fix(configdb): opt-in config-audit retention purge + after-state size cap (review 2026-10-21 08/G1)

tests/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests/AuditServiceTests.cs

@@ -212,4 +212,20 @@ public class AuditServiceTests : IDisposable
         Assert.Contains("node", audit.AfterStateJson);
         Assert.Single(await _context.Templates.Where(t => t.Name == "CyclicAuditTemplate").ToListAsync());
     }
+
+    /// <summary>An oversized after-state is replaced by a small valid-JSON truncation marker (review 08/G1).</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task LogAsync_OversizedAfterState_IsTruncatedToMarker()
+    {
+        await _auditService.LogAsync("admin", "Update", "Template", "1", "Big",
+            new { Code = new string('x', AuditService.MaxAfterStateChars + 10) });
+        await _context.SaveChangesAsync();
+
+        var json = _context.AuditLogEntries.Single().AfterStateJson!;
+        Assert.True(json.Length < 16 * 1024);
+        using var doc = JsonDocument.Parse(json);
+        Assert.True(doc.RootElement.GetProperty("AuditTruncated").GetBoolean());
+        Assert.True(doc.RootElement.GetProperty("OriginalLength").GetInt32() > AuditService.MaxAfterStateChars);
+    }
 }

tests/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests/Maintenance/ConfigAuditPurgeServiceTests.cs

@@ -0,0 +1,78 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Options;
+using ZB.MOM.WW.ScadaBridge.Commons.Entities.Audit;
+using ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Maintenance;
+
+namespace ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests.Maintenance;
+
+/// <summary>Tests for the opt-in config-audit retention purge (review 2026-10-21 08/G1).</summary>
+public class ConfigAuditPurgeServiceTests : IDisposable
+{
+    private readonly ScadaBridgeDbContext _context = SqliteTestHelper.CreateInMemoryContext();
+
+    public void Dispose()
+    {
+        _context.Database.CloseConnection();
+        _context.Dispose();
+    }
+
+    private ConfigAuditPurgeService Create(ConfigAuditOptions opts)
+    {
+        var services = new ServiceCollection();
+        services.AddSingleton(_context);
+        return new ConfigAuditPurgeService(
+            services.BuildServiceProvider().GetRequiredService<IServiceScopeFactory>(),
+            Options.Create(opts),
+            TimeProvider.System,
+            NullLogger<ConfigAuditPurgeService>.Instance);
+    }
+
+    private async Task SeedAsync(int oldCount, int recentCount)
+    {
+        var now = DateTimeOffset.UtcNow;
+        for (var i = 0; i < oldCount; i++)
+            _context.AuditLogEntries.Add(new AuditLogEntry("u", "Create", "Template", $"o{i}", $"Old{i}") { Timestamp = now.AddDays(-100).AddMinutes(i) });
+        for (var i = 0; i < recentCount; i++)
+            _context.AuditLogEntries.Add(new AuditLogEntry("u", "Create", "Template", $"r{i}", $"New{i}") { Timestamp = now.AddDays(-1) });
+        await _context.SaveChangesAsync();
+    }
+
+    [Fact]
+    public async Task RetentionZero_DeletesNothing()
+    {
+        await SeedAsync(5, 2);
+        var deleted = await Create(new ConfigAuditOptions { RetentionDays = 0 }).PurgeOnceAsync();
+        Assert.Equal(0, deleted);
+        Assert.Equal(7, _context.AuditLogEntries.Count());
+    }
+
+    [Fact]
+    public async Task Retention_DeletesOnlyOlderThanWindow_AcrossBatches()
+    {
+        await SeedAsync(25, 3);
+        var deleted = await Create(new ConfigAuditOptions { RetentionDays = 30, PurgeBatchSize = 10 }).PurgeOnceAsync();
+        Assert.Equal(25, deleted);
+        Assert.Equal(3, _context.AuditLogEntries.Count());
+    }
+
+    [Fact]
+    public async Task Retention_MaxBatchesPerTick_TimeSlicesTheBacklog()
+    {
+        await SeedAsync(25, 0);
+        var svc = Create(new ConfigAuditOptions { RetentionDays = 30, PurgeBatchSize = 10, MaxBatchesPerTick = 2 });
+        Assert.Equal(20, await svc.PurgeOnceAsync());
+        Assert.Equal(5, await svc.PurgeOnceAsync());
+    }
+
+    [Fact]
+    public void Validator_RejectsNegativeRetention_AcceptsZero()
+    {
+        var v = new ConfigAuditOptionsValidator();
+        Assert.True(v.Validate(null, new ConfigAuditOptions { RetentionDays = 0 }).Succeeded);
+        Assert.True(v.Validate(null, new ConfigAuditOptions { RetentionDays = 90 }).Succeeded);
+        Assert.False(v.Validate(null, new ConfigAuditOptions { RetentionDays = -1 }).Succeeded);
+        Assert.False(v.Validate(null, new ConfigAuditOptions { PurgeBatchSize = 0 }).Succeeded);
+    }
+}