UA-.NETStandard/Libraries/Opc.Ua.Server/Diagnostics/DiagnosticsNodeManager.AliasNames.cs

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using Opc.Ua.Server.AliasNames;

namespace Opc.Ua.Server
{
    /// <summary>
    /// OPC UA Part 17 (Alias Names) integration for the standard
    /// well-known nodes loaded by <c>DiagnosticsNodeManager</c> from
    /// <c>Opc.Ua.NodeSet2.xml</c>.
    /// </summary>
    /// <remarks>
    /// The standard NodeSet ships three <c>AliasNameCategoryType</c>
    /// instances under the Server object (Part 17 §9):
    /// <list type="bullet">
    ///   <item><description><c>Aliases (i=23470)</c> — with mandatory
    ///   <c>FindAlias (i=23476)</c> and a <c>LastChange (i=32852)</c>
    ///   property;</description></item>
    ///   <item><description><c>TagVariables (i=23479)</c> — with mandatory
    ///   <c>FindAlias (i=23485)</c>;</description></item>
    ///   <item><description><c>Topics (i=23488)</c> — with mandatory
    ///   <c>FindAlias (i=23494)</c>.</description></item>
    /// </list>
    /// None of the optional Part 17 children
    /// (<c>FindAliasVerbose</c>/<c>AddAliasesToCategory</c>/<c>DeleteAliasesFromCategory</c>)
    /// are instantiated by the standard NodeSet on these well-known nodes,
    /// so this binder only wires <c>FindAlias</c> and (for
    /// <c>Aliases</c>) <c>LastChange</c>. Optional methods on
    /// application-defined categories are wired by
    /// <see cref="AliasNameNodeManager"/> instead.
    /// </remarks>
    public partial class DiagnosticsNodeManager
    {
        /// <summary>
        /// Resolves the server's <see cref="IAliasNameStoreRegistry"/>
        /// (via the optional <see cref="IAliasNameStoreRegistryProvider"/>
        /// interface) and wires the standard well-known
        /// <c>Aliases</c>/<c>TagVariables</c>/<c>Topics</c> <c>FindAlias</c>
        /// methods (plus <c>Aliases.LastChange</c>) to dispatch through
        /// it. The wiring is "live" — the registry is queried at each
        /// call rather than snapshotted at load time — so stores
        /// registered after this point are also reachable.
        /// </summary>
        private void WireStandardAliasMethods()
        {
            IAliasNameStoreRegistry? registry =
                (Server as IAliasNameStoreRegistryProvider)?.AliasNameStoreRegistry;
            if (registry == null)
            {
                return;
            }

            m_aliasRegistry = registry;
            m_aliasRegistry.Changed += OnAliasRegistryChanged;

            WireStandardCategory(ObjectIds.Aliases, includeLastChange: true);
            WireStandardCategory(ObjectIds.TagVariables, includeLastChange: false);
            WireStandardCategory(ObjectIds.Topics, includeLastChange: false);
        }

        private void WireStandardCategory(NodeId categoryId, bool includeLastChange)
        {
            AliasNameCategoryState? category =
                FindPredefinedNode<AliasNameCategoryState>(categoryId);
            if (category == null)
            {
                return;
            }

            category.FindAlias?.OnCallAsync = (ctx, method, objId, pattern, refType, ct) =>
                    AliasNameMethodDispatcher.FindAliasAsync(
                        m_aliasRegistry!,
                        Server.TypeTree,
                        objId.IsNull ? categoryId : objId,
                        pattern,
                        refType,
                        ct);

            if (includeLastChange && category.LastChange != null)
            {
                uint? seed = null;
                foreach (IAliasNameStore store in m_aliasRegistry!.Stores)
                {
                    uint? v = store.GetLastChange(categoryId);
                    if (v.HasValue)
                    {
                        seed = v;
                        break;
                    }
                }
                if (seed.HasValue)
                {
                    category.LastChange.Value = seed.Value;
                    category.LastChange.ClearChangeMasks(SystemContext, false);
                }
                m_aliasesLastChangeNode = category.LastChange;
            }
        }

        private void OnAliasRegistryChanged(object? sender, AliasStoreChangedEventArgs e)
        {
            // Only the standard Aliases (i=23470) node carries a LastChange
            // property in the shipped NodeSet; mirror its store value.
            if (m_aliasesLastChangeNode != null &&
                e.CategoryId == ObjectIds.Aliases)
            {
                m_aliasesLastChangeNode.Value = e.LastChange;
                m_aliasesLastChangeNode.ClearChangeMasks(SystemContext, false);
            }
        }

        /// <summary>
        /// Detaches the <see cref="OnAliasRegistryChanged"/> handler.
        /// Invoked from <c>Dispose(bool)</c> so the registry — which
        /// outlives this manager when other node managers share the same
        /// server — does not hold a stale reference into the disposed
        /// <see cref="DiagnosticsNodeManager"/>.
        /// </summary>
        private void UnwireStandardAliasMethods()
        {
            IAliasNameStoreRegistry? registry = m_aliasRegistry;
            if (registry != null)
            {
                registry.Changed -= OnAliasRegistryChanged;
                m_aliasRegistry = null;
            }
            m_aliasesLastChangeNode = null;
        }

        private IAliasNameStoreRegistry? m_aliasRegistry;
        private PropertyState<uint>? m_aliasesLastChangeNode;
    }
}