lmxopcua/tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/OpcUa/OpcUaPublishActorRebuildTests.cs

using System.Collections.Concurrent;
using System.Text.Json;
using Akka.Actor;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging.Abstractions;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;
using ZB.MOM.WW.OtOpcUa.Commons.Types;
using ZB.MOM.WW.OtOpcUa.Configuration;
using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
using ZB.MOM.WW.OtOpcUa.Configuration.Enums;
using ZB.MOM.WW.OtOpcUa.OpcUaServer;
using ZB.MOM.WW.OtOpcUa.Runtime.OpcUa;
using ZB.MOM.WW.OtOpcUa.Runtime.Tests.Harness;

namespace ZB.MOM.WW.OtOpcUa.Runtime.Tests.OpcUa;

public sealed class OpcUaPublishActorRebuildTests : RuntimeActorTestBase
{
    /// <summary>R2-07 — RebuildAddressSpace with dbFactory loads the artifact, composes, and applies. Two
    /// brand-new equipment are a PureAdd: the Materialise passes create the equipment folders WITHOUT a full
    /// rebuild (existing subscriptions survive), and the added parents are announced via NodeAdded. (Was:
    /// pre-R2-07 this asserted one full rebuild.)</summary>
    [Fact]
    public void RebuildAddressSpace_with_dbFactory_loads_artifact_composes_and_applies()
    {
        var db = NewInMemoryDbFactory();
        var sink = new RecordingSink();
        var applier = new AddressSpaceApplier(sink, NullLogger<AddressSpaceApplier>.Instance);

        SeedDeployment(db, equipmentIds: new[] { "eq-1", "eq-2" }, driverIds: new[] { "drv-1" });

        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(
            sink: sink,
            dbFactory: db,
            applier: applier));

        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId()));

        AwaitAssert(() =>
        {
            // PureAdd: the equipment folders are materialised, no full rebuild, and the added parent
            // (the shared line-1) is announced exactly once.
            sink.Calls.ShouldContain("EF:eq-1");
            sink.Calls.ShouldContain("EF:eq-2");
            sink.Calls.ShouldContain("NA:line-1");
        }, duration: PresenceBudget);
        sink.RebuildCalls.ShouldBe(0);
    }

    /// <summary>Tests that rebuild with no artifact is idempotent no-op.</summary>
    [Fact]
    public void Rebuild_with_no_artifact_is_idempotent_no_op()
    {
        var db = NewInMemoryDbFactory();
        var sink = new RecordingSink();
        var applier = new AddressSpaceApplier(sink, NullLogger<AddressSpaceApplier>.Instance);

        // No deployment seeded — LoadLatestArtifact returns empty blob.
        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(
            sink: sink,
            dbFactory: db,
            applier: applier));

        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId()));
        Thread.Sleep(200);

        sink.RebuildCalls.ShouldBe(0);
    }

    /// <summary>Tests that a second rebuild with the same artifact is an empty-plan no-op. The first deploy
    /// (one new equipment) is a PureAdd — no full rebuild, but it DOES materialise the folder; the second
    /// deploy of the identical composition diffs to an empty plan and the actor short-circuits, adding no
    /// further sink calls.</summary>
    [Fact]
    public void Second_rebuild_with_same_artifact_is_empty_plan_no_op()
    {
        var db = NewInMemoryDbFactory();
        var sink = new RecordingSink();
        var applier = new AddressSpaceApplier(sink, NullLogger<AddressSpaceApplier>.Instance);
        SeedDeployment(db, equipmentIds: new[] { "eq-1" }, driverIds: Array.Empty<string>());

        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(
            sink: sink, dbFactory: db, applier: applier));

        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId()));
        AwaitAssert(() => sink.Calls.ShouldContain("EF:eq-1"), duration: PresenceBudget);
        sink.RebuildCalls.ShouldBe(0);          // PureAdd — no full rebuild
        var callsAfterFirst = sink.Calls.Count;

        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId()));
        Thread.Sleep(200);
        // Same composition ⇒ plan IsEmpty ⇒ applier + materialise passes not run again.
        sink.Calls.Count.ShouldBe(callsAfterFirst);
        sink.RebuildCalls.ShouldBe(0);
    }

    /// <summary>Tests that rebuild without dbFactory falls back to raw sink rebuild.</summary>
    [Fact]
    public void Rebuild_without_dbFactory_falls_back_to_raw_sink_rebuild()
    {
        // Pre-#109 behavior: no dbFactory wired ⇒ RebuildAddressSpace calls _sink.RebuildAddressSpace
        // directly. The dev/Mac path before the full integration is bound.
        var sink = new RecordingSink();
        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(sink: sink));

        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId()));

        AwaitAssert(() => sink.RebuildCalls.ShouldBe(1), duration: PresenceBudget);
    }

    /// <summary>
    ///     mesh-phase4 — the wipe-prevention test. A driver-only node has a NULL dbFactory (ConfigDb is
    ///     admin-only now) but a WIRED applier. A RebuildAddressSpace carrying the artifact bytes in hand
    ///     (from the fetch/cache) must drive the REAL diff-and-apply (the equipment folder is materialised)
    ///     and must NOT take the raw-sink <c>RebuildAddressSpace()</c> fallback, which wipes the address
    ///     space without re-materialising. Before the guard split, a null dbFactory routed straight to that
    ///     fallback and the applier never ran — a FetchAndCache node deployed green but served EMPTY.
    /// </summary>
    [Fact]
    public void Rebuild_with_null_factory_but_wired_applier_diff_applies_from_in_hand_bytes()
    {
        var sink = new RecordingSink();
        var applier = new AddressSpaceApplier(sink, NullLogger<AddressSpaceApplier>.Instance);
        var artifact = BuildNamedEquipmentArtifact(("eq-1", "Pump-1"));

        // Driver-only node: null dbFactory, wired applier.
        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(
            sink: sink, dbFactory: null, applier: applier));

        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId(), Artifact: artifact));

        // The in-hand bytes drove the real diff-and-apply — the equipment folder was materialised…
        AwaitAssert(() => sink.Calls.ShouldContain("EF:eq-1"), duration: PresenceBudget);
        // …and the address-space-wiping raw-sink fallback was NOT taken.
        sink.RebuildCalls.ShouldBe(0);
    }

    /// <summary>
    ///     mesh-phase4 / #485 negative — a driver-only node (null dbFactory, wired applier) that gets a
    ///     RebuildAddressSpace with NO artifact bytes has no way to obtain a config (there is no ConfigDb to
    ///     read). The artifact source yields <c>Array.Empty&lt;byte&gt;()</c>, which the #485 zero-length
    ///     guard treats as "no answer": the rebuild is abandoned WITHOUT touching the served address space —
    ///     the applier never runs and the raw-sink wipe fallback is never taken. Last-known-good stands.
    /// </summary>
    [Fact]
    public void Rebuild_with_null_factory_and_no_artifact_abandons_without_wiping()
    {
        var sink = new RecordingSink();
        var applier = new AddressSpaceApplier(sink, NullLogger<AddressSpaceApplier>.Instance);

        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(
            sink: sink, dbFactory: null, applier: applier));

        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId()));
        Thread.Sleep(200);

        sink.RebuildCalls.ShouldBe(0);   // the raw-sink wipe fallback was NOT taken
        sink.Calls.ShouldBeEmpty();      // the applier's diff-and-apply never ran
    }

    /// <summary>
    ///     mesh-phase4 regression (dev seam) — a node with NO applier at all still falls back to the raw-sink
    ///     rebuild, and now the fallback is keyed on the applier ALONE: even WITH a dbFactory wired, a null
    ///     applier takes the F10b/dev fallback. Proves the guard split did not change the no-applier seam.
    /// </summary>
    [Fact]
    public void Rebuild_with_null_applier_falls_back_to_raw_sink_even_with_dbFactory()
    {
        var db = NewInMemoryDbFactory();
        var sink = new RecordingSink();

        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(
            sink: sink, dbFactory: db, applier: null));

        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId()));

        AwaitAssert(() => sink.RebuildCalls.ShouldBe(1), duration: PresenceBudget);
    }

    /// <summary>
    ///     mesh-phase4 regression (Direct mode) — a DB-backed node (dbFactory wired, applier wired) with no
    ///     in-hand bytes but a DeploymentId still loads the artifact from the ConfigDb via <c>LoadArtifact</c>
    ///     and drives the applier. The guard split must leave the Direct path byte-identical.
    /// </summary>
    [Fact]
    public void Rebuild_direct_mode_with_dbFactory_and_deploymentId_still_loads_and_applies()
    {
        var db = NewInMemoryDbFactory();
        var sink = new RecordingSink();
        var applier = new AddressSpaceApplier(sink, NullLogger<AddressSpaceApplier>.Instance);
        var dep = SeedNamedEquipmentDeployment(db, ("eq-1", "Pump-1"));

        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(
            sink: sink, dbFactory: db, applier: applier));

        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId(), new DeploymentId(dep)));

        AwaitAssert(() => sink.Calls.ShouldContain("EF:eq-1"), duration: PresenceBudget);
        sink.RebuildCalls.ShouldBe(0);
    }

    /// <summary>
    ///     Wiring proof for per-ClusterId scoping: a multi-cluster artifact must materialise ONLY the local
    ///     node's cluster slice. MAIN and SITE-A each own a raw folder → Modbus driver → device → tag; the
    ///     scoped rebuild on the SITE-A node must surface SITE-A's raw variable
    ///     (<c>SA/Modbus/dev-sa/S1</c>) and NOT MAIN's (<c>Main/Modbus/dev-main/M1</c>), and the mirror
    ///     must hold on the MAIN node. Without <c>DeploymentArtifact.ResolveClusterScope</c>, the unscoped
    ///     parse materialises BOTH on every node.
    ///     <para>Revived from the <c>EquipmentTagsDarkBatch4</c> skip. It was parked on equipment-tag plans
    ///     lighting up "at Batch 4"; Batch 4 retired them instead, so the subject moved to the raw subtree.
    ///     The behaviour under test — cluster scoping — never went dark, and matters more since the mesh
    ///     split (a site node must not materialise another cluster's tags).</para>
    /// </summary>
    [Fact]
    public void Rebuild_materialises_only_the_nodes_cluster()
    {
        // --- SITE-A node: only the SITE-A tag's variable, never MAIN's. ---
        var dbA = NewInMemoryDbFactory();
        var sinkA = new RecordingSink();
        var applierA = new AddressSpaceApplier(sinkA, NullLogger<AddressSpaceApplier>.Instance);
        SeedMultiClusterDeployment(dbA);

        var siteActor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(
            sink: sinkA,
            dbFactory: dbA,
            applier: applierA,
            localNode: NodeId.Parse("site-a-1:4053")));

        siteActor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId()));

        // PureAdd ⇒ no full rebuild; the materialise passes still run the cluster slice.
        AwaitAssert(() => sinkA.Calls.ShouldContain("EV:SA/Modbus/dev-sa/S1"), duration: PresenceBudget);
        sinkA.RebuildCalls.ShouldBe(0);
        // MAIN's raw tag must NOT leak onto the SITE-A node.
        sinkA.Calls.ShouldNotContain("EV:Main/Modbus/dev-main/M1");

        // --- MAIN node: the mirror — only MAIN's tag's variable, never SITE-A's. ---
        var dbM = NewInMemoryDbFactory();
        var sinkM = new RecordingSink();
        var applierM = new AddressSpaceApplier(sinkM, NullLogger<AddressSpaceApplier>.Instance);
        SeedMultiClusterDeployment(dbM);

        var mainActor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(
            sink: sinkM,
            dbFactory: dbM,
            applier: applierM,
            localNode: NodeId.Parse("central-1:4053")));

        mainActor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId()));

        AwaitAssert(() => sinkM.Calls.ShouldContain("EV:Main/Modbus/dev-main/M1"), duration: PresenceBudget);
        sinkM.RebuildCalls.ShouldBe(0);
        sinkM.Calls.ShouldNotContain("EV:SA/Modbus/dev-sa/S1");
    }

    /// <summary>
    ///     Seal a 2-cluster deployment (MAIN + SITE-A) whose artifact mirrors the v3 multi-cluster shape:
    ///     a <c>Clusters</c> + <c>Nodes</c> map, and per cluster a raw folder → Modbus driver → device →
    ///     tag chain plus its UNS area/line/equipment. Used by
    ///     <see cref="Rebuild_materialises_only_the_nodes_cluster"/>.
    /// </summary>
    private static void SeedMultiClusterDeployment(IDbContextFactory<OtOpcUaConfigDbContext> dbFactory)
    {
        var artifact = JsonSerializer.SerializeToUtf8Bytes(new
        {
            Clusters = new[] { new { ClusterId = "MAIN" }, new { ClusterId = "SITE-A" } },
            Nodes = new[]
            {
                new { NodeId = "central-1:4053", ClusterId = "MAIN" },
                new { NodeId = "site-a-1:4053", ClusterId = "SITE-A" },
            },
            UnsAreas = new[]
            {
                new { UnsAreaId = "area-main", ClusterId = "MAIN",   Name = "main-area" },
                new { UnsAreaId = "area-sa",   ClusterId = "SITE-A", Name = "sa-area" },
            },
            UnsLines = new[]
            {
                new { UnsLineId = "line-main", UnsAreaId = "area-main", Name = "main-line" },
                new { UnsLineId = "line-sa",   UnsAreaId = "area-sa",   Name = "sa-line" },
            },
            Equipment = new[]
            {
                new { EquipmentId = "eq-main", UnsLineId = "line-main", Name = "eq-main", MachineCode = "EQ-MAIN" },
                new { EquipmentId = "eq-sa",   UnsLineId = "line-sa",   Name = "eq-sa",   MachineCode = "EQ-SA" },
            },
            RawFolders = new[]
            {
                new { RawFolderId = "rf-main", ParentRawFolderId = (string?)null, Name = "Main", ClusterId = "MAIN" },
                new { RawFolderId = "rf-sa",   ParentRawFolderId = (string?)null, Name = "SA",   ClusterId = "SITE-A" },
            },
            DriverInstances = new[]
            {
                new { DriverInstanceId = "main-modbus", DriverType = "Modbus", DriverConfig = "{}", Name = "Modbus", RawFolderId = "rf-main", ClusterId = "MAIN" },
                new { DriverInstanceId = "sa-modbus",   DriverType = "Modbus", DriverConfig = "{}", Name = "Modbus", RawFolderId = "rf-sa",   ClusterId = "SITE-A" },
            },
            Devices = new[]
            {
                new { DeviceId = "dev-main", DriverInstanceId = "main-modbus", Name = "dev-main", DeviceConfig = "{}" },
                new { DeviceId = "dev-sa",   DriverInstanceId = "sa-modbus",   Name = "dev-sa",   DeviceConfig = "{}" },
            },
            TagGroups = Array.Empty<object>(),
            Tags = new[]
            {
                new { TagId = "t-main", DeviceId = "dev-main", TagGroupId = (string?)null, Name = "M1", DataType = "Boolean", AccessLevel = 0, TagConfig = "{}" },
                new { TagId = "t-sa",   DeviceId = "dev-sa",   TagGroupId = (string?)null, Name = "S1", DataType = "Boolean", AccessLevel = 0, TagConfig = "{}" },
            },
            UnsTagReferences = Array.Empty<object>(),
            ScriptedAlarms = Array.Empty<object>(),
        });

        using var ctx = dbFactory.CreateDbContext();
        ctx.Deployments.Add(new Deployment
        {
            DeploymentId = Guid.NewGuid(),
            RevisionHash = new string('b', 64),
            Status = DeploymentStatus.Sealed,
            CreatedBy = "test",
            SealedAtUtc = DateTime.UtcNow,
            ArtifactBlob = artifact,
        });
        ctx.SaveChanges();
    }

    /// <summary>R2-07 T4b — a PureAdd deploy (here a single new equipment) does NOT rebuild, and the
    /// NodeAdded announcement is raised AFTER the Materialise passes have created the node (so the node
    /// exists when a re-browsing client arrives). Proven via the ordered <c>Calls</c> queue: the "NA:"
    /// announcement index is strictly after the "EF:" materialise index.</summary>
    [Fact]
    public void Pure_add_announces_node_after_materialising_and_never_rebuilds()
    {
        var db = NewInMemoryDbFactory();
        var sink = new RecordingSink();
        var applier = new AddressSpaceApplier(sink, NullLogger<AddressSpaceApplier>.Instance);
        SeedDeployment(db, equipmentIds: new[] { "eq-1" }, driverIds: Array.Empty<string>());

        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(sink: sink, dbFactory: db, applier: applier));
        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId()));

        AwaitAssert(() => sink.Calls.ShouldContain("NA:line-1"), duration: PresenceBudget);
        sink.RebuildCalls.ShouldBe(0);

        var calls = sink.Calls.ToList();
        var materialiseIdx = calls.IndexOf("EF:eq-1");
        var announceIdx = calls.IndexOf("NA:line-1");
        materialiseIdx.ShouldBeGreaterThanOrEqualTo(0);
        announceIdx.ShouldBeGreaterThan(materialiseIdx); // announced AFTER the node was materialised
    }

    /// <summary>R2-07 T4b — when a deploy forces a full rebuild (here a renamed equipment ⇒ ChangedEquipment
    /// ⇒ Rebuild) even though it ALSO adds an equipment, the post-materialise announce hook is SKIPPED (the
    /// rebuild made subscriptions moot). Proven by capturing the NodeAdded count after the first pure-add
    /// deploy and asserting the rebuild-forcing second deploy adds none.</summary>
    [Fact]
    public void Rebuild_kind_deploy_skips_the_node_added_announce()
    {
        var db = NewInMemoryDbFactory();
        var sink = new RecordingSink();
        var applier = new AddressSpaceApplier(sink, NullLogger<AddressSpaceApplier>.Instance);

        var dep1 = SeedNamedEquipmentDeployment(db, ("eq-1", "Pump-1"));
        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(sink: sink, dbFactory: db, applier: applier));

        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId(), new DeploymentId(dep1)));
        AwaitAssert(() => sink.Calls.Count(c => c.StartsWith("NA:")).ShouldBe(1), duration: PresenceBudget);
        sink.RebuildCalls.ShouldBe(0);
        var naAfterFirst = sink.Calls.Count(c => c.StartsWith("NA:"));

        // Second deploy: eq-1 RENAMED (ChangedEquipment ⇒ Rebuild) AND a new eq-2 (an add). The rebuild
        // fires, so the announce hook is skipped despite eq-2 being added.
        var dep2 = SeedNamedEquipmentDeployment(db, ("eq-1", "Pump-1-RENAMED"), ("eq-2", "Pump-2"));
        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId(), new DeploymentId(dep2)));

        AwaitAssert(() => sink.RebuildCalls.ShouldBe(1), duration: PresenceBudget);
        // No new NodeAdded announcement was raised for the rebuild-kind deploy.
        sink.Calls.Count(c => c.StartsWith("NA:")).ShouldBe(naAfterFirst);
    }

    /// <summary>
    ///     Issue #485 — a transient ConfigDb error while loading a deploy's artifact must NOT empty the
    ///     served address space. The loader's own log already claims "rebuild becomes no-op", but an
    ///     unreadable artifact used to become an EMPTY composition, which the planner then diffed against
    ///     the live one as a PureRemove and tore every node down. A blip on the way to the database is not
    ///     evidence that the operator deployed an empty configuration: the last-known-good address space
    ///     must stand until a real artifact says otherwise.
    /// </summary>
    [Fact]
    public void Rebuild_keeps_the_last_known_good_address_space_when_the_artifact_load_fails()
    {
        var db = new FlakyDbFactory(NewInMemoryDbFactory());
        var sink = new RecordingSink();
        var applier = new AddressSpaceApplier(sink, NullLogger<AddressSpaceApplier>.Instance);
        var dep1 = SeedNamedEquipmentDeployment(db, ("eq-1", "Pump-1"), ("eq-2", "Pump-2"));

        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(sink: sink, dbFactory: db, applier: applier));
        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId(), new DeploymentId(dep1)));
        AwaitAssert(() => sink.Calls.ShouldContain("EF:eq-2"), duration: PresenceBudget);
        var callsAfterFirst = sink.Calls.Count;

        // The next deploy arrives while the ConfigDb is briefly unreachable.
        db.Fail = true;
        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId(), new DeploymentId(Guid.NewGuid())));
        Thread.Sleep(200);

        sink.Calls.ShouldNotContain(c => c.StartsWith("RE:"));   // no equipment subtree torn down
        sink.RebuildCalls.ShouldBe(0);
        sink.Calls.Count.ShouldBe(callsAfterFirst);              // the failed load touched nothing at all

        // …and the actor still remembers WHAT is applied: once the database is back, re-applying the same
        // composition diffs to an empty plan. A clobbered _lastApplied would re-materialise everything.
        db.Fail = false;
        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId(), new DeploymentId(dep1)));
        Thread.Sleep(200);
        sink.Calls.Count.ShouldBe(callsAfterFirst);
    }

    /// <summary>
    ///     Positive control for <see cref="Rebuild_keeps_the_last_known_good_address_space_when_the_artifact_load_fails"/>:
    ///     the guard suppresses teardown ONLY when the artifact could not be read. A real deploy that
    ///     genuinely drops an equipment still tears its subtree down, so the removal path is not simply dead.
    /// </summary>
    [Fact]
    public void Rebuild_still_removes_equipment_a_readable_artifact_genuinely_dropped()
    {
        var db = new FlakyDbFactory(NewInMemoryDbFactory());
        var sink = new RecordingSink();
        var applier = new AddressSpaceApplier(sink, NullLogger<AddressSpaceApplier>.Instance);
        var dep1 = SeedNamedEquipmentDeployment(db, ("eq-1", "Pump-1"), ("eq-2", "Pump-2"));

        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(sink: sink, dbFactory: db, applier: applier));
        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId(), new DeploymentId(dep1)));
        AwaitAssert(() => sink.Calls.ShouldContain("EF:eq-2"), duration: PresenceBudget);

        // eq-2 really is gone from the next artifact — that IS a configuration change, so it must apply.
        var dep2 = SeedNamedEquipmentDeployment(db, ("eq-1", "Pump-1"));
        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId(), new DeploymentId(dep2)));

        AwaitAssert(() => sink.Calls.ShouldContain("RE:eq-2"), duration: PresenceBudget);
    }

    /// <summary>An <see cref="IDbContextFactory{TContext}"/> whose <c>CreateDbContext</c> can be made to
    /// throw the way a real transient ConfigDb outage does, so the artifact load fails exactly where issue
    /// #485 observed it failing.</summary>
    private sealed class FlakyDbFactory(IDbContextFactory<OtOpcUaConfigDbContext> inner)
        : IDbContextFactory<OtOpcUaConfigDbContext>
    {
        /// <summary>Gets or sets a value indicating whether the next context creation should throw.</summary>
        public bool Fail { get; set; }

        /// <summary>Creates a context, or throws when <see cref="Fail"/> is set.</summary>
        /// <returns>A new context.</returns>
        public OtOpcUaConfigDbContext CreateDbContext() => Fail
            ? throw new InvalidOperationException(
                "An error occurred using the connection to database 'OtOpcUa' on server 'sql,1433'.")
            : inner.CreateDbContext();
    }

    /// <summary>Build the artifact bytes for the given (equipmentId, name) rows under a shared line —
    /// WITHOUT sealing them into a deployment. This is what a driver-only / FetchAndCache node carries
    /// in <c>RebuildAddressSpace.Artifact</c> (no ConfigDb read), so tests can drive the in-hand-bytes
    /// path directly.</summary>
    private static byte[] BuildNamedEquipmentArtifact(params (string Id, string Name)[] equipment) =>
        JsonSerializer.SerializeToUtf8Bytes(new
        {
            UnsAreas = new[] { new { UnsAreaId = "area-1", ClusterId = "c1", Name = "Area" } },
            UnsLines = new[] { new { UnsLineId = "line-1", UnsAreaId = "area-1", Name = "Line" } },
            Equipment = equipment.Select(e => new
            {
                EquipmentId = e.Id,
                DriverInstanceId = (string?)null,
                UnsLineId = "line-1",
                Name = e.Name,
                MachineCode = e.Id.ToUpperInvariant(),
            }).ToArray(),
            DriverInstances = Array.Empty<object>(),
            Namespaces = Array.Empty<object>(),
            Tags = Array.Empty<object>(),
            ScriptedAlarms = Array.Empty<object>(),
        });

    /// <summary>Seal a deployment carrying the given (equipmentId, name) rows under a shared line, returning
    /// the new DeploymentId so a test can target THAT artifact. Renaming an equipment across two such
    /// deployments produces a ChangedEquipment delta (Rebuild), while adding a row is a PureAdd.</summary>
    private static Guid SeedNamedEquipmentDeployment(
        IDbContextFactory<OtOpcUaConfigDbContext> dbFactory,
        params (string Id, string Name)[] equipment)
    {
        var artifact = BuildNamedEquipmentArtifact(equipment);

        var id = Guid.NewGuid();
        using var ctx = dbFactory.CreateDbContext();
        ctx.Deployments.Add(new Deployment
        {
            DeploymentId = id,
            RevisionHash = new string('d', 64),
            Status = DeploymentStatus.Sealed,
            CreatedBy = "test",
            SealedAtUtc = DateTime.UtcNow,
            ArtifactBlob = artifact,
        });
        ctx.SaveChanges();
        return id;
    }

    private static void SeedDeployment(
        IDbContextFactory<OtOpcUaConfigDbContext> dbFactory,
        string[] equipmentIds,
        string[] driverIds)
    {
        var artifact = JsonSerializer.SerializeToUtf8Bytes(new
        {
            Equipment = equipmentIds.Select(id => new
            {
                EquipmentId = id,
                MachineCode = id.ToUpperInvariant(),
                UnsLineId = "line-1",
                Name = id,
            }).ToArray(),
            DriverInstances = driverIds.Select(id => new
            {
                DriverInstanceId = id,
                DriverType = "Modbus",
                Enabled = true,
                DriverConfig = "{}",
            }).ToArray(),
            ScriptedAlarms = Array.Empty<object>(),
        });

        using var ctx = dbFactory.CreateDbContext();
        ctx.Deployments.Add(new Deployment
        {
            DeploymentId = Guid.NewGuid(),
            RevisionHash = new string('a', 64),
            Status = DeploymentStatus.Sealed,
            CreatedBy = "test",
            SealedAtUtc = DateTime.UtcNow,
            ArtifactBlob = artifact,
        });
        ctx.SaveChanges();
    }

    /// <summary>OpcUaServer-001 — a deploy whose ONLY change is a UNS Area rename (the area Name differs;
    /// no equipment/driver/alarm/tag delta) must NOT short-circuit at the actor's IsEmpty gate: the second
    /// RebuildAddressSpace drives the in-place folder display-name refresh (a surgical
    /// <c>UpdateFolderDisplayName</c> call) without a full rebuild. Proves the planner→applier→sink chain
    /// reaches the apply path through the actor for a rename-only redeploy.</summary>
    [Fact]
    public void Rebuild_with_area_rename_only_updates_folder_in_place_without_rebuild()
    {
        var db = NewInMemoryDbFactory();
        var sink = new RecordingSink();
        var applier = new AddressSpaceApplier(sink, NullLogger<AddressSpaceApplier>.Instance);
        var dep1 = SeedAreaDeployment(db, areaName: "Plant North");

        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(
            sink: sink, dbFactory: db, applier: applier));

        // First deploy: the area folder is materialised with the OLD name. R2-07 — this is now a PureAdd
        // (area + line + equipment all added), so NO full rebuild; the folder is materialised directly.
        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId(), new DeploymentId(dep1)));
        AwaitAssert(() => sink.Calls.ShouldContain("EF:area-1"), duration: PresenceBudget);
        sink.RebuildCalls.ShouldBe(0);

        // Second deploy: ONLY the area Name changed — a rename. The actor must reach the apply path and
        // drive a surgical in-place folder rename (NOT a rebuild, NOT a no-op).
        var dep2 = SeedAreaDeployment(db, areaName: "Plant South");
        actor.Tell(new OpcUaPublishActor.RebuildAddressSpace(CorrelationId.NewId(), new DeploymentId(dep2)));

        AwaitAssert(() =>
        {
            sink.FolderRenameCalls.ShouldContain(("area-1", "Plant South"));
        }, duration: PresenceBudget);
        sink.RebuildCalls.ShouldBe(0); // the rename did NOT force a full rebuild
    }

    /// <summary>Seal a deployment whose area carries <paramref name="areaName"/>, with a line + one
    /// equipment under it. The equipment makes the FIRST deploy a structural rebuild (so the area folder is
    /// materialised); a later redeploy that changes ONLY the area Name is then a pure rename. Returns the
    /// new DeploymentId so the test can target THAT artifact (apply-time, not-yet-sealed semantics).</summary>
    private static Guid SeedAreaDeployment(IDbContextFactory<OtOpcUaConfigDbContext> dbFactory, string areaName)
    {
        var artifact = JsonSerializer.SerializeToUtf8Bytes(new
        {
            UnsAreas = new[] { new { UnsAreaId = "area-1", ClusterId = "c1", Name = areaName } },
            UnsLines = new[] { new { UnsLineId = "line-1", UnsAreaId = "area-1", Name = "Cell A" } },
            Equipment = new[] { new { EquipmentId = "eq-1", DriverInstanceId = (string?)null, UnsLineId = "line-1", Name = "Pump-1", MachineCode = "EQ-1" } },
            DriverInstances = Array.Empty<object>(),
            Namespaces = Array.Empty<object>(),
            Tags = Array.Empty<object>(),
            ScriptedAlarms = Array.Empty<object>(),
        });

        var id = Guid.NewGuid();
        using var ctx = dbFactory.CreateDbContext();
        ctx.Deployments.Add(new Deployment
        {
            DeploymentId = id,
            RevisionHash = new string('c', 64),
            Status = DeploymentStatus.Sealed,
            CreatedBy = "test",
            SealedAtUtc = DateTime.UtcNow,
            ArtifactBlob = artifact,
        });
        ctx.SaveChanges();
        return id;
    }

    private sealed class RecordingSink : IOpcUaAddressSpaceSink, ISurgicalAddressSpaceSink
    {
        /// <summary>Gets the list of recorded sink calls.</summary>
        public ConcurrentQueue<string> Calls { get; } = new();
        /// <summary>Gets or sets the count of rebuild address space calls.</summary>
        public int RebuildCalls;
        /// <summary>Gets the queue of surgical in-place folder display-name update calls (OpcUaServer-001).</summary>
        public ConcurrentQueue<(string FolderNodeId, string DisplayName)> FolderRenameQueue { get; } = new();
        /// <summary>Gets the list of recorded surgical folder display-name update calls.</summary>
        public List<(string FolderNodeId, string DisplayName)> FolderRenameCalls => FolderRenameQueue.ToList();
        /// <summary>Records a value write call.</summary>
        /// <param name="nodeId">The OPC UA node ID.</param>
        /// <param name="value">The value to write.</param>
        /// <param name="quality">The OPC UA quality code.</param>
        /// <param name="ts">The timestamp of the write.</param>
        public void WriteValue(string nodeId, object? value, OpcUaQuality quality, DateTime ts, AddressSpaceRealm realm = AddressSpaceRealm.Uns)
            => Calls.Enqueue($"WV:{nodeId}");
        /// <summary>Records an alarm condition write call.</summary>
        /// <param name="alarmNodeId">The alarm node ID.</param>
        /// <param name="state">The full condition state snapshot.</param>
        /// <param name="ts">The timestamp of the state change.</param>
        public void WriteAlarmQuality(string alarmNodeId, OpcUaQuality quality, DateTime sourceTimestampUtc, AddressSpaceRealm realm) { }
        public void WriteAlarmCondition(string alarmNodeId, AlarmConditionSnapshot state, DateTime ts, AddressSpaceRealm realm = AddressSpaceRealm.Uns)
            => Calls.Enqueue($"WA:{alarmNodeId}");
        /// <summary>Records a materialise-alarm-condition call.</summary>
        /// <param name="alarmNodeId">The alarm node ID (== ScriptedAlarmId).</param>
        /// <param name="equipmentNodeId">The equipment folder node ID.</param>
        /// <param name="displayName">The condition display name.</param>
        /// <param name="alarmType">The domain alarm type.</param>
        /// <param name="severity">The domain severity.</param>
        public void MaterialiseAlarmCondition(string alarmNodeId, string equipmentNodeId, string displayName, string alarmType, int severity, AddressSpaceRealm realm, bool isNative = false)
            => Calls.Enqueue($"MA:{alarmNodeId}");
        /// <summary>Records a folder ensure call.</summary>
        /// <param name="folderNodeId">The folder node ID.</param>
        /// <param name="parentNodeId">The parent node ID, or null if this is a root folder.</param>
        /// <param name="displayName">The display name of the folder.</param>
        public void EnsureFolder(string folderNodeId, string? parentNodeId, string displayName, AddressSpaceRealm realm = AddressSpaceRealm.Uns)
            => Calls.Enqueue($"EF:{folderNodeId}");
        /// <summary>Records a variable ensure call.</summary>
        /// <param name="variableNodeId">The variable node ID.</param>
        /// <param name="parentFolderNodeId">The parent folder node ID, or null if this is a root variable.</param>
        /// <param name="displayName">The display name of the variable.</param>
        /// <param name="dataType">The OPC UA built-in type name.</param>
        /// <param name="writable">Whether the node is created read/write.</param>
        /// <param name="historianTagname">The resolved historian tagname (null ⇒ not historized).</param>
        public void EnsureVariable(string variableNodeId, string? parentFolderNodeId, string displayName, string dataType, bool writable, AddressSpaceRealm realm, string? historianTagname = null, bool isArray = false, uint? arrayLength = null)
            => Calls.Enqueue($"EV:{variableNodeId}");
        /// <summary>Records a rebuild address space call.</summary>
        public void RebuildAddressSpace() => Interlocked.Increment(ref RebuildCalls);
        /// <summary>Records a NodeAdded model-change announcement.</summary>
        /// <param name="affectedNodeId">The node under which discovered nodes were added.</param>
        public void RaiseNodesAddedModelChange(string affectedNodeId, AddressSpaceRealm realm = AddressSpaceRealm.Uns) => Calls.Enqueue($"NA:{affectedNodeId}");
        public void WireAlarmNotifiers(string alarmNodeId, AddressSpaceRealm alarmRealm, IReadOnlyList<string> notifierFolderNodeIds, AddressSpaceRealm notifierFolderRealm) { }
        public void AddReference(string sourceNodeId, AddressSpaceRealm sourceRealm, string targetNodeId, AddressSpaceRealm targetRealm, string referenceType = "Organizes") { }
        /// <summary>Records a surgical in-place tag-attribute update (always succeeds in this recording sink).</summary>
        public bool UpdateTagAttributes(string variableNodeId, bool writable, string? historianTagname, string dataType, bool isArray, uint? arrayLength, AddressSpaceRealm realm = AddressSpaceRealm.Uns)
        {
            Calls.Enqueue($"UT:{variableNodeId}");
            return true;
        }
        /// <summary>Records a surgical in-place folder display-name update (always succeeds in this recording sink).</summary>
        /// <param name="folderNodeId">The folder node ID to update in place.</param>
        /// <param name="displayName">The new display name to apply.</param>
        public bool UpdateFolderDisplayName(string folderNodeId, string displayName, AddressSpaceRealm realm = AddressSpaceRealm.Uns)
        {
            FolderRenameQueue.Enqueue((folderNodeId, displayName));
            return true;
        }
        /// <summary>Records a surgical variable-node removal (always succeeds in this recording sink).</summary>
        public bool RemoveVariableNode(string variableNodeId, AddressSpaceRealm realm = AddressSpaceRealm.Uns)
        {
            Calls.Enqueue($"RV:{variableNodeId}");
            return true;
        }
        /// <summary>Records a surgical alarm-condition-node removal (always succeeds in this recording sink).</summary>
        public bool RemoveAlarmConditionNode(string alarmNodeId, AddressSpaceRealm realm = AddressSpaceRealm.Uns)
        {
            Calls.Enqueue($"RA:{alarmNodeId}");
            return true;
        }
        /// <summary>Records a surgical equipment-subtree removal (always succeeds in this recording sink).</summary>
        public bool RemoveEquipmentSubtree(string equipmentNodeId, AddressSpaceRealm realm = AddressSpaceRealm.Uns)
        {
            Calls.Enqueue($"RE:{equipmentNodeId}");
            return true;
        }
    }
}