import 'dart:math';
import 'package:flutter/material.dart';

class ProductItem {
  final String id;
  final String name;
  final double price;
  final int stock;
  final String code;

  ProductItem({
    required this.id,
    required this.name,
    required this.price,
    required this.stock,
    required this.code,
  });
}

class BillingItem {
  final ProductItem product;
  int quantity;

  BillingItem({
    required this.product,
    required this.quantity,
  });
}

class BillingDashboardScreen extends StatefulWidget {
  final String businessName;
  final String businessType;
  final String gstin;
  final bool barcodeScanner;
  final bool kotManagement;
  final bool inventoryAlerts;

  const BillingDashboardScreen({
    super.key,
    required this.businessName,
    required this.businessType,
    required this.gstin,
    required this.barcodeScanner,
    required this.kotManagement,
    required this.inventoryAlerts,
  });

  @override
  State<BillingDashboardScreen> createState() => _BillingDashboardScreenState();
}

class _BillingDashboardScreenState extends State<BillingDashboardScreen> {
  late List<ProductItem> _products;
  final List<BillingItem> _billingList = [];
  bool _printingInvoice = false;
  String _invoiceNumber = 'POZO-26402';
  String _scanMessage = '';

  final Map<String, List<ProductItem>> _inventoryPresets = {
    'supermarket': [
      ProductItem(id: 'sm1', name: 'Premium Basmati Rice (1kg)', price: 120.0, stock: 45, code: '89012300052'),
      ProductItem(id: 'sm2', name: 'Fresh Farm Milk (1L)', price: 65.0, stock: 2, code: '89045300010'),
      ProductItem(id: 'sm3', name: 'Refined Cooking Oil (1L)', price: 165.0, stock: 18, code: '89010320491'),
      ProductItem(id: 'sm4', name: 'Refined White Sugar (1kg)', price: 48.0, stock: 3, code: '89034200421'),
      ProductItem(id: 'sm5', name: 'Organic Green T-Tea (250g)', price: 110.0, stock: 24, code: '89512300011'),
      ProductItem(id: 'sm6', name: 'Whole Wheat Atta (5kg)', price: 230.0, stock: 7, code: '89011210042'),
    ],
    'restaurant': [
      ProductItem(id: 'rt1', name: 'Fresh Paneer Butter Masala', price: 240.0, stock: 19, code: '9901230'),
      ProductItem(id: 'rt2', name: 'Butter Tandoori Naan', price: 45.0, stock: 15, code: '9904530'),
      ProductItem(id: 'rt3', name: 'Dum Veg Biryani Deluxe', price: 190.0, stock: 2, code: '9901032'),
      ProductItem(id: 'rt4', name: 'Crispy Butter Masala Dosa', price: 90.0, stock: 22, code: '9903420'),
      ProductItem(id: 'rt5', name: 'Rich Chocolate Milkshake', price: 120.0, stock: 3, code: '9951230'),
      ProductItem(id: 'rt6', name: 'Hot Roasted Filter Coffee', price: 50.0, stock: 30, code: '9901121'),
    ],
    'clothing': [
      ProductItem(id: 'cl1', name: 'Premium Oxford Cotton Shirt', price: 899.0, stock: 8, code: '77012301'),
      ProductItem(id: 'cl2', name: 'Slim Fit Dark Jeans', price: 1599.0, stock: 2, code: '77045302'),
      ProductItem(id: 'cl3', name: 'Designer Summer Slip Dress', price: 1299.0, stock: 5, code: '77010323'),
      ProductItem(id: 'cl4', name: 'Graphic Printed Tee-Shirt', price: 450.0, stock: 40, code: '77034204'),
      ProductItem(id: 'cl5', name: 'Breathable Sports Sneakers', price: 1899.0, stock: 3, code: '77512305'),
      ProductItem(id: 'cl6', name: 'Stitch Leather Belt Brown', price: 349.0, stock: 12, code: '77011216'),
    ],
    'kirana': [
      ProductItem(id: 'kr1', name: 'Premium Toor Dal (1kg)', price: 145.0, stock: 15, code: '4401230'),
      ProductItem(id: 'kr2', name: 'Iodized Powdered Salt (1kg)', price: 22.0, stock: 50, code: '4404530'),
      ProductItem(id: 'kr3', name: 'Herbal Moisturizer Soap', price: 42.0, stock: 2, code: '4401032'),
      ProductItem(id: 'kr4', name: 'Anti-Germ Toothpaste (200g)', price: 85.0, stock: 16, code: '4403420'),
      ProductItem(id: 'kr5', name: 'Dishwash Cleaning Soap', price: 25.0, stock: 3, code: '4451230'),
      ProductItem(id: 'kr6', name: 'Red Chili Powder (200g)', price: 65.0, stock: 18, code: '4401121'),
    ],
    'others': [
      ProductItem(id: 'ot1', name: 'Utility Household Scrubber', price: 35.0, stock: 33, code: '5501230'),
      ProductItem(id: 'ot2', name: 'AAA Rechargeable Batteries', price: 120.0, stock: 4, code: '5504530'),
      ProductItem(id: 'ot3', name: 'LED High Bright Focus Bulb', price: 140.0, stock: 2, code: '5501032'),
      ProductItem(id: 'ot4', name: 'Water Bottle Stainless (1L)', price: 320.0, stock: 11, code: '5503420'),
      ProductItem(id: 'ot5', name: 'Microfiber Floor Duster', price: 75.0, stock: 24, code: '5551230'),
      ProductItem(id: 'ot6', name: 'Multi-plug Protection Adapter', price: 240.0, stock: 9, code: '5501121'),
    ]
  };

  @override
  void initState() {
    super.initState();
    _products = _inventoryPresets[widget.businessType] ?? _inventoryPresets['supermarket']!;
  }

  void _handleAddItem(ProductItem product) {
    setState(() {
      final index = _billingList.indexWhere((element) => element.product.id == product.id);
      if (index != -1) {
        final existingItem = _billingList[index];
        if (existingItem.quantity >= product.stock && widget.inventoryAlerts) {
          _showErrorSnackBar('Cannot add more. Inventory limit reached for ${product.name}!');
          return;
        }
        existingItem.quantity += 1;
      } else {
        _billingList.add(BillingItem(product: product, quantity: 1));
      }
    });
  }

  void _handleRemoveOne(String productId) {
    setState(() {
      final index = _billingList.indexWhere((element) => element.product.id == productId);
      if (index != -1) {
        if (_billingList[index].quantity > 1) {
          _billingList[index].quantity -= 1;
        } else {
          _billingList.removeAt(index);
        }
      }
    });
  }

  void _simulateBarcodeScan() {
    if (!widget.barcodeScanner) return;
    final random = Random();
    final randomProduct = _products[random.nextInt(_products.length)];
    _handleAddItem(randomProduct);

    setState(() {
      _scanMessage = '🎯 Scanned EAN Barcode [${randomProduct.code}] - Added ${randomProduct.name}!';
    });

    Future.delayed(const Duration(milliseconds: 3000), () {
      if (mounted) {
        setState(() {
          _scanMessage = '';
        });
      }
    });
  }

  void _clearRegister() {
    setState(() {
      _billingList.clear();
    });
  }

  void _showErrorSnackBar(String message) {
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(
        content: Text(message),
        backgroundColor: Colors.red[800],
        behavior: SnackBarBehavior.floating,
      ),
    );
  }

  double get _subtotal {
    return _billingList.fold(0.0, (sum, item) => sum + (item.product.price * item.quantity));
  }

  bool get _hasGstin {
    return widget.gstin.trim().isNotEmpty;
  }

  double get _cgst => _hasGstin ? _subtotal * 0.09 : 0.0;
  double get _sgst => _hasGstin ? _subtotal * 0.09 : 0.0;
  double get _total => _subtotal + _cgst + _sgst;

  void _handleReviewAndGenerate() {
    final random = Random();
    final invoiceVal = 'POZO-${random.nextInt(90000) + 10000}';
    setState(() {
      _invoiceNumber = invoiceVal;
      _printingInvoice = true;
    });
  }

  void _closeReceiptAndReset() {
    setState(() {
      _printingInvoice = false;
      _billingList.clear();
    });
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final isDesktop = MediaQuery.of(context).size.width >= 600;

    return Stack(
      children: [
        Scaffold(
          backgroundColor: const Color(0xFF1E293B), // Slate-900 like
          appBar: AppBar(
            backgroundColor: const Color(0xFF0F172A), // Slate-950 like
            elevation: 4,
            leading: IconButton(
              icon: const Icon(Icons.arrow_back, color: Colors.white),
              onPressed: () => Navigator.pop(context),
            ),
            title: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Text(
                  widget.businessName.isNotEmpty ? widget.businessName : 'Sharma General Store',
                  style: const TextStyle(
                    color: Colors.white,
                    fontWeight: FontWeight.bold,
                    fontSize: 15,
                  ),
                ),
                Row(
                  children: [
                    Container(
                      width: 6,
                      height: 6,
                      decoration: const BoxDecoration(
                        color: Color(0xFF10B981),
                        shape: BoxShape.circle,
                      ),
                    ),
                    const SizedBox(width: 4),
                    const Text(
                      'Live Register',
                      style: TextStyle(
                        color: Colors.grey,
                        fontSize: 10,
                        fontWeight: FontWeight.bold,
                      ),
                    ),
                  ],
                ),
              ],
            ),
            actions: [
              if (widget.barcodeScanner)
                Padding(
                  padding: const EdgeInsets.only(right: 8.0),
                  child: Directionality(
                    textDirection: TextDirection.rtl,
                    child: ElevatedButton.icon(
                      onPressed: _simulateBarcodeScan,
                      style: ElevatedButton.styleFrom(
                        minimumSize: const Size(0, 32),
                        backgroundColor: theme.colorScheme.primary,
                        foregroundColor: Colors.white,
                        padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 8),
                        shape: RoundedRectangleBorder(
                          borderRadius: BorderRadius.circular(12),
                        ),
                      ),
                      icon: const Icon(Icons.qr_code_scanner, size: 16),
                      label: const Text(
                        'Scan Item',
                        style: TextStyle(fontSize: 10, fontWeight: FontWeight.bold),
                      ),
                    ),
                  ),
                ),
              if (widget.kotManagement)
                Container(
                  margin: const EdgeInsets.symmetric(horizontal: 4, vertical: 12),
                  padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
                  decoration: BoxDecoration(
                    color: Colors.cyan.withOpacity(0.15),
                    borderRadius: BorderRadius.circular(8),
                    border: Border.all(color: Colors.cyan.withOpacity(0.3)),
                  ),
                  child: const Center(
                    child: Text(
                      'KOT',
                      style: TextStyle(
                        color: Colors.cyanAccent,
                        fontSize: 10,
                        fontWeight: FontWeight.bold,
                      ),
                    ),
                  ),
                ),
              const SizedBox(width: 8),
            ],
          ),
          body: SafeArea(
            child: Column(
              children: [
                // Scan Banner Message
                if (_scanMessage.isNotEmpty)
                  Container(
                    width: double.infinity,
                    color: const Color(0xFF10B981),
                    padding: const EdgeInsets.symmetric(vertical: 8, horizontal: 16),
                    child: Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: [
                        const Icon(Icons.stars, color: Colors.white, size: 16),
                        const SizedBox(width: 8),
                        Expanded(
                          child: Text(
                            _scanMessage,
                            style: const TextStyle(
                              color: Colors.white,
                              fontSize: 12,
                              fontWeight: FontWeight.bold,
                            ),
                            textAlign: TextAlign.center,
                          ),
                        ),
                      ],
                    ),
                  ),

                // Main Layout Split
                Expanded(
                  child: isDesktop
                      ? Row(
                          children: [
                            Expanded(child: _buildCatalogPart(theme)),
                            _buildLedgerTrayPart(theme, isDesktop),
                          ],
                        )
                      : Column(
                          children: [
                            Expanded(child: _buildCatalogPart(theme)),
                            const Divider(color: Color(0xFF334155), height: 1),
                            SizedBox(
                              height: 240,
                              child: _buildLedgerTrayPart(theme, isDesktop),
                            ),
                          ],
                        ),
                ),

                // Bottom Checkout sum action for Mobile ONLY
                if (!isDesktop) _buildBottomComputationBar(theme),
              ],
            ),
          ),
        ),

        // Custom Overlay for Printable Invoice
        if (_printingInvoice) _buildThermalReceiptOverlay(theme),
      ],
    );
  }

  Widget _buildCatalogPart(ThemeData theme) {
    return Padding(
      padding: const EdgeInsets.all(12.0),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              const Text(
                'STORE CATALOG',
                style: TextStyle(
                  color: Colors.grey,
                  fontWeight: FontWeight.bold,
                  fontSize: 11,
                  letterSpacing: 1.0,
                ),
              ),
              Container(
                padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
                decoration: BoxDecoration(
                  color: const Color(0xFF334155),
                  borderRadius: BorderRadius.circular(10),
                ),
                child: Text(
                  widget.businessType.toUpperCase(),
                  style: const TextStyle(
                    color: Colors.white70,
                    fontSize: 9,
                    fontWeight: FontWeight.bold,
                  ),
                ),
              ),
            ],
          ),
          const SizedBox(height: 10),
          Expanded(
            child: GridView.builder(
              physics: const BouncingScrollPhysics(),
              gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
                crossAxisCount: 2,
                crossAxisSpacing: 10,
                mainAxisSpacing: 10,
                childAspectRatio: 1.4,
              ),
              itemCount: _products.length,
              itemBuilder: (context, index) {
                final prod = _products[index];
                final billingIndex = _billingList.indexWhere((element) => element.product.id == prod.id);
                final countInCart = billingIndex != -1 ? _billingList[billingIndex].quantity : 0;
                final remainingStock = prod.stock - countInCart;
                final isLowStock = widget.inventoryAlerts && remainingStock <= 3;
                final isOutOfStock = widget.inventoryAlerts && remainingStock <= 0;

                return InkWell(
                  onTap: isOutOfStock ? null : () => _handleAddItem(prod),
                  borderRadius: BorderRadius.circular(16),
                  child: Container(
                    padding: const EdgeInsets.all(10),
                    decoration: BoxDecoration(
                      color: countInCart > 0
                          ? const Color(0xFF1E1B4B) // Deep indigo accent
                          : const Color(0xFF1E293B).withOpacity(0.8),
                      borderRadius: BorderRadius.circular(16),
                      border: Border.all(
                        color: countInCart > 0 ? theme.colorScheme.primary : const Color(0xFF334155),
                        width: countInCart > 0 ? 1.5 : 1.0,
                      ),
                    ),
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      mainAxisAlignment: MainAxisAlignment.spaceBetween,
                      children: [
                        Expanded(
                          child: Column(
                            crossAxisAlignment: CrossAxisAlignment.start,
                            children: [
                              Text(
                                prod.name,
                                maxLines: 2,
                                overflow: TextOverflow.ellipsis,
                                style: const TextStyle(
                                  color: Colors.white,
                                  fontWeight: FontWeight.bold,
                                  fontSize: 11,
                                ),
                              ),
                              const SizedBox(height: 4),
                              Text(
                                '₹${prod.price.toStringAsFixed(0)}',
                                style: TextStyle(
                                  color: theme.colorScheme.primary,
                                  fontWeight: FontWeight.w800,
                                  fontSize: 13,
                                ),
                              ),
                            ],
                          ),
                        ),
                        Row(
                          mainAxisAlignment: MainAxisAlignment.spaceBetween,
                          children: [
                            if (widget.inventoryAlerts)
                              Container(
                                padding: const EdgeInsets.symmetric(horizontal: 6, vertical: 2),
                                decoration: BoxDecoration(
                                  color: isLowStock
                                      ? Colors.red.withOpacity(0.15)
                                      : const Color(0xFF334155),
                                  borderRadius: BorderRadius.circular(6),
                                ),
                                child: Text(
                                  isOutOfStock ? 'Out of stock' : '$remainingStock Stock',
                                  style: TextStyle(
                                    color: isLowStock ? Colors.redAccent : Colors.grey,
                                    fontSize: 8,
                                    fontWeight: FontWeight.bold,
                                  ),
                                ),
                              )
                            else
                              const SizedBox(),
                            if (countInCart > 0)
                              Container(
                                width: 20,
                                height: 20,
                                decoration: BoxDecoration(
                                  color: theme.colorScheme.primary,
                                  shape: BoxShape.circle,
                                ),
                                alignment: Alignment.center,
                                child: Text(
                                  '$countInCart',
                                  style: const TextStyle(
                                    color: Colors.white,
                                    fontWeight: FontWeight.bold,
                                    fontSize: 10,
                                  ),
                                ),
                              )
                          ],
                        )
                      ],
                    ),
                  ),
                );
              },
            ),
          )
        ],
      ),
    );
  }

  Widget _buildLedgerTrayPart(ThemeData theme, bool isDesktop) {
    return Container(
      width: isDesktop ? 300 : double.infinity,
      color: const Color(0xFF0F172A).withOpacity(0.3),
      padding: const EdgeInsets.all(12),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              Text(
                'BILLING TRAY (${_billingList.length})',
                style: const TextStyle(
                  color: Colors.grey,
                  fontWeight: FontWeight.bold,
                  fontSize: 11,
                  letterSpacing: 1.0,
                ),
              ),
              if (_billingList.isNotEmpty)
                GestureDetector(
                  onTap: _clearRegister,
                  child: const Row(
                    children: [
                      Icon(Icons.refresh, color: Colors.grey, size: 12),
                      SizedBox(width: 4),
                      Text(
                        'Clear',
                        style: TextStyle(
                          color: Colors.grey,
                          fontWeight: FontWeight.bold,
                          fontSize: 10,
                        ),
                      )
                    ],
                  ),
                )
            ],
          ),
          const SizedBox(height: 10),
          Expanded(
            child: _billingList.isEmpty
                ? Center(
                    child: Column(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: [
                        Icon(Icons.shopping_cart_outlined, color: Colors.grey[600], size: 30),
                        const SizedBox(height: 8),
                        const Text(
                          'No products selected.',
                          style: TextStyle(color: Colors.grey, fontSize: 11),
                        ),
                        const Text(
                          'Tap items in catalog above.',
                          style: TextStyle(color: Colors.white30, fontSize: 10),
                        ),
                      ],
                    ),
                  )
                : ListView.builder(
                    physics: const BouncingScrollPhysics(),
                    itemCount: _billingList.length,
                    itemBuilder: (context, index) {
                      final item = _billingList[index];
                      return Container(
                        margin: const EdgeInsets.only(bottom: 8),
                        padding: const EdgeInsets.all(8),
                        decoration: BoxDecoration(
                          color: const Color(0xFF1E293B),
                          borderRadius: BorderRadius.circular(12),
                          border: Border.all(color: const Color(0xFF334155), width: 0.5),
                        ),
                        child: Row(
                          children: [
                            Expanded(
                              child: Column(
                                crossAxisAlignment: CrossAxisAlignment.start,
                                children: [
                                  Text(
                                    item.product.name,
                                    maxLines: 1,
                                    overflow: TextOverflow.ellipsis,
                                    style: const TextStyle(
                                      color: Colors.white,
                                      fontWeight: FontWeight.bold,
                                      fontSize: 11,
                                    ),
                                  ),
                                  const SizedBox(height: 2),
                                  Text(
                                    '₹${item.product.price.toStringAsFixed(0)} × ${item.quantity}',
                                    style: const TextStyle(
                                      color: Colors.grey,
                                      fontSize: 10,
                                      fontWeight: FontWeight.bold,
                                    ),
                                  ),
                                ],
                              ),
                            ),
                            Row(
                              children: [
                                GestureDetector(
                                  onTap: () => _handleRemoveOne(item.product.id),
                                  child: Container(
                                    padding: const EdgeInsets.all(4),
                                    decoration: BoxDecoration(
                                      color: const Color(0xFF334155),
                                      borderRadius: BorderRadius.circular(6),
                                    ),
                                    child: const Icon(Icons.remove, size: 14, color: Colors.white),
                                  ),
                                ),
                                Padding(
                                  padding: const EdgeInsets.symmetric(horizontal: 8.0),
                                  child: Text(
                                    '${item.quantity}',
                                    style: const TextStyle(
                                      color: Colors.white,
                                      fontWeight: FontWeight.bold,
                                      fontSize: 12,
                                    ),
                                  ),
                                ),
                                GestureDetector(
                                  onTap: () => _handleAddItem(item.product),
                                  child: Container(
                                    padding: const EdgeInsets.all(4),
                                    decoration: BoxDecoration(
                                      color: const Color(0xFF334155),
                                      borderRadius: BorderRadius.circular(6),
                                    ),
                                    child: const Icon(Icons.add, size: 14, color: Colors.white),
                                  ),
                                ),
                              ],
                            ),
                          ],
                        ),
                      );
                    },
                  ),
          ),
          if (isDesktop) ...[
            const Divider(color: Color(0xFF334155), height: 16),
            _buildComputationCalculations(theme),
            const SizedBox(height: 10),
            ElevatedButton(
              onPressed: _billingList.isEmpty ? null : _handleReviewAndGenerate,
              style: ElevatedButton.styleFrom(
                backgroundColor: theme.colorScheme.primary,
                disabledBackgroundColor: const Color(0xFF1E293B),
                minimumSize: const Size.fromHeight(48),
              ),
              child: const Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Icon(Icons.receipt, size: 16),
                  SizedBox(width: 8),
                  Text('Generate Invoice'),
                ],
              ),
            )
          ]
        ],
      ),
    );
  }

  Widget _buildComputationCalculations(ThemeData theme) {
    return Column(
      children: [
        Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            const Text('Subtotal', style: TextStyle(color: Colors.grey, fontSize: 11)),
            Text('₹${_subtotal.toStringAsFixed(2)}', style: const TextStyle(color: Colors.white, fontSize: 11, fontWeight: FontWeight.bold)),
          ],
        ),
        if (_hasGstin) ...[
          const SizedBox(height: 4),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              const Text('CGST (9%)', style: TextStyle(color: Colors.grey, fontSize: 11)),
              Text('₹${_cgst.toStringAsFixed(2)}', style: const TextStyle(color: Colors.white70, fontSize: 11)),
            ],
          ),
          const SizedBox(height: 4),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              const Text('SGST (9%)', style: TextStyle(color: Colors.grey, fontSize: 11)),
              Text('₹${_sgst.toStringAsFixed(2)}', style: const TextStyle(color: Colors.white70, fontSize: 11)),
            ],
          ),
        ],
        const Padding(
          padding: EdgeInsets.symmetric(vertical: 6.0),
          child: Divider(color: Color(0xFF334155), height: 1),
        ),
        Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            const Text('Grand Total', style: TextStyle(color: Colors.white, fontSize: 13, fontWeight: FontWeight.bold)),
            Text(
              '₹${_total.toStringAsFixed(2)}',
              style: TextStyle(
                color: theme.colorScheme.primary,
                fontSize: 14,
                fontWeight: FontWeight.w900,
              ),
            ),
          ],
        ),
      ],
    );
  }

  Widget _buildBottomComputationBar(ThemeData theme) {
    return Container(
      color: const Color(0xFF0F172A),
      padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  const Text('GRAND TOTAL', style: TextStyle(color: Colors.grey, fontSize: 9, fontWeight: FontWeight.bold)),
                  Text(
                    '₹${_total.toStringAsFixed(2)}',
                    style: TextStyle(
                      color: theme.colorScheme.primary,
                      fontSize: 18,
                      fontWeight: FontWeight.w900,
                    ),
                  )
                ],
              ),
              ElevatedButton(
                onPressed: _billingList.isEmpty ? null : _handleReviewAndGenerate,
                style: ElevatedButton.styleFrom(
                  padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 12),
                  minimumSize: const Size(180, 44),
                ),
                child: const Row(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    Icon(Icons.print, size: 16),
                    SizedBox(width: 8),
                    Text('Review & Invoice', style: TextStyle(fontSize: 12)),
                  ],
                ),
              )
            ],
          )
        ],
      ),
    );
  }

  Widget _buildThermalReceiptOverlay(ThemeData theme) {
    return Scaffold(
      backgroundColor: Colors.black87,
      body: Center(
        child: SingleChildScrollView(
          padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 30),
          child: Container(
            width: double.infinity,
            constraints: const BoxConstraints(maxWidth: 340),
            padding: const EdgeInsets.all(16),
            decoration: BoxDecoration(
              color: Colors.white,
              borderRadius: BorderRadius.circular(20),
            ),
            child: Column(
              mainAxisSize: MainAxisSize.min,
              children: [
                // Thermal dotted-dash receipt border box
                Container(
                  padding: const EdgeInsets.all(12),
                  decoration: BoxDecoration(
                    border: Border.all(color: Colors.grey[400]!, width: 2, style: BorderStyle.solid),
                    borderRadius: BorderRadius.circular(4),
                  ),
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Center(
                        child: Column(
                          children: [
                            Text(
                              widget.businessName.isNotEmpty ? widget.businessName.toUpperCase() : 'SHARMA GENERAL STORE',
                              textAlign: TextAlign.center,
                              style: const TextStyle(
                                color: Colors.black,
                                fontWeight: FontWeight.w900,
                                fontSize: 16,
                                fontFamily: 'monospace',
                              ),
                            ),
                            const SizedBox(height: 2),
                            Text(
                              '${widget.businessType.toUpperCase()} COUNTER',
                              style: const TextStyle(
                                color: Colors.grey,
                                fontSize: 9,
                                fontFamily: 'monospace',
                              ),
                            ),
                            if (_hasGstin) ...[
                              const SizedBox(height: 4),
                              Text(
                                'GSTIN: ${widget.gstin}',
                                style: const TextStyle(
                                  color: Colors.black,
                                  fontSize: 8,
                                  fontWeight: FontWeight.bold,
                                  fontFamily: 'monospace',
                                ),
                              ),
                            ]
                          ],
                        ),
                      ),
                      const SizedBox(height: 12),
                      const Divider(color: Colors.black38, thickness: 1),
                      const SizedBox(height: 4),

                      // Metadata Info
                      _buildReceiptRow('Invoice No', _invoiceNumber),
                      _buildReceiptRow('Date Track', '${DateTime.now().day}/${DateTime.now().month}/${DateTime.now().year}'),
                      _buildReceiptRow('Terminal', 'Pozo Counter'),
                      const SizedBox(height: 4),
                      const Divider(color: Colors.black38, thickness: 1),
                      const SizedBox(height: 4),

                      // Headers
                      const Row(
                        children: [
                          Expanded(
                            flex: 6,
                            child: Text('Item Description', style: TextStyle(fontWeight: FontWeight.bold, color: Colors.black, fontSize: 8, fontFamily: 'monospace')),
                          ),
                          Expanded(
                            flex: 2,
                            child: Text('Qty', textAlign: TextAlign.right, style: TextStyle(fontWeight: FontWeight.bold, color: Colors.black, fontSize: 8, fontFamily: 'monospace')),
                          ),
                          Expanded(
                            flex: 4,
                            child: Text('Price', textAlign: TextAlign.right, style: TextStyle(fontWeight: FontWeight.bold, color: Colors.black, fontSize: 8, fontFamily: 'monospace')),
                          ),
                        ],
                      ),
                      const SizedBox(height: 6),

                      // Products
                      ..._billingList.map((item) => Padding(
                            padding: const EdgeInsets.only(bottom: 6.0),
                            child: Row(
                              children: [
                                Expanded(
                                  flex: 6,
                                  child: Text(
                                    item.product.name,
                                    maxLines: 1,
                                    overflow: TextOverflow.ellipsis,
                                    style: const TextStyle(color: Colors.black87, fontSize: 9, fontFamily: 'monospace'),
                                  ),
                                ),
                                Expanded(
                                  flex: 2,
                                  child: Text(
                                    'x${item.quantity}',
                                    textAlign: TextAlign.right,
                                    style: const TextStyle(color: Colors.black87, fontSize: 9, fontFamily: 'monospace'),
                                  ),
                                ),
                                Expanded(
                                  flex: 4,
                                  child: Text(
                                    '₹${(item.product.price * item.quantity).toStringAsFixed(0)}',
                                    textAlign: TextAlign.right,
                                    style: const TextStyle(color: Colors.black, fontWeight: FontWeight.bold, fontSize: 9, fontFamily: 'monospace'),
                                  ),
                                ),
                              ],
                            ),
                          )),

                      const Divider(color: Colors.black38, thickness: 1),
                      const SizedBox(height: 4),

                      // Ledger math sum
                      _buildReceiptRow('Cart Total:', '₹${_subtotal.toStringAsFixed(2)}'),
                      if (_hasGstin) ...[
                        _buildReceiptRow('CGST (9%):', '₹${_cgst.toStringAsFixed(2)}'),
                        _buildReceiptRow('SGST (9%):', '₹${_sgst.toStringAsFixed(2)}'),
                      ],
                      const SizedBox(height: 4),
                      _buildReceiptRow('NET TOTAL:', '₹${_total.toStringAsFixed(2)}', isBold: true),

                      const SizedBox(height: 8),
                      const Divider(color: Colors.black38, thickness: 1),
                      const SizedBox(height: 8),

                      const Center(
                        child: Column(
                          children: [
                            Text(
                              'THANK YOU FOR YOUR PATRONAGE!',
                              style: TextStyle(color: Colors.black54, fontSize: 8, fontWeight: FontWeight.bold, fontFamily: 'monospace'),
                            ),
                            SizedBox(height: 4),
                            Text(
                              'Powered by PozoApp',
                              style: TextStyle(color: Colors.red, fontSize: 8, fontWeight: FontWeight.bold, fontFamily: 'monospace'),
                            ),
                          ],
                        ),
                      ),
                    ],
                  ),
                ),
                const SizedBox(height: 16),
                ElevatedButton.icon(
                  onPressed: () {
                    ScaffoldMessenger.of(context).showSnackBar(
                      SnackBar(
                        content: Text('🧾 Thermal Printed: $_invoiceNumber successfully!'),
                        backgroundColor: const Color(0xFF10B981),
                        behavior: SnackBarBehavior.floating,
                      ),
                    );
                  },
                  icon: const Icon(Icons.print, size: 16),
                  label: const Text('Simulate Print Receipt', style: TextStyle(fontSize: 12)),
                  style: ElevatedButton.styleFrom(
                    backgroundColor: Colors.black,
                    foregroundColor: Colors.white,
                    minimumSize: const Size.fromHeight(42),
                  ),
                ),
                const SizedBox(height: 8),
                ElevatedButton(
                  onPressed: _closeReceiptAndReset,
                  style: ElevatedButton.styleFrom(
                    backgroundColor: theme.colorScheme.primary,
                    minimumSize: const Size.fromHeight(42),
                  ),
                  child: const Text('New Ledger Sale', style: TextStyle(fontSize: 12)),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }

  Widget _buildReceiptRow(String label, String val, {bool isBold = false}) {
    return Padding(
      padding: const EdgeInsets.symmetric(vertical: 2.0),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: [
          Text(
            label,
            style: TextStyle(
              fontSize: 9,
              fontFamily: 'monospace',
              fontWeight: isBold ? FontWeight.bold : FontWeight.normal,
              color: isBold ? Colors.black : Colors.black87,
            ),
          ),
          Text(
            val,
            style: TextStyle(
              fontSize: 9,
              fontFamily: 'monospace',
              fontWeight: isBold ? FontWeight.bold : FontWeight.normal,
              color: isBold ? Colors.black : Colors.black87,
            ),
          ),
        ],
      ),
    );
  }
}