clean up

lib/domain/entities/invoice.dart

@@ -0,0 +1,32 @@
+import 'package.dart';
+import 'receipt.dart';
+
+class Invoice {
+  String invoiceNumber;
+  DateTime invoiceDate;
+  String customerName;
+  String customerPhoneNumber;
+  double amount;
+  String discount;
+  String status;
+  String paymentAttachment;
+
+  List<Package> packages;
+  List<Receipt> receipts;
+  List<String> receiptPhotos;
+
+  Invoice(
+      {this.invoiceNumber,
+      this.invoiceDate,
+      this.customerName,
+      this.customerPhoneNumber,
+      this.amount,
+      this.discount,
+      this.status,
+      this.paymentAttachment,
+      this.packages,
+      this.receiptPhotos,
+      this.receipts});
+
+  double get getAmount => packages.fold(0, (p, e) => (e.rate * e.weight) + p);
+}