fix(alarms): populate EventType/SourceNode/SourceName on conditions (#473)

MaterialiseAlarmCondition never assigned the three mandatory BaseEventType
identity fields, so all three arrived null on every condition event — native
and scripted. The SDK does not synthesise them on this path: Create() builds
the children from the type definition but leaves them unset, the auto-filling
BaseEventState.Initialize overload is only used for transient events, and
ReportEvent / InstanceStateSnapshot copy children verbatim. A conforming
client could not attribute an alarm to its source.

  EventType  = the concrete materialised type (TypeDefinitionId)
  SourceNode = the condition's own NodeId (== ConditionId) — the condition IS
               the source; an alarm-bearing raw tag materialises only the
               condition, with no sibling value variable
  SourceName = the same identifying id string: RawPath (native) /
               ScriptedAlarmId (scripted)

SourceName carries the unique id rather than the leaf name: the leaf collides
across devices (HR200 on two PLCs) and is already carried by ConditionName, so
nothing is lost. Documented in docs/AlarmTracking.md, including that clients
must key on ConditionId and must not compose SourceName with ConditionName,
and that SourceName is NOT a live<->history join key (the alarm-history writer
stamps it with the EquipmentPath — a pre-existing divergence, now called out).

Tests: NativeAlarmEventIdentityFieldDeliveryTests is the wire-level guard —
a real client subscription using the standard [EventType, SourceNode,
SourceName, Time, Message, Severity] select clause, verified to fail against
the pre-fix server. NodeManagerAlarmSourceFieldsTests guards the node across
both realms, the base-type fallback, and the kind-swap re-materialise.

The HistoryRead events projection is a separate path (it projects historian
rows, not node fields) and is unaffected — its EventType => Variant.Null
assertions still hold.

tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/NodeManagerAlarmSourceFieldsTests.cs

@@ -0,0 +1,188 @@
+using Microsoft.Extensions.Logging.Abstractions;
+using Opc.Ua;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;
+
+namespace ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests;
+
+/// <summary>
+///     Issue #473 — every materialised Part 9 condition must carry the mandatory <c>BaseEventType</c>
+///     identity fields <c>EventType</c> / <c>SourceNode</c> / <c>SourceName</c>. The SDK does NOT synthesise
+///     them on this path: <see cref="NodeState.Create"/> initialises from the type's embedded definition,
+///     which declares all three as mandatory children with NO default value, and the auto-filling
+///     <see cref="BaseEventState.Initialize(ISystemContext, NodeState, EventSeverity, LocalizedText)"/>
+///     overload (which would set SourceNode/SourceName from a source node) is only used for transient
+///     events. <c>ReportEvent</c> and <c>InstanceStateSnapshot</c> copy the children verbatim and synthesise
+///     nothing — so a field left null at materialise arrives null on the wire on EVERY condition event.
+///     <para>
+///         The contract locked in here (see <c>docs/AlarmTracking.md</c>): the condition node IS the source
+///         node — a native-alarm raw tag materialises ONLY a condition (no separate value variable), so
+///         <c>SourceNode</c> self-references the condition's own NodeId and <c>SourceName</c> carries the
+///         same identifying id string (<c>alarmNodeId</c>: the RawPath for native, the ScriptedAlarmId for
+///         scripted), matching <c>ConditionId</c>. The leaf/display name stays on <c>ConditionName</c>, so
+///         no information is lost by SourceName carrying the unique id rather than the ambiguous leaf.
+///     </para>
+/// </summary>
+public sealed class NodeManagerAlarmSourceFieldsTests : IDisposable
+{
+    private static CancellationToken Ct => TestContext.Current.CancellationToken;
+
+    private const string RawDeviceFolder = "Plant/Modbus/dev1";
+    private const string RawAlarmPath = "Plant/Modbus/dev1/HR200";
+
+    private readonly string _pkiRoot = Path.Combine(
+        Path.GetTempPath(),
+        $"otopcua-alarm-src-fields-{Guid.NewGuid():N}");
+
+    /// <summary>A NATIVE condition (Raw realm, ConditionId = RawPath) carries all three identity fields:
+    /// EventType = its type definition, SourceNode = its own NodeId, SourceName = the RawPath. The leaf name
+    /// remains on ConditionName so the short name is still available to clients.</summary>
+    [Trait("Category", "Unit")]
+    [Fact]
+    public async Task Native_condition_carries_EventType_SourceNode_and_SourceName()
+    {
+        await using var host = await BootAsync();
+        var nm = host.Nm;
+        var rawNs = nm.NamespaceIndexForRealm(AddressSpaceRealm.Raw);
+
+        nm.EnsureFolder(RawDeviceFolder, parentNodeId: null, displayName: "dev1", realm: AddressSpaceRealm.Raw);
+        nm.MaterialiseAlarmCondition(RawAlarmPath, RawDeviceFolder, "HR200", "OffNormalAlarm", 700,
+            realm: AddressSpaceRealm.Raw, isNative: true);
+
+        var condition = nm.TryGetAlarmCondition(RawAlarmPath, AddressSpaceRealm.Raw);
+        condition.ShouldNotBeNull();
+
+        // EventType — the concrete condition type, so a client reading the FIELD (not just an OfType
+        // where-clause) can resolve the type.
+        condition.EventType.ShouldNotBeNull();
+        condition.EventType.Value.ShouldBe(ObjectTypeIds.OffNormalAlarmType);
+
+        // SourceNode — the condition's own NodeId (it IS the source: no separate value variable exists
+        // for an alarm-bearing raw tag). Equal to ConditionId.
+        condition.SourceNode.ShouldNotBeNull();
+        condition.SourceNode.Value.ShouldBe(new NodeId(RawAlarmPath, rawNs));
+
+        // SourceName — the RawPath: unique across devices, matching ConditionId/SourceNode.
+        condition.SourceName.ShouldNotBeNull();
+        condition.SourceName.Value.ShouldBe(RawAlarmPath);
+
+        // The leaf name is NOT lost — it stays on ConditionName.
+        condition.ConditionName!.Value.ShouldBe("HR200");
+
+    }
+
+    /// <summary>A SCRIPTED condition (UNS realm, ConditionId = ScriptedAlarmId) follows the SAME uniform rule:
+    /// SourceNode = its own NodeId, SourceName = the ScriptedAlarmId. Scripted and native conditions share the
+    /// materialise path, so neither may regress independently.</summary>
+    [Trait("Category", "Unit")]
+    [Fact]
+    public async Task Scripted_condition_carries_EventType_SourceNode_and_SourceName()
+    {
+        await using var host = await BootAsync();
+        var nm = host.Nm;
+        var unsNs = nm.NamespaceIndexForRealm(AddressSpaceRealm.Uns);
+
+        nm.EnsureFolder("eq-1", parentNodeId: null, displayName: "Station 1", realm: AddressSpaceRealm.Uns);
+        nm.MaterialiseAlarmCondition("tank-overflow", "eq-1", "Tank Overflow", "OffNormalAlarm", 700,
+            realm: AddressSpaceRealm.Uns, isNative: false);
+
+        var condition = nm.TryGetAlarmCondition("tank-overflow", AddressSpaceRealm.Uns);
+        condition.ShouldNotBeNull();
+
+        condition.EventType!.Value.ShouldBe(ObjectTypeIds.OffNormalAlarmType);
+        condition.SourceNode!.Value.ShouldBe(new NodeId("tank-overflow", unsNs));
+        condition.SourceName!.Value.ShouldBe("tank-overflow");
+        // The human-readable name stays on ConditionName.
+        condition.ConditionName!.Value.ShouldBe("Tank Overflow");
+
+    }
+
+    /// <summary>EventType tracks the ACTUAL materialised type, not a hardcoded constant: an unknown alarm type
+    /// falls back to the base <see cref="AlarmConditionState"/> and its EventType must report that base type
+    /// rather than a subtype the node does not have.</summary>
+    [Trait("Category", "Unit")]
+    [Fact]
+    public async Task EventType_reflects_the_fallback_base_type_for_an_unknown_alarm_type()
+    {
+        await using var host = await BootAsync();
+        var nm = host.Nm;
+
+        nm.EnsureFolder("eq-2", parentNodeId: null, displayName: "Station 2", realm: AddressSpaceRealm.Uns);
+        nm.MaterialiseAlarmCondition("alm-x", "eq-2", "Generic", "LimitAlarm", 500,
+            realm: AddressSpaceRealm.Uns, isNative: false);
+
+        var condition = nm.TryGetAlarmCondition("alm-x", AddressSpaceRealm.Uns);
+        condition.ShouldNotBeNull();
+        condition.GetType().ShouldBe(typeof(AlarmConditionState)); // base-type fallback
+        condition.EventType!.Value.ShouldBe(ObjectTypeIds.AlarmConditionType);
+
+    }
+
+    /// <summary>The identity fields survive a re-materialise that DROPS and re-creates the node (the native↔scripted
+    /// kind-swap path), so a redeploy can never leave a condition emitting null identity.</summary>
+    [Trait("Category", "Unit")]
+    [Fact]
+    public async Task Identity_fields_survive_a_kind_swap_rematerialise()
+    {
+        await using var host = await BootAsync();
+        var nm = host.Nm;
+        var unsNs = nm.NamespaceIndexForRealm(AddressSpaceRealm.Uns);
+
+        nm.EnsureFolder("eq-3", parentNodeId: null, displayName: "Station 3", realm: AddressSpaceRealm.Uns);
+        nm.MaterialiseAlarmCondition("alm-swap", "eq-3", "Swap", "OffNormalAlarm", 700,
+            realm: AddressSpaceRealm.Uns, isNative: false);
+        // Kind swap (scripted → native) drops the prior instance and re-creates it.
+        nm.MaterialiseAlarmCondition("alm-swap", "eq-3", "Swap", "OffNormalAlarm", 700,
+            realm: AddressSpaceRealm.Uns, isNative: true);
+
+        var condition = nm.TryGetAlarmCondition("alm-swap", AddressSpaceRealm.Uns);
+        condition.ShouldNotBeNull();
+        condition.EventType!.Value.ShouldBe(ObjectTypeIds.OffNormalAlarmType);
+        condition.SourceNode!.Value.ShouldBe(new NodeId("alm-swap", unsNs));
+        condition.SourceName!.Value.ShouldBe("alm-swap");
+
+    }
+
+    /// <summary>A booted server + its node manager, disposed via <c>await using</c> so an assertion failure
+    /// cannot leak a live server (and its bound port) into the rest of the test run.</summary>
+    private sealed class BootedServer(OpcUaApplicationHost host, OtOpcUaNodeManager nm) : IAsyncDisposable
+    {
+        public OtOpcUaNodeManager Nm { get; } = nm;
+        public ValueTask DisposeAsync() => host.DisposeAsync();
+    }
+
+    private async Task<BootedServer> BootAsync()
+    {
+        var host = new OpcUaApplicationHost(
+            new OpcUaApplicationHostOptions
+            {
+                ApplicationName = "OtOpcUa.AlarmSourceFieldsTest",
+                ApplicationUri = $"urn:OtOpcUa.AlarmSourceFieldsTest:{Guid.NewGuid():N}",
+                OpcUaPort = AllocateFreePort(),
+                PublicHostname = "localhost",
+                PkiStoreRoot = _pkiRoot,
+            },
+            NullLogger<OpcUaApplicationHost>.Instance);
+
+        var server = new OtOpcUaSdkServer();
+        await host.StartAsync(server, Ct);
+        return new BootedServer(host, server.NodeManager!);
+    }
+
+    private static int AllocateFreePort()
+    {
+        using var listener = new System.Net.Sockets.TcpListener(System.Net.IPAddress.Loopback, 0);
+        listener.Start();
+        return ((System.Net.IPEndPoint)listener.LocalEndpoint).Port;
+    }
+
+    public void Dispose()
+    {
+        if (Directory.Exists(_pkiRoot))
+        {
+            try { Directory.Delete(_pkiRoot, recursive: true); }
+            catch { /* best-effort */ }
+        }
+    }
+}