Refactor ProcessSettlement to reduce method complexity

[Copilot]

SettlementDomainService.ProcessSettlement had accumulated aggregate loading, settlement state transitions, and transaction fee processing into a single high-branching method. This change breaks that flow into focused helpers while preserving the existing retry and failure behavior.

• Refactor settlement orchestration

  • Moved the main ProcessSettlement body into ProcessSettlementInternal(...) so the public method is limited to policy execution and top-level exception handling.
  • Kept aggregate ID calculation, settlement lookup, merchant lookup, and early exit for missing settlement state unchanged.

• Isolate settlement state preparation

  • Extracted settlement update logic into PrepareSettlementForProcessing(...).
  • Centralized the immediate-settlement path, fee discovery, settlement start-processing transition, and settlement aggregate save handling.

• Isolate fee application to transactions

  • Extracted per-fee transaction processing into ProcessSettlementFees(...).
  • Preserved existing behavior for:
    • transaction aggregate retrieval failures
    • transaction save failures
    • per-transaction exception logging and aggregated failure reporting

Example of the resulting structure:

public async Task<Result<Guid>> ProcessSettlement(ProcessSettlementCommand command,
                                                  CancellationToken cancellationToken) {
    IAsyncPolicy<Result<Guid>> retryPolicy =
        PolicyFactory.CreatePolicy<Result<Guid>>("SettlementDomainService - ProcessSettlement");

    try {
        return await PolicyFactory.ExecuteWithPolicyAsync(
            () => this.ProcessSettlementInternal(command, cancellationToken),
            retryPolicy,
            "SettlementDomainService - ProcessSettlement");
    }
    catch (Exception ex) {
        return Result.Failure(ex.GetExceptionMessages());
    }
}

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• f.feedz.io
  • Triggering command: /usr/bin/dotnet dotnet test /home/REDACTED/work/TransactionProcessor/TransactionProcessor/TransactionProcessor.BusinessLogic.Tests/TransactionProcessor.BusinessLogic.Tests.csproj --filter SettlementDomainService_ProcessSettlement -nologo (dns block)
  • Triggering command: /usr/bin/dotnet dotnet test /home/REDACTED/work/TransactionProcessor/TransactionProcessor/TransactionProcessor.BusinessLogic.Tests/TransactionProcessor.BusinessLogic.Tests.csproj --filter SettlementDomainService_ProcessSettlement -p:RestoreIgnoreFailedSources=true -nologo (dns block)
  • Triggering command: /opt/hostedtoolcache/CodeQL/2.24.2/x64/codeql/csharp/tools/linux64/Semmle.Autobuild.CSharp /opt/hostedtoolcache/CodeQL/2.24.2/x64/codeql/csharp/tools/linux64/Semmle.Autobuild.CSharp (dns block)

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Complexity] Method SettlementDomainService::ProcessSettlement has a cyclomatic complexity of 13 (limit is 8)</issue_title>
<issue_description>Codacy ID: d391070116051a5f8f455be7ba7044f

File: TransactionProcessor.BusinessLogic/Services/SettlementDomainService.cs
Line: 38
Rule: Complexity (Warning)
Commit: 5b8f3e64d731c7b181b225e9d4117fda74faa3ac

Message: Method SettlementDomainService::ProcessSettlement has a cyclomatic complexity of 13 (limit is 8)

**Code Snippet:**
```csharp
        public async Task<Result<Guid>> ProcessSettlement(SettlementCommands.ProcessSettlementCommand command, 
```

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Complexity] Method SettlementDomainService::ProcessSettlement has a cyclomatic complexity of 13 (limit is 8) #1404

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