payfrit-app/lib/screens/menu_browse_screen.dart

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";

class MenuBrowseScreen extends StatefulWidget {
  const MenuBrowseScreen({super.key});

  @override
  State<MenuBrowseScreen> createState() => _MenuBrowseScreenState();
}

class _MenuBrowseScreenState extends State<MenuBrowseScreen> {
  Future<List<MenuItem>>? _future;
  int? _businessId;
  int? _servicePointId;
  int? _userId;

  List<MenuItem> _allItems = [];
  final Map<int, List<MenuItem>> _itemsByCategory = {};
  final Map<int, List<MenuItem>> _itemsByParent = {};

  int? _asIntNullable(dynamic v) {
    if (v == null) return null;
    if (v is int) return v;
    if (v is num) return v.toInt();
    if (v is String) {
      final s = v.trim();
      if (s.isEmpty) return null;
      return int.tryParse(s);
    }
    return null;
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();

    final appState = context.watch<AppState>();
    final u = appState.userId;

    final args = ModalRoute.of(context)?.settings.arguments;
    if (args is Map) {
      final b = _asIntNullable(args["BusinessID"]) ?? _asIntNullable(args["businessId"]);
      final sp = _asIntNullable(args["ServicePointID"]) ?? _asIntNullable(args["servicePointId"]);

      if (_businessId != b || _servicePointId != sp || _userId != u || _future == null) {
        _businessId = b;
        _servicePointId = sp;
        _userId = u;

        if (_businessId != null && _businessId! > 0) {
          _future = _loadMenu();
        } else {
          _future = Future.value(<MenuItem>[]);
        }
      }
    }
  }

  Future<List<MenuItem>> _loadMenu() async {
    final items = await Api.listMenuItems(businessId: _businessId!);

    setState(() {
      _allItems = items;
      _organizeItems();
    });

    return items;
  }

  void _organizeItems() {
    _itemsByCategory.clear();
    _itemsByParent.clear();

    for (final item in _allItems) {
      // Skip inactive items
      if (!item.isActive) continue;

      if (item.isRootItem) {
        _itemsByCategory.putIfAbsent(item.categoryId, () => []).add(item);
      } else {
        // Prevent an item from being its own child
        if (item.itemId != item.parentItemId) {
          _itemsByParent.putIfAbsent(item.parentItemId, () => []).add(item);
        }
      }
    }

    // Sort items within each category by sortOrder
    for (final list in _itemsByCategory.values) {
      list.sort((a, b) => a.sortOrder.compareTo(b.sortOrder));
    }

    // Sort modifiers within each parent
    for (final list in _itemsByParent.values) {
      list.sort((a, b) => a.sortOrder.compareTo(b.sortOrder));
    }
  }

  List<int> _getUniqueCategoryIds() {
    final categoryIds = _itemsByCategory.keys.toList();
    categoryIds.sort();
    return categoryIds;
  }

  @override
  Widget build(BuildContext context) {
    final appState = context.watch<AppState>();
    final businessName = appState.selectedBusinessName ?? "Menu";

    return Scaffold(
      appBar: AppBar(
        title: Row(
          children: [
            // Business logo
            if (_businessId != null)
              Padding(
                padding: const EdgeInsets.only(right: 12),
                child: ClipRRect(
                  borderRadius: BorderRadius.circular(6),
                  child: SizedBox(
                    width: 36,
                    height: 36,
                    child: Image.network(
                      "$_imageBaseUrl/logos/$_businessId.png",
                      fit: BoxFit.cover,
                      errorBuilder: (context, error, stackTrace) {
                        return Image.network(
                          "$_imageBaseUrl/logos/$_businessId.jpg",
                          fit: BoxFit.cover,
                          errorBuilder: (context, error, stackTrace) {
                            return Container(
                              decoration: BoxDecoration(
                                color: Theme.of(context).colorScheme.primaryContainer,
                                borderRadius: BorderRadius.circular(6),
                              ),
                              child: Icon(
                                Icons.store,
                                size: 20,
                                color: Theme.of(context).colorScheme.onPrimaryContainer,
                              ),
                            );
                          },
                        );
                      },
                    ),
                  ),
                ),
              ),
            Expanded(
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                mainAxisSize: MainAxisSize.min,
                children: [
                  Text(
                    businessName,
                    style: const TextStyle(fontSize: 18),
                  ),
                  if (appState.selectedServicePointName != null)
                    Text(
                      appState.selectedServicePointName!,
                      style: const TextStyle(
                        fontSize: 12,
                        fontWeight: FontWeight.normal,
                      ),
                    ),
                ],
              ),
            ),
          ],
        ),
        actions: [
          IconButton(
            icon: Badge(
              label: Text("${appState.cartItemCount}"),
              isLabelVisible: appState.cartItemCount > 0,
              child: const Icon(Icons.shopping_cart),
            ),
            onPressed: () {
              Navigator.of(context).pushNamed(AppRoutes.cartView);
            },
          ),
        ],
      ),
      body: (_businessId == null || _businessId! <= 0)
          ? const Padding(
              padding: EdgeInsets.all(16),
              child: Text("Missing BusinessID"),
            )
          : FutureBuilder<List<MenuItem>>(
              future: _future,
              builder: (context, snapshot) {
                if (snapshot.connectionState == ConnectionState.waiting) {
                  return const Center(child: CircularProgressIndicator());
                }

                if (snapshot.hasError) {
                  return Padding(
                    padding: const EdgeInsets.all(16),
                    child: Column(
                      children: [
                        Text("Error loading menu: ${snapshot.error}"),
                        const SizedBox(height: 16),
                        ElevatedButton(
                          onPressed: () => setState(() => _future = _loadMenu()),
                          child: const Text("Retry"),
                        ),
                      ],
                    ),
                  );
                }

                if (_allItems.isEmpty) {
                  return const Padding(
                    padding: EdgeInsets.all(16),
                    child: Text("No menu items available"),
                  );
                }

                final categoryIds = _getUniqueCategoryIds();

                return ListView.builder(
                  itemCount: categoryIds.length + 1, // +1 for header
                  itemBuilder: (context, index) {
                    // First item is the business header
                    if (index == 0) {
                      return _buildBusinessHeader();
                    }

                    final categoryIndex = index - 1;
                    final categoryId = categoryIds[categoryIndex];
                    final items = _itemsByCategory[categoryId] ?? [];
                    final categoryName = items.isNotEmpty
                        ? items.first.categoryName
                        : "Category $categoryId";

                    return Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        _buildCategoryHeader(categoryId, categoryName),
                        ...items.map((item) => _buildMenuItem(item)),
                        const SizedBox(height: 16),
                      ],
                    );
                  },
                );
              },
            ),
    );
  }

  static const String _imageBaseUrl = "https://biz.payfrit.com/uploads";

  Widget _buildBusinessHeader() {
    if (_businessId == null) return const SizedBox.shrink();

    final appState = context.read<AppState>();
    final businessName = appState.selectedBusinessName ?? "Restaurant";

    return Container(
      width: double.infinity,
      height: 180,
      margin: const EdgeInsets.only(bottom: 8),
      child: Stack(
        fit: StackFit.expand,
        children: [
          // Header background image
          Image.network(
            "$_imageBaseUrl/headers/$_businessId.png",
            fit: BoxFit.cover,
            errorBuilder: (context, error, stackTrace) {
              return Image.network(
                "$_imageBaseUrl/headers/$_businessId.jpg",
                fit: BoxFit.cover,
                errorBuilder: (context, error, stackTrace) {
                  // No header image - show gradient background
                  return Container(
                    decoration: BoxDecoration(
                      gradient: LinearGradient(
                        begin: Alignment.topLeft,
                        end: Alignment.bottomRight,
                        colors: [
                          Theme.of(context).colorScheme.primary,
                          Theme.of(context).colorScheme.secondary,
                        ],
                      ),
                    ),
                  );
                },
              );
            },
          ),
          // Dark gradient overlay
          Container(
            decoration: BoxDecoration(
              gradient: LinearGradient(
                begin: Alignment.topCenter,
                end: Alignment.bottomCenter,
                colors: [
                  Colors.black.withAlpha(0),
                  Colors.black.withAlpha(179),
                ],
              ),
            ),
          ),
          // Business info overlay
          Positioned(
            left: 16,
            right: 16,
            bottom: 16,
            child: Row(
              children: [
                // Logo
                ClipRRect(
                  borderRadius: BorderRadius.circular(8),
                  child: SizedBox(
                    width: 56,
                    height: 56,
                    child: Image.network(
                      "$_imageBaseUrl/logos/$_businessId.png",
                      fit: BoxFit.cover,
                      errorBuilder: (context, error, stackTrace) {
                        return Image.network(
                          "$_imageBaseUrl/logos/$_businessId.jpg",
                          fit: BoxFit.cover,
                          errorBuilder: (context, error, stackTrace) {
                            return Container(
                              color: Colors.white24,
                              child: const Icon(
                                Icons.store,
                                size: 32,
                                color: Colors.white,
                              ),
                            );
                          },
                        );
                      },
                    ),
                  ),
                ),
                const SizedBox(width: 12),
                // Business name and info
                Expanded(
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    mainAxisSize: MainAxisSize.min,
                    children: [
                      Text(
                        businessName,
                        style: Theme.of(context).textTheme.headlineSmall?.copyWith(
                              color: Colors.white,
                              fontWeight: FontWeight.bold,
                              shadows: [
                                const Shadow(
                                  offset: Offset(1, 1),
                                  blurRadius: 3,
                                  color: Colors.black54,
                                ),
                              ],
                            ),
                      ),
                      if (appState.selectedServicePointName != null)
                        Text(
                          appState.selectedServicePointName!,
                          style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                                color: Colors.white70,
                              ),
                        ),
                    ],
                  ),
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildItemImage(int itemId) {
    return ClipRRect(
      borderRadius: BorderRadius.circular(8),
      child: SizedBox(
        width: 64,
        height: 64,
        child: Image.network(
          "$_imageBaseUrl/items/$itemId.png",
          fit: BoxFit.cover,
          errorBuilder: (context, error, stackTrace) {
            // Try jpg if png fails
            return Image.network(
              "$_imageBaseUrl/items/$itemId.jpg",
              fit: BoxFit.cover,
              errorBuilder: (context, error, stackTrace) {
                // Show placeholder if no image
                return Container(
                  decoration: BoxDecoration(
                    color: Theme.of(context).colorScheme.primaryContainer,
                    borderRadius: BorderRadius.circular(8),
                  ),
                  child: Icon(
                    Icons.restaurant,
                    color: Theme.of(context).colorScheme.onPrimaryContainer,
                    size: 28,
                  ),
                );
              },
            );
          },
        ),
      ),
    );
  }

  Widget _buildCategoryHeader(int categoryId, String categoryName) {
    return Container(
      width: double.infinity,
      height: 120,
      decoration: BoxDecoration(
        color: Theme.of(context).colorScheme.surfaceContainerHighest,
      ),
      child: Stack(
        fit: StackFit.expand,
        children: [
          // Category image background
          Image.network(
            "$_imageBaseUrl/categories/$categoryId.png",
            fit: BoxFit.cover,
            errorBuilder: (context, error, stackTrace) {
              return Image.network(
                "$_imageBaseUrl/categories/$categoryId.jpg",
                fit: BoxFit.cover,
                errorBuilder: (context, error, stackTrace) {
                  // No image - just show solid color
                  return Container(
                    color: Theme.of(context).colorScheme.primaryContainer,
                  );
                },
              );
            },
          ),
          // Dark gradient overlay for text readability
          Container(
            decoration: BoxDecoration(
              gradient: LinearGradient(
                begin: Alignment.topCenter,
                end: Alignment.bottomCenter,
                colors: [
                  Colors.black.withAlpha(0),
                  Colors.black.withAlpha(179),
                ],
              ),
            ),
          ),
          // Category name
          Positioned(
            left: 16,
            bottom: 12,
            right: 16,
            child: Text(
              categoryName,
              style: Theme.of(context).textTheme.headlineSmall?.copyWith(
                    fontWeight: FontWeight.bold,
                    color: Colors.white,
                    shadows: [
                      const Shadow(
                        offset: Offset(1, 1),
                        blurRadius: 3,
                        color: Colors.black54,
                      ),
                    ],
                  ),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildMenuItem(MenuItem item) {
    final hasModifiers = _itemsByParent.containsKey(item.itemId);

    return Container(
      margin: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
      decoration: BoxDecoration(
        color: Theme.of(context).colorScheme.surface,
        borderRadius: BorderRadius.circular(12),
        border: Border.all(
          color: Theme.of(context).colorScheme.outlineVariant.withAlpha(128),
        ),
      ),
      child: InkWell(
        borderRadius: BorderRadius.circular(12),
        onTap: () {
          if (hasModifiers) {
            _showItemCustomization(item);
          } else {
            _addToCart(item, {});
          }
        },
        child: Padding(
          padding: const EdgeInsets.all(16),
          child: Row(
            children: [
              // Item image or placeholder
              _buildItemImage(item.itemId),
              const SizedBox(width: 16),
              // Item details
              Expanded(
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    Text(
                      item.name,
                      style: Theme.of(context).textTheme.titleMedium?.copyWith(
                            fontWeight: FontWeight.w600,
                          ),
                    ),
                    if (item.description.isNotEmpty) ...[
                      const SizedBox(height: 4),
                      Text(
                        item.description,
                        maxLines: 2,
                        overflow: TextOverflow.ellipsis,
                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
                              color: Theme.of(context).colorScheme.onSurfaceVariant,
                            ),
                      ),
                    ],
                    if (hasModifiers) ...[
                      const SizedBox(height: 4),
                      Text(
                        "Customizable",
                        style: Theme.of(context).textTheme.labelSmall?.copyWith(
                              color: Theme.of(context).colorScheme.primary,
                              fontWeight: FontWeight.w500,
                            ),
                      ),
                    ],
                  ],
                ),
              ),
              const SizedBox(width: 12),
              // Price and add button
              Column(
                crossAxisAlignment: CrossAxisAlignment.end,
                children: [
                  Text(
                    "\$${item.price.toStringAsFixed(2)}",
                    style: Theme.of(context).textTheme.titleMedium?.copyWith(
                          fontWeight: FontWeight.bold,
                          color: Theme.of(context).colorScheme.primary,
                        ),
                  ),
                  const SizedBox(height: 4),
                  Icon(
                    Icons.add_circle,
                    color: Theme.of(context).colorScheme.primary,
                    size: 20,
                  ),
                ],
              ),
            ],
          ),
        ),
      ),
    );
  }

  void _showItemCustomization(MenuItem item) {
    showModalBottomSheet(
      context: context,
      isScrollControlled: true,
      builder: (context) => _ItemCustomizationSheet(
        item: item,
        itemsByParent: _itemsByParent,
        onAdd: (selectedItemIds) {
          Navigator.pop(context);
          _addToCart(item, selectedItemIds);
        },
      ),
    );
  }

  Future<void> _addToCart(MenuItem item, Set<int> selectedModifierIds) async {
    // Check if user is logged in - if not, navigate to login
    if (_userId == null) {
      final shouldLogin = await showDialog<bool>(
        context: context,
        builder: (context) => AlertDialog(
          title: const Text("Login Required"),
          content: const Text("Please login to add items to your cart."),
          actions: [
            TextButton(
              onPressed: () => Navigator.pop(context, false),
              child: const Text("Cancel"),
            ),
            FilledButton(
              onPressed: () => Navigator.pop(context, true),
              child: const Text("Login"),
            ),
          ],
        ),
      );

      if (shouldLogin == true && mounted) {
        Navigator.of(context).pushNamed(AppRoutes.login);
      }
      return;
    }

    if (_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
        );
        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!);
      }

      // Check if this item already exists in the cart (as a root item)
      final existingItem = cart.lineItems.where(
        (li) => li.itemId == item.itemId && li.parentOrderLineItemId == 0 && !li.isDeleted
      ).firstOrNull;

      final newQuantity = (existingItem?.quantity ?? 0) + 1;

      // Add root item (or update quantity if it exists)
      cart = await Api.setLineItem(
        orderId: cart.orderId,
        parentOrderLineItemId: 0,
        itemId: item.itemId,
        isSelected: true,
        quantity: newQuantity,
      );

      // Find the OrderLineItemID of the root item we just added
      final rootLineItem = cart.lineItems.lastWhere(
        (li) => li.itemId == item.itemId && li.parentOrderLineItemId == 0 && !li.isDeleted,
        orElse: () => throw StateError('Root line item not found for ItemID=${item.itemId}'),
      );

      // Add all selected modifiers recursively
      print('[MenuBrowse] Adding ${selectedModifierIds.length} modifiers to root item OrderLineItemID=${rootLineItem.orderLineItemId}');
      await _addModifiersRecursively(
        cart.orderId,
        rootLineItem.orderLineItemId,
        item.itemId,
        selectedModifierIds,
      );

      // Refresh cart to get final state
      print('[MenuBrowse] Refreshing cart to get final state');
      cart = await Api.getCart(orderId: cart.orderId);
      print('[MenuBrowse] Final cart has ${cart.lineItems.length} total line items');

      appState.updateCartItemCount(cart.itemCount);

      if (!mounted) return;

      final message = selectedModifierIds.isEmpty
          ? "Added ${item.name} to cart (${cart.itemCount} item${cart.itemCount == 1 ? '' : 's'})"
          : "Added ${item.name} with ${selectedModifierIds.length} customizations (${cart.itemCount} item${cart.itemCount == 1 ? '' : 's'})";

      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 parentOrderLineItemId,
    int parentItemId,
    Set<int> selectedItemIds,
  ) async {
    final children = _itemsByParent[parentItemId] ?? [];
    print('[MenuBrowse] _addModifiersRecursively: parentItemId=$parentItemId has ${children.length} children');

    for (final child in children) {
      final isSelected = selectedItemIds.contains(child.itemId);
      final grandchildren = _itemsByParent[child.itemId] ?? [];
      final hasGrandchildren = grandchildren.isNotEmpty;
      final hasSelectedDescendants = _hasSelectedDescendants(child.itemId, selectedItemIds);

      print('[MenuBrowse]   Child ${child.name} (ItemID=${child.itemId}): selected=$isSelected, hasChildren=$hasGrandchildren, hasSelectedDescendants=$hasSelectedDescendants');

      // Add this item if it's selected OR if it has selected descendants (to maintain hierarchy)
      if (isSelected || hasSelectedDescendants) {
        print('[MenuBrowse]   Adding ${isSelected ? "selected" : "container"} item ${child.name} with ParentOrderLineItemID=$parentOrderLineItemId');
        final cart = await Api.setLineItem(
          orderId: orderId,
          parentOrderLineItemId: parentOrderLineItemId,
          itemId: child.itemId,
          isSelected: true,
        );

        // Find the OrderLineItemID of this item we just added
        final childLineItem = cart.lineItems.lastWhere(
          (li) => li.itemId == child.itemId && li.parentOrderLineItemId == parentOrderLineItemId && !li.isDeleted,
          orElse: () => throw StateError('Child line item not found for ItemID=${child.itemId}'),
        );

        // Recursively add children with this item as the new parent
        if (hasGrandchildren) {
          await _addModifiersRecursively(
            orderId,
            childLineItem.orderLineItemId,
            child.itemId,
            selectedItemIds,
          );
        }
      }
    }
  }

  /// Check if any descendants of this item are selected
  bool _hasSelectedDescendants(int itemId, Set<int> selectedItemIds) {
    final children = _itemsByParent[itemId] ?? [];
    for (final child in children) {
      if (selectedItemIds.contains(child.itemId)) {
        return true;
      }
      if (_hasSelectedDescendants(child.itemId, selectedItemIds)) {
        return true;
      }
    }
    return false;
  }
}

/// Recursive item customization sheet with full rule support
class _ItemCustomizationSheet extends StatefulWidget {
  final MenuItem item;
  final Map<int, List<MenuItem>> itemsByParent;
  final Function(Set<int>) onAdd;

  const _ItemCustomizationSheet({
    required this.item,
    required this.itemsByParent,
    required this.onAdd,
  });

  @override
  State<_ItemCustomizationSheet> createState() => _ItemCustomizationSheetState();
}

class _ItemCustomizationSheetState extends State<_ItemCustomizationSheet> {
  final Set<int> _selectedItemIds = {};
  String? _validationError;

  @override
  void initState() {
    super.initState();
    _initializeDefaults(widget.item.itemId);
  }

  /// Recursively initialize default selections
  void _initializeDefaults(int parentId) {
    final children = widget.itemsByParent[parentId] ?? [];
    for (final child in children) {
      if (child.isCheckedByDefault) {
        _selectedItemIds.add(child.itemId);
        _initializeDefaults(child.itemId);
      }
    }
  }

  /// Calculate total price including all selected items recursively
  double _calculateTotal() {
    double total = widget.item.price;

    void addPriceRecursively(int itemId) {
      final children = widget.itemsByParent[itemId] ?? [];
      for (final child in children) {
        if (_selectedItemIds.contains(child.itemId)) {
          total += child.price;
          addPriceRecursively(child.itemId);
        }
      }
    }

    addPriceRecursively(widget.item.itemId);
    return total;
  }

  /// Validate selections before adding to cart
  bool _validate() {
    setState(() => _validationError = null);

    bool validateRecursive(int parentId, MenuItem parent) {
      final children = widget.itemsByParent[parentId] ?? [];
      if (children.isEmpty) return true;

      final selectedChildren = children.where((c) => _selectedItemIds.contains(c.itemId)).toList();

      // Check if child selection is required
      if (parent.requiresChildSelection && selectedChildren.isEmpty) {
        setState(() => _validationError = "Please select an option for: ${parent.name}");
        return false;
      }

      // Check max selection limit
      if (parent.maxNumSelectionReq > 0 && selectedChildren.length > parent.maxNumSelectionReq) {
        setState(() => _validationError = "${parent.name}: Max ${parent.maxNumSelectionReq} selections allowed");
        return false;
      }

      // Recursively validate selected children
      for (final child in selectedChildren) {
        if (!validateRecursive(child.itemId, child)) {
          return false;
        }
      }

      return true;
    }

    return validateRecursive(widget.item.itemId, widget.item);
  }

  void _handleAdd() {
    if (_validate()) {
      widget.onAdd(_selectedItemIds);
    }
  }

  @override
  Widget build(BuildContext context) {
    return DraggableScrollableSheet(
      initialChildSize: 0.75,
      minChildSize: 0.5,
      maxChildSize: 0.95,
      expand: false,
      builder: (context, scrollController) {
        return Column(
          children: [
            // Header
            Container(
              padding: const EdgeInsets.all(20),
              decoration: BoxDecoration(
                color: Theme.of(context).colorScheme.surface,
                border: Border(
                  bottom: BorderSide(
                    color: Theme.of(context).colorScheme.outlineVariant,
                    width: 1,
                  ),
                ),
              ),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Row(
                    children: [
                      Container(
                        width: 12,
                        height: 4,
                        margin: const EdgeInsets.only(right: 8),
                        decoration: BoxDecoration(
                          color: Theme.of(context).colorScheme.onSurfaceVariant,
                          borderRadius: BorderRadius.circular(2),
                        ),
                      ),
                    ],
                  ),
                  const SizedBox(height: 16),
                  Text(
                    widget.item.name,
                    style: Theme.of(context).textTheme.headlineSmall?.copyWith(
                          fontWeight: FontWeight.bold,
                        ),
                  ),
                  if (widget.item.description.isNotEmpty) ...[
                    const SizedBox(height: 8),
                    Text(
                      widget.item.description,
                      style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                            color: Theme.of(context).colorScheme.onSurfaceVariant,
                          ),
                    ),
                  ],
                  const SizedBox(height: 12),
                  Container(
                    padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
                    decoration: BoxDecoration(
                      color: Theme.of(context).colorScheme.primaryContainer,
                      borderRadius: BorderRadius.circular(20),
                    ),
                    child: Text(
                      "Base: \$${widget.item.price.toStringAsFixed(2)}",
                      style: Theme.of(context).textTheme.labelLarge?.copyWith(
                            color: Theme.of(context).colorScheme.onPrimaryContainer,
                            fontWeight: FontWeight.w600,
                          ),
                    ),
                  ),
                ],
              ),
            ),

            // Scrollable content
            Expanded(
              child: ListView(
                controller: scrollController,
                padding: const EdgeInsets.all(16),
                children: _buildModifierTree(widget.item.itemId, 0),
              ),
            ),

            // Footer with validation error and add button
            Container(
              padding: const EdgeInsets.all(16),
              decoration: BoxDecoration(
                color: Theme.of(context).colorScheme.surface,
                boxShadow: [
                  BoxShadow(
                    color: Colors.black.withAlpha(25),
                    blurRadius: 4,
                    offset: const Offset(0, -2),
                  ),
                ],
              ),
              child: SafeArea(
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    if (_validationError != null) ...[
                      Container(
                        padding: const EdgeInsets.all(12),
                        margin: const EdgeInsets.only(bottom: 12),
                        decoration: BoxDecoration(
                          color: Colors.red.shade50,
                          borderRadius: BorderRadius.circular(8),
                          border: Border.all(color: Colors.red.shade300),
                        ),
                        child: Row(
                          children: [
                            Icon(Icons.error_outline, color: Colors.red.shade700),
                            const SizedBox(width: 12),
                            Expanded(
                              child: Text(
                                _validationError!,
                                style: TextStyle(color: Colors.red.shade900),
                              ),
                            ),
                          ],
                        ),
                      ),
                    ],
                    SizedBox(
                      width: double.infinity,
                      child: FilledButton(
                        onPressed: _handleAdd,
                        child: Text("Add to Cart - \$${_calculateTotal().toStringAsFixed(2)}"),
                      ),
                    ),
                  ],
                ),
              ),
            ),
          ],
        );
      },
    );
  }

  /// Recursively build modifier tree
  List<Widget> _buildModifierTree(int parentId, int depth) {
    final children = widget.itemsByParent[parentId] ?? [];
    if (children.isEmpty) return [];

    final parent = _findItemById(parentId);
    if (parent == null) return [];

    final widgets = <Widget>[];

    for (final child in children) {
      final hasGrandchildren = widget.itemsByParent.containsKey(child.itemId);

      if (hasGrandchildren && child.isCollapsible) {
        // Collapsible section with ExpansionTile
        widgets.add(_buildExpansionTile(child, parent, depth));
      } else {
        // Regular checkbox/radio item
        widgets.add(_buildSelectableItem(child, parent, depth));

        // Recursively add grandchildren
        if (hasGrandchildren && _selectedItemIds.contains(child.itemId)) {
          widgets.addAll(_buildModifierTree(child.itemId, depth + 1));
        }
      }
    }

    return widgets;
  }

  Widget _buildExpansionTile(MenuItem item, MenuItem parent, int depth) {
    final isSelected = _selectedItemIds.contains(item.itemId);

    return Padding(
      padding: EdgeInsets.only(left: depth * 16.0),
      child: ExpansionTile(
        title: Text(item.name),
        subtitle: item.price > 0
            ? Text("+\$${item.price.toStringAsFixed(2)}")
            : null,
        initiallyExpanded: isSelected || item.isCheckedByDefault,
        leading: _buildSelectionWidget(item, parent),
        children: _buildModifierTree(item.itemId, depth + 1),
      ),
    );
  }

  Widget _buildSelectableItem(MenuItem item, MenuItem parent, int depth) {
    return Padding(
      padding: EdgeInsets.only(left: depth * 16.0),
      child: ListTile(
        leading: _buildSelectionWidget(item, parent),
        title: Text(item.name),
        subtitle: item.price > 0
            ? Text("+\$${item.price.toStringAsFixed(2)}")
            : null,
        onTap: () => _toggleSelection(item, parent),
      ),
    );
  }

  Widget _buildSelectionWidget(MenuItem item, MenuItem parent) {
    final isSelected = _selectedItemIds.contains(item.itemId);
    final siblings = widget.itemsByParent[parent.itemId] ?? [];

    // Determine if this should behave as a radio button group:
    // 1. Explicit: maxNumSelectionReq == 1
    // 2. Inferred: Group has exactly one default-checked item (implies single selection)
    final isRadioGroup = parent.maxNumSelectionReq == 1 ||
        (siblings.where((s) => s.isCheckedByDefault).length == 1 &&
         siblings.every((s) => !s.requiresChildSelection));

    if (isRadioGroup) {
      return Radio<int>(
        value: item.itemId,
        groupValue: _getSelectedInGroup(parent.itemId),
        onChanged: (_) => _toggleSelection(item, parent),
      );
    }

    // Checkbox for multiple or unlimited selections
    return Checkbox(
      value: isSelected,
      onChanged: (_) => _toggleSelection(item, parent),
    );
  }

  int? _getSelectedInGroup(int parentId) {
    final children = widget.itemsByParent[parentId] ?? [];
    for (final child in children) {
      if (_selectedItemIds.contains(child.itemId)) {
        return child.itemId;
      }
    }
    return null;
  }

  void _toggleSelection(MenuItem item, MenuItem parent) {
    setState(() {
      _validationError = null;

      final isCurrentlySelected = _selectedItemIds.contains(item.itemId);
      final siblings = widget.itemsByParent[parent.itemId] ?? [];

      // Determine if this should behave as a radio button group:
      // 1. Explicit: maxNumSelectionReq == 1
      // 2. Inferred: Group has exactly one default-checked item (implies single selection)
      final isRadioGroup = parent.maxNumSelectionReq == 1 ||
          (siblings.where((s) => s.isCheckedByDefault).length == 1 &&
           siblings.every((s) => !s.requiresChildSelection));

      // For radio buttons, deselect siblings and always select the clicked item
      if (isRadioGroup) {
        for (final sibling in siblings) {
          _selectedItemIds.remove(sibling.itemId);
          _deselectDescendants(sibling.itemId);
        }
        // Always select the clicked item (radio buttons can't be deselected)
        _selectedItemIds.add(item.itemId);
        return;
      }

      // For checkboxes, allow toggle on/off
      if (isCurrentlySelected) {
        // Deselect this item and all descendants
        _selectedItemIds.remove(item.itemId);
        _deselectDescendants(item.itemId);
      } else {
        // Check max selection limit
        if (parent.maxNumSelectionReq > 0) {
          final siblings = widget.itemsByParent[parent.itemId] ?? [];
          final selectedSiblings = siblings.where((s) => _selectedItemIds.contains(s.itemId)).length;

          if (selectedSiblings >= parent.maxNumSelectionReq) {
            _validationError = "${parent.name}: Max ${parent.maxNumSelectionReq} selections allowed";
            return;
          }
        }

        // Select this item
        _selectedItemIds.add(item.itemId);
      }
    });
  }

  void _deselectDescendants(int parentId) {
    final children = widget.itemsByParent[parentId] ?? [];
    for (final child in children) {
      _selectedItemIds.remove(child.itemId);
      _deselectDescendants(child.itemId);
    }
  }

  MenuItem? _findItemById(int itemId) {
    for (final list in widget.itemsByParent.values) {
      for (final item in list) {
        if (item.itemId == itemId) return item;
      }
    }
    return widget.item.itemId == itemId ? widget.item : null;
  }
}