feat: move inventory to own view model, add signing keys

lib/viewmodels/bar_screen_view_model.dart

@@ -4,15 +4,15 @@ import '../models/bar_tab.dart';
 import '../models/product.dart';
 import '../models/tab_item.dart';
 import '../services/bar_tab_service.dart';
-import '../services/product_service.dart';
+import 'inventory_view_model.dart';
 
 class BarScreenViewModel extends ChangeNotifier {
   final BarTabService barTabService;
-  final ProductService productService;
+  final InventoryViewModel inventory;
 
   BarScreenViewModel({
     required this.barTabService,
-    required this.productService,
+    required this.inventory,
   });
 
   List<BarTab> _tabs = [];
@@ -96,7 +96,7 @@ class BarScreenViewModel extends ChangeNotifier {
       product: product,
     );
 
-    await productService.decreaseStock(product.id, 1);
+    await inventory.decreaseStock(product.id, 1);
 
     await _reloadTabs();
   }
@@ -110,9 +110,9 @@ class BarScreenViewModel extends ChangeNotifier {
     );
 
     if (difference > 0) {
-      await productService.decreaseStock(item.productId, difference);
+      await inventory.decreaseStock(item.productId, difference);
     } else if (difference < 0) {
-      await productService.increaseStock(item.productId, -difference);
+      await inventory.increaseStock(item.productId, -difference);
     }
 
     await _reloadTabs();

lib/viewmodels/inventory_view_model.dart

@@ -0,0 +1,61 @@
+import 'package:flutter/foundation.dart';
+
+import '../models/product.dart';
+import '../services/product_service.dart';
+
+class InventoryViewModel extends ChangeNotifier {
+  final ProductService productService;
+
+  InventoryViewModel({
+    required this.productService,
+  });
+
+  List<Product> _products = [];
+
+  List<Product> get products => _products;
+
+  Future<void> load() async {
+    _products = await productService.getProducts();
+    notifyListeners();
+  }
+
+  Future<void> decreaseStock(
+      String productId,
+      int amount,
+      ) async {
+    await productService.decreaseStock(productId, amount);
+
+    final index = _products.indexWhere(
+          (product) => product.id == productId,
+    );
+
+    if (index != -1) {
+      _products[index] = _products[index].copyWith(
+        stockQuantity:
+        _products[index].stockQuantity - amount,
+      );
+    }
+
+    notifyListeners();
+  }
+
+  Future<void> increaseStock(
+      String productId,
+      int amount,
+      ) async {
+    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();
+  }
+}

lib/viewmodels/product_list_view_model.dart

@@ -2,12 +2,15 @@ import 'package:flutter/foundation.dart';
 
 import '../models/product.dart';
 import '../services/product_service.dart';
+import 'inventory_view_model.dart';
 
 class ProductListViewModel extends ChangeNotifier {
   final ProductService productService;
+  final InventoryViewModel inventory;
 
   ProductListViewModel({
     required this.productService,
+    required this.inventory,
   });
 
   static const List<String> _defaultCategories = [
@@ -21,12 +24,11 @@ class ProductListViewModel extends ChangeNotifier {
     'Other',
   ];
 
-  List<Product> _products = [];
   bool _isLoading = false;
   bool _hasLoaded = false;
   String? _errorMessage;
 
-  List<Product> get products => _products;
+  List<Product> get products => inventory.products;
 
   bool get isLoading => _isLoading;
 
@@ -48,7 +50,7 @@ class ProductListViewModel extends ChangeNotifier {
     notifyListeners();
 
     try {
-      _products = await productService.getProducts();
+      await inventory.load();
     } catch (_) {
       _errorMessage = 'Could not load products.';
     } finally {
@@ -109,7 +111,7 @@ class ProductListViewModel extends ChangeNotifier {
   List<String> get categories {
     final categories = {
       ..._defaultCategories,
-      ..._products
+      ...inventory.products
           .map((p) => p.category.trim())
           .where((c) => c.isNotEmpty),
     }.toList();