feat(historian): HistoryRead override (Raw/Processed/AtTime) over IHistorianDataSource

2026-06-14 19:31:39 -04:00
parent 50e1141fc2
commit 13fba8f8fb
4 changed files with 910 additions and 0 deletions
@@ -0,0 +1,81 @@
+namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+/// <summary>
+///     A no-op <see cref="IHistorianDataSource"/> — the server's default historian backend when no
+///     real historian has been registered. Every read returns an EMPTY result (no samples / events,
+///     null continuation point) so the node-manager's HistoryRead override surfaces
+///     <c>GoodNoData</c> for a historized node rather than faulting, and
+///     <see cref="GetHealthSnapshot"/> reports a fully-disabled (zeroed, disconnected) snapshot.
+///     <para>
+///         A process-wide singleton via <see cref="Instance"/> (private ctor): it carries no state
+///         and is immutable, so one shared instance is safe to assign as the node-manager's
+///         <c>HistorianDataSource</c> default until the Host wires a real source post-start (Task 5).
+///     </para>
+/// </summary>
+public sealed class NullHistorianDataSource : IHistorianDataSource
+{
+    /// <summary>The shared singleton instance.</summary>
+    public static readonly NullHistorianDataSource Instance = new();
+
+    private static readonly HistoryReadResult EmptyRead = new(Array.Empty<DataValueSnapshot>(), null);
+    private static readonly HistoricalEventsResult EmptyEvents = new(Array.Empty<HistoricalEvent>(), null);
+
+    private NullHistorianDataSource()
+    {
+    }
+
+    /// <inheritdoc />
+    public Task<HistoryReadResult> ReadRawAsync(
+        string fullReference,
+        DateTime startUtc,
+        DateTime endUtc,
+        uint maxValuesPerNode,
+        CancellationToken cancellationToken) => Task.FromResult(EmptyRead);
+
+    /// <inheritdoc />
+    public Task<HistoryReadResult> ReadProcessedAsync(
+        string fullReference,
+        DateTime startUtc,
+        DateTime endUtc,
+        TimeSpan interval,
+        HistoryAggregateType aggregate,
+        CancellationToken cancellationToken) => Task.FromResult(EmptyRead);
+
+    /// <inheritdoc />
+    public Task<HistoryReadResult> ReadAtTimeAsync(
+        string fullReference,
+        IReadOnlyList<DateTime> timestampsUtc,
+        CancellationToken cancellationToken) => Task.FromResult(EmptyRead);
+
+    /// <inheritdoc />
+    public Task<HistoricalEventsResult> ReadEventsAsync(
+        string? sourceName,
+        DateTime startUtc,
+        DateTime endUtc,
+        int maxEvents,
+        CancellationToken cancellationToken) => Task.FromResult(EmptyEvents);
+
+    /// <summary>
+    ///     Returns a fully-disabled snapshot — no connections open, every counter zero, every nullable
+    ///     field null, no cluster nodes. Pure; never blocks.
+    /// </summary>
+    public HistorianHealthSnapshot GetHealthSnapshot() => new(
+        TotalQueries: 0,
+        TotalSuccesses: 0,
+        TotalFailures: 0,
+        ConsecutiveFailures: 0,
+        LastSuccessTime: null,
+        LastFailureTime: null,
+        LastError: null,
+        ProcessConnectionOpen: false,
+        EventConnectionOpen: false,
+        ActiveProcessNode: null,
+        ActiveEventNode: null,
+        Nodes: Array.Empty<HistorianClusterNodeState>());
+
+    /// <summary>No-op — the null source owns no unmanaged resources.</summary>
+    public void Dispose()
+    {
+        // Stateless singleton; nothing to release.
+    }
+}