ColaFlow/docs/plans/sprint_2_story_1_task_3.md

task_id, story, status, estimated_hours, created_date, start_date, assignee

task_id	story	status	estimated_hours	created_date	start_date	assignee
sprint_2_story_1_task_3	sprint_2_story_1	in_progress	6	2025-11-05	2025-11-05	Backend Team

Task 3: Implement EF Core SaveChangesInterceptor

Story: Story 1 - Audit Log Foundation (Phase 1) Estimated: 6 hours

Description

Implement EF Core SaveChangesInterceptor to automatically capture and log all Create/Update/Delete operations on auditable entities. This is the core mechanism for transparent audit logging.

Acceptance Criteria

• AuditLogInterceptor class created
• Automatic detection of Create/Update/Delete operations
• Audit log entries created for each operation
• TenantId and UserId automatically captured
• Interceptor registered in DI container
• Performance overhead < 5ms per SaveChanges

Implementation Details

Files to Create:

1. Interceptor: colaflow-api/src/ColaFlow.Infrastructure/Interceptors/AuditLogInterceptor.cs

public class AuditLogInterceptor : SaveChangesInterceptor
{
    private readonly ITenantContext _tenantContext;
    private readonly IHttpContextAccessor _httpContextAccessor;

    public AuditLogInterceptor(ITenantContext tenantContext, IHttpContextAccessor httpContextAccessor)
    {
        _tenantContext = tenantContext;
        _httpContextAccessor = httpContextAccessor;
    }

    public override async ValueTask<InterceptionResult<int>> SavingChangesAsync(
        DbContextEventData eventData,
        InterceptionResult<int> result,
        CancellationToken cancellationToken = default)
    {
        if (eventData.Context is null) return result;

        var auditEntries = CreateAuditEntries(eventData.Context);

        // Add audit logs to context
        foreach (var auditEntry in auditEntries)
        {
            eventData.Context.Add(auditEntry);
        }

        return result;
    }

    private List<AuditLog> CreateAuditEntries(DbContext context)
    {
        var auditLogs = new List<AuditLog>();
        var entries = context.ChangeTracker.Entries()
            .Where(e => e.State == EntityState.Added ||
                        e.State == EntityState.Modified ||
                        e.State == EntityState.Deleted)
            .Where(e => IsAuditable(e.Entity))
            .ToList();

        foreach (var entry in entries)
        {
            var auditLog = new AuditLog
            {
                Id = Guid.NewGuid(),
                TenantId = _tenantContext.TenantId,
                EntityType = entry.Entity.GetType().Name,
                EntityId = GetEntityId(entry),
                Action = entry.State switch
                {
                    EntityState.Added => AuditAction.Create,
                    EntityState.Modified => AuditAction.Update,
                    EntityState.Deleted => AuditAction.Delete,
                    _ => throw new InvalidOperationException()
                },
                UserId = GetCurrentUserId(),
                Timestamp = DateTime.UtcNow,
                OldValues = entry.State == EntityState.Modified ? SerializeOldValues(entry) : null,
                NewValues = entry.State != EntityState.Deleted ? SerializeNewValues(entry) : null
            };

            auditLogs.Add(auditLog);
        }

        return auditLogs;
    }

    private bool IsAuditable(object entity)
    {
        // Check if entity implements IAuditable interface or is in auditable types list
        return entity is Project || entity is Epic || entity is Story || entity is WorkTask;
    }

    private Guid GetEntityId(EntityEntry entry)
    {
        var keyValue = entry.Properties.FirstOrDefault(p => p.Metadata.IsPrimaryKey())?.CurrentValue;
        return keyValue is Guid id ? id : Guid.Empty;
    }

    private Guid? GetCurrentUserId()
    {
        var userIdClaim = _httpContextAccessor.HttpContext?.User?.FindFirst(ClaimTypes.NameIdentifier);
        return userIdClaim != null ? Guid.Parse(userIdClaim.Value) : null;
    }

    private string? SerializeOldValues(EntityEntry entry)
    {
        var oldValues = entry.Properties
            .Where(p => p.IsModified)
            .ToDictionary(p => p.Metadata.Name, p => p.OriginalValue);
        return JsonSerializer.Serialize(oldValues);
    }

    private string? SerializeNewValues(EntityEntry entry)
    {
        var newValues = entry.Properties
            .Where(p => !p.Metadata.IsPrimaryKey())
            .ToDictionary(p => p.Metadata.Name, p => p.CurrentValue);
        return JsonSerializer.Serialize(newValues);
    }
}

2. DI Registration: Update colaflow-api/src/ColaFlow.Infrastructure/DependencyInjection.cs

services.AddDbContext<ColaFlowDbContext>((serviceProvider, options) =>
{
    options.UseNpgsql(connectionString);
    options.AddInterceptors(serviceProvider.GetRequiredService<AuditLogInterceptor>());
});

services.AddScoped<AuditLogInterceptor>();

Technical Notes

• Phase 1 captures basic Create/Update/Delete operations
• Changed Fields tracking (old vs new values diff) will be enhanced in Phase 2
• Performance optimization: Consider async operations and batching
• Use System.Text.Json for serialization (faster than Newtonsoft.Json)

Testing

• Unit tests for interceptor logic
• Integration tests for automatic audit logging
• Performance benchmark: < 5ms overhead
• Verify TenantId and UserId are captured correctly

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Created: 2025-11-05 by Backend Agent