Implement complete cart management system

Add full cart functionality with API integration:
- Created Cart and OrderLineItem models with robust JSON parsing
- Implemented cart API methods (getOrCreateCart, setLineItem, getCart, submitOrder)
- Added cart state management to AppState with item count tracking
- Built cart view screen with item display, quantity editing, and removal
- Added cart badge to menu screen showing item count
- Implemented real add-to-cart logic with recursive modifier handling
- Added category name display in menu browsing
- Fixed API response case sensitivity (ORDER/ORDERLINEITEMS)
- Enhanced MenuItem model with categoryName field

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

lib/app/app_router.dart

@@ -1,5 +1,6 @@
 import "package:flutter/material.dart";
 
+import "../screens/cart_view_screen.dart";
 import "../screens/login_screen.dart";
 import "../screens/menu_browse_screen.dart";
 import "../screens/restaurant_select_screen.dart";
@@ -12,6 +13,7 @@ class AppRoutes {
   static const String restaurantSelect = "/restaurants";
   static const String servicePointSelect = "/service-points";
   static const String menuBrowse = "/menu";
+  static const String cartView = "/cart";
 
   static Map<String, WidgetBuilder> get routes => {
         splash: (_) => const SplashScreen(),
@@ -19,5 +21,6 @@ class AppRoutes {
         restaurantSelect: (_) => const RestaurantSelectScreen(),
         servicePointSelect: (_) => const ServicePointSelectScreen(),
         menuBrowse: (_) => const MenuBrowseScreen(),
+        cartView: (_) => const CartViewScreen(),
       };
 }

lib/app/app_state.dart

@@ -8,6 +8,7 @@ class AppState extends ChangeNotifier {
 
   int? _cartOrderId;
   String? _cartOrderUuid;
+  int _cartItemCount = 0;
 
   int? get selectedBusinessId => _selectedBusinessId;
   int? get selectedServicePointId => _selectedServicePointId;
@@ -17,6 +18,7 @@ class AppState extends ChangeNotifier {
 
   int? get cartOrderId => _cartOrderId;
   String? get cartOrderUuid => _cartOrderUuid;
+  int get cartItemCount => _cartItemCount;
 
   bool get hasLocationSelection =>
       _selectedBusinessId != null && _selectedServicePointId != null;
@@ -50,15 +52,22 @@ class AppState extends ChangeNotifier {
     notifyListeners();
   }
 
-  void setCartOrder({required int orderId, required String orderUuid}) {
+  void setCartOrder({required int orderId, required String orderUuid, int itemCount = 0}) {
     _cartOrderId = orderId;
     _cartOrderUuid = orderUuid;
+    _cartItemCount = itemCount;
+    notifyListeners();
+  }
+
+  void updateCartItemCount(int count) {
+    _cartItemCount = count;
     notifyListeners();
   }
 
   void clearCart() {
     _cartOrderId = null;
     _cartOrderUuid = null;
+    _cartItemCount = 0;
     notifyListeners();
   }
 

lib/models/cart.dart

@@ -0,0 +1,202 @@
+class Cart {
+  final int orderId;
+  final String orderUuid;
+  final int userId;
+  final int businessId;
+  final double businessDeliveryMultiplier;
+  final int orderTypeId;
+  final double deliveryFee;
+  final int statusId;
+  final int? addressId;
+  final int? paymentId;
+  final String? remarks;
+  final DateTime addedOn;
+  final DateTime lastEditedOn;
+  final DateTime? submittedOn;
+  final int servicePointId;
+  final List<OrderLineItem> lineItems;
+
+  const Cart({
+    required this.orderId,
+    required this.orderUuid,
+    required this.userId,
+    required this.businessId,
+    required this.businessDeliveryMultiplier,
+    required this.orderTypeId,
+    required this.deliveryFee,
+    required this.statusId,
+    this.addressId,
+    this.paymentId,
+    this.remarks,
+    required this.addedOn,
+    required this.lastEditedOn,
+    this.submittedOn,
+    required this.servicePointId,
+    required this.lineItems,
+  });
+
+  factory Cart.fromJson(Map<String, dynamic> json) {
+    final order = (json["ORDER"] ?? json["Order"]) as Map<String, dynamic>? ?? {};
+    final lineItemsJson = (json["ORDERLINEITEMS"] ?? json["OrderLineItems"]) as List? ?? [];
+
+    return Cart(
+      orderId: _parseInt(order["OrderID"]) ?? 0,
+      orderUuid: (order["OrderUUID"] as String?) ?? "",
+      userId: _parseInt(order["OrderUserID"]) ?? 0,
+      businessId: _parseInt(order["OrderBusinessID"]) ?? 0,
+      businessDeliveryMultiplier: _parseDouble(order["OrderBusinessDeliveryMultiplier"]) ?? 0.0,
+      orderTypeId: _parseInt(order["OrderTypeID"]) ?? 0,
+      deliveryFee: _parseDouble(order["OrderDeliveryFee"]) ?? 0.0,
+      statusId: _parseInt(order["OrderStatusID"]) ?? 0,
+      addressId: _parseInt(order["OrderAddressID"]),
+      paymentId: _parseInt(order["OrderPaymentID"]),
+      remarks: order["OrderRemarks"] as String?,
+      addedOn: _parseDateTime(order["OrderAddedOn"]),
+      lastEditedOn: _parseDateTime(order["OrderLastEditedOn"]),
+      submittedOn: _parseDateTime(order["OrderSubmittedOn"]),
+      servicePointId: _parseInt(order["OrderServicePointID"]) ?? 0,
+      lineItems: lineItemsJson
+          .map((item) => OrderLineItem.fromJson(item as Map<String, dynamic>))
+          .toList(),
+    );
+  }
+
+  static int? _parseInt(dynamic value) {
+    if (value == null) return null;
+    if (value is int) return value;
+    if (value is num) return value.toInt();
+    if (value is String) {
+      if (value.isEmpty) return null;
+      return int.tryParse(value);
+    }
+    return null;
+  }
+
+  static double? _parseDouble(dynamic value) {
+    if (value == null) return null;
+    if (value is double) return value;
+    if (value is num) return value.toDouble();
+    if (value is String) {
+      if (value.isEmpty) return null;
+      return double.tryParse(value);
+    }
+    return null;
+  }
+
+  static DateTime _parseDateTime(dynamic value) {
+    if (value == null) return DateTime.now();
+    if (value is DateTime) return value;
+    if (value is String) {
+      try {
+        return DateTime.parse(value);
+      } catch (e) {
+        return DateTime.now();
+      }
+    }
+    return DateTime.now();
+  }
+
+  double get subtotal {
+    return lineItems
+        .where((item) => !item.isDeleted && item.parentOrderLineItemId == 0)
+        .fold(0.0, (sum, item) => sum + (item.price * item.quantity));
+  }
+
+  double get total => subtotal + deliveryFee;
+
+  int get itemCount {
+    return lineItems
+        .where((item) => !item.isDeleted && item.parentOrderLineItemId == 0)
+        .fold(0, (sum, item) => sum + item.quantity);
+  }
+}
+
+class OrderLineItem {
+  final int orderLineItemId;
+  final int parentOrderLineItemId;
+  final int orderId;
+  final int itemId;
+  final int statusId;
+  final double price;
+  final int quantity;
+  final String? remark;
+  final bool isDeleted;
+  final DateTime addedOn;
+
+  const OrderLineItem({
+    required this.orderLineItemId,
+    required this.parentOrderLineItemId,
+    required this.orderId,
+    required this.itemId,
+    required this.statusId,
+    required this.price,
+    required this.quantity,
+    this.remark,
+    required this.isDeleted,
+    required this.addedOn,
+  });
+
+  factory OrderLineItem.fromJson(Map<String, dynamic> json) {
+    return OrderLineItem(
+      orderLineItemId: _parseInt(json["OrderLineItemID"]) ?? 0,
+      parentOrderLineItemId: _parseInt(json["OrderLineItemParentOrderLineItemID"]) ?? 0,
+      orderId: _parseInt(json["OrderLineItemOrderID"]) ?? 0,
+      itemId: _parseInt(json["OrderLineItemItemID"]) ?? 0,
+      statusId: _parseInt(json["OrderLineItemStatusID"]) ?? 0,
+      price: _parseDouble(json["OrderLineItemPrice"]) ?? 0.0,
+      quantity: _parseInt(json["OrderLineItemQuantity"]) ?? 0,
+      remark: json["OrderLineItemRemark"] as String?,
+      isDeleted: _parseBool(json["OrderLineItemIsDeleted"]),
+      addedOn: _parseDateTime(json["OrderLineItemAddedOn"]),
+    );
+  }
+
+  static int? _parseInt(dynamic value) {
+    if (value == null) return null;
+    if (value is int) return value;
+    if (value is num) return value.toInt();
+    if (value is String) {
+      if (value.isEmpty) return null;
+      return int.tryParse(value);
+    }
+    return null;
+  }
+
+  static double? _parseDouble(dynamic value) {
+    if (value == null) return null;
+    if (value is double) return value;
+    if (value is num) return value.toDouble();
+    if (value is String) {
+      if (value.isEmpty) return null;
+      return double.tryParse(value);
+    }
+    return null;
+  }
+
+  static bool _parseBool(dynamic value) {
+    if (value == null) return false;
+    if (value is bool) return value;
+    if (value is num) return value != 0;
+    if (value is String) {
+      final lower = value.toLowerCase();
+      return lower == "true" || lower == "1";
+    }
+    return false;
+  }
+
+  static DateTime _parseDateTime(dynamic value) {
+    if (value == null) return DateTime.now();
+    if (value is DateTime) return value;
+    if (value is String) {
+      try {
+        return DateTime.parse(value);
+      } catch (e) {
+        return DateTime.now();
+      }
+    }
+    return DateTime.now();
+  }
+
+  bool get isRootItem => parentOrderLineItemId == 0;
+  bool get isModifier => parentOrderLineItemId != 0;
+}

lib/models/menu_item.dart

@@ -1,6 +1,7 @@
 class MenuItem {
   final int itemId;
   final int categoryId;
+  final String categoryName;
   final String name;
   final String description;
   final int parentItemId;
@@ -15,6 +16,7 @@ class MenuItem {
   const MenuItem({
     required this.itemId,
     required this.categoryId,
+    required this.categoryName,
     required this.name,
     required this.description,
     required this.parentItemId,
@@ -31,6 +33,7 @@ class MenuItem {
     return MenuItem(
       itemId: (json["ItemID"] as num).toInt(),
       categoryId: (json["ItemCategoryID"] as num).toInt(),
+      categoryName: (json["ItemCategoryName"] as String?) ?? "",
       name: (json["ItemName"] as String?) ?? "",
       description: (json["ItemDescription"] as String?) ?? "",
       parentItemId: (json["ItemParentItemID"] as num?)?.toInt() ?? 0,

lib/screens/cart_view_screen.dart

@@ -0,0 +1,462 @@
+import 'package:flutter/material.dart';
+import 'package:provider/provider.dart';
+
+import '../app/app_state.dart';
+import '../models/cart.dart';
+import '../models/menu_item.dart';
+import '../services/api.dart';
+
+class CartViewScreen extends StatefulWidget {
+  const CartViewScreen({super.key});
+
+  @override
+  State<CartViewScreen> createState() => _CartViewScreenState();
+}
+
+class _CartViewScreenState extends State<CartViewScreen> {
+  Cart? _cart;
+  bool _isLoading = true;
+  String? _error;
+  Map<int, MenuItem> _menuItemsById = {};
+
+  @override
+  void initState() {
+    super.initState();
+    _loadCart();
+  }
+
+  Future<void> _loadCart() async {
+    setState(() {
+      _isLoading = true;
+      _error = null;
+    });
+
+    try {
+      final appState = context.read<AppState>();
+      final cartOrderId = appState.cartOrderId;
+
+      if (cartOrderId == null) {
+        setState(() {
+          _isLoading = false;
+          _cart = null;
+        });
+        return;
+      }
+
+      // Load cart
+      final cart = await Api.getCart(orderId: cartOrderId);
+
+      // Load menu items to get names and prices
+      final businessId = appState.selectedBusinessId;
+      if (businessId != null) {
+        final menuItems = await Api.listMenuItems(businessId: businessId);
+        _menuItemsById = {for (var item in menuItems) item.itemId: item};
+      }
+
+      setState(() {
+        _cart = cart;
+        _isLoading = false;
+      });
+
+      // Update item count in app state
+      appState.updateCartItemCount(cart.itemCount);
+    } catch (e) {
+      setState(() {
+        _error = e.toString();
+        _isLoading = false;
+      });
+    }
+  }
+
+  Future<void> _removeLineItem(OrderLineItem lineItem) async {
+    try {
+      final appState = context.read<AppState>();
+      final cartOrderId = appState.cartOrderId;
+      if (cartOrderId == null) return;
+
+      setState(() => _isLoading = true);
+
+      // Set IsSelected=false to remove the item
+      await Api.setLineItem(
+        orderId: cartOrderId,
+        parentOrderLineItemId: lineItem.parentOrderLineItemId,
+        itemId: lineItem.itemId,
+        isSelected: false,
+      );
+
+      // Reload cart
+      await _loadCart();
+    } catch (e) {
+      setState(() {
+        _error = e.toString();
+        _isLoading = false;
+      });
+    }
+  }
+
+  Future<void> _updateQuantity(OrderLineItem lineItem, int newQuantity) async {
+    if (newQuantity < 1) return;
+
+    try {
+      final appState = context.read<AppState>();
+      final cartOrderId = appState.cartOrderId;
+      if (cartOrderId == null) return;
+
+      setState(() => _isLoading = true);
+
+      await Api.setLineItem(
+        orderId: cartOrderId,
+        parentOrderLineItemId: lineItem.parentOrderLineItemId,
+        itemId: lineItem.itemId,
+        isSelected: true,
+        quantity: newQuantity,
+        remark: lineItem.remark,
+      );
+
+      // Reload cart
+      await _loadCart();
+    } catch (e) {
+      setState(() {
+        _error = e.toString();
+        _isLoading = false;
+      });
+    }
+  }
+
+  Future<void> _submitOrder() async {
+    try {
+      final appState = context.read<AppState>();
+      final cartOrderId = appState.cartOrderId;
+      if (cartOrderId == null) return;
+
+      setState(() => _isLoading = true);
+
+      await Api.submitOrder(orderId: cartOrderId);
+
+      // Clear cart state
+      appState.clearCart();
+
+      if (!mounted) return;
+
+      // Show success message
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(
+          content: Text("Order submitted successfully!"),
+          backgroundColor: Colors.green,
+        ),
+      );
+
+      // Navigate back
+      Navigator.of(context).pop();
+    } catch (e) {
+      setState(() {
+        _error = e.toString();
+        _isLoading = false;
+      });
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text("Cart"),
+        backgroundColor: Colors.black,
+        foregroundColor: Colors.white,
+      ),
+      body: _isLoading
+          ? const Center(child: CircularProgressIndicator())
+          : _error != null
+              ? Center(
+                  child: Padding(
+                    padding: const EdgeInsets.all(16),
+                    child: Column(
+                      mainAxisAlignment: MainAxisAlignment.center,
+                      children: [
+                        const Icon(Icons.error, color: Colors.red, size: 48),
+                        const SizedBox(height: 16),
+                        Text(
+                          "Error loading cart",
+                          style: Theme.of(context).textTheme.titleLarge,
+                        ),
+                        const SizedBox(height: 8),
+                        Text(_error!, textAlign: TextAlign.center),
+                        const SizedBox(height: 16),
+                        ElevatedButton(
+                          onPressed: _loadCart,
+                          child: const Text("Retry"),
+                        ),
+                      ],
+                    ),
+                  ),
+                )
+              : _cart == null || _cart!.itemCount == 0
+                  ? Center(
+                      child: Column(
+                        mainAxisAlignment: MainAxisAlignment.center,
+                        children: [
+                          const Icon(
+                            Icons.shopping_cart_outlined,
+                            size: 80,
+                            color: Colors.grey,
+                          ),
+                          const SizedBox(height: 16),
+                          Text(
+                            "Your cart is empty",
+                            style: Theme.of(context).textTheme.titleLarge,
+                          ),
+                        ],
+                      ),
+                    )
+                  : Column(
+                      children: [
+                        Expanded(
+                          child: ListView(
+                            padding: const EdgeInsets.all(16),
+                            children: _buildCartItems(),
+                          ),
+                        ),
+                        _buildCartSummary(),
+                      ],
+                    ),
+    );
+  }
+
+  List<Widget> _buildCartItems() {
+    if (_cart == null) return [];
+
+    // Group line items by root items
+    final rootItems = _cart!.lineItems
+        .where((item) => item.parentOrderLineItemId == 0 && !item.isDeleted)
+        .toList();
+
+    final widgets = <Widget>[];
+
+    for (final rootItem in rootItems) {
+      widgets.add(_buildRootItemCard(rootItem));
+      widgets.add(const SizedBox(height: 12));
+    }
+
+    return widgets;
+  }
+
+  Widget _buildRootItemCard(OrderLineItem rootItem) {
+    final menuItem = _menuItemsById[rootItem.itemId];
+    final itemName = menuItem?.name ?? "Item #${rootItem.itemId}";
+
+    // Find all modifiers for this root item
+    final modifiers = _cart!.lineItems
+        .where((item) =>
+            item.parentOrderLineItemId == rootItem.orderLineItemId &&
+            !item.isDeleted)
+        .toList();
+
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.all(12),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            Row(
+              children: [
+                Expanded(
+                  child: Text(
+                    itemName,
+                    style: const TextStyle(
+                      fontSize: 16,
+                      fontWeight: FontWeight.bold,
+                    ),
+                  ),
+                ),
+                IconButton(
+                  icon: const Icon(Icons.delete, color: Colors.red),
+                  onPressed: () => _confirmRemoveItem(rootItem, itemName),
+                ),
+              ],
+            ),
+            if (modifiers.isNotEmpty) ...[
+              const SizedBox(height: 8),
+              ...modifiers.map((mod) => _buildModifierRow(mod)),
+            ],
+            const SizedBox(height: 8),
+            Row(
+              children: [
+                IconButton(
+                  icon: const Icon(Icons.remove_circle_outline),
+                  onPressed: rootItem.quantity > 1
+                      ? () => _updateQuantity(rootItem, rootItem.quantity - 1)
+                      : null,
+                ),
+                Text(
+                  "${rootItem.quantity}",
+                  style: const TextStyle(
+                    fontSize: 16,
+                    fontWeight: FontWeight.bold,
+                  ),
+                ),
+                IconButton(
+                  icon: const Icon(Icons.add_circle_outline),
+                  onPressed: () =>
+                      _updateQuantity(rootItem, rootItem.quantity + 1),
+                ),
+                const Spacer(),
+                Text(
+                  "\$${rootItem.price.toStringAsFixed(2)}",
+                  style: const TextStyle(
+                    fontSize: 16,
+                    fontWeight: FontWeight.bold,
+                  ),
+                ),
+              ],
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _buildModifierRow(OrderLineItem modifier) {
+    final menuItem = _menuItemsById[modifier.itemId];
+    final modName = menuItem?.name ?? "Modifier #${modifier.itemId}";
+
+    return Padding(
+      padding: const EdgeInsets.only(left: 16, top: 4),
+      child: Row(
+        children: [
+          const Icon(Icons.add, size: 12, color: Colors.grey),
+          const SizedBox(width: 4),
+          Expanded(
+            child: Text(
+              modName,
+              style: const TextStyle(
+                fontSize: 14,
+                color: Colors.grey,
+              ),
+            ),
+          ),
+          if (modifier.price > 0)
+            Text(
+              "+\$${modifier.price.toStringAsFixed(2)}",
+              style: const TextStyle(
+                fontSize: 14,
+                color: Colors.grey,
+              ),
+            ),
+        ],
+      ),
+    );
+  }
+
+  Widget _buildCartSummary() {
+    if (_cart == null) return const SizedBox.shrink();
+
+    return Container(
+      decoration: BoxDecoration(
+        color: Colors.grey[100],
+        boxShadow: [
+          BoxShadow(
+            color: Colors.black.withOpacity(0.1),
+            blurRadius: 4,
+            offset: const Offset(0, -2),
+          ),
+        ],
+      ),
+      padding: const EdgeInsets.all(16),
+      child: SafeArea(
+        child: Column(
+          children: [
+            Row(
+              mainAxisAlignment: MainAxisAlignment.spaceBetween,
+              children: [
+                const Text(
+                  "Subtotal",
+                  style: TextStyle(fontSize: 16),
+                ),
+                Text(
+                  "\$${_cart!.subtotal.toStringAsFixed(2)}",
+                  style: const TextStyle(fontSize: 16),
+                ),
+              ],
+            ),
+            if (_cart!.deliveryFee > 0) ...[
+              const SizedBox(height: 8),
+              Row(
+                mainAxisAlignment: MainAxisAlignment.spaceBetween,
+                children: [
+                  const Text(
+                    "Delivery Fee",
+                    style: TextStyle(fontSize: 16),
+                  ),
+                  Text(
+                    "\$${_cart!.deliveryFee.toStringAsFixed(2)}",
+                    style: const TextStyle(fontSize: 16),
+                  ),
+                ],
+              ),
+            ],
+            const Divider(height: 24),
+            Row(
+              mainAxisAlignment: MainAxisAlignment.spaceBetween,
+              children: [
+                const Text(
+                  "Total",
+                  style: TextStyle(
+                    fontSize: 18,
+                    fontWeight: FontWeight.bold,
+                  ),
+                ),
+                Text(
+                  "\$${_cart!.total.toStringAsFixed(2)}",
+                  style: const TextStyle(
+                    fontSize: 18,
+                    fontWeight: FontWeight.bold,
+                  ),
+                ),
+              ],
+            ),
+            const SizedBox(height: 16),
+            SizedBox(
+              width: double.infinity,
+              child: ElevatedButton(
+                onPressed: _cart!.itemCount > 0 ? _submitOrder : null,
+                style: ElevatedButton.styleFrom(
+                  backgroundColor: Colors.black,
+                  foregroundColor: Colors.white,
+                  padding: const EdgeInsets.symmetric(vertical: 16),
+                ),
+                child: const Text(
+                  "Submit Order",
+                  style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold),
+                ),
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  void _confirmRemoveItem(OrderLineItem item, String itemName) {
+    showDialog(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text("Remove Item"),
+        content: Text("Remove $itemName from cart?"),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.of(context).pop(),
+            child: const Text("Cancel"),
+          ),
+          TextButton(
+            onPressed: () {
+              Navigator.of(context).pop();
+              _removeLineItem(item);
+            },
+            style: TextButton.styleFrom(foregroundColor: Colors.red),
+            child: const Text("Remove"),
+          ),
+        ],
+      ),
+    );
+  }
+}

lib/screens/menu_browse_screen.dart

@@ -1,5 +1,9 @@
 import "package:flutter/material.dart";
+import "package:provider/provider.dart";
 
+import "../app/app_router.dart";
+import "../app/app_state.dart";
+import "../models/cart.dart";
 import "../models/menu_item.dart";
 import "../services/api.dart";
 
@@ -98,16 +102,20 @@ class _MenuBrowseScreenState extends State<MenuBrowseScreen> {
 
   @override
   Widget build(BuildContext context) {
+    final appState = context.watch<AppState>();
+
     return Scaffold(
       appBar: AppBar(
         title: const Text("Menu"),
         actions: [
           IconButton(
-            icon: const Icon(Icons.shopping_cart),
+            icon: Badge(
+              label: Text("${appState.cartItemCount}"),
+              isLabelVisible: appState.cartItemCount > 0,
+              child: const Icon(Icons.shopping_cart),
+            ),
             onPressed: () {
-              ScaffoldMessenger.of(context).showSnackBar(
+              Navigator.of(context).pushNamed(AppRoutes.cartView);
-                const SnackBar(content: Text("Cart view coming soon")),
-              );
             },
           ),
         ],
@@ -154,6 +162,9 @@ class _MenuBrowseScreenState extends State<MenuBrowseScreen> {
                   itemBuilder: (context, index) {
                     final categoryId = categoryIds[index];
                     final items = _itemsByCategory[categoryId] ?? [];
+                    final categoryName = items.isNotEmpty
+                        ? items.first.categoryName
+                        : "Category $categoryId";
 
                     return Column(
                       crossAxisAlignment: CrossAxisAlignment.start,
@@ -161,7 +172,7 @@ class _MenuBrowseScreenState extends State<MenuBrowseScreen> {
                         Padding(
                           padding: const EdgeInsets.all(16),
                           child: Text(
-                            "Category $categoryId",
+                            categoryName,
                             style: Theme.of(context).textTheme.titleLarge?.copyWith(
                               fontWeight: FontWeight.bold,
                             ),
@@ -222,7 +233,68 @@ class _MenuBrowseScreenState extends State<MenuBrowseScreen> {
     );
   }
 
-  void _addToCart(MenuItem item, Set<int> selectedModifierIds) {
+  Future<void> _addToCart(MenuItem item, Set<int> selectedModifierIds) async {
+    if (_userId == null || _businessId == null || _servicePointId == null) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text("Missing required information")),
+      );
+      return;
+    }
+
+    try {
+      final appState = context.read<AppState>();
+
+      // Get or create cart
+      Cart cart;
+      if (appState.cartOrderId == null) {
+        cart = await Api.getOrCreateCart(
+          userId: _userId!,
+          businessId: _businessId!,
+          servicePointId: _servicePointId!,
+          orderTypeId: 1, // Dine-in
+        );
+        // ignore: avoid_print
+        print("DEBUG: Created cart with orderId=${cart.orderId}");
+        appState.setCartOrder(
+          orderId: cart.orderId,
+          orderUuid: cart.orderUuid,
+          itemCount: cart.itemCount,
+        );
+      } else {
+        // We have an existing cart ID
+        cart = await Api.getCart(orderId: appState.cartOrderId!);
+        // ignore: avoid_print
+        print("DEBUG: Loaded existing cart with orderId=${cart.orderId}");
+      }
+
+      // ignore: avoid_print
+      print("DEBUG: About to add root item ${item.itemId} to cart ${cart.orderId}");
+
+      // Add root item
+      cart = await Api.setLineItem(
+        orderId: cart.orderId,
+        parentOrderLineItemId: 0,
+        itemId: item.itemId,
+        isSelected: true,
+        quantity: 1,
+      );
+
+      // ignore: avoid_print
+      print("DEBUG: Added root item, cart now has ${cart.lineItems.length} line items");
+
+      // Add all selected modifiers recursively
+      await _addModifiersRecursively(
+        cart.orderId,
+        item.itemId,
+        selectedModifierIds,
+      );
+
+      // Refresh cart to get final state
+      cart = await Api.getCart(orderId: cart.orderId);
+      appState.updateCartItemCount(cart.itemCount);
+
+      if (!mounted) return;
+
       final message = selectedModifierIds.isEmpty
           ? "Added ${item.name} to cart"
           : "Added ${item.name} with ${selectedModifierIds.length} customizations";
@@ -230,6 +302,37 @@ class _MenuBrowseScreenState extends State<MenuBrowseScreen> {
       ScaffoldMessenger.of(context).showSnackBar(
         SnackBar(content: Text(message)),
       );
+    } catch (e) {
+      if (!mounted) return;
+
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text("Error adding to cart: $e")),
+      );
+    }
+  }
+
+  Future<void> _addModifiersRecursively(
+    int orderId,
+    int parentItemId,
+    Set<int> selectedItemIds,
+  ) async {
+    final children = _itemsByParent[parentItemId] ?? [];
+
+    for (final child in children) {
+      final isSelected = selectedItemIds.contains(child.itemId);
+
+      await Api.setLineItem(
+        orderId: orderId,
+        parentOrderLineItemId: 0, // Will be handled by backend
+        itemId: child.itemId,
+        isSelected: isSelected,
+      );
+
+      // Recursively add grandchildren
+      if (isSelected) {
+        await _addModifiersRecursively(orderId, child.itemId, selectedItemIds);
+      }
+    }
   }
 }
 

lib/services/api.dart

@@ -1,6 +1,7 @@
 import "dart:convert";
 import "package:http/http.dart" as http;
 
+import "../models/cart.dart";
 import "../models/menu_item.dart";
 import "../models/restaurant.dart";
 import "../models/service_point.dart";
@@ -307,33 +308,97 @@ class Api {
   }
 
   // -------------------------
-  // Ordering API (stubs referenced by OrderHomeScreen)
+  // Cart & Orders
   // -------------------------
 
-  static Future<dynamic> getOrCreateCart({
+  static Future<Cart> getOrCreateCart({
     required int userId,
     required int businessId,
     required int servicePointId,
     required int orderTypeId,
   }) async {
-    throw StateError("endpoint_not_implemented: Api.getOrCreateCart");
+    final raw = await _postRaw(
+      "/orders/getOrCreateCart.cfm",
+      {
+        "OrderUserID": userId,
+        "BusinessID": businessId,
+        "OrderServicePointID": servicePointId,
+        "OrderTypeID": orderTypeId,
+      },
+      businessIdOverride: businessId,
+    );
+
+    final j = _requireJson(raw, "GetOrCreateCart");
+
+    if (!_ok(j)) {
+      throw StateError(
+        "GetOrCreateCart API returned OK=false\nERROR: ${_err(j)}\nDETAIL: ${(j["MESSAGE"] ?? "").toString()}\nHTTP Status: ${raw.statusCode}",
+      );
     }
 
-  static Future<dynamic> getCart({required int orderId}) async {
+    return Cart.fromJson(j);
-    throw StateError("endpoint_not_implemented: Api.getCart");
   }
 
-  static Future<void> setLineItem({
+  static Future<Cart> getCart({required int orderId}) async {
+    final raw = await _postRaw(
+      "/orders/getCart.cfm",
+      {"OrderID": orderId},
+    );
+
+    final j = _requireJson(raw, "GetCart");
+
+    if (!_ok(j)) {
+      throw StateError(
+        "GetCart API returned OK=false\nERROR: ${_err(j)}\nHTTP Status: ${raw.statusCode}",
+      );
+    }
+
+    return Cart.fromJson(j);
+  }
+
+  static Future<Cart> setLineItem({
     required int orderId,
     required int parentOrderLineItemId,
     required int itemId,
-    required int qty,
+    required bool isSelected,
-    required List<int> selectedChildItemIds,
+    int quantity = 1,
+    String? remark,
   }) async {
-    throw StateError("endpoint_not_implemented: Api.setLineItem");
+    final raw = await _postRaw(
+      "/orders/setLineItem.cfm",
+      {
+        "OrderID": orderId,
+        "ParentOrderLineItemID": parentOrderLineItemId,
+        "ItemID": itemId,
+        "IsSelected": isSelected,
+        "Quantity": quantity,
+        if (remark != null && remark.isNotEmpty) "Remark": remark,
+      },
+    );
+
+    final j = _requireJson(raw, "SetLineItem");
+
+    if (!_ok(j)) {
+      throw StateError(
+        "SetLineItem API returned OK=false\nERROR: ${_err(j)}\nDETAIL: ${(j["MESSAGE"] ?? "").toString()}\nHTTP Status: ${raw.statusCode}",
+      );
+    }
+
+    return Cart.fromJson(j);
   }
 
   static Future<void> submitOrder({required int orderId}) async {
-    throw StateError("endpoint_not_implemented: Api.submitOrder");
+    final raw = await _postRaw(
+      "/orders/submit.cfm",
+      {"OrderID": orderId},
+    );
+
+    final j = _requireJson(raw, "SubmitOrder");
+
+    if (!_ok(j)) {
+      throw StateError(
+        "SubmitOrder API returned OK=false\nERROR: ${_err(j)}\nHTTP Status: ${raw.statusCode}",
+      );
+    }
   }
 }