1) Flutter calls a Rust command and renders the typed result.
//   2) Flutter subscribes to a Rust event stream and renders ticks live.
//
// This is PoC code, not product UI. The Chanora Design System (Material 3)
// lives in docs/ui-ux/ and is owned by the product Flutter app, not here.

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter_rust_bridge_hello/src/rust/api/simple.dart';
import 'package:flutter_rust_bridge_hello/src/rust/frb_generated.dart';

Future<void> main() async {
  await RustLib.init();
  runApp(const PocApp());
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Chanora PoC — FRB hello',
      theme: ThemeData(
        useMaterial3: true,
        colorSchemeSeed: const Color(0xFF3F51B5),
      ),
      home: const PocHome(),
    );
  }
}

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

  @override
  State<PocHome> createState() => _PocHomeState();
}

class _PocHomeState extends State<PocHome> {
  final _nameCtl = TextEditingController(text: 'Chanora');
  String _greetOutput = '(no call yet)';
  bool _greetOk = true;

  StreamSubscription<CounterTick>? _streamSub;
  final List<CounterTick> _ticks = <CounterTick>[];
  bool _streamRunning = false;

  @override
  void dispose() {
    _streamSub?.cancel();
    _nameCtl.dispose();
    super.dispose();
  }

  void _callGreet() {
    try {
      final r = greet(name: _nameCtl.text);
      setState(() {
        _greetOk = true;
        _greetOutput = '${r.message}\n(elapsed: ${r.elapsedMicros} µs)';
      });
    } catch (e) {
      setState(() {
        _greetOk = false;
        _greetOutput = 'error: $e';
      });
    }
  }

  void _startStream() {
    _streamSub?.cancel();
    setState(() {
      _ticks.clear();
      _streamRunning = true;
    });
    final stream = counterStream(count: 5, intervalMs: 400);
    _streamSub = stream.listen(
      (tick) => setState(() => _ticks.add(tick)),
      onDone: () => setState(() => _streamRunning = false),
      onError: (e) => setState(() {
        _streamRunning = false;
        _ticks.add(CounterTick(seq: BigInt.from(-1), note: 'error: $e'));
      }),
    );
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Scaffold(
      appBar: AppBar(
        title: const Text('Chanora PoC — flutter_rust_bridge hello'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16),
        child: ListView(
          children: [
            Text('1. Command (Dart → Rust → typed Result)', style: theme.textTheme.titleMedium),
            const SizedBox(height: 8),
            Row(
              children: [
                Expanded(
                  child: TextField(
                    controller: _nameCtl,
                    decoration: const InputDecoration(
                      labelText: 'name',
                      border: OutlineInputBorder(),
                    ),
                  ),
                ),
                const SizedBox(width: 12),
                FilledButton(onPressed: _callGreet, child: const Text('greet')),
              ],
            ),
            const SizedBox(height: 8),
            Container(
              padding: const EdgeInsets.all(12),
              decoration: BoxDecoration(
                color: _greetOk
                    ? theme.colorScheme.surfaceContainerHighest
                    : theme.colorScheme.errorContainer,
                borderRadius: BorderRadius.circular(8),
              ),
              child: Text(_greetOutput, style: const TextStyle(fontFamily: 'monospace')),
            ),
            const Divider(height: 32),
            Text('2. Event stream (Rust → Dart Stream<CounterTick>)', style: theme.textTheme.titleMedium),
            const SizedBox(height: 8),
            Row(
              children: [
                FilledButton(
                  onPressed: _streamRunning ? null : _startStream,
                  child: Text(_streamRunning ? 'streaming…' : 'start counter_stream'),
                ),
                const SizedBox(width: 12),
                Text('${_ticks.length} ticks received'),
              ],
            ),
            const SizedBox(height: 8),
            Container(
              constraints: const BoxConstraints(minHeight: 120),
              padding: const EdgeInsets.all(12),
              decoration: BoxDecoration(
                color: theme.colorScheme.surfaceContainerHighest,
                borderRadius: BorderRadius.circular(8),
              ),
              child: _ticks.isEmpty
                  ? const Text('(no ticks yet)')
                  : Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        for (final t in _ticks)
                          Text('seq=${t.seq}  ${t.note}',
                              style: const TextStyle(fontFamily: 'monospace')),
                      ],
                    ),
            ),
            const SizedBox(height: 24),
            Text(
              'PoC exit criterion (docs/architecture/proof-of-concept-plan.md §2):\n'
              '"Flutter can call Rust and receive event stream data."',
              style: theme.textTheme.bodySmall,
            ),
          ],
        ),
      ),
    );
  }
}