feat: condivisione piano pasti via QR code

Porta la funzionalità QR code dalla versione Vue a Flutter.

Condividi: pulsante in fondo alla tab Pasti (attivo solo con piano
non vuoto) → bottom sheet con QR code generato da qr_flutter.
Payload: { "v": 1, "meals": { ... } }, limite 2953 byte.

Ricevi: pulsante sempre visibile → QrScanPage full-screen con
fotocamera via mobile_scanner, cornice di mira, validazione
struttura JSON e importazione via MealPlannerProvider.importPlan().

Nuovi package: qr_flutter ^4.1.0, mobile_scanner ^5.0.0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/features/meal_planner/presentation/pages/meal_planner_page.dart

@@ -2,6 +2,8 @@ import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 import '../../providers/meal_planner_provider.dart';
 import '../widgets/meal_card.dart';
+import '../widgets/qr_share_sheet.dart';
+import '../pages/qr_scan_page.dart';
 import '../../../shopping_list/providers/shopping_list_provider.dart';
 import '../../../../core/constants/app_constants.dart';
 
@@ -136,6 +138,32 @@ class MealPlannerPage extends StatelessWidget {
                   child: const Text('Svuota piano'),
                 ),
               ],
+              const SizedBox(height: 8),
+              Row(
+                children: [
+                  Expanded(
+                    child: OutlinedButton.icon(
+                      onPressed: provider.plan.hasAnyMeal
+                          ? () => showQrShareSheet(context, provider.plan)
+                          : null,
+                      icon: const Icon(Icons.qr_code, size: 18),
+                      label: const Text('Condividi'),
+                    ),
+                  ),
+                  const SizedBox(width: 8),
+                  Expanded(
+                    child: OutlinedButton.icon(
+                      onPressed: () => Navigator.push(
+                        context,
+                        MaterialPageRoute(
+                            builder: (_) => const QrScanPage()),
+                      ),
+                      icon: const Icon(Icons.qr_code_scanner, size: 18),
+                      label: const Text('Ricevi'),
+                    ),
+                  ),
+                ],
+              ),
             ],
           ),
         ),

lib/features/meal_planner/presentation/pages/qr_scan_page.dart

@@ -0,0 +1,120 @@
+import 'dart:convert';
+import 'package:flutter/material.dart';
+import 'package:mobile_scanner/mobile_scanner.dart';
+import 'package:provider/provider.dart';
+import '../../models/meal_plan.dart';
+import '../../providers/meal_planner_provider.dart';
+import '../../../../core/constants/app_constants.dart';
+
+class QrScanPage extends StatefulWidget {
+  const QrScanPage({super.key});
+
+  @override
+  State<QrScanPage> createState() => _QrScanPageState();
+}
+
+class _QrScanPageState extends State<QrScanPage> {
+  bool _handled = false;
+
+  void _onDetect(BarcodeCapture capture, BuildContext context) {
+    if (_handled) return;
+    final raw = capture.barcodes.firstOrNull?.rawValue;
+    if (raw == null) return;
+
+    setState(() => _handled = true);
+
+    try {
+      final parsed = jsonDecode(raw) as Map<String, dynamic>;
+      if (parsed['v'] != 1 || parsed['meals'] is! Map) {
+        _showError(context, 'QR non valido: dati non riconosciuti.');
+        return;
+      }
+      final mealsMap = parsed['meals'] as Map<String, dynamic>;
+      for (final day in kDayIds) {
+        final dayData = mealsMap[day];
+        if (dayData is! Map) {
+          _showError(context, 'QR non valido: struttura dati errata.');
+          return;
+        }
+        for (final slot in kMealSlots) {
+          if (dayData[slot] is! List) {
+            _showError(context, 'QR non valido: struttura dati errata.');
+            return;
+          }
+        }
+      }
+
+      final plan = MealPlan(Map.fromEntries(
+        kDayIds.map((day) {
+          final d = mealsMap[day] as Map<String, dynamic>;
+          return MapEntry(
+            day,
+            DayPlan(
+              colazione: List<String>.from(d['colazione'] as List),
+              pranzo: List<String>.from(d['pranzo'] as List),
+              cena: List<String>.from(d['cena'] as List),
+            ),
+          );
+        }),
+      ));
+
+      context.read<MealPlannerProvider>().importPlan(plan);
+
+      if (context.mounted) {
+        Navigator.pop(context);
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(content: Text('Piano ricevuto!')),
+        );
+      }
+    } catch (_) {
+      _showError(context, 'QR non riconosciuto.');
+    }
+  }
+
+  void _showError(BuildContext context, String msg) {
+    if (!context.mounted) return;
+    Navigator.pop(context);
+    ScaffoldMessenger.of(context).showSnackBar(
+      SnackBar(
+        content: Text(msg),
+        backgroundColor: Theme.of(context).colorScheme.error,
+      ),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final scheme = Theme.of(context).colorScheme;
+
+    return Scaffold(
+      appBar: AppBar(title: const Text('Scansiona QR')),
+      body: Stack(
+        children: [
+          MobileScanner(
+            onDetect: (capture) => _onDetect(capture, context),
+          ),
+          // cornice di mira
+          Center(
+            child: Container(
+              width: 220,
+              height: 220,
+              decoration: BoxDecoration(
+                border: Border.all(color: scheme.primary, width: 3),
+                borderRadius: BorderRadius.circular(12),
+              ),
+            ),
+          ),
+          Positioned(
+            bottom: 40,
+            left: 0, right: 0,
+            child: Text(
+              'Inquadra il codice QR dell\'altro dispositivo',
+              textAlign: TextAlign.center,
+              style: const TextStyle(color: Colors.white, fontSize: 14),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}

lib/features/meal_planner/presentation/widgets/qr_share_sheet.dart

@@ -0,0 +1,99 @@
+import 'dart:convert';
+import 'package:flutter/material.dart';
+import 'package:qr_flutter/qr_flutter.dart';
+import '../../models/meal_plan.dart';
+
+const int _kQrMaxBytes = 2953;
+
+void showQrShareSheet(BuildContext context, MealPlan plan) {
+  showModalBottomSheet(
+    context: context,
+    isScrollControlled: true,
+    shape: const RoundedRectangleBorder(
+      borderRadius: BorderRadius.vertical(top: Radius.circular(16)),
+    ),
+    builder: (_) => _QrShareSheet(plan: plan),
+  );
+}
+
+class _QrShareSheet extends StatelessWidget {
+  final MealPlan plan;
+  const _QrShareSheet({required this.plan});
+
+  String? _buildPayload() {
+    final payload = jsonEncode({'v': 1, 'meals': plan.days.map(
+      (k, v) => MapEntry(k, {
+        'colazione': v.colazione,
+        'pranzo': v.pranzo,
+        'cena': v.cena,
+      }),
+    )});
+    if (payload.length > _kQrMaxBytes) return null;
+    return payload;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final payload = _buildPayload();
+    final scheme = Theme.of(context).colorScheme;
+
+    return SafeArea(
+      child: Padding(
+        padding: const EdgeInsets.fromLTRB(20, 12, 20, 32),
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            // handle
+            Container(
+              width: 36, height: 4,
+              decoration: BoxDecoration(
+                color: scheme.outlineVariant,
+                borderRadius: BorderRadius.circular(2),
+              ),
+            ),
+            const SizedBox(height: 16),
+            Row(
+              mainAxisAlignment: MainAxisAlignment.spaceBetween,
+              children: [
+                Text('Condividi piano',
+                    style: Theme.of(context)
+                        .textTheme
+                        .titleMedium
+                        ?.copyWith(fontWeight: FontWeight.bold)),
+                IconButton(
+                  icon: const Icon(Icons.close),
+                  onPressed: () => Navigator.pop(context),
+                ),
+              ],
+            ),
+            const SizedBox(height: 4),
+            Text(
+              'Fai scansionare questo codice dall\'altro dispositivo',
+              style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                    color: scheme.onSurfaceVariant,
+                  ),
+            ),
+            const SizedBox(height: 20),
+            if (payload == null)
+              Padding(
+                padding: const EdgeInsets.symmetric(vertical: 24),
+                child: Text(
+                  'Dati troppo grandi per un QR code.\nRiduci il numero di alimenti inseriti.',
+                  textAlign: TextAlign.center,
+                  style: TextStyle(color: scheme.error),
+                ),
+              )
+            else
+              QrImageView(
+                data: payload,
+                version: QrVersions.auto,
+                size: 260,
+                errorCorrectionLevel: QrErrorCorrectLevel.L,
+                backgroundColor: Colors.white,
+              ),
+          ],
+        ),
+      ),
+    );
+  }
+}

lib/features/meal_planner/providers/meal_planner_provider.dart

@@ -59,4 +59,10 @@ class MealPlannerProvider extends ChangeNotifier {
     notifyListeners();
     _save();
   }
+
+  void importPlan(MealPlan plan) {
+    _plan = plan;
+    notifyListeners();
+    _save();
+  }
 }

pubspec.yaml

@@ -11,6 +11,8 @@ dependencies:
     sdk: flutter
   provider: ^6.1.2
   shared_preferences: ^2.3.2
+  qr_flutter: ^4.1.0
+  mobile_scanner: ^5.0.0
 
 dev_dependencies:
   flutter_test: