third commit

lib/domain/entities/product.dart

@@ -51,6 +51,7 @@ class Product extends Equatable {
     this.imageUrl,
     this.unit = UnitOfMeasure.piece,
     this.gstRate = AppConstants.defaultGstRate,
+    this.hsnCode,
     this.brand,
     this.isActive = true,
   });
@@ -72,6 +73,11 @@ class Product extends Equatable {
   final String? imageUrl;
   final UnitOfMeasure unit;
   final double gstRate;
+
+  /// HSN/SAC code. Printed on the tax invoice — legally required on a GST
+  /// invoice above the turnover threshold. Blank when the catalogue omits it.
+  final String? hsnCode;
+
   final String? brand;
   final bool isActive;
 
@@ -124,6 +130,7 @@ class Product extends Equatable {
       imageUrl: imageUrl,
       unit: unit,
       gstRate: gstRate,
+      hsnCode: hsnCode,
       brand: brand,
       isActive: isActive ?? this.isActive,
     );

lib/domain/entities/shift_report.dart

@@ -124,6 +124,76 @@ class ShiftReport extends Equatable {
     );
   }
 
+  /// Rebuilds a report from an archived day row.
+  factory ShiftReport.fromArchive({
+    required Map<String, Object?> row,
+    required Map<PaymentMethod, double> payments,
+    required DateTime businessDate,
+    required String terminalId,
+    required String cashierName,
+  }) {
+    DateTime? at(Object? v) =>
+        v == null ? null : DateTime.fromMillisecondsSinceEpoch(v as int);
+
+    return ShiftReport(
+      businessDate: businessDate,
+      terminalId: terminalId,
+      cashierName: cashierName,
+      billCount: (row['bill_count'] as int?) ?? 0,
+      itemCount: (row['item_count'] as num?)?.toDouble() ?? 0,
+      grossSales: (row['gross_sales'] as num?)?.toDouble() ?? 0,
+      taxCollected: (row['tax_collected'] as num?)?.toDouble() ?? 0,
+      discountGiven: (row['discount_given'] as num?)?.toDouble() ?? 0,
+      roundOff: (row['round_off'] as num?)?.toDouble() ?? 0,
+      paymentBreakdown: payments,
+      loyaltyPointsIssued: (row['points_issued'] as int?) ?? 0,
+      loyaltyPointsRedeemed: (row['points_redeemed'] as int?) ?? 0,
+      firstBillAt: at(row['first_bill_at']),
+      lastBillAt: at(row['last_bill_at']),
+    );
+  }
+
+  /// Adds two reports for the same day.
+  ///
+  /// Needed because synced bills are deleted from the terminal: the day's true
+  /// figures are the archived totals plus whatever is still held locally.
+  ShiftReport operator +(ShiftReport other) {
+    final payments = <PaymentMethod, double>{...paymentBreakdown};
+    other.paymentBreakdown.forEach((k, v) {
+      payments[k] = ((payments[k] ?? 0) + v).asMoney;
+    });
+
+    DateTime? earliest(DateTime? a, DateTime? b) {
+      if (a == null) return b;
+      if (b == null) return a;
+      return a.isBefore(b) ? a : b;
+    }
+
+    DateTime? latest(DateTime? a, DateTime? b) {
+      if (a == null) return b;
+      if (b == null) return a;
+      return a.isAfter(b) ? a : b;
+    }
+
+    return ShiftReport(
+      businessDate: businessDate,
+      terminalId: terminalId,
+      cashierName: cashierName,
+      billCount: billCount + other.billCount,
+      itemCount: itemCount + other.itemCount,
+      grossSales: (grossSales + other.grossSales).asMoney,
+      taxCollected: (taxCollected + other.taxCollected).asMoney,
+      discountGiven: (discountGiven + other.discountGiven).asMoney,
+      roundOff: (roundOff + other.roundOff).asMoney,
+      paymentBreakdown: payments,
+      loyaltyPointsIssued: loyaltyPointsIssued + other.loyaltyPointsIssued,
+      loyaltyPointsRedeemed:
+          loyaltyPointsRedeemed + other.loyaltyPointsRedeemed,
+      firstBillAt: earliest(firstBillAt, other.firstBillAt),
+      lastBillAt: latest(lastBillAt, other.lastBillAt),
+    );
+  }
+
   /// The JSON body that would be sent to the back office.
   Map<String, Object?> toPayload() => {
         'business_date': businessDate.toIso8601String().substring(0, 10),