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using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using Opc.Ua.Security.Certificates;
using Opc.Ua.Server;
using Quickstarts.ReferenceServer;

namespace Opc.Ua.Client.TestFramework
{
    /// <summary>
    /// <para>
    /// Reference Server modification which allows to change the maximum number
    /// of (browse) continuation points during the execution of a test.
    /// This makes it easier to compare browse results without any restriction
    /// with results where the server may allocate only a limited number of
    /// continuation points.
    /// To make this work some other classes must be derived and modified, as
    /// well (see the ServerSessionWithLimits, SessionManagerWithLimits and
    /// MasterNodeManagerWithLimits classes).
    /// </para>
    /// <para>
    /// Use with care. This class and especially its dedicated functionality
    /// should be used for test purposes only.
    /// </para>
    /// </summary>
    public class ReferenceServerWithLimits : ReferenceServer
    {
        public ReferenceServerWithLimits(ITelemetryContext telemetry)
            : base(telemetry)
        {
        }

        public uint TestMaxBrowseReferencesPerNode { get; set; } = 10u;
        private MasterNodeManager MasterNodeManagerReference { get; set; } = null!;
        private SessionManagerWithLimits SessionManagerForTest { get; set; } = null!;

        public override ValueTask<BrowseResponse> BrowseAsync(
            SecureChannelContext secureChannelContext,
            RequestHeader? requestHeader,
            ViewDescription? view,
            uint requestedMaxReferencesPerNode,
            ArrayOf<BrowseDescription> nodesToBrowse,
            RequestLifetime requestLifetime)
        {
            return base.BrowseAsync(
                secureChannelContext,
                requestHeader,
                view,
                TestMaxBrowseReferencesPerNode,
                nodesToBrowse,
                requestLifetime);
        }

        public void SetMaxNumberOfContinuationPoints(uint maxNumberOfContinuationPoints)
        {
            Configuration!.ServerConfiguration!.MaxBrowseContinuationPoints
                = (int)maxNumberOfContinuationPoints;
            ((MasterNodeManagerWithLimits)MasterNodeManagerReference)
                .MaxContinuationPointsPerBrowseForUnitTest =
                maxNumberOfContinuationPoints;
            foreach (Server.ISession session in SessionManagerForTest.GetSessions().ToList())
            {
                try
                {
                    ((ServerSessionWithLimits)session).SetMaxNumberOfContinuationPoints(
                        maxNumberOfContinuationPoints);
                }
                catch
                {
                }
            }
        }

        protected override IMasterNodeManager CreateMasterNodeManager(
            IServerInternal server,
            ApplicationConfiguration configuration)
        {
            m_logger.LogInformation(
                Utils.TraceMasks.StartStop,
                "Creating the Reference Server Node Manager.");

            var nodeManagers = new List<INodeManager>();

            // create the custom node manager (ownership transfers to MasterNodeManager).
#pragma warning disable CA2000 // Dispose objects before losing scope - ownership transfers to MasterNodeManagerWithLimits
            var referenceNodeManager = new ReferenceNodeManager(
                server,
                configuration);
#pragma warning restore CA2000
            List<IAsyncNodeManager> asyncNodeManagers = [referenceNodeManager];

            foreach (INodeManagerFactory nodeManagerFactory in NodeManagerFactories)
            {
                nodeManagers.Add(nodeManagerFactory.Create(server, configuration));
            }
            //this.MasterNodeManagerReference = new MasterNodeManager(server, configuration, null, nodeManagers.ToArray());
            MasterNodeManagerReference = new MasterNodeManagerWithLimits(
                server,
                configuration,
                null!,
                asyncNodeManagers,
                [.. nodeManagers]);
            // create master node manager.
            return MasterNodeManagerReference;
        }

        protected override ISessionManager CreateSessionManager(
            IServerInternal server,
            ApplicationConfiguration configuration)
        {
            SessionManagerForTest = new SessionManagerWithLimits(server, configuration);
            return SessionManagerForTest;
        }
    }

    /// <summary>
    /// provide a means to set the maximum number of browse continuation points to
    /// the (Server) session.
    /// </summary>
    public class ServerSessionWithLimits : Server.Session
    {
        public ServerSessionWithLimits(
            OperationContext context,
            IServerInternal server,
            Certificate serverCertificate,
            NodeId authenticationToken,
            ByteString clientNonce,
            Nonce serverNonce,
            string sessionName,
            ApplicationDescription clientDescription,
            string endpointUrl,
            Certificate clientCertificate,
            CertificateCollection clientCertificateChain,
            double sessionTimeout,
            uint maxResponseMessageSize,
            double maxRequestAge,
            int maxBrowseContinuationPoints,
            int maxHistoryContinuationPoints)
            : base(
                context,
                server,
                serverCertificate,
                authenticationToken,
                clientNonce,
                serverNonce,
                sessionName,
                clientDescription,
                endpointUrl,
                clientCertificate,
                clientCertificateChain,
                sessionTimeout,
                maxBrowseContinuationPoints,
                maxHistoryContinuationPoints)
        {
        }

        public void SetMaxNumberOfContinuationPoints(uint maxNumberOfContinuationPoints)
        {
            MaxBrowseContinuationPoints = (int)maxNumberOfContinuationPoints;
        }
    }

    /// <summary>
    /// ensures that the (Server) session is the derived one for the test.
    /// </summary>
    public class SessionManagerWithLimits : SessionManager
    {
        private readonly IServerInternal m_4TestServer;
        private readonly int m_4TestMaxRequestAge;
        private readonly int m_4TestMaxBrowseContinuationPoints;
        private readonly int m_4TestMaxHistoryContinuationPoints;

        public SessionManagerWithLimits(
            IServerInternal server,
            ApplicationConfiguration configuration)
            : base(server, configuration)
        {
            m_4TestServer = server;
            m_4TestMaxRequestAge = configuration.ServerConfiguration!.MaxRequestAge;
            m_4TestMaxBrowseContinuationPoints = configuration.ServerConfiguration
                .MaxBrowseContinuationPoints;
            m_4TestMaxHistoryContinuationPoints = configuration.ServerConfiguration
                .MaxHistoryContinuationPoints;
        }

        /// <summary>
        /// TBD - Remove unused parameter.
        /// </summary>
        protected override Server.ISession CreateSession(
            OperationContext context,
            IServerInternal server,
            Certificate serverCertificate,
            NodeId sessionCookie,
            ByteString clientNonce,
            Nonce serverNonce,
            string sessionName,
            ApplicationDescription clientDescription,
            string endpointUrl,
            Certificate clientCertificate,
            CertificateCollection clientCertificateChain,
            double sessionTimeout,
            uint maxResponseMessageSize,
            int maxRequestAge, // TBD - Remove unused parameter.
            int maxContinuationPoints)
        {
            return new ServerSessionWithLimits(
                context,
                m_4TestServer,
                serverCertificate,
                sessionCookie,
                clientNonce,
                serverNonce,
                sessionName,
                clientDescription,
                endpointUrl,
                clientCertificate,
                clientCertificateChain,
                sessionTimeout,
                maxResponseMessageSize,
                m_4TestMaxRequestAge,
                m_4TestMaxBrowseContinuationPoints,
                m_4TestMaxHistoryContinuationPoints);
        }
    }

    /// <summary>
    /// Hack which ensures the injected maximum number of browse continuation points
    /// is really used when the browse service call is executed.
    /// </summary>
    public class MasterNodeManagerWithLimits : MasterNodeManager
    {
        public MasterNodeManagerWithLimits(
            IServerInternal server,
            ApplicationConfiguration configuration,
            string dynamicNamespaceUri,
            IEnumerable<IAsyncNodeManager> additionalManagers,
            IEnumerable<INodeManager> additionalSyncManagers)
            : base(server, configuration, dynamicNamespaceUri, additionalManagers, additionalSyncManagers)
        {
            m_logger = server.Telemetry.CreateLogger<MasterNodeManagerWithLimits>();
        }

        public uint MaxContinuationPointsPerBrowseForUnitTest { get; set; }

        /// <summary>
        /// Returns the set of references that meet the filter criteria.
        /// </summary>
        /// <exception cref="ArgumentNullException"><paramref name="context"/> is <c>null</c>.</exception>
        /// <exception cref="ServiceResultException"></exception>
        public override async ValueTask<(ArrayOf<BrowseResult> results, ArrayOf<DiagnosticInfo> diagnosticInfos)> BrowseAsync(
            OperationContext context,
            ViewDescription view,
            uint maxReferencesPerNode,
            ArrayOf<BrowseDescription> nodesToBrowse,
            CancellationToken cancellationToken = default)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            if (view != null && !view.ViewId.IsNull)
            {
                (object? viewHandle, IAsyncNodeManager? viewManager) =
                    await GetManagerHandleAsync(view.ViewId, cancellationToken)
                    .ConfigureAwait(false);

                if (viewHandle == null || viewManager == null)
                {
                    throw new ServiceResultException(StatusCodes.BadViewIdUnknown);
                }

                NodeMetadata metadata = await viewManager.GetNodeMetadataAsync(
                        context,
                        viewHandle,
                        BrowseResultMask.NodeClass,
                        cancellationToken)
                    .ConfigureAwait(false);

                if (metadata == null || metadata.NodeClass != NodeClass.View)
                {
                    throw new ServiceResultException(StatusCodes.BadViewIdUnknown);
                }

                // validate access rights and role permissions
                ServiceResult validationResult = await ValidatePermissionsAsync(
                        context,
                        viewManager,
                        viewHandle,
                        PermissionType.Browse,
                        null,
                        true,
                        cancellationToken)
                    .ConfigureAwait(false);
                if (ServiceResult.IsBad(validationResult))
                {
                    throw new ServiceResultException(validationResult);
                }
                view.Handle = viewHandle;
            }

            bool diagnosticsExist = false;
            var results = new List<BrowseResult>(nodesToBrowse.Count);
            var diagnosticInfos = new List<DiagnosticInfo>(nodesToBrowse.Count);

            uint continuationPointsAssigned = 0;

            for (int ii = 0; ii < nodesToBrowse.Count; ii++)
            {
                // check if request has timed out or been cancelled.
                if (StatusCode.IsBad(context.OperationStatus))
                {
                    // release all allocated continuation points.
                    foreach (BrowseResult current in results)
                    {
                        if (current != null && !current.ContinuationPoint.IsEmpty)
                        {
                            ContinuationPoint cp = context.Session
                                .ContinuationPoints.RestoreBrowse(current.ContinuationPoint)!;
                            cp!.Dispose();
                        }
                    }

                    throw new ServiceResultException(context.OperationStatus);
                }

                BrowseDescription nodeToBrowse = nodesToBrowse[ii];

                // initialize result.
                var result = new BrowseResult { StatusCode = StatusCodes.Good };
                results.Add(result);

                ServiceResult error;

                // need to trap unexpected exceptions to handle bugs in the node managers.
                try
                {
                    error = await BrowseAsync(
                        context,
                        view,
                        maxReferencesPerNode,
                        MaxContinuationPointsPerBrowseForUnitTest <= 0 ||
                        continuationPointsAssigned < MaxContinuationPointsPerBrowseForUnitTest,
                        nodeToBrowse,
                        result,
                        cancellationToken).ConfigureAwait(false);
                }
                catch (Exception e)
                {
                    error = ServiceResult.Create(
                        e,
                        StatusCodes.BadUnexpectedError,
                        "Unexpected error browsing node.");
                }

                // check for continuation point.
                if (!result.ContinuationPoint.IsEmpty)
                {
                    continuationPointsAssigned++;
                }

                // check for error.
                result.StatusCode = error.StatusCode;

                if ((context.DiagnosticsMask & DiagnosticsMasks.OperationAll) != 0)
                {
                    DiagnosticInfo? diagnosticInfo = null;

                    if (error != null && error.Code != StatusCodes.Good)
                    {
                        diagnosticInfo = ServerUtils.CreateDiagnosticInfo(Server, context, error, m_logger)!;
                        diagnosticsExist = true;
                    }

                    diagnosticInfos.Add(diagnosticInfo!);
                }
            }

            // clear the diagnostics array if no diagnostics requested or no errors occurred.
            UpdateDiagnostics(context, diagnosticsExist, ref diagnosticInfos);

            return (results, diagnosticInfos);
        }

        private readonly ILogger m_logger;
    }
}