From 2e4ceb993d71da948c86fc860438203087ec0cd9 Mon Sep 17 00:00:00 2001
From: Stuart Ferguson <stuart_ferguson1@btinternet.com>
Date: Tue, 25 Feb 2025 13:09:38 +0000
Subject: [PATCH] Add retry policy for domain event handling

Introduced a retry mechanism using Polly in `MerchantDomainEventHandler.cs` to handle specific domain events. The new implementation allows for up to two retries if the event processing fails. Additionally, reorganized and cleaned up the `using` directives for improved readability.
---
 .../MerchantDomainEventHandler.cs             | 53 +++++++++----------
 1 file changed, 24 insertions(+), 29 deletions(-)

diff --git a/TransactionProcessor.BusinessLogic/EventHandling/MerchantDomainEventHandler.cs b/TransactionProcessor.BusinessLogic/EventHandling/MerchantDomainEventHandler.cs
index 7c03f67b..6e338924 100644
--- a/TransactionProcessor.BusinessLogic/EventHandling/MerchantDomainEventHandler.cs
+++ b/TransactionProcessor.BusinessLogic/EventHandling/MerchantDomainEventHandler.cs
@@ -1,14 +1,16 @@
-using System;
-using System.Threading;
-using System.Threading.Tasks;
-using MediatR;
+using MediatR;
 using Newtonsoft.Json;
+using Polly;
 using Shared.DomainDrivenDesign.EventSourcing;
 using Shared.EventStore.Aggregate;
 using Shared.EventStore.EventHandling;
 using Shared.Results;
 using SimpleResults;
+using System;
+using System.Threading;
+using System.Threading.Tasks;
 using TransactionProcessor.Aggregates;
+using TransactionProcessor.BusinessLogic.Common;
 using TransactionProcessor.BusinessLogic.Events;
 using TransactionProcessor.BusinessLogic.Requests;
 using TransactionProcessor.Models.Merchant;
@@ -59,34 +61,27 @@ public async Task<Result> Handle(IDomainEvent domainEvent,
         private async Task<Result> HandleSpecificDomainEvent(CallbackReceivedEnrichedEvent domainEvent,
                                                      CancellationToken cancellationToken)
         {
-            if (domainEvent.TypeString == typeof(CallbackHandler.DataTransferObjects.Deposit).ToString())
-            {
-                // Work out the merchant id from the reference field (second part, split on hyphen)
-                String merchantReference = domainEvent.Reference.Split("-")[1];
-
-                Result<Merchant> result = await this.EstateReportingRepository.GetMerchantFromReference(domainEvent.EstateId, merchantReference, cancellationToken);
-                if (result.IsFailed)
-                    return ResultHelpers.CreateFailure(result);
-
-                // We now need to deserialise the message from the callback
-                CallbackHandler.DataTransferObjects.Deposit callbackMessage = JsonConvert.DeserializeObject<CallbackHandler.DataTransferObjects.Deposit>(domainEvent.CallbackMessage);
-
-                MerchantCommands.MakeMerchantDepositCommand command = new(domainEvent.EstateId,
-                                                                          result.Data.MerchantId,
-                                                                          DataTransferObjects.Requests.Merchant.MerchantDepositSource.Automatic,
-                                                                          new MakeMerchantDepositRequest
-                                                                          {
-                                                                              DepositDateTime = callbackMessage.DateTime,
-                                                                              Reference = callbackMessage.Reference,
-                                                                              Amount = callbackMessage.Amount,
-                                                                          });
-                return await this.Mediator.Send(command, cancellationToken);
-            }
-            return Result.Success();
-        }
+            IAsyncPolicy<Result> retryPolicy = PolicyFactory.CreatePolicy(2, policyTag: "MerchantSettlementDomainEventHandler - MerchantFeeSettledEvent");
+
+            return await retryPolicy.ExecuteAsync(async () => {
+                if (domainEvent.TypeString == typeof(CallbackHandler.DataTransferObjects.Deposit).ToString()) {
+                    // Work out the merchant id from the reference field (second part, split on hyphen)
+                    String merchantReference = domainEvent.Reference.Split("-")[1];
 
+                    Result<Merchant> result = await this.EstateReportingRepository.GetMerchantFromReference(domainEvent.EstateId, merchantReference, cancellationToken);
+                    if (result.IsFailed)
+                        return ResultHelpers.CreateFailure(result);
 
+                    // We now need to deserialise the message from the callback
+                    CallbackHandler.DataTransferObjects.Deposit callbackMessage = JsonConvert.DeserializeObject<CallbackHandler.DataTransferObjects.Deposit>(domainEvent.CallbackMessage);
 
+                    MerchantCommands.MakeMerchantDepositCommand command = new(domainEvent.EstateId, result.Data.MerchantId, DataTransferObjects.Requests.Merchant.MerchantDepositSource.Automatic, new MakeMerchantDepositRequest { DepositDateTime = callbackMessage.DateTime, Reference = callbackMessage.Reference, Amount = callbackMessage.Amount, });
+                    return await this.Mediator.Send(command, cancellationToken);
+                }
+
+                return Result.Success();
+            });
+        }
 
         #endregion
     }