add alot

lib/viewmodels/bar_screen_view_model.dart

@@ -8,9 +8,11 @@ import '../services/product_service.dart';
 
 class BarScreenViewModel extends ChangeNotifier {
   final BarTabService barTabService;
+  final ProductService productService;
 
   BarScreenViewModel({
     required this.barTabService,
+    required this.productService,
   });
 
   List<BarTab> _tabs = [];
@@ -74,9 +76,7 @@ class BarScreenViewModel extends ChangeNotifier {
   }
 
   Future<void> createTab(String customerName) async {
-    final tab = await barTabService.createTab(
-      customerName: customerName,
-    );
+    final tab = await barTabService.createTab(customerName: customerName);
 
     _selectedTabId = tab.id;
     await _reloadTabs();
@@ -87,23 +87,34 @@ class BarScreenViewModel extends ChangeNotifier {
 
     if (tab == null) return;
 
+    if (product.stockQuantity <= 0) {
+      throw Exception('Product is out of stock.');
+    }
+
     await barTabService.addProductToTab(
       tabId: tab.id,
       product: product,
     );
 
+    await productService.decreaseStock(product.id, 1);
+
     await _reloadTabs();
   }
 
-  Future<void> changeItemQuantity(
-      TabItem item,
-      int quantity,
-      ) async {
+  Future<void> changeItemQuantity(TabItem item, int quantity) async {
+    final difference = quantity - item.quantity;
+
     await barTabService.updateTabItemQuantity(
       tabItemId: item.id,
       quantity: quantity,
     );
 
+    if (difference > 0) {
+      await productService.decreaseStock(item.productId, difference);
+    } else if (difference < 0) {
+      await productService.increaseStock(item.productId, -difference);
+    }
+
     await _reloadTabs();
   }
 
@@ -126,10 +137,11 @@ class BarScreenViewModel extends ChangeNotifier {
   Future<void> _reloadTabs() async {
     _tabs = await barTabService.getOpenTabs();
 
-    if (_selectedTabId == null || !_tabs.any((tab) => tab.id == _selectedTabId)) {
+    if (_selectedTabId == null ||
+        !_tabs.any((tab) => tab.id == _selectedTabId)) {
       _selectedTabId = _tabs.isEmpty ? null : _tabs.first.id;
     }
 
     notifyListeners();
   }
-}
+}