Refactor EventViewerX EVTX query contract and thin report entry points

[PrzemyslawKlys]

Summary: add reusable EVTX query contract/executor, expose TryBuildFromFile report entry points, centralize EVTX stats aggregates, add tests.\n\nValidation: dotnet test Sources/EventViewerX.Tests/EventViewerX.Tests.csproj -v minimal

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[claude]

Claude finished @PrzemyslawKlys's task —— View job

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Pull Request Review

This PR introduces a well-designed, centralized EVTX query infrastructure with good separation of concerns. The refactoring successfully standardizes how EVTX files are queried across the codebase.

Review Tasks:

• Read repository guidelines (CLAUDE.md)
• Analyze new EVTX query infrastructure
• Review modified report builders
• Assess test coverage and quality
• Check for security and performance concerns
• Provide comprehensive feedback

✅ Strengths

Architecture & Design

• Excellent separation of concerns: The new EvtxQueryExecutor provides a clean contract-based API that isolates query logic from report building
• Consistent error handling: The EvtxQueryFailure enum provides structured error categorization (InvalidArgument, NotFound, AccessDenied, IoError, Exception)
• Standardized patterns: All three security report builders now follow the same pattern with TryBuildFromFile methods

Code Quality

• Comprehensive input validation: EvtxQueryExecutor.TryRead validates all input parameters with clear error messages
• Good use of modern C# patterns: Uses nullable reference types, readonly collections, and proper async/cancellation support
• Consistent naming: Method names and parameter names follow .NET conventions
• Defensive programming: Null checks and validation throughout

Performance Considerations

• Efficient memory usage: Uses IReadOnlyList<T> and defensive copying where appropriate
• Cancellation support: Proper CancellationToken propagation throughout the call chain
• Lazy evaluation: Event processing is done in streaming fashion rather than loading all events into memory

⚠️ Areas for Improvement

Test Coverage Gaps

The test coverage, while good for basic validation, has some gaps:

• Missing positive test cases: No tests verify successful EVTX reading with actual files
• Limited edge case coverage: Missing tests for boundary conditions (e.g., MaxEvents = 0, empty event collections)
• No integration tests: Tests only verify error conditions, not end-to-end functionality

Minor Code Issues

1. Redundant validation logic in SecurityUserLogonsReportBuilder.Add() (lines 108-122):

   // This validation is repeated after the switch statement
   if (string.IsNullOrWhiteSpace(targetUser)) {
       targetUser = Get(data, "TargetUserName") ?? Get(data, "AccountName") ?? string.Empty;
   }

2. Potential performance issue: Multiple dictionary lookups for the same key in security builders could be optimized

3. Magic numbers: Event IDs like 4624, 4625 could be defined as constants for better maintainability

Documentation

• Missing usage examples: The XML documentation could benefit from usage examples
• API contract clarity: Some method signatures could clarify whether empty collections vs null are meaningful

🔒 Security Assessment

✅ No security concerns identified:

• File path validation prevents directory traversal
• No SQL injection vectors (file-based queries)
• Proper exception handling prevents information leakage
• No hardcoded credentials or sensitive data

🚀 Performance Assessment

✅ Good performance characteristics:

• Streaming event processing minimizes memory usage
• Efficient dictionary-based aggregations
• Proper cancellation token usage for responsive cancellation

📋 Recommendations

High Priority

1. Add positive test cases: Include tests with mock/sample EVTX data to verify successful scenarios
2. Add integration tests: Test the full pipeline from file to report generation

Medium Priority

3. Extract constants: Define event ID constants (EventIds.SuccessfulLogon = 4624, etc.)
4. Optimize redundant lookups: Cache dictionary lookups in security report builders
5. Add boundary tests: Test edge cases like MaxEvents = 0, very large files, etc.

Low Priority

6. Enhance documentation: Add usage examples to XML docs
7. Consider builder pattern: For complex EvtxQueryRequest construction

📊 Overall Assessment

This is a high-quality refactoring that significantly improves the codebase:

• ✅ Maintainability: Centralized query logic reduces duplication
• ✅ Testability: Clean separation makes unit testing easier
• ✅ Extensibility: New report types can easily reuse the query infrastructure
• ✅ Reliability: Comprehensive error handling and validation

The code follows .NET best practices and demonstrates solid software engineering principles. The minor issues identified are optimization opportunities rather than blocking concerns.

Recommendation: ✅ Approve - This PR successfully achieves its goals and improves the codebase architecture. The suggested improvements can be addressed in future iterations.