Refactor InvoiceService by Anton Skvortsov

README.md

@@ -24,3 +24,93 @@ The overall objective is to refactor the code and keep the tests passing.  There
 
 
 
+### Code refactoring improvements
+* Validation Separation: Moved validation logic to dedicated InvoiceValidator
+* Process Decomposition: Split payment processing into discrete, focused methods
+* Interface Contracts: Established clear interfaces for all dependencies
+* Method Simplification: Broke down monolithic ProcessPayment into single-responsibility methods
+* Control Flow: Eliminated nested conditionals for linear readability
+* Error Handling: Implemented structured exception handling with code safety
+* Added logging for issues investigation
+
+* The string return type in ProcessPayment is problematic as it forces client to parse unstructured messages; 
+* a strongly-typed response object would provide clearer contracts and better programmability.
+
+
+* Client side, before:
+
+// Returns unstructured string messages
+
+        string result = _invoiceService.ProcessPayment(payment);
+
+// Client must parse strings to determine outcome. How to do that efficiently?
+
+* Client side, after:
+
+      PaymentResult result = _invoiceService.ProcessPayment(payment);
+
+      if (result.IsSuccess)
+      {
+          switch (result.Code)
+          {
+              case ResultCode.FinalPaymentComplete:
+              _receiptService.Generate(invoice, result.AmountPaid);
+              _auditService.LogPaymentComplete(result.TransactionId);
+              break;
+
+              case ResultCode.PartialPaymentComplete:
+                  _paymentTracker.ScheduleFollowUp(
+                      result.RemainingAmount,
+                      DateTime.Now.AddDays(7));
+              break;
+
+              case ResultCode.NoPaymentNeeded:
+              case ResultCode.AlreadyFullyPaid:
+                  // Handle these cases as needed
+                  break;
+          }
+      }
+      else
+      {
+          // Handle failure scenarios
+          switch (result.Code)
+          {
+              case ResultCode.InvoiceNotFound:
+              _alertService.TriggerSupportAlert(result);
+              break;
+
+              case ResultCode.PaymentExceedsRemainingAmount:
+              case ResultCode.PaymentExceedsInvoiceAmount:
+                  // Handle these cases as needed
+              break;
+
+              case ResultCode.ProcessingError:
+              case ResultCode.InvalidInvoiceState:
+                  // Handle these cases as needed
+              break;
+
+              default:
+                  _alertService.TriggerSupportAlert(result);
+              break;
+          }
+      }
+
+*** Architectural improvements
+* Proper layering with domain entities, services, and persistence
+* Dependency injection for better testability
+* Clear boundaries between components
+* Each class has a single responsibility, easier to modify or extend behavior. Clear separation makes it easier to add new features.
+
+
+*** Suggested Business Object Enhancements (not implemented):
+
+
+* Invoice/Payment Data Enrichment
+* Currently missing critical transaction details: Payer/recipient identification (names, contact info)
+* Banking/payment details
+* Transaction references
+
+
+
+
+

RefactorThis.Domain.Tests/App.config

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?><configuration>
+  <runtime>
+    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
+      <dependentAssembly>
+        <assemblyIdentity name="System.Runtime.CompilerServices.Unsafe" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-6.0.1.0" newVersion="6.0.1.0" />
+      </dependentAssembly>
+    </assemblyBinding>
+  </runtime>
+</configuration>