feat: add alot

lib/viewmodels/inventory_view_model.dart

@@ -1,80 +1,60 @@
+import 'dart:async';
+
 import 'package:flutter/foundation.dart';
 import 'package:sentry_flutter/sentry_flutter.dart';
 
+import '../models/app_error.dart';
 import '../models/product.dart';
 import '../services/product_service.dart';
 
+/// The app-wide product list, kept in sync with the database. Stock changes
+/// from tabs show up here automatically.
 class InventoryViewModel extends ChangeNotifier {
   final ProductService productService;
 
   InventoryViewModel({required this.productService});
 
+  StreamSubscription<List<Product>>? _subscription;
   List<Product> _products = [];
+  bool _hasLoaded = false;
+  AppError? _loadError;
 
   List<Product> get products => _products;
 
-  Future<void> load() async {
-    try {
-      _products = await productService.getProducts();
-      notifyListeners();
-    } catch (e, stack) {
-      debugPrint('InventoryViewModel: load error: $e');
-      Sentry.captureException(e, stackTrace: stack);
-      rethrow;
-    }
-  }
+  bool get hasLoaded => _hasLoaded;
 
-  Future<void> decreaseStock(String productId, int amount) async {
-    try {
-      await productService.decreaseStock(productId, amount);
+  bool get isLoading => !_hasLoaded;
 
-      final index = _products.indexWhere((product) => product.id == productId);
+  AppError? get loadError => _loadError;
 
-      if (index != -1) {
-        _products[index] = _products[index].copyWith(
-          stockQuantity: _products[index].stockQuantity - amount,
-        );
-      }
+  void ensureLoaded() {
+    if (_subscription != null) return;
 
-      notifyListeners();
-    } catch (e, stack) {
-      if (e is InsufficientStockException) rethrow;
-
-      debugPrint('InventoryViewModel: decreaseStock error: $e');
-      Sentry.captureException(e, stackTrace: stack);
-      rethrow;
-    }
-  }
-
-  Future<void> increaseStock(String productId, int amount) async {
-    try {
-      await productService.increaseStock(productId, amount);
-
-      final index = _products.indexWhere((product) => product.id == productId);
-
-      if (index != -1) {
-        _products[index] = _products[index].copyWith(
-          stockQuantity: _products[index].stockQuantity + amount,
-        );
-      }
-
-      notifyListeners();
-    } catch (e, stack) {
-      debugPrint('InventoryViewModel: increaseStock error: $e');
-      Sentry.captureException(e, stackTrace: stack);
-      rethrow;
-    }
-  }
-
-  void applyStockDelta(String productId, int delta) {
-    if (delta == 0) return;
-
-    final index = _products.indexWhere((product) => product.id == productId);
-    if (index == -1) return;
-
-    _products[index] = _products[index].copyWith(
-      stockQuantity: _products[index].stockQuantity + delta,
+    _subscription = productService.watchProducts().listen(
+      _onProducts,
+      onError: _onLoadError,
     );
+  }
+
+  void _onProducts(List<Product> products) {
+    _products = products;
+    _hasLoaded = true;
+    _loadError = null;
     notifyListeners();
   }
+
+  void _onLoadError(Object error, StackTrace stack) {
+    debugPrint('InventoryViewModel: load error: $error');
+    unawaited(Sentry.captureException(error, stackTrace: stack));
+
+    _hasLoaded = true;
+    _loadError = AppError.loadProducts;
+    notifyListeners();
+  }
+
+  @override
+  void dispose() {
+    _subscription?.cancel();
+    super.dispose();
+  }
 }