/* ========================================================================
 * Copyright (c) 2005-2025 The OPC Foundation, Inc. All rights reserved.
 *
 * OPC Foundation MIT License 1.00
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
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 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * The complete license agreement can be found here:
 * http://opcfoundation.org/License/MIT/1.00/
 * ======================================================================*/

using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.Threading;
using System.Threading.Tasks;
using Opc.Ua.Identity;

namespace Opc.Ua.Server
{
    /// <summary>
    /// A class that stores the globally accessible state of a server instance.
    /// </summary>
    /// <remarks>
    /// <para>
    /// This is a readonly class that is initialized when the server starts up. It provides
    /// access to global objects and data that different parts of the server may require.
    /// It also defines some global methods.
    /// </para>
    /// <para>
    /// This object is constructed is three steps:
    /// - the configuration is provided.
    /// - the node managers et. al. are provided.
    /// - the session/subscription managers are provided.
    /// </para>
    /// <para>The server is not running until all three steps are complete.</para>
    /// <para>
    /// The references returned from this object do not change after all three states are complete.
    /// This ensures the object is thread safe even though it does not use a lock.
    /// Objects returned from this object can be assumed to be threadsafe unless otherwise stated.
    /// </para>
    /// </remarks>
    public class ServerInternalData :
        IServerInternal,
        AliasNames.IAliasNameStoreRegistryProvider,
        Historian.IHistorianRegistryProvider,
        ITransportListenerRegistryProvider,
        ITimeProviderProvider
    {
        /// <summary>
        /// Initializes the datastore with the server configuration.
        /// </summary>
        /// <param name="serverDescription">The server description.</param>
        /// <param name="configuration">The configuration.</param>
        /// <param name="messageContext">The message context.</param>
        public ServerInternalData(
            ServerProperties serverDescription,
            ApplicationConfiguration configuration,
            IServiceMessageContext messageContext)
            : this(serverDescription, configuration, messageContext, null)
        {
        }

        /// <summary>
        /// Initializes the datastore with the server configuration.
        /// </summary>
        /// <param name="serverDescription">The server description.</param>
        /// <param name="configuration">The configuration.</param>
        /// <param name="messageContext">The message context.</param>
        /// <param name="timeProvider">The time provider used for all
        /// time / duration calculations performed by the server, or
        /// <c>null</c> to use <see cref="TimeProvider.System"/>.</param>
        public ServerInternalData(
            ServerProperties serverDescription,
            ApplicationConfiguration configuration,
            IServiceMessageContext messageContext,
            TimeProvider? timeProvider)
        {
            m_timeProvider = timeProvider ?? TimeProvider.System;
            m_serverDescription = serverDescription;
            m_configuration = configuration;
            MessageContext = messageContext;

            m_endpointAddresses = [];

            foreach (string baseAddresses in m_configuration.ServerConfiguration!.BaseAddresses)
            {
                Uri? url = Utils.ParseUri(baseAddresses);

                if (url != null)
                {
                    m_endpointAddresses.Add(url);
                }
            }

            NamespaceUris = MessageContext.NamespaceUris;
            Factory = MessageContext.Factory;

            ServerUris = new StringTable();
            TypeTree = new TypeTable(NamespaceUris);
            HistorianRegistry = new Historian.HistorianProviderRegistry(NamespaceUris);

            // add the server uri to the server table.
            ServerUris.Append(m_configuration.ApplicationUri!);

            // create the default system context.
            DefaultSystemContext = new ServerSystemContext(this);
        }

        /// <summary>
        /// Frees any unmanaged resources.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// An overrideable version of the Dispose.
        /// </summary>
        /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
        protected virtual void Dispose(bool disposing)
        {
            if (disposing)
            {
                m_roleStateBinding?.Dispose();
                m_roleStateBinding = null;
                (RoleManager as IDisposable)?.Dispose();
                ResourceManager?.Dispose();
                RequestManager?.Dispose();
                AggregateManager?.Dispose();
                ModellingRulesManager?.Dispose();
                (NodeManager as IDisposable)?.Dispose();
                SessionManager?.Dispose();
                SubscriptionManager?.Dispose();
                MonitoredItemQueueFactory?.Dispose();
                (AliasNameStoreRegistry as IDisposable)?.Dispose();
                (HistorianRegistry as IDisposable)?.Dispose();
            }
        }

        /// <summary>
        /// The server-wide registry of OPC UA Part 17 alias-name stores.
        /// Surfaces through the optional
        /// <see cref="AliasNames.IAliasNameStoreRegistryProvider"/>
        /// interface so consumers can discover it without any change to
        /// <see cref="IServerInternal"/>; never <c>null</c>.
        /// </summary>
        public AliasNames.IAliasNameStoreRegistry AliasNameStoreRegistry { get; }
            = new AliasNames.AliasNameStoreRegistry();

        /// <summary>
        /// A snapshot of the transport listeners currently bound to the
        /// server. Populated by <see cref="StandardServer"/> once
        /// listeners are opened so consumers such as
        /// <see cref="ConfigurationNodeManager"/> can fan-out post-
        /// response channel cuts per OPC UA Part 12 §7.10.9.
        /// </summary>
        /// <remarks>
        /// Returns an empty list before listeners are bound or after the
        /// server has shut them down. Surfaced through the optional
        /// <see cref="ITransportListenerRegistryProvider"/> interface so
        /// external/mocked <see cref="IServerInternal"/> implementations
        /// remain unaffected.
        /// </remarks>
        public IReadOnlyList<ITransportListener> TransportListeners
            => m_transportListeners ?? (IReadOnlyList<ITransportListener>)Array.Empty<ITransportListener>();

        /// <summary>
        /// Called by <see cref="StandardServer"/> after listeners are
        /// bound (or torn down) to make them visible to downstream
        /// consumers via <see cref="ITransportListenerRegistryProvider"/>.
        /// </summary>
        /// <param name="listeners">
        /// The current listener registry. Passing <c>null</c> resets to
        /// an empty snapshot.
        /// </param>
        public void SetTransportListenerRegistry(IReadOnlyList<ITransportListener>? listeners)
        {
            m_transportListeners = listeners;
        }


        /// <summary>
        /// The server-wide registry of Part 11 historian providers.
        /// Surfaces through the optional
        /// <see cref="Historian.IHistorianRegistryProvider"/> interface so
        /// consumers can discover it without any change to
        /// <see cref="IServerInternal"/>; never <c>null</c>.
        /// </summary>
        public Historian.IHistorianProviderRegistry HistorianRegistry { get; }

        /// <summary>
        /// The time provider used for all time / duration calculations
        /// performed by the server. Surfaces through the optional
        /// <see cref="ITimeProviderProvider"/> interface so consumers can
        /// discover it without any change to <see cref="IServerInternal"/>;
        /// never <c>null</c>.
        /// </summary>
        public TimeProvider TimeProvider => m_timeProvider;

        /// <summary>
        /// The session manager to use with the server.
        /// </summary>
        /// <value>The session manager.</value>
        public ISessionManager SessionManager { get; private set; } = null!;

        /// <inheritdoc/>
        public IRoleManager RoleManager { get; private set; } = new RoleManager();

        /// <inheritdoc/>
        public IServerIdentityRegistry IdentityRegistry { get; private set; } = new ServerIdentityRegistry();

        /// <inheritdoc/>
        public UserManagement.IUserManagement? UserManagement { get; private set; }

        /// <summary>
        /// The subscription manager to use with the server.
        /// </summary>
        /// <value>The subscription manager.</value>
        public ISubscriptionManager SubscriptionManager { get; private set; } = null!;

        /// <summary>
        /// Stores the MasterNodeManager, the DiagnosticsNodeManager and the CoreNodeManager
        /// </summary>
        /// <param name="nodeManager">The node manager.</param>
        [MemberNotNull(
            nameof(NodeManager),
            nameof(DiagnosticsNodeManager),
            nameof(ConfigurationNodeManager),
            nameof(CoreNodeManager))]
        public void SetNodeManager(IMasterNodeManager nodeManager)
        {
            NodeManager = nodeManager;
            DiagnosticsNodeManager = nodeManager.DiagnosticsNodeManager!;
            ConfigurationNodeManager = nodeManager.ConfigurationNodeManager!;
            CoreNodeManager = nodeManager.CoreNodeManager!;
        }

        /// <summary>
        /// Stores the MainNodeManagerFactory
        /// </summary>
        /// <param name="mainNodeManagerFactory">The main node manager factory.</param>
        [MemberNotNull(nameof(MainNodeManagerFactory))]
        public void SetMainNodeManagerFactory(IMainNodeManagerFactory mainNodeManagerFactory)
        {
            MainNodeManagerFactory = mainNodeManagerFactory;
        }

        /// <summary>
        /// Sets the EventManager, the ResourceManager, the RequestManager and the AggregateManager.
        /// </summary>
        /// <param name="eventManager">The event manager.</param>
        /// <param name="resourceManager">The resource manager.</param>
        /// <param name="requestManager">The request manager.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        [MemberNotNull(
            nameof(EventManager),
            nameof(ResourceManager),
            nameof(RequestManager),
            nameof(ServerObject),
            nameof(NonThreadSafeStatus),
            nameof(ServerDiagnostics))]
        public async ValueTask CreateServerObjectAsync(
            EventManager eventManager,
            ResourceManager resourceManager,
            RequestManager requestManager,
            CancellationToken cancellationToken = default)
        {
            EventManager = eventManager;
            ResourceManager = resourceManager;
            RequestManager = requestManager;

            // create the server object.
            await CreateServerObjectAsync(cancellationToken).ConfigureAwait(false);
        }

        /// <summary>
        /// Stores the SessionManager, the SubscriptionManager in the datastore.
        /// </summary>
        /// <param name="sessionManager">The session manager.</param>
        /// <param name="subscriptionManager">The subscription manager.</param>
        [MemberNotNull(nameof(SessionManager), nameof(SubscriptionManager))]
        public void SetSessionManager(
            ISessionManager sessionManager,
            ISubscriptionManager subscriptionManager)
        {
            SessionManager = sessionManager;
            SubscriptionManager = subscriptionManager;
        }

        /// <summary>
        /// Stores the MonitoredItemQueueFactory in the datastore.
        /// </summary>
        /// <param name="monitoredItemQueueFactory">The MonitoredItemQueueFactory.</param>
        [MemberNotNull(nameof(MonitoredItemQueueFactory))]
        public void SetMonitoredItemQueueFactory(
            IMonitoredItemQueueFactory monitoredItemQueueFactory)
        {
            MonitoredItemQueueFactory = monitoredItemQueueFactory;
        }

        /// <summary>
        /// Stores the Subscriptionstore in the datastore.
        /// </summary>
        /// <param name="subscriptionStore">The subscriptionstore.</param>
        [MemberNotNull(nameof(SubscriptionStore))]
        public void SetSubscriptionStore(ISubscriptionStore subscriptionStore)
        {
            SubscriptionStore = subscriptionStore;
        }

        /// <inheritdoc/>
        public void SetRoleManager(IRoleManager roleManager)
        {
            RoleManager = roleManager ?? throw new ArgumentNullException(nameof(roleManager));
        }

        /// <inheritdoc/>
        public void SetIdentityRegistry(IServerIdentityRegistry registry)
        {
            IdentityRegistry = registry ?? throw new ArgumentNullException(nameof(registry));
        }

        /// <inheritdoc/>
        public void SetUserManagement(UserManagement.IUserManagement userManagement)
        {
            UserManagement = userManagement ?? throw new ArgumentNullException(nameof(userManagement));
        }

        /// <summary>
        /// Stores the AggregateManager in the datastore.
        /// </summary>
        /// <param name="aggregateManager">The AggregateManager.</param>
        [MemberNotNull(nameof(AggregateManager))]
        public void SetAggregateManager(AggregateManager aggregateManager)
        {
            AggregateManager = aggregateManager;
        }

        /// <summary>
        /// Stores the ModellingRulesManager in the datastore.
        /// </summary>
        /// <param name="modellingRulesManager">The ModellingRulesManager.</param>
        [MemberNotNull(nameof(ModellingRulesManager))]
        public void SetModellingRulesManager(ModellingRulesManager modellingRulesManager)
        {
            ModellingRulesManager = modellingRulesManager;
        }

        /// <summary>
        /// The endpoint addresses used by the server.
        /// </summary>
        /// <value>The endpoint addresses.</value>
        public IEnumerable<Uri> EndpointAddresses => m_endpointAddresses;

        /// <summary>
        /// The context to use when serializing/deserializing extension objects.
        /// </summary>
        /// <value>The message context.</value>
        public IServiceMessageContext MessageContext { get; }

        /// <summary>
        /// The default system context for the server.
        /// </summary>
        /// <value>The default system context.</value>
        public ServerSystemContext DefaultSystemContext { get; }

        /// <summary>
        /// The table of namespace uris known to the server.
        /// </summary>
        /// <value>The namespace URIs.</value>
        public NamespaceTable NamespaceUris { get; }

        /// <summary>
        /// The table of remote server uris known to the server.
        /// </summary>
        /// <value>The server URIs.</value>
        public StringTable ServerUris { get; }

        /// <summary>
        /// The factory used to create encodeable objects that the server understands.
        /// </summary>
        /// <value>The factory.</value>
        public IEncodeableFactory Factory { get; }

        /// <summary>
        /// The datatypes, object types and variable types known to the server.
        /// </summary>
        /// <value>The type tree.</value>
        /// <remarks>
        /// The type tree table is a global object that all components of a server have access to.
        /// Node managers must populate this table with all types that they define.
        /// This object is thread safe.
        /// </remarks>
        public TypeTable TypeTree { get; }

        /// <summary>
        /// The master node manager for the server.
        /// </summary>
        /// <value>The node manager.</value>
        public IMasterNodeManager NodeManager { get; private set; } = null!;

        /// <inheritdoc/>
        public IMainNodeManagerFactory MainNodeManagerFactory { get; private set; } = null!;

        /// <summary>
        /// The internal node manager for the servers.
        /// </summary>
        /// <value>The core node manager.</value>
        public ICoreNodeManager CoreNodeManager { get; private set; } = null!;

        /// <summary>
        /// Returns the node manager that managers the server diagnostics.
        /// </summary>
        /// <value>The diagnostics node manager.</value>
        public IDiagnosticsNodeManager DiagnosticsNodeManager { get; private set; } = null!;

        /// <inheritdoc/>
        public IConfigurationNodeManager ConfigurationNodeManager { get; private set; } = null!;

        /// <summary>
        /// The manager for events that all components use to queue events that occur.
        /// </summary>
        /// <value>The event manager.</value>
        public EventManager EventManager { get; private set; } = null!;

        /// <summary>
        /// A manager for localized resources that components can use to localize text.
        /// </summary>
        /// <value>The resource manager.</value>
        public ResourceManager ResourceManager { get; private set; } = null!;

        /// <summary>
        /// A manager for outstanding requests that allows components to receive notifications if the timeout or are cancelled.
        /// </summary>
        /// <value>The request manager.</value>
        public RequestManager RequestManager { get; private set; } = null!;

        /// <summary>
        /// A manager for aggregate calculators supported by the server.
        /// </summary>
        /// <value>The aggregate manager.</value>
        public AggregateManager AggregateManager { get; private set; } = null!;

        /// <summary>
        /// A manager for modelling rules supported by the server.
        /// </summary>
        /// <value>The modelling rules manager.</value>
        public ModellingRulesManager ModellingRulesManager { get; private set; } = null!;

        /// <summary>
        /// The manager for active sessions.
        /// </summary>
        /// <value>The session manager.</value>
        ISessionManager IServerInternal.SessionManager => SessionManager;

        /// <summary>
        /// The manager for active subscriptions.
        /// </summary>
        ISubscriptionManager IServerInternal.SubscriptionManager => SubscriptionManager;

        /// <summary>
        /// The factory for durable monitored item queues
        /// </summary>
        public IMonitoredItemQueueFactory MonitoredItemQueueFactory { get; private set; } = null!;

        /// <summary>
        /// The store to persist and retrieve subscriptions
        /// </summary>
        public ISubscriptionStore SubscriptionStore { get; private set; } = null!;

        /// <inheritdoc/>
        public ITelemetryContext Telemetry => MessageContext.Telemetry;

        /// <summary>
        /// Returns the status object for the server.
        /// </summary>
        /// <value>The status.</value>
        [Obsolete("No longer thread safe. To read the value use CurrentState, to write use UpdateServerStatus.")]
        public ServerStatusValue Status => NonThreadSafeStatus;

        /// <summary>
        /// Gets or sets the current state of the server.
        /// </summary>
        /// <value>The state of the current.</value>
        public ServerState CurrentState
        {
            get
            {
                lock (NonThreadSafeStatus.Lock)
                {
                    return NonThreadSafeStatus.Value.State;
                }
            }
            set
            {
                lock (NonThreadSafeStatus.Lock)
                {
                    NonThreadSafeStatus.Value.State = value;
                }
            }
        }

        /// <summary>
        /// Returns the Server object node
        /// </summary>
        /// <value>The Server object node.</value>
        public ServerObjectState ServerObject { get; private set; } = null!;

        /// <summary>
        /// Used to synchronize access to the server diagnostics.
        /// </summary>
        /// <value>The diagnostics lock.</value>
        public object DiagnosticsLock { get; } = new object();

        /// <summary>
        /// Used to synchronize write access to
        /// the server diagnostics.
        /// </summary>
        /// <value>The diagnostics lock.</value>
        public object DiagnosticsWriteLock
        {
            get
            {
                // implicitly force diagnostics update
                DiagnosticsNodeManager?.ForceDiagnosticsScan();
                return DiagnosticsLock;
            }
        }

        /// <summary>
        /// Returns the diagnostics structure for the server.
        /// </summary>
        /// <value>The server diagnostics.</value>
        public ServerDiagnosticsSummaryDataType ServerDiagnostics { get; private set; } = null!;

        /// <summary>
        /// Whether the server is currently running.
        /// </summary>
        /// <value>
        /// <c>true</c> if this instance is running; otherwise, <c>false</c>.
        /// </value>
        /// <remarks>
        /// This flag is set to false when the server shuts down. Threads running should check this flag whenever
        /// they return from a blocking operation. If it is false the thread should clean up and terminate.
        /// </remarks>
        public bool IsRunning
        {
            get
            {
                if (NonThreadSafeStatus == null)
                {
                    return false;
                }

                lock (NonThreadSafeStatus.Lock)
                {
                    if (NonThreadSafeStatus.Value.State == ServerState.Running)
                    {
                        return true;
                    }

                    if (NonThreadSafeStatus.Value.State == ServerState.Shutdown &&
                        NonThreadSafeStatus.Value.SecondsTillShutdown > 0)
                    {
                        return true;
                    }

                    return false;
                }
            }
        }

        /// <summary>
        /// Whether the server is collecting diagnostics.
        /// </summary>
        /// <value><c>true</c> if diagnostics are enabled; otherwise, <c>false</c>.</value>
        public bool DiagnosticsEnabled
        {
            get
            {
                if (DiagnosticsNodeManager == null)
                {
                    return false;
                }

                return DiagnosticsNodeManager.DiagnosticsEnabled;
            }
        }

        /// <summary>
        /// Status but non thread safe - internal so not part of public api
        /// </summary>
        internal ServerStatusValue NonThreadSafeStatus { get; private set; } = null!;

        /// <summary>
        /// Closes the specified session.
        /// </summary>
        /// <param name="context">The context.</param>
        /// <param name="sessionId">The session identifier.</param>
        /// <param name="deleteSubscriptions">if set to <c>true</c> subscriptions are to be deleted.</param>
        [Obsolete("Use CloseSessionAsync instead.")]
        public void CloseSession(
            OperationContext context,
            NodeId sessionId,
            bool deleteSubscriptions)
        {
            CloseSessionAsync(context, sessionId, deleteSubscriptions)
                .AsTask().GetAwaiter().GetResult();
        }

        /// <summary>
        /// Closes the specified session.
        /// </summary>
        /// <param name="context">The context.</param>
        /// <param name="sessionId">The session identifier.</param>
        /// <param name="deleteSubscriptions">if set to <c>true</c> subscriptions are to be deleted.</param>
        /// <param name="cancellationToken">The cancellationToken</param>
        public async ValueTask CloseSessionAsync(
            OperationContext context,
            NodeId sessionId,
            bool deleteSubscriptions,
            CancellationToken cancellationToken = default)
        {
            await NodeManager.SessionClosingAsync(context, sessionId, deleteSubscriptions, cancellationToken)
                .ConfigureAwait(false);
            await SubscriptionManager.SessionClosingAsync(context, sessionId, deleteSubscriptions, cancellationToken)
                .ConfigureAwait(false);
            await SessionManager.CloseSessionAsync(sessionId, cancellationToken).ConfigureAwait(false);
        }

        /// <summary>
        /// Deletes the specified subscription.
        /// </summary>
        /// <param name="subscriptionId">The subscription identifier.</param>
        /// <param name="cancellationToken">The cancellation token</param>
        public async ValueTask DeleteSubscriptionAsync(uint subscriptionId, CancellationToken cancellationToken = default)
        {
            await SubscriptionManager.DeleteSubscriptionAsync(null!, subscriptionId, cancellationToken).ConfigureAwait(false);
        }

        /// <summary>
        /// Called by any component to report a global event.
        /// </summary>
        /// <param name="e">The event.</param>
        public void ReportEvent(IFilterTarget e)
        {
            ReportEvent(DefaultSystemContext, e);
        }

        /// <summary>
        /// Called by any component to report a global event.
        /// </summary>
        /// <param name="context">The context.</param>
        /// <param name="e">The event.</param>
        public void ReportEvent(ISystemContext context, IFilterTarget e)
        {
            if ((!Auditing) && (e is AuditEventState))
            {
                // do not report auditing events if server Auditing flag is false
                return;
            }

            ServerObject?.ReportEvent(context, e);
        }

        /// <summary>
        /// Refreshes the conditions for the specified subscription.
        /// </summary>
        /// <param name="context">The context.</param>
        /// <param name="subscriptionId">The subscription identifier.</param>
        public void ConditionRefresh(OperationContext context, uint subscriptionId)
        {
            SubscriptionManager.ConditionRefresh(context, subscriptionId);
        }

        /// <summary>
        /// Refreshes the conditions for the specified subscription.
        /// </summary>
        /// <param name="context">The context.</param>
        /// <param name="subscriptionId">The subscription identifier.</param>
        /// <param name="monitoredItemId">The monitored item identifier.</param>
        public void ConditionRefresh2(
            OperationContext context,
            uint subscriptionId,
            uint monitoredItemId)
        {
            SubscriptionManager.ConditionRefresh2(context, subscriptionId, monitoredItemId);
        }

        /// <summary>
        /// Updates the server status safely.
        /// </summary>
        /// <param name="action">Action to perform on the server status object.</param>
        /// <exception cref="ArgumentNullException"><paramref name="action"/> is <c>null</c>.</exception>
        public void UpdateServerStatus(Action<ServerStatusValue> action)
        {
            if (action == null)
            {
                throw new ArgumentNullException(nameof(action));
            }

            lock (NonThreadSafeStatus.Lock)
            {
                action.Invoke(NonThreadSafeStatus);
            }
        }

        /// <inheritdoc/>
        public bool Auditing { get; private set; }

        /// <inheritdoc/>
        public ISystemContext DefaultAuditContext => DefaultSystemContext.Copy();

        /// <inheritdoc/>
        public void ReportAuditEvent(ISystemContext context, AuditEventState e)
        {
            if (!Auditing)
            {
                // do not report auditing events if server Auditing flag is false
                return;
            }

            ReportEvent(context, e);
        }

        /// <summary>
        /// Creates the ServerObject and attaches it to the NodeManager.
        /// </summary>
        [MemberNotNull(
            nameof(ServerObject),
            nameof(NonThreadSafeStatus),
            nameof(ServerDiagnostics))]
        private async ValueTask CreateServerObjectAsync(CancellationToken cancellationToken = default)
        {
            // get the server object.
            ServerObjectState serverObject = ServerObject =
                DiagnosticsNodeManager.FindPredefinedNode<ServerObjectState>(ObjectIds.Server);

            // update server capabilities.
            ServerCapabilitiesState serverCapabilities = serverObject.ServerCapabilities!;
            serverObject.ServiceLevel!.Value = 255;
            serverCapabilities.LocaleIdArray!.Value = ResourceManager
                .GetAvailableLocales();
            serverCapabilities.ServerProfileArray!.Value =
            [
                .. m_configuration.ServerConfiguration!.ServerProfileArray
            ];

            BaseVariableState conformanceUnits = DiagnosticsNodeManager.FindPredefinedNode<BaseVariableState>(
                VariableIds.Server_ServerCapabilities_ConformanceUnits);
            if (conformanceUnits != null)
            {
                conformanceUnits.Value = Variant.From(Array.Empty<QualifiedName>().ToArrayOf());
            }

            serverCapabilities.MinSupportedSampleRate!.Value = 0;
            serverCapabilities.MaxBrowseContinuationPoints!.Value = (ushort)
                m_configuration.ServerConfiguration.MaxBrowseContinuationPoints;
            serverCapabilities.MaxQueryContinuationPoints!.Value = (ushort)
                m_configuration.ServerConfiguration.MaxQueryContinuationPoints;
            serverCapabilities.MaxHistoryContinuationPoints!.Value = (ushort)
                m_configuration.ServerConfiguration.MaxHistoryContinuationPoints;
            serverCapabilities.MaxArrayLength!.Value = (uint)
                m_configuration.TransportQuotas!.MaxArrayLength;
            serverCapabilities.MaxStringLength!.Value = (uint)
                m_configuration.TransportQuotas.MaxStringLength;
            serverCapabilities.MaxByteStringLength!.Value = (uint)
                m_configuration.TransportQuotas.MaxByteStringLength;
            serverCapabilities.MaxSessions!.Value = (uint)
                m_configuration.ServerConfiguration.MaxSessionCount;
            serverCapabilities.MaxSubscriptions!.Value = (uint)
                m_configuration.ServerConfiguration.MaxSubscriptionCount;

            // Expose MaxSubscriptionsPerSession (optional property
            // on ServerCapabilitiesType per Part 5 §6.3) so clients that
            // enumerate per-session limits get a defined value instead of a
            // missing-attribute response. Use the configured global
            // MaxSubscriptionCount as the per-session ceiling — the SDK
            // doesn't track per-session limits separately at this layer.
            if (serverCapabilities.MaxSubscriptionsPerSession == null)
            {
                serverCapabilities.AddMaxSubscriptionsPerSession(DefaultSystemContext);
            }
            serverCapabilities.MaxSubscriptionsPerSession!.Value = (uint)Math.Max(1,
                m_configuration.ServerConfiguration.MaxSubscriptionCount);

            // Any operational limits Property that is provided shall have a non zero value.
            OperationLimitsState? operationLimits = serverCapabilities.OperationLimits;
            OperationLimits configOperationLimits = m_configuration.ServerConfiguration
                .OperationLimits;
            if (configOperationLimits != null)
            {
                operationLimits!.MaxNodesPerRead = SetPropertyValue(
                    operationLimits.MaxNodesPerRead!,
                    configOperationLimits.MaxNodesPerRead);
                operationLimits.MaxNodesPerHistoryReadData = SetPropertyValue(
                    operationLimits.MaxNodesPerHistoryReadData!,
                    configOperationLimits.MaxNodesPerHistoryReadData);
                operationLimits.MaxNodesPerHistoryReadEvents = SetPropertyValue(
                    operationLimits.MaxNodesPerHistoryReadEvents!,
                    configOperationLimits.MaxNodesPerHistoryReadEvents);
                operationLimits.MaxNodesPerWrite = SetPropertyValue(
                    operationLimits.MaxNodesPerWrite!,
                    configOperationLimits.MaxNodesPerWrite);
                operationLimits.MaxNodesPerHistoryUpdateData = SetPropertyValue(
                    operationLimits.MaxNodesPerHistoryUpdateData!,
                    configOperationLimits.MaxNodesPerHistoryUpdateData);
                operationLimits.MaxNodesPerHistoryUpdateEvents = SetPropertyValue(
                    operationLimits.MaxNodesPerHistoryUpdateEvents!,
                    configOperationLimits.MaxNodesPerHistoryUpdateEvents);
                operationLimits.MaxNodesPerMethodCall = SetPropertyValue(
                    operationLimits.MaxNodesPerMethodCall!,
                    configOperationLimits.MaxNodesPerMethodCall);
                operationLimits.MaxNodesPerBrowse = SetPropertyValue(
                    operationLimits.MaxNodesPerBrowse!,
                    configOperationLimits.MaxNodesPerBrowse);
                operationLimits.MaxNodesPerRegisterNodes = SetPropertyValue(
                    operationLimits.MaxNodesPerRegisterNodes!,
                    configOperationLimits.MaxNodesPerRegisterNodes);
                operationLimits.MaxNodesPerTranslateBrowsePathsToNodeIds = SetPropertyValue(
                    operationLimits.MaxNodesPerTranslateBrowsePathsToNodeIds!,
                    configOperationLimits.MaxNodesPerTranslateBrowsePathsToNodeIds);
                operationLimits.MaxNodesPerNodeManagement = SetPropertyValue(
                    operationLimits.MaxNodesPerNodeManagement!,
                    configOperationLimits.MaxNodesPerNodeManagement);
                operationLimits.MaxMonitoredItemsPerCall = SetPropertyValue(
                    operationLimits.MaxMonitoredItemsPerCall!,
                    configOperationLimits.MaxMonitoredItemsPerCall);
            }
            else
            {
                operationLimits!.MaxNodesPerRead =
                    operationLimits.MaxNodesPerHistoryReadData =
                    operationLimits.MaxNodesPerHistoryReadEvents =
                    operationLimits.MaxNodesPerWrite =
                    operationLimits.MaxNodesPerHistoryUpdateData =
                    operationLimits.MaxNodesPerHistoryUpdateEvents =
                    operationLimits.MaxNodesPerMethodCall =
                    operationLimits.MaxNodesPerBrowse =
                    operationLimits.MaxNodesPerRegisterNodes =
                    operationLimits.MaxNodesPerTranslateBrowsePathsToNodeIds =
                    operationLimits.MaxNodesPerNodeManagement =
                    operationLimits.MaxMonitoredItemsPerCall =
                        null;
            }

            // setup PublishSubscribe Status State value
            const PubSubState pubSubState = PubSubState.Disabled;

            BaseVariableState default_PubSubState =
                DiagnosticsNodeManager.FindPredefinedNode<BaseVariableState>(
                    VariableIds.PublishSubscribe_Status_State);
            default_PubSubState.Value = Variant.From(pubSubState);

            // setup value for SupportedTransportProfiles
            BaseVariableState default_SupportedTransportProfiles =
                DiagnosticsNodeManager.FindPredefinedNode<BaseVariableState>(
                    VariableIds.PublishSubscribe_SupportedTransportProfiles);
            default_SupportedTransportProfiles.Value = "uadp";

            // setup callbacks for dynamic values.
            serverObject.NamespaceArray!.OnSimpleReadValue = OnReadNamespaceArray;
            serverObject.NamespaceArray.MinimumSamplingInterval = 1000;

            serverObject.ServerArray!.OnSimpleReadValue = OnReadServerArray;
            serverObject.ServerArray.MinimumSamplingInterval = 1000;

            // dynamic change of enabledFlag is disabled to pass CTT
            serverObject.ServerDiagnostics!.EnabledFlag!.AccessLevel = AccessLevels.CurrentRead;
            serverObject.ServerDiagnostics.EnabledFlag.UserAccessLevel = AccessLevels
                .CurrentRead;
            serverObject.ServerDiagnostics.EnabledFlag.OnSimpleReadValue
                = OnReadDiagnosticsEnabledFlag;
            serverObject.ServerDiagnostics.EnabledFlag.OnSimpleWriteValue
                = OnWriteDiagnosticsEnabledFlag;
            serverObject.ServerDiagnostics.EnabledFlag.MinimumSamplingInterval = 1000;

            // initialize status.
            DateTime nowUtc = m_timeProvider.GetUtcNow().UtcDateTime;
            var serverStatus = new ServerStatusDataType
            {
                StartTime = nowUtc,
                CurrentTime = nowUtc,
                State = ServerState.Shutdown
            };

            var buildInfo = new BuildInfo
            {
                ProductName = m_serverDescription.ProductName,
                ProductUri = m_serverDescription.ProductUri,
                ManufacturerName = m_serverDescription.ManufacturerName,
                SoftwareVersion = m_serverDescription.SoftwareVersion,
                BuildNumber = m_serverDescription.BuildNumber,
                BuildDate = m_serverDescription.BuildDate
            };
            BuildInfoVariableState buildInfoVariableState =
                DiagnosticsNodeManager.FindPredefinedNode<BuildInfoVariableState>(
                    VariableIds.Server_ServerStatus_BuildInfo);
            var buildInfoVariable = new BuildInfoVariableValue(
                buildInfoVariableState,
                buildInfo,
                null!);
            serverStatus.BuildInfo = buildInfoVariable.Value;

            serverObject.ServerStatus!.MinimumSamplingInterval = 1000;
            serverObject.ServerStatus.CurrentTime!.MinimumSamplingInterval = 1000;

            NonThreadSafeStatus = new ServerStatusValue(
                serverObject.ServerStatus,
                serverStatus,
                DiagnosticsLock)
            {
                Timestamp = nowUtc,
                OnBeforeRead = OnReadServerStatus
            };

            // initialize diagnostics.
            ServerDiagnostics = new ServerDiagnosticsSummaryDataType
            {
                ServerViewCount = 0,
                CurrentSessionCount = 0,
                CumulatedSessionCount = 0,
                SecurityRejectedSessionCount = 0,
                RejectedSessionCount = 0,
                SessionTimeoutCount = 0,
                SessionAbortCount = 0,
                PublishingIntervalCount = 0,
                CurrentSubscriptionCount = 0,
                CumulatedSubscriptionCount = 0,
                SecurityRejectedRequestsCount = 0,
                RejectedRequestsCount = 0
            };

            await DiagnosticsNodeManager.CreateServerDiagnosticsAsync(
                DefaultSystemContext,
                ServerDiagnostics,
                OnUpdateDiagnostics,
                cancellationToken).ConfigureAwait(false);

            // set the diagnostics enabled state.
            await DiagnosticsNodeManager.SetDiagnosticsEnabledAsync(
                DefaultSystemContext,
                m_configuration.ServerConfiguration.DiagnosticsEnabled,
                cancellationToken).ConfigureAwait(false);

            var configurationNodeManager = DiagnosticsNodeManager as ConfigurationNodeManager;
            configurationNodeManager?.CreateServerConfiguration(
                    DefaultSystemContext,
                m_configuration);

            // Initialize history capabilities and update Server EventNotifier accordingly
            await DiagnosticsNodeManager.UpdateServerEventNotifierAsync(cancellationToken)
                .ConfigureAwait(false);

            Auditing = m_configuration.ServerConfiguration.AuditingEnabled;
            PropertyState<bool>? auditing = serverObject.Auditing;
            auditing!.OnSimpleWriteValue += OnWriteAuditing;
            auditing.OnSimpleReadValue += OnReadAuditing;
            auditing.Value = Auditing;
            auditing.AccessLevel = AccessLevels.CurrentRead;
            auditing.UserAccessLevel = AccessLevels.CurrentReadOrWrite;
            auditing.MinimumSamplingInterval = 1000;

            // Wire RoleManager into the well-known role nodes per Part 18 §4.
            // The binding upgrades RoleSet to the typed RoleSetState proxy,
            // wires typed OnCallAsync delegates on each Role's method-state
            // children, applies the SecurityAdmin + SignAndEncrypt
            // authorization gate, and raises RoleMappingRuleChangedAuditEvent
            // on every successful mutation.
            if (DiagnosticsNodeManager is AsyncCustomNodeManager diagnosticsCustom)
            {
                m_roleStateBinding = RoleStateBinding.Bind(diagnosticsCustom, RoleManager, this);
            }
        }

        /// <summary>
        /// Updates the server status before a read.
        /// </summary>
        private void OnReadServerStatus(
            ISystemContext context,
            BaseVariableValue variable,
            NodeState component)
        {
            lock (NonThreadSafeStatus.Lock)
            {
                DateTime now = m_timeProvider.GetUtcNow().UtcDateTime;
                NonThreadSafeStatus.Timestamp = now;
                NonThreadSafeStatus.Value.CurrentTime = now;

                // update other timestamps in NodeState objects which are used to derive the source timestamp
                if (variable is ServerStatusValue serverStatusValue &&
                    serverStatusValue.Variable is ServerStatusState serverStatusState)
                {
                    serverStatusState.Timestamp = now;
                    serverStatusState.CurrentTime!.Timestamp = now;
                    serverStatusState.State!.Timestamp = now;
                }
            }
        }

        /// <summary>
        /// Returns a copy of the namespace array.
        /// </summary>
        private ServiceResult OnReadNamespaceArray(
            ISystemContext context,
            NodeState node,
            ref Variant value)
        {
            value = NamespaceUris.ToArrayOf();
            return ServiceResult.Good;
        }

        /// <summary>
        /// Returns a copy of the server array.
        /// </summary>
        private ServiceResult OnReadServerArray(
            ISystemContext context,
            NodeState node,
            ref Variant value)
        {
            value = ServerUris.ToArrayOf();
            return ServiceResult.Good;
        }

        /// <summary>
        /// Returns Diagnostics.EnabledFlag
        /// </summary>
        private ServiceResult OnReadDiagnosticsEnabledFlag(
            ISystemContext context,
            NodeState node,
            ref Variant value)
        {
            value = DiagnosticsNodeManager.DiagnosticsEnabled;
            return ServiceResult.Good;
        }

        /// <summary>
        /// Sets the Diagnostics.EnabledFlag
        /// </summary>
        private ServiceResult OnWriteDiagnosticsEnabledFlag(
            ISystemContext context,
            NodeState node,
            ref Variant value)
        {
            bool enabled = (bool)value;
            DiagnosticsNodeManager.SetDiagnosticsEnabledAsync(DefaultSystemContext, enabled)
                .AsTask().GetAwaiter().GetResult();

            return ServiceResult.Good;
        }

        /// <summary>
        /// Updates the Server.Auditing flag.
        /// </summary>
        private ServiceResult OnWriteAuditing(
            ISystemContext context,
            NodeState node,
            ref Variant value)
        {
            Auditing = Convert.ToBoolean(value, CultureInfo.InvariantCulture);
            return ServiceResult.Good;
        }

        /// <summary>
        /// Reads the Server.Auditing flag.
        /// </summary>
        private ServiceResult OnReadAuditing(
            ISystemContext context,
            NodeState node,
            ref Variant value)
        {
            value = Auditing;
            return ServiceResult.Good;
        }

        /// <summary>
        /// Returns a copy of the current diagnostics.
        /// </summary>
        private ServiceResult OnUpdateDiagnostics(
            ISystemContext context,
            NodeState node,
            ref Variant value)
        {
            lock (ServerDiagnostics)
            {
                value = Variant.FromStructure(ServerDiagnostics);
            }

            return ServiceResult.Good;
        }

        /// <summary>
        /// Set the property to null if the value is zero,
        /// to the value otherwise.
        /// </summary>
        private static PropertyState<uint> SetPropertyValue(
            PropertyState<uint> property,
            uint value)
        {
            if (value != 0)
            {
                property.Value = value;
            }
            else
            {
                property = null!;
            }
            return property;
        }

        private readonly ServerProperties m_serverDescription;
        private readonly ApplicationConfiguration m_configuration;
        private readonly List<Uri> m_endpointAddresses;
        private readonly TimeProvider m_timeProvider;
        private RoleStateBinding? m_roleStateBinding;
        private volatile IReadOnlyList<ITransportListener>? m_transportListeners;
    }
}