third commit

lib/core/constants/app_constants.dart

@@ -6,6 +6,16 @@ class AppConstants {
   static const String storeName = 'Nearle Daily';
   static const String storeAddress = '12 Gandhipuram Main Rd, Coimbatore 641012';
   static const String storeGstin = '33ABCDE1234F1Z5';
+  static const String storeCin = 'U52190TZ2024PTC012345';
+  static const String storeFssai = '12417812000447';
+  static const String storeLegalName = 'Nearle Retail Private Limited';
+
+  /// Place of supply, printed on the tax invoice.
+  static const String stateCode = '33';
+  static const String stateName = 'TN';
+
+  static const String storeCode = '6709';
+  static const String posNumber = 'R120';
   static const String storePhone = '+91 90000 12345';
   static const String currencySymbol = '\u20B9';
   static const String locale = 'en_IN';

lib/core/services/receipt_service.dart

@@ -4,7 +4,10 @@ import 'package:flutter/foundation.dart';
 import 'package:pdf/pdf.dart';
 import 'package:pdf/widgets.dart' as pw;
 import 'package:printing/printing.dart';
+import 'package:url_launcher/url_launcher.dart';
 
+import '../../domain/entities/cart.dart';
+import '../utils/extensions.dart';
 import '../../domain/entities/transaction.dart';
 import '../constants/app_constants.dart';
 import '../utils/formatters.dart';
@@ -18,40 +21,66 @@ class ReceiptService {
   /// 80mm roll with a small safety margin.
   static const double _rollWidth = 78 * PdfPageFormat.mm;
 
+  /// One GST slab's worth of the bill, as the invoice groups it.
+  ///
+  /// A compliant Indian tax invoice lists items under their rate and then
+  /// repeats the arithmetic in a breakup table, so both are derived once here.
+  static List<_Slab> _slabs(SaleTransaction txn) {
+    final cart = txn.cart;
+
+    // Bill-level discounts are spread across lines, so the slab figures still
+    // add up to the amount actually charged.
+    final factor = cart.subtotal <= 0 ? 1.0 : cart.netAmount / cart.subtotal;
+
+    final grouped = <double, List<CartLine>>{};
+    for (final line in cart.lines) {
+      grouped.putIfAbsent(line.product.gstRate, () => []).add(line);
+    }
+
+    final rates = grouped.keys.toList()..sort();
+    return [
+      for (var i = 0; i < rates.length; i++)
+        _Slab(
+          index: i + 1,
+          rate: rates[i],
+          lines: grouped[rates[i]]!,
+          factor: factor,
+        ),
+    ];
+  }
+
   Future<Uint8List> build(SaleTransaction txn) async {
     final doc = pw.Document(title: txn.invoiceNumber);
-    final font = await PdfGoogleFonts.interRegular();
-    final bold = await PdfGoogleFonts.interSemiBold();
+    final font = await PdfGoogleFonts.robotoMonoRegular();
+    final bold = await PdfGoogleFonts.robotoMonoBold();
 
-    final cart = txn.cart;
+    final slabs = _slabs(txn);
 
     doc.addPage(
       pw.Page(
         pageFormat: PdfPageFormat(
           _rollWidth,
           double.infinity,
-          marginAll: 6 * PdfPageFormat.mm,
+          marginAll: 5 * PdfPageFormat.mm,
         ),
         theme: pw.ThemeData.withFont(base: font, bold: bold),
         build: (context) => pw.Column(
           crossAxisAlignment: pw.CrossAxisAlignment.stretch,
           children: [
             _header(txn),
-            _divider(),
+            _savingsLine(txn),
+            _rule(),
+            _invoiceTitle(),
             _meta(txn),
-            _divider(),
-            _itemsTable(txn),
-            _divider(),
+            _rule(),
+            _itemsBySlab(slabs),
+            _rule(),
             _totals(txn),
-            _divider(),
-            _taxSummary(txn),
-            _divider(),
-            _payments(txn),
-            if (cart.customer != null) ...[
-              _divider(),
-              _loyalty(txn),
-            ],
-            pw.SizedBox(height: 8),
+            pw.SizedBox(height: 4),
+            _gstBreakup(txn, slabs),
+            _rule(),
+            _references(txn),
+            pw.SizedBox(height: 6),
             _footer(txn),
           ],
         ),
@@ -66,241 +95,370 @@ class ReceiptService {
         pw.Text(
           AppConstants.storeName.toUpperCase(),
           style: pw.TextStyle(fontSize: 15, fontWeight: pw.FontWeight.bold),
-          textAlign: pw.TextAlign.center,
         ),
+        pw.Text(AppConstants.storeLegalName,
+            style: const pw.TextStyle(fontSize: 7)),
         pw.SizedBox(height: 2),
-        pw.Text(
-          AppConstants.storeAddress,
-          style: const pw.TextStyle(fontSize: 7),
-          textAlign: pw.TextAlign.center,
-        ),
-        pw.Text(
-          'GSTIN: ${AppConstants.storeGstin}  |  ${AppConstants.storePhone}',
-          style: const pw.TextStyle(fontSize: 7),
-          textAlign: pw.TextAlign.center,
-        ),
-        pw.SizedBox(height: 4),
-        pw.Text(
-          'TAX INVOICE',
-          style: pw.TextStyle(fontSize: 9, fontWeight: pw.FontWeight.bold),
-        ),
+        pw.Text(AppConstants.storeAddress,
+            style: const pw.TextStyle(fontSize: 6.5),
+            textAlign: pw.TextAlign.center),
+        pw.Text('Customer care : ${AppConstants.storePhone}',
+            style: const pw.TextStyle(fontSize: 6.5)),
+        pw.Text('CIN No : ${AppConstants.storeCin}',
+            style: const pw.TextStyle(fontSize: 6.5)),
+        pw.Text('GSTIN : ${AppConstants.storeGstin}',
+            style: const pw.TextStyle(fontSize: 6.5)),
+        pw.Text('FSSAI Lic No : ${AppConstants.storeFssai}',
+            style: const pw.TextStyle(fontSize: 6.5)),
+      ]);
+
+  pw.Widget _savingsLine(SaleTransaction txn) {
+    final saved = _grossSalesValue(txn) - txn.cart.netAmount;
+    if (saved <= 0) return pw.SizedBox(height: 4);
+
+    return pw.Padding(
+      padding: const pw.EdgeInsets.symmetric(vertical: 4),
+      child: pw.Text(
+        'You have saved Rs.${saved.toStringAsFixed(2)}',
+        style: pw.TextStyle(fontSize: 9, fontWeight: pw.FontWeight.bold),
+        textAlign: pw.TextAlign.center,
+      ),
+    );
+  }
+
+  pw.Widget _invoiceTitle() => pw.Column(children: [
+        pw.Text('TAX INVOICE',
+            style: pw.TextStyle(fontSize: 9, fontWeight: pw.FontWeight.bold)),
+        pw.SizedBox(height: 1),
+        pw.Text('xxxxxx Original for Recipient xxxxxx',
+            style: const pw.TextStyle(fontSize: 6)),
       ]);
 
   pw.Widget _meta(SaleTransaction txn) {
     final c = txn.customer;
-    return pw.Column(children: [
-      _row('Invoice', txn.invoiceNumber),
-      _row('Date', Formatters.receiptStamp(txn.createdAt)),
-      _row('Cashier', txn.cashierName),
-      _row('Terminal', txn.terminalId),
-      _row('Customer', c == null ? 'Walk-in' : c.name),
-      if (c != null) _row('Mobile', Formatters.mobile(c.mobile)),
-    ]);
+    return pw.Column(
+      crossAxisAlignment: pw.CrossAxisAlignment.start,
+      children: [
+        pw.SizedBox(height: 2),
+        _line('Place of Supply & State Code: '
+            '${AppConstants.stateCode} ${AppConstants.stateName}'),
+        // URD = unregistered dealer, the correct marking for retail walk-ins.
+        _line('Customer Type: ${c == null ? 'URD' : 'REG'}'),
+        _split(
+          'Date:${Formatters.receiptStamp(txn.createdAt)}',
+          'Bill No:${txn.invoiceNumber.split('-').last}',
+        ),
+        _split(
+          'Store:${AppConstants.storeCode}  Cashier:${txn.cashierName}',
+          'Pos No:${AppConstants.posNumber}',
+        ),
+        if (c != null) _line('Customer: ${c.name}  ${c.mobile}'),
+      ],
+    );
   }
 
-  pw.Widget _itemsTable(SaleTransaction txn) {
+  pw.Widget _itemsBySlab(List<_Slab> slabs) {
     return pw.Column(
       crossAxisAlignment: pw.CrossAxisAlignment.stretch,
       children: [
         pw.Row(children: [
-          pw.Expanded(flex: 5, child: _th('Item')),
-          pw.Expanded(flex: 2, child: _th('Qty', align: pw.TextAlign.center)),
-          pw.Expanded(flex: 3, child: _th('Rate', align: pw.TextAlign.right)),
-          pw.Expanded(flex: 3, child: _th('Amt', align: pw.TextAlign.right)),
+          pw.Expanded(flex: 12, child: _th('HSN')),
+          pw.Expanded(flex: 34, child: _th('Item Description')),
+          pw.Expanded(flex: 16, child: _th('Net Price', right: true)),
+          pw.Expanded(flex: 8, child: _th('Qty', right: true)),
+          pw.Expanded(flex: 18, child: _th('Value', right: true)),
         ]),
         pw.SizedBox(height: 2),
-        ...txn.cart.lines.map((line) => pw.Padding(
-              padding: const pw.EdgeInsets.symmetric(vertical: 1.5),
-              child: pw.Column(children: [
-                pw.Row(children: [
-                  pw.Expanded(flex: 5, child: _td(line.product.name)),
-                  pw.Expanded(
-                    flex: 2,
-                    child: _td(
-                      _qty(line.quantity),
-                      align: pw.TextAlign.center,
-                    ),
-                  ),
-                  pw.Expanded(
-                    flex: 3,
-                    child: _td(
-                      line.product.price.toStringAsFixed(2),
-                      align: pw.TextAlign.right,
-                    ),
-                  ),
-                  pw.Expanded(
-                    flex: 3,
-                    child: _td(
-                      line.payable.toStringAsFixed(2),
-                      align: pw.TextAlign.right,
-                    ),
-                  ),
-                ]),
-                if (line.discount.isActive)
-                  pw.Row(children: [
-                    pw.Expanded(
-                      child: _td(
-                        '   ${line.discount.label}  '
-                        '-${line.discountAmount.toStringAsFixed(2)}',
-                        size: 6.5,
-                      ),
-                    ),
-                  ]),
+        for (final slab in slabs) ...[
+          pw.Padding(
+            padding: const pw.EdgeInsets.only(top: 3, bottom: 1),
+            child: pw.Text(
+              '${slab.index}) CGST @ ${slab.halfPercent}  '
+              'SGST @ ${slab.halfPercent}',
+              style: pw.TextStyle(fontSize: 7, fontWeight: pw.FontWeight.bold),
+            ),
+          ),
+          for (final line in slab.lines)
+            pw.Padding(
+              padding: const pw.EdgeInsets.symmetric(vertical: 0.6),
+              child: pw.Row(children: [
+                pw.Expanded(
+                  flex: 12,
+                  child: _td(line.product.hsnCode ?? '-', size: 6.5),
+                ),
+                pw.Expanded(
+                  flex: 34,
+                  child: _td(_description(line), size: 6.5),
+                ),
+                pw.Expanded(
+                  flex: 16,
+                  child: _td(line.product.price.toStringAsFixed(2),
+                      right: true, size: 6.5),
+                ),
+                pw.Expanded(
+                  flex: 8,
+                  child: _td(_qty(line.quantity), right: true, size: 6.5),
+                ),
+                pw.Expanded(
+                  flex: 18,
+                  child: _td(line.payable.toStringAsFixed(2),
+                      right: true, size: 6.5),
+                ),
               ]),
-            )),
+            ),
+        ],
       ],
     );
   }
 
   pw.Widget _totals(SaleTransaction txn) {
     final cart = txn.cart;
+    final gross = _grossSalesValue(txn);
+    final discount = gross - cart.netAmount;
+
     return pw.Column(children: [
-      _row('Items', '${cart.lineCount}  (Qty ${_qty(cart.totalQuantity)})'),
-      _row('Subtotal', cart.subtotal.toStringAsFixed(2)),
-      if (cart.membershipDiscountAmount > 0)
-        _row(
-          '${cart.customer!.tier.label} discount',
-          '-${cart.membershipDiscountAmount.toStringAsFixed(2)}',
-        ),
-      if (cart.manualBillDiscountAmount > 0)
-        _row('Discount', '-${cart.manualBillDiscountAmount.toStringAsFixed(2)}'),
-      if (cart.loyaltyRedemptionValue > 0)
-        _row(
-          'Points redeemed (${cart.pointsRedeemed})',
-          '-${cart.loyaltyRedemptionValue.toStringAsFixed(2)}',
-        ),
-      _row('Taxable value', cart.taxableAmount.toStringAsFixed(2)),
-      _row('CGST', cart.cgst.toStringAsFixed(2)),
-      _row('SGST', cart.sgst.toStringAsFixed(2)),
-      if (cart.roundOff != 0)
-        _row('Round off', cart.roundOff.toStringAsFixed(2)),
-      pw.SizedBox(height: 3),
-      pw.Row(
-        mainAxisAlignment: pw.MainAxisAlignment.spaceBetween,
-        children: [
-          pw.Text('TOTAL',
-              style: pw.TextStyle(fontSize: 12, fontWeight: pw.FontWeight.bold)),
-          pw.Text(
-            '${AppConstants.currencySymbol}${txn.total.toStringAsFixed(2)}',
-            style: pw.TextStyle(fontSize: 12, fontWeight: pw.FontWeight.bold),
-          ),
-        ],
+      _split(
+        'Items:${cart.lineCount}',
+        'Qty:${_qty(cart.totalQuantity)}    '
+            '${cart.netAmount.toStringAsFixed(2)}',
       ),
-      if (cart.totalSavings > 0) ...[
-        pw.SizedBox(height: 2),
-        pw.Text(
-          'You saved ${AppConstants.currencySymbol}'
-          '${cart.totalSavings.toStringAsFixed(2)} on this bill',
-          style: pw.TextStyle(fontSize: 7.5, fontWeight: pw.FontWeight.bold),
-          textAlign: pw.TextAlign.center,
+      pw.SizedBox(height: 2),
+      _amount('Gross Sales Value', gross),
+      if (discount > 0) _amount('Total Discount', discount),
+      _amount('Net Sales Value (Inclusive of GST)', cart.netAmount),
+      if (cart.roundOff != 0) _amount('Round Off', cart.roundOff),
+      _amount('Total Amount Paid', txn.total, bold: true),
+      for (final p in txn.payments)
+        _amount(
+          p.method.label.toUpperCase() +
+              (p.reference != null ? ' ${p.reference}' : ''),
+          p.amount,
         ),
+      if (txn.changeDue > 0) _amount('Change Returned', txn.changeDue),
+      pw.SizedBox(height: 1),
+      pw.Text('(AMOUNT INCLUSIVE OF APPLICABLE TAXES)',
+          style: const pw.TextStyle(fontSize: 6)),
+    ]);
+  }
+
+  pw.Widget _gstBreakup(SaleTransaction txn, List<_Slab> slabs) {
+    return pw.Column(children: [
+      pw.Text('------GST Breakup Details------ Amount (INR)',
+          style: const pw.TextStyle(fontSize: 6.5)),
+      pw.SizedBox(height: 3),
+      pw.Row(children: [
+        pw.Expanded(flex: 10, child: _th('GST\nIND', size: 6)),
+        pw.Expanded(flex: 20, child: _th('Taxable\nAmount', right: true, size: 6)),
+        pw.Expanded(flex: 16, child: _th('CGST', right: true, size: 6)),
+        pw.Expanded(flex: 16, child: _th('SGST', right: true, size: 6)),
+        pw.Expanded(flex: 14, child: _th('CESS', right: true, size: 6)),
+        pw.Expanded(flex: 20, child: _th('Total\nAmount', right: true, size: 6)),
+      ]),
+      pw.SizedBox(height: 2),
+      for (final s in slabs)
+        pw.Padding(
+          padding: const pw.EdgeInsets.symmetric(vertical: 0.8),
+          child: pw.Row(children: [
+            pw.Expanded(flex: 10, child: _td('${s.index}', size: 6.5)),
+            pw.Expanded(
+                flex: 20,
+                child: _td(s.taxable.toStringAsFixed(2),
+                    right: true, size: 6.5)),
+            pw.Expanded(
+                flex: 16,
+                child: _td(s.cgst.toStringAsFixed(2), right: true, size: 6.5)),
+            pw.Expanded(
+                flex: 16,
+                child: _td(s.sgst.toStringAsFixed(2), right: true, size: 6.5)),
+            pw.Expanded(flex: 14, child: _td('0.00', right: true, size: 6.5)),
+            pw.Expanded(
+                flex: 20,
+                child:
+                    _td(s.total.toStringAsFixed(2), right: true, size: 6.5)),
+          ]),
+        ),
+      pw.Divider(height: 4, borderStyle: pw.BorderStyle.dashed),
+      pw.Row(children: [
+        pw.Expanded(flex: 10, child: _th('Total', size: 6.5)),
+        pw.Expanded(
+            flex: 20,
+            child: _th(
+                slabs.fold(0.0, (a, s) => a + s.taxable).toStringAsFixed(2),
+                right: true,
+                size: 6.5)),
+        pw.Expanded(
+            flex: 16,
+            child: _th(slabs.fold(0.0, (a, s) => a + s.cgst).toStringAsFixed(2),
+                right: true, size: 6.5)),
+        pw.Expanded(
+            flex: 16,
+            child: _th(slabs.fold(0.0, (a, s) => a + s.sgst).toStringAsFixed(2),
+                right: true, size: 6.5)),
+        pw.Expanded(flex: 14, child: _th('0.00', right: true, size: 6.5)),
+        pw.Expanded(
+            flex: 20,
+            child: _th(
+                slabs.fold(0.0, (a, s) => a + s.total).toStringAsFixed(2),
+                right: true,
+                size: 6.5)),
+      ]),
+    ]);
+  }
+
+  pw.Widget _references(SaleTransaction txn) {
+    final c = txn.customer;
+    return pw.Column(
+      crossAxisAlignment: pw.CrossAxisAlignment.start,
+      children: [
+        _line('TaxInvoice# ${txn.invoiceNumber}'),
+        _line('PaymentRefNo# ${txn.id.replaceAll('-', '').substring(0, 16)}'),
+        if (c != null)
+          _line('Loyalty Pts: earned ${txn.pointsEarned}'
+              '${txn.pointsRedeemed > 0 ? ', used ${txn.pointsRedeemed}' : ''}'
+              '  Bal: ${c.loyaltyPoints - txn.pointsRedeemed + txn.pointsEarned}'),
+        _line('Terms & Conditions Apply'),
       ],
-    ]);
-  }
-
-  pw.Widget _taxSummary(SaleTransaction txn) {
-    final breakdown = txn.cart.taxBreakdown.entries
-        .where((e) => e.value > 0)
-        .toList()
-      ..sort((a, b) => a.key.compareTo(b.key));
-
-    if (breakdown.isEmpty) {
-      return _td('All items zero-rated', size: 7);
-    }
-
-    return pw.Column(children: [
-      _th('GST Summary'),
-      ...breakdown.map((e) => _row(
-            'GST @ ${(e.key * 100).toStringAsFixed(0)}%',
-            e.value.toStringAsFixed(2),
-            size: 7,
-          )),
-    ]);
-  }
-
-  pw.Widget _payments(SaleTransaction txn) => pw.Column(children: [
-        ...txn.payments.map((p) => _row(
-              p.method.label +
-                  (p.reference != null ? ' (${p.reference})' : ''),
-              p.amount.toStringAsFixed(2),
-            )),
-        if (txn.changeDue > 0)
-          _row('Change returned', txn.changeDue.toStringAsFixed(2)),
-      ]);
-
-  pw.Widget _loyalty(SaleTransaction txn) {
-    final c = txn.customer!;
-    final balance = c.loyaltyPoints - txn.pointsRedeemed + txn.pointsEarned;
-    return pw.Column(children: [
-      _row('Points earned', '+${txn.pointsEarned}'),
-      if (txn.pointsRedeemed > 0)
-        _row('Points redeemed', '-${txn.pointsRedeemed}'),
-      _row('Points balance', '$balance'),
-      _row('Membership', c.tier.label),
-    ]);
+    );
   }
 
   pw.Widget _footer(SaleTransaction txn) => pw.Column(children: [
         pw.BarcodeWidget(
           barcode: pw.Barcode.code128(),
           data: txn.invoiceNumber,
-          width: 140,
-          height: 34,
+          width: 150,
+          height: 32,
           drawText: false,
         ),
-        pw.SizedBox(height: 4),
-        pw.Text(txn.invoiceNumber, style: const pw.TextStyle(fontSize: 7)),
-        pw.SizedBox(height: 4),
-        pw.Text('Thank you for shopping with us!',
-            style: pw.TextStyle(fontSize: 8, fontWeight: pw.FontWeight.bold)),
-        pw.Text('Goods once sold are exchangeable within 7 days with this bill.',
-            style: const pw.TextStyle(fontSize: 6),
+        pw.SizedBox(height: 2),
+        pw.Text(txn.invoiceNumber, style: const pw.TextStyle(fontSize: 6.5)),
+        pw.SizedBox(height: 5),
+        pw.Text(
+          'I/We hereby certify that food/foods mentioned in this invoice '
+          'is/are warranted to be of the nature and quality which it/these '
+          'purports/purported to be.',
+          style: const pw.TextStyle(fontSize: 5.5),
+          textAlign: pw.TextAlign.center,
+        ),
+        pw.SizedBox(height: 3),
+        pw.Text('* Thank You for Shopping with us *',
+            style: pw.TextStyle(fontSize: 7, fontWeight: pw.FontWeight.bold)),
+        pw.Text('Goods once sold are exchangeable within 7 days with this bill',
+            style: const pw.TextStyle(fontSize: 5.5),
             textAlign: pw.TextAlign.center),
         pw.SizedBox(height: 2),
-        pw.Text('Powered by Nearle POS', style: const pw.TextStyle(fontSize: 6)),
+        pw.Text('Powered by Nearle POS',
+            style: const pw.TextStyle(fontSize: 5.5)),
       ]);
 
   // -------------------------------------------------------------- Helpers
+  /// Pre-discount value, using printed MRP where one is known.
+  static double _grossSalesValue(SaleTransaction txn) => txn.cart.lines
+      .fold(0.0, (s, l) => s + (l.product.mrp ?? l.product.price) * l.quantity);
+
+  String _description(CartLine line) => line.product.name.toUpperCase();
+
   String _qty(double q) =>
       q % 1 == 0 ? q.toStringAsFixed(0) : q.toStringAsFixed(3);
 
-  pw.Widget _divider() => pw.Padding(
+  pw.Widget _rule() => pw.Padding(
         padding: const pw.EdgeInsets.symmetric(vertical: 3),
         child: pw.Divider(height: 0.5, borderStyle: pw.BorderStyle.dashed),
       );
 
-  pw.Widget _th(String text, {pw.TextAlign align = pw.TextAlign.left}) =>
-      pw.Text(text,
-          textAlign: align,
-          style: pw.TextStyle(fontSize: 7.5, fontWeight: pw.FontWeight.bold));
+  pw.Widget _line(String text) => pw.Padding(
+        padding: const pw.EdgeInsets.symmetric(vertical: 0.5),
+        child: pw.Text(text, style: const pw.TextStyle(fontSize: 6.5)),
+      );
 
-  pw.Widget _td(String text,
-          {pw.TextAlign align = pw.TextAlign.left, double size = 7.5}) =>
-      pw.Text(text, textAlign: align, style: pw.TextStyle(fontSize: size));
-
-  pw.Widget _row(String label, String value, {double size = 7.5}) => pw.Padding(
-        padding: const pw.EdgeInsets.symmetric(vertical: 0.8),
+  pw.Widget _split(String left, String right) => pw.Padding(
+        padding: const pw.EdgeInsets.symmetric(vertical: 0.5),
         child: pw.Row(
           mainAxisAlignment: pw.MainAxisAlignment.spaceBetween,
           children: [
-            pw.Text(label, style: pw.TextStyle(fontSize: size)),
-            pw.Text(value, style: pw.TextStyle(fontSize: size)),
+            pw.Text(left, style: const pw.TextStyle(fontSize: 6.5)),
+            pw.Text(right, style: const pw.TextStyle(fontSize: 6.5)),
           ],
         ),
       );
 
+  pw.Widget _amount(String label, double value, {bool bold = false}) =>
+      pw.Padding(
+        padding: const pw.EdgeInsets.symmetric(vertical: 0.6),
+        child: pw.Row(
+          mainAxisAlignment: pw.MainAxisAlignment.spaceBetween,
+          children: [
+            pw.Text(label,
+                style: pw.TextStyle(
+                  fontSize: 6.8,
+                  fontWeight: bold ? pw.FontWeight.bold : pw.FontWeight.normal,
+                )),
+            pw.Text(value.toStringAsFixed(2),
+                style: pw.TextStyle(
+                  fontSize: 6.8,
+                  fontWeight: bold ? pw.FontWeight.bold : pw.FontWeight.normal,
+                )),
+          ],
+        ),
+      );
+
+  pw.Widget _th(String text, {bool right = false, double size = 6.8}) =>
+      pw.Text(text,
+          textAlign: right ? pw.TextAlign.right : pw.TextAlign.left,
+          style: pw.TextStyle(fontSize: size, fontWeight: pw.FontWeight.bold));
+
+  pw.Widget _td(String text, {bool right = false, double size = 6.8}) =>
+      pw.Text(text,
+          maxLines: 1,
+          overflow: pw.TextOverflow.clip,
+          textAlign: right ? pw.TextAlign.right : pw.TextAlign.left,
+          style: pw.TextStyle(fontSize: size));
+
   // --------------------------------------------------------- Printing / IO
-  /// Silent print to the default roll printer — no OS dialog, so the cashier
-  /// is never blocked between sales.
-  Future<bool> printDirect(SaleTransaction txn) async {
+  /// Opens the system print preview.
+  ///
+  /// This is the on-terminal path: it renders the receipt on screen and works
+  /// with no printer attached. When a roll printer is wired up, switch the
+  /// receipt screen to [printDirect] and this becomes the fallback.
+  Future<void> printPreview(SaleTransaction txn) async {
+    final bytes = await build(txn);
+    await Printing.layoutPdf(
+      onLayout: (_) async => bytes,
+      name: txn.invoiceNumber,
+    );
+  }
+
+  /// Printers the operating system can see.
+  ///
+  /// A USB or network thermal printer shows up here once its driver is
+  /// installed — the terminal does not talk to the hardware itself.
+  Future<List<Printer>> availablePrinters() async {
     try {
+      return await Printing.listPrinters();
+    } catch (e) {
+      debugPrint('Printer discovery failed: $e');
+      return const [];
+    }
+  }
+
+  /// Silent print with no OS dialog, so the cashier is never blocked.
+  ///
+  /// [printerUrl] is the value saved from Settings. When it is null or the
+  /// printer has gone away, this falls back to the system default; when there
+  /// is no printer at all it returns false so the caller can show the preview
+  /// instead of pretending the bill was printed.
+  Future<bool> printDirect(
+    SaleTransaction txn, {
+    String? printerUrl,
+  }) async {
+    try {
+      final printers = await availablePrinters();
+      if (printers.isEmpty) return false;
+
+      final target = printers.where((p) => p.url == printerUrl).firstOrNull ??
+          printers.where((p) => p.isDefault).firstOrNull ??
+          printers.first;
+
       final bytes = await build(txn);
-      final printers = await Printing.listPrinters();
-      final target = printers.where((p) => p.isDefault).firstOrNull ??
-          (printers.isNotEmpty ? printers.first : null);
-
-      if (target == null) return false;
-
       return await Printing.directPrintPdf(
         printer: target,
         onLayout: (_) async => bytes,
@@ -312,24 +470,187 @@ class ReceiptService {
     }
   }
 
-  /// Falls back to the system print preview.
-  Future<void> printWithDialog(SaleTransaction txn) async {
-    final bytes = await build(txn);
-    await Printing.layoutPdf(
-      onLayout: (_) async => bytes,
-      name: txn.invoiceNumber,
-    );
+  /// Sends a one-page test slip to confirm the printer is wired up.
+  Future<bool> printTestPage({String? printerUrl}) async {
+    try {
+      final printers = await availablePrinters();
+      if (printers.isEmpty) return false;
+
+      final target = printers.where((p) => p.url == printerUrl).firstOrNull ??
+          printers.first;
+
+      final doc = pw.Document();
+      final font = await PdfGoogleFonts.robotoMonoRegular();
+      doc.addPage(
+        pw.Page(
+          pageFormat: PdfPageFormat(
+            _rollWidth,
+            double.infinity,
+            marginAll: 5 * PdfPageFormat.mm,
+          ),
+          theme: pw.ThemeData.withFont(base: font),
+          build: (_) => pw.Column(children: [
+            pw.Text(AppConstants.storeName.toUpperCase(),
+                style: pw.TextStyle(fontSize: 14, fontWeight: pw.FontWeight.bold)),
+            pw.SizedBox(height: 6),
+            pw.Text('PRINTER TEST', style: const pw.TextStyle(fontSize: 10)),
+            pw.SizedBox(height: 4),
+            pw.Text(target.name, style: const pw.TextStyle(fontSize: 7)),
+            pw.Text(Formatters.dateTime(DateTime.now()),
+                style: const pw.TextStyle(fontSize: 7)),
+            pw.SizedBox(height: 6),
+            pw.Text('1234567890 ABCDEFGHIJ',
+                style: const pw.TextStyle(fontSize: 8)),
+            pw.Text('₹ 1,234.56', style: const pw.TextStyle(fontSize: 8)),
+            pw.SizedBox(height: 6),
+            pw.BarcodeWidget(
+              barcode: pw.Barcode.code128(),
+              data: 'NEARLE-TEST',
+              width: 140,
+              height: 30,
+              drawText: false,
+            ),
+          ]),
+        ),
+      );
+
+      return await Printing.directPrintPdf(
+        printer: target,
+        onLayout: (_) async => doc.save(),
+        name: 'Nearle printer test',
+      );
+    } catch (e) {
+      debugPrint('Test print failed: $e');
+      return false;
+    }
   }
 
-  Future<void> share(SaleTransaction txn) async {
+  /// Shares the receipt PDF through the OS share sheet.
+  Future<void> sharePdf(SaleTransaction txn) async {
     final bytes = await build(txn);
     await Printing.sharePdf(bytes: bytes, filename: '${txn.invoiceNumber}.pdf');
   }
 
-  /// Opens the cash drawer via the ESC/POS kick pulse on pin 2.
-  Future<void> openCashDrawer() async {
-    // ESC p m t1 t2 — sent to the receipt printer's serial passthrough.
-    // Wired up here as a no-op placeholder for the concrete driver.
-    debugPrint('Cash drawer kick: ESC p 0 25 250');
+  /// Opens WhatsApp with the bill addressed to the customer's number.
+  ///
+  /// WhatsApp cannot accept an attachment through a deep link, so the bill is
+  /// sent as formatted text. Returns false when there is no number to send to
+  /// or WhatsApp is not installed.
+  Future<bool> sendToWhatsApp(SaleTransaction txn) async {
+    final mobile = txn.customer?.mobile.replaceAll(RegExp(r'\D'), '');
+    if (mobile == null || mobile.length < 10) return false;
+
+    final uri = Uri.parse(
+      'https://wa.me/91$mobile?text=${Uri.encodeComponent(whatsAppText(txn))}',
+    );
+
+    try {
+      return await launchUrl(uri, mode: LaunchMode.externalApplication);
+    } catch (e) {
+      debugPrint('WhatsApp launch failed: $e');
+      return false;
+    }
   }
+
+  /// Plain-text bill for messaging.
+  String whatsAppText(SaleTransaction txn) {
+    final cart = txn.cart;
+    final b = StringBuffer()
+      ..writeln('*${AppConstants.storeName}*')
+      ..writeln(AppConstants.storeAddress)
+      ..writeln('GSTIN: ${AppConstants.storeGstin}')
+      ..writeln()
+      ..writeln('Invoice: ${txn.invoiceNumber}')
+      ..writeln('Date: ${Formatters.dateTime(txn.createdAt)}')
+      ..writeln()
+      ..writeln('--------------------');
+
+    for (final line in cart.lines) {
+      final qty = line.quantity % 1 == 0
+          ? line.quantity.toStringAsFixed(0)
+          : line.quantity.toStringAsFixed(2);
+      b.writeln('$qty x ${line.product.name}'
+          '  ${Formatters.money(line.payable)}');
+    }
+
+    b
+      ..writeln('--------------------')
+      ..writeln('Subtotal: ${Formatters.money(cart.subtotal)}');
+
+    if (cart.billDiscountTotal > 0) {
+      b.writeln('Discount: -${Formatters.money(cart.billDiscountTotal)}');
+    }
+
+    b
+      ..writeln('GST: ${Formatters.money(cart.taxAmount)}')
+      ..writeln('*TOTAL: ${Formatters.money(txn.total)}*')
+      ..writeln()
+      ..writeln('Paid by ${txn.paymentSummary}');
+
+    if (txn.pointsEarned > 0) {
+      b.writeln('Points earned: +${txn.pointsEarned}');
+    }
+
+    b
+      ..writeln()
+      ..writeln('Thank you for shopping with us!');
+
+    return b.toString();
+  }
+
+  /// ESC/POS drawer kick: `ESC p m t1 t2` on pin 2.
+  ///
+  /// Most drawers are wired to the printer's RJ11 port and open when the
+  /// printer receives this. It cannot be sent through the PDF pipeline — a
+  /// PDF is rendered by the driver, not passed through as bytes — so this
+  /// needs a raw channel to the printer.
+  ///
+  /// On desktop with a driver-installed printer there is no raw path from
+  /// Flutter, so this stays a no-op. Wire it up when you move to ESC/POS:
+  /// send [drawerKickCommand] over the same socket or Bluetooth link that
+  /// carries the receipt.
+  Future<void> openCashDrawer() async {
+    debugPrint(
+      'Cash drawer kick requested — needs a raw ESC/POS channel, '
+      'not the PDF driver. Command: ${drawerKickCommand.join(' ')}',
+    );
+  }
+
+  /// `ESC p 0 25 250` — pin 2, 50ms on, 500ms off.
+  static const List<int> drawerKickCommand = [27, 112, 0, 25, 250];
+}
+
+/// One GST rate's slice of a bill.
+class _Slab {
+  _Slab({
+    required this.index,
+    required this.rate,
+    required this.lines,
+    required this.factor,
+  });
+
+  /// 1-based, printed both above the item group and in the breakup table.
+  final int index;
+
+  final double rate;
+  final List<CartLine> lines;
+
+  /// Share of the bill left after bill-level discounts.
+  final double factor;
+
+  /// e.g. "2.50%" — half the slab, since CGST and SGST each take half.
+  String get halfPercent => '${(rate * 100 / 2).toStringAsFixed(2)}%';
+
+  /// GST-inclusive value charged for this slab.
+  double get total =>
+      lines.fold(0.0, (s, l) => s + l.payable * factor).asMoney;
+
+  double get taxAmount =>
+      lines.fold(0.0, (s, l) => s + l.taxAmount * factor).asMoney;
+
+  double get taxable => (total - taxAmount).asMoney;
+
+  double get cgst => (taxAmount / 2).asMoney;
+
+  double get sgst => (taxAmount - cgst).asMoney;
 }