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 * OPC Foundation MIT License 1.00
 *
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 * obtaining a copy of this software and associated documentation
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 *
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 * http://opcfoundation.org/License/MIT/1.00/
 * ======================================================================*/

// CA2007: tests run without a SynchronizationContext; ConfigureAwait(false)
// adds noise without a behavioural benefit. Disabled file-level for the suite.
#pragma warning disable CA2007
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using NUnit.Framework;
using Opc.Ua.Client;
using Opc.Ua.Configuration;
using Opc.Ua.Security.Certificates;
using Opc.Ua.Server.TestFramework;
using Opc.Ua.Tests;
using Quickstarts.ReferenceServer;

namespace Opc.Ua.Server.Tests
{
    /// <summary>
    /// Tests for CreateSession client certificate ApplicationUri validation.
    /// Validates that StandardServer.CreateSession correctly verifies that the ApplicationUri
    /// in the ApplicationDescription parameter matches the URIs in the client certificate.
    /// Tests include single URI, multiple URIs, matching and non-matching scenarios.
    /// </summary>
    [TestFixture]
    [Category("Server")]
    [SetCulture("en-us")]
    [SetUICulture("en-us")]
    [Parallelizable]
    public class CreateSessionApplicationUriValidationTests
    {
        private const string kClientApplicationUri = "urn:localhost:opcfoundation.org:TestClient";
        private const string kClientSubjectName = "CN=TestClient, O=OPC Foundation";
        private ServerFixture<StandardServer> m_serverFixture;
        private string m_pkiRoot;

        /// <summary>
        /// Certificate types to test.
        /// Note: Currently only testing RSA certificates. ECC certificates require ECC-compatible
        /// security policies which add complexity beyond the scope of ApplicationUri validation testing.
        /// </summary>
        private static readonly NodeId[] s_certificateTypes =
        [
            ObjectTypeIds.RsaMinApplicationCertificateType
        ];

        [OneTimeSetUp]
        public async Task OneTimeSetUpAsync()
        {
            m_pkiRoot = Path.GetTempPath() + Path.GetRandomFileName() + Path.DirectorySeparatorChar;

            // Start a server for testing CreateSession
            m_serverFixture = new ServerFixture<StandardServer>(t => new ReferenceServer(t))
            {
                AutoAccept = true,
                AllNodeManagers = true,
                SecurityNone = false // Require encryption to enable certificate validation
            };

            await m_serverFixture.LoadConfigurationAsync(m_pkiRoot).ConfigureAwait(false);
            await m_serverFixture.StartAsync().ConfigureAwait(false);
        }

        [OneTimeTearDown]
        public async Task OneTimeTearDownAsync()
        {
            if (m_serverFixture != null)
            {
                await m_serverFixture.StopAsync().ConfigureAwait(false);
            }

            try
            {
                if (Directory.Exists(m_pkiRoot))
                {
                    Directory.Delete(m_pkiRoot, true);
                }
            }
            catch
            {
                // Ignore cleanup errors
            }
        }

        /// <summary>
        /// Test that CreateSession succeeds when client certificate has matching ApplicationUri.
        /// </summary>
        [Test]
        [TestCaseSource(nameof(s_certificateTypes))]
        public async Task CreateSessionWithMatchingApplicationUriSucceedsAsync(NodeId certificateType)
        {
            // Skip test if certificate type is not supported on this platform
            if (!Utils.IsSupportedCertificateType(certificateType))
            {
                Assert.Ignore($"Certificate type {certificateType} is not supported on this platform.");
            }

            // Create client certificate with matching ApplicationUri
            using Certificate clientCert = CreateCertificateWithMultipleUris(
                [kClientApplicationUri],
                kClientSubjectName,
                [Utils.GetHostName()],
                certificateType);

            // Attempt to create session - should succeed
            Client.ISession session = await CreateSessionWithCustomCertificateAsync(clientCert, kClientApplicationUri).ConfigureAwait(false);
            Assert.That(session, Is.Not.Null);
            Assert.That(session.Connected, Is.True, "Session should be connected");

            // Verify session is functional by reading server state
            DataValue result = await session.ReadValueAsync(VariableIds.Server_ServerStatus_State).ConfigureAwait(false);
            Assert.That(result.IsNull, Is.False, "Should be able to read server state");
            Assert.That(result.StatusCode, Is.EqualTo(StatusCodes.Good), "Read operation should succeed");

            await session.CloseAsync(5_000, true).ConfigureAwait(false);
            session.Dispose();
        }

        /// <summary>
        /// Test that CreateSession throws BadCertificateUriInvalid when client certificate ApplicationUri doesn't match.
        /// </summary>
        [Test]
        [TestCaseSource(nameof(s_certificateTypes))]
        public void CreateSessionWithMismatchedApplicationUriThrows(NodeId certificateType)
        {
            // Skip test if certificate type is not supported on this platform
            if (!Utils.IsSupportedCertificateType(certificateType))
            {
                Assert.Ignore($"Certificate type {certificateType} is not supported on this platform.");
            }

            // Create client certificate with different ApplicationUri
            const string certUri = "urn:localhost:opcfoundation.org:WrongClient";
            using Certificate clientCert = CreateCertificateWithMultipleUris(
                [certUri],
                kClientSubjectName,
                [Utils.GetHostName()],
                certificateType);

            // Attempt to create session - should throw BadCertificateUriInvalid
            ServiceResultException ex = Assert.ThrowsAsync<ServiceResultException>(async () =>
                await CreateSessionWithCustomCertificateAsync(clientCert, kClientApplicationUri).ConfigureAwait(false));
            Assert.That(ex.StatusCode, Is.EqualTo(StatusCodes.BadCertificateUriInvalid));
        }

        /// <summary>
        /// Test that CreateSession succeeds when client certificate has multiple URIs and one matches.
        /// </summary>
        [Test]
        [TestCaseSource(nameof(s_certificateTypes))]
        public async Task CreateSessionWithMultipleUrisOneMatchesSucceedsAsync(NodeId certificateType)
        {
            // Skip test if certificate type is not supported on this platform
            if (!Utils.IsSupportedCertificateType(certificateType))
            {
                Assert.Ignore($"Certificate type {certificateType} is not supported on this platform.");
            }

            // Create client certificate with multiple URIs, including the matching one
            const string uri1 = "urn:localhost:opcfoundation.org:App1";
            const string uri2 = kClientApplicationUri; // This matches
            const string uri3 = "https://localhost:8080/OpcUaApp";

            using Certificate clientCert = CreateCertificateWithMultipleUris(
                [uri1, uri2, uri3],
                kClientSubjectName,
                [Utils.GetHostName()],
                certificateType);

            // Verify certificate has multiple URIs
            IReadOnlyList<string> uris = X509Utils.GetApplicationUrisFromCertificate(clientCert);
            Assert.That(uris, Has.Count.EqualTo(3));
            Assert.Contains(uri1, uris.ToList());
            Assert.Contains(uri2, uris.ToList());
            Assert.Contains(uri3, uris.ToList());

            // Attempt to create session - should succeed because one URI matches
            Client.ISession session = await CreateSessionWithCustomCertificateAsync(clientCert, kClientApplicationUri).ConfigureAwait(false);
            Assert.That(session, Is.Not.Null);
            Assert.That(session.Connected, Is.True, "Session should be connected");

            // Verify session is functional by reading server state
            DataValue result = await session.ReadValueAsync(VariableIds.Server_ServerStatus_State).ConfigureAwait(false);
            Assert.That(result.IsNull, Is.False, "Should be able to read server state");
            Assert.That(result.StatusCode, Is.EqualTo(StatusCodes.Good), "Read operation should succeed");

            await session.CloseAsync(5_000, true).ConfigureAwait(false);
            session.Dispose();
        }

        /// <summary>
        /// Test that CreateSession throws BadCertificateUriInvalid when client certificate has multiple URIs but none match.
        /// </summary>
        [Test]
        [TestCaseSource(nameof(s_certificateTypes))]
        public void CreateSessionWithMultipleUrisNoneMatchThrows(NodeId certificateType)
        {
            // Skip test if certificate type is not supported on this platform
            if (!Utils.IsSupportedCertificateType(certificateType))
            {
                Assert.Ignore($"Certificate type {certificateType} is not supported on this platform.");
            }

            // Create client certificate with multiple URIs, none matching
            const string uri1 = "urn:localhost:opcfoundation.org:App1";
            const string uri2 = "urn:localhost:opcfoundation.org:App2";
            const string uri3 = "https://localhost:8080/OpcUaApp";

            using Certificate clientCert = CreateCertificateWithMultipleUris(
                [uri1, uri2, uri3],
                kClientSubjectName,
                [Utils.GetHostName()],
                certificateType);

            // Verify certificate has multiple URIs
            IReadOnlyList<string> uris = X509Utils.GetApplicationUrisFromCertificate(clientCert);
            Assert.That(uris, Has.Count.EqualTo(3));
            Assert.Contains(uri1, uris.ToList());
            Assert.Contains(uri2, uris.ToList());
            Assert.Contains(uri3, uris.ToList());

            // Attempt to create session - should throw BadCertificateUriInvalid
            ServiceResultException ex = Assert.ThrowsAsync<ServiceResultException>(async () =>
                await CreateSessionWithCustomCertificateAsync(clientCert, kClientApplicationUri).ConfigureAwait(false));
            Assert.That(ex.StatusCode, Is.EqualTo(StatusCodes.BadCertificateUriInvalid));
        }

        /// <summary>
        /// Helper method to create a session with a custom client certificate.
        /// </summary>
        private async Task<Client.ISession> CreateSessionWithCustomCertificateAsync(
            Certificate clientCertificate,
            string clientApplicationUri)
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            ILogger logger = telemetry.CreateLogger<CreateSessionApplicationUriValidationTests>();

            // Create temporary PKI directory
            string clientPkiRoot = Path.GetTempPath() + Path.GetRandomFileName() + Path.DirectorySeparatorChar;
            Directory.CreateDirectory(clientPkiRoot);

            try
            {
                // Save certificate to a temporary store
                string certStorePath = Path.Combine(clientPkiRoot, "own");
                Directory.CreateDirectory(certStorePath);

                using (ICertificateStore store = CertificateStoreIdentifier.CreateStore(CertificateStoreType.Directory, telemetry))
                {
                    store.Open(certStorePath, false);
                    await store.AddAsync(clientCertificate).ConfigureAwait(false);
                }

                // Create certificate identifier pointing to the stored
                // certificate. The identifier is metadata-only — the
                // resolver loads the cert from the store on demand.
                var certIdentifier = new CertificateIdentifier
                {
                    StoreType = CertificateStoreType.Directory,
                    StorePath = certStorePath,
                    SubjectName = clientCertificate.SubjectName.Name,
                    Thumbprint = clientCertificate.Thumbprint,
                    CertificateType = CertificateIdentifier.GetCertificateType(clientCertificate)
                };

                // Create client application configuration
                var clientApp = new ApplicationInstance(telemetry)
                {
                    ApplicationName = "TestClient",
                    ApplicationType = ApplicationType.Client
                };
                await using (clientApp.ConfigureAwait(false))
                {
                    ApplicationConfiguration clientConfig = await clientApp
                        .Build(clientApplicationUri, "uri:opcfoundation.org:TestClient")
                        .AsClient()
                        .AddSecurityConfiguration([certIdentifier], clientPkiRoot)
                        .SetMinimumCertificateKeySize(256)
                        .SetAutoAcceptUntrustedCertificates(true)
                        .CreateAsync()
                        .ConfigureAwait(false);

                    // Get server endpoint with RSA-compatible security policy
                    EndpointDescription endpoint = m_serverFixture.Server.GetEndpoints()
                        .Find(e => e.SecurityMode == MessageSecurityMode.SignAndEncrypt &&
                            e.SecurityPolicyUri == SecurityPolicies.Basic256Sha256);

                    Assert.That(endpoint, Is.Not.Null, "No suitable endpoint found");

                    var endpointConfiguration = EndpointConfiguration.Create(clientConfig);
                    endpointConfiguration.OperationTimeout = 10000;
                    var configuredEndpoint = new ConfiguredEndpoint(null, endpoint, endpointConfiguration);

                    // Create and open session with retry logic for transient errors
                    var sessionFactory = new DefaultSessionFactory(telemetry);
                    const int maxAttempts = 40;
                    const int delayMs = 5000;
                    for (int attempt = 0; ; attempt++)
                    {
                        try
                        {
                            return await sessionFactory.CreateAsync(
                                clientConfig,
                                configuredEndpoint,
                                false, // updateBeforeConnect
                                false, // checkDomain
                                "TestSession",
                                60000, // sessionTimeout
                                null, // userIdentity
                                default) // preferredLocales
                                .ConfigureAwait(false);
                        }
                        catch (ServiceResultException e) when (
                        (
                            e.StatusCode == StatusCodes.BadServerHalted ||
                            e.StatusCode == StatusCodes.BadSecureChannelClosed ||
                            e.StatusCode == StatusCodes.BadNoCommunication ||
                            e.StatusCode == StatusCodes.BadNotConnected
                        ) &&
                        attempt < maxAttempts)
                        {
                            // Retry for transient connection errors (can happen on busy CI environments)
                            logger.LogWarning(
                                e,
                                "Failed to create session (attempt {Attempt}/{MaxAttempts}). Retrying in {DelayMs}ms... Error: {StatusCode}",
                                attempt + 1,
                                maxAttempts,
                                delayMs,
                                e.Code);
                            await Task.Delay(delayMs).ConfigureAwait(false);
                        }
                    }
                }
            }
            finally
            {
                // Clean up temp PKI
                try
                {
                    if (Directory.Exists(clientPkiRoot))
                    {
                        Directory.Delete(clientPkiRoot, true);
                    }
                }
                catch
                {
                    // Ignore cleanup errors
                }
            }
        }

        /// <summary>
        /// Creates a certificate with multiple application URIs in the SAN extension.
        /// </summary>
        private static Certificate CreateCertificateWithMultipleUris(
            IList<string> applicationUris,
            string subjectName,
            IList<string> domainNames,
            NodeId certificateType = default)
        {
            DateTime notBefore = DateTime.Today.AddDays(-1);
            DateTime notAfter = DateTime.Today.AddYears(1);

            // Default to RSA if not specified
            if (certificateType.IsNull)
            {
                certificateType = ObjectTypeIds.RsaSha256ApplicationCertificateType;
            }
            // Create the SAN extension with multiple URIs
            var subjectAltName = new X509SubjectAltNameExtension(applicationUris, domainNames);

            // Build the certificate with the custom SAN extension
            ICertificateBuilder builder = CertificateBuilder
                .Create(subjectName)
                .SetNotBefore(notBefore)
                .SetNotAfter(notAfter)
                .AddExtension(subjectAltName);

            // Create certificate based on type
            if (certificateType == ObjectTypeIds.RsaSha256ApplicationCertificateType ||
                certificateType == ObjectTypeIds.RsaMinApplicationCertificateType)
            {
                return builder.SetRSAKeySize(CertificateFactory.DefaultKeySize).CreateForRSA();
            }
            else if (certificateType == ObjectTypeIds.EccNistP256ApplicationCertificateType)
            {
                return builder.SetECCurve(ECCurve.NamedCurves.nistP256).CreateForECDsa();
            }
            else if (certificateType == ObjectTypeIds.EccNistP384ApplicationCertificateType)
            {
                return builder.SetECCurve(ECCurve.NamedCurves.nistP384).CreateForECDsa();
            }
            else if (certificateType == ObjectTypeIds.EccBrainpoolP256r1ApplicationCertificateType)
            {
                return builder.SetECCurve(ECCurve.NamedCurves.brainpoolP256r1).CreateForECDsa();
            }
            else if (certificateType == ObjectTypeIds.EccBrainpoolP384r1ApplicationCertificateType)
            {
                return builder.SetECCurve(ECCurve.NamedCurves.brainpoolP384r1).CreateForECDsa();
            }
            else
            {
                // Default to RSA for unknown types
                return builder.SetRSAKeySize(CertificateFactory.DefaultKeySize).CreateForRSA();
            }
        }
    }
}