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 * OPC Foundation MIT License 1.00
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using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using NUnit.Framework;
using Opc.Ua.Bindings;
using Opc.Ua.Tests;

namespace Opc.Ua.Server.Tests
{
    /// <summary>
    /// Deterministic, offline unit tests for the guard clauses and state helpers
    /// of <see cref="StandardServer"/> that are reachable without starting the server.
    /// </summary>
    [TestFixture]
    [Category("StandardServer")]
    [Parallelizable(ParallelScope.All)]
    public class StandardServerCoverageTests
    {
        private sealed class TestableStandardServer : StandardServer
        {
            public TestableStandardServer(ITelemetryContext telemetry)
                : base(telemetry)
            {
            }

            public TestableStandardServer(ITelemetryContext telemetry, TimeProvider timeProvider)
                : base(telemetry, timeProvider)
            {
            }

            public TimeProvider TimeProviderAccessor => TimeProvider;

            public void ValidateRequestPublic(RequestHeader requestHeader)
            {
                ValidateRequest(requestHeader);
            }

            public ValueTask<OperationContext> ValidateRequestInScopePublicAsync()
            {
                return ValidateRequestAsync(
                    null!,
                    new RequestHeader(),
                    RequestType.Read,
                    RequestLifetime.None);
            }

            public void SetServerStatePublic(ServerState state)
            {
                SetServerState(state);
            }

            public void SetServerErrorPublic(ServiceResult error)
            {
                SetServerError(error);
            }

            public void OnApplicationCertificateErrorPublic(ByteString clientCertificate, ServiceResult result)
            {
                OnApplicationCertificateError(clientCertificate, result);
            }

            public async Task InitializeAndDiscardServiceHostsAsync(
                ApplicationConfiguration configuration,
                ITransportBindingRegistry registry)
            {
                await InitializeServiceHostsAsync(configuration, registry).ConfigureAwait(false);
            }
        }

        private sealed class TestTimeProvider : TimeProvider;

        private static TestableStandardServer CreateServer()
        {
            return new TestableStandardServer(NUnitTelemetryContext.Create());
        }

        [Test]
        public void ConstructorUsesSystemTimeProviderByDefault()
        {
            using TestableStandardServer server = CreateServer();

            Assert.That(server.TimeProviderAccessor, Is.SameAs(TimeProvider.System));
        }

        [Test]
        public void ConstructorUsesProvidedTimeProvider()
        {
            var custom = new TestTimeProvider();
            using var server = new TestableStandardServer(NUnitTelemetryContext.Create(), custom);

            Assert.That(server.TimeProviderAccessor, Is.SameAs(custom));
        }

        [Test]
        public void DisposeCanBeCalledMoreThanOnce()
        {
            TestableStandardServer server = CreateServer();

            server.Dispose();

            Assert.DoesNotThrow(server.Dispose);
        }

        [Test]
        public void LoadComplexTypesDefaultsToTrue()
        {
            using TestableStandardServer server = CreateServer();

            Assert.That(server.LoadComplexTypes, Is.True);
        }

        [Test]
        public void LoadComplexTypesCanBeDisabled()
        {
            using TestableStandardServer server = CreateServer();

            server.LoadComplexTypes = false;

            Assert.That(server.LoadComplexTypes, Is.False);
        }

        [Test]
        public void CurrentInstanceThrowsWhenNotStarted()
        {
            using TestableStandardServer server = CreateServer();

            ServiceResultException ex = Assert.Throws<ServiceResultException>(
                () => _ = server.CurrentInstance);
            Assert.That(ex.StatusCode, Is.EqualTo((uint)StatusCodes.BadServerHalted));
        }

        [Test]
        public void CurrentStateThrowsWhenNotStarted()
        {
            using TestableStandardServer server = CreateServer();

            ServiceResultException ex = Assert.Throws<ServiceResultException>(
                () => _ = server.CurrentState);
            Assert.That(ex.StatusCode, Is.EqualTo((uint)StatusCodes.BadServerHalted));
        }

        [Test]
        public void GetStatusThrowsWhenNotStarted()
        {
            using TestableStandardServer server = CreateServer();

#pragma warning disable CS0618 // GetStatus is obsolete but still exercised for coverage.
            ServiceResultException ex = Assert.Throws<ServiceResultException>(
                () => server.GetStatus());
#pragma warning restore CS0618
            Assert.That(ex.StatusCode, Is.EqualTo((uint)StatusCodes.BadServerHalted));
        }

        [Test]
        public void ValidateRequestThrowsWhenNotStarted()
        {
            using TestableStandardServer server = CreateServer();

            ServiceResultException ex = Assert.Throws<ServiceResultException>(
                () => server.ValidateRequestPublic(new RequestHeader()));
            Assert.That(ex.StatusCode, Is.EqualTo((uint)StatusCodes.BadServerHalted));
        }

        [Test]
        public Task ValidateRequestInScopeThrowsWhenNotStartedAsync()
        {
            using TestableStandardServer server = CreateServer();

            ServiceResultException exception = Assert.ThrowsAsync<ServiceResultException>(
                async () => await server
                    .ValidateRequestInScopePublicAsync()
                    .ConfigureAwait(false));

            Assert.That(
                exception.StatusCode,
                Is.EqualTo((uint)StatusCodes.BadServerHalted));
            return Task.CompletedTask;
        }

        [Test]
        public void SetServerStateThrowsWhenNotStarted()
        {
            using TestableStandardServer server = CreateServer();

            ServiceResultException ex = Assert.Throws<ServiceResultException>(
                () => server.SetServerStatePublic(ServerState.Running));
            Assert.That(ex.StatusCode, Is.EqualTo((uint)StatusCodes.BadServerHalted));
        }

        [Test]
        public void SetServerErrorUpdatesServerErrorProperty()
        {
            using TestableStandardServer server = CreateServer();
            var error = new ServiceResult(StatusCodes.BadInternalError);

            server.SetServerErrorPublic(error);

            Assert.That(server.ServerError, Is.EqualTo(error));
        }

        [Test]
        public void ValidateRequestThrowsServerErrorWhenSet()
        {
            using TestableStandardServer server = CreateServer();
            server.SetServerErrorPublic(new ServiceResult(StatusCodes.BadInternalError));

            ServiceResultException ex = Assert.Throws<ServiceResultException>(
                () => server.ValidateRequestPublic(new RequestHeader()));
            Assert.That(ex.StatusCode, Is.EqualTo((uint)StatusCodes.BadInternalError));
        }

        [Test]
        public void SetServerStateThrowsServerErrorWhenSet()
        {
            using TestableStandardServer server = CreateServer();
            server.SetServerErrorPublic(new ServiceResult(StatusCodes.BadInternalError));

            ServiceResultException ex = Assert.Throws<ServiceResultException>(
                () => server.SetServerStatePublic(ServerState.Running));
            Assert.That(ex.StatusCode, Is.EqualTo((uint)StatusCodes.BadInternalError));
        }

        [Test]
        public void OnApplicationCertificateErrorMapsToSecurityChecksFailed()
        {
            StatusCode[] certStatusCodes =
            [
                StatusCodes.BadCertificateInvalid,
                StatusCodes.BadCertificateRevoked,
                StatusCodes.BadCertificateUntrusted,
                StatusCodes.BadCertificateIssuerRevoked,
                StatusCodes.BadCertificateRevocationUnknown,
                StatusCodes.BadCertificateChainIncomplete,
                StatusCodes.BadCertificateIssuerRevocationUnknown,
                StatusCodes.BadCertificatePolicyCheckFailed
            ];
            using TestableStandardServer server = CreateServer();

            foreach (StatusCode certStatusCode in certStatusCodes)
            {
                ServiceResultException ex = Assert.Throws<ServiceResultException>(
                    () => server.OnApplicationCertificateErrorPublic(
                        ByteString.Empty,
                        new ServiceResult(certStatusCode)));
                Assert.That(ex.StatusCode, Is.EqualTo((uint)StatusCodes.BadSecurityChecksFailed));
            }
        }

        [Test]
        public void OnApplicationCertificateErrorPassesThroughUnmappedCode()
        {
            using TestableStandardServer server = CreateServer();

            ServiceResultException ex = Assert.Throws<ServiceResultException>(
                () => server.OnApplicationCertificateErrorPublic(
                    ByteString.Empty,
                    new ServiceResult(StatusCodes.BadCertificateTimeInvalid)));
            Assert.That(ex.StatusCode, Is.EqualTo((uint)StatusCodes.BadCertificateTimeInvalid));
        }

        [Test]
        public void OnApplicationCertificateErrorMapsNestedRevocationErrorToSecurityChecksFailed()
        {
            // the certificate validator nests every failed check; an expired certificate whose
            // issuer has no revocation list must not reveal the revocation state (Part 4 §6.1.3).
            using TestableStandardServer server = CreateServer();

            ServiceResultException ex = Assert.Throws<ServiceResultException>(
                () => server.OnApplicationCertificateErrorPublic(
                    ByteString.Empty,
                    new ServiceResult(
                        StatusCodes.BadCertificateTimeInvalid,
                        new ServiceResult(StatusCodes.BadCertificateIssuerRevocationUnknown))));
            Assert.That(ex.StatusCode, Is.EqualTo((uint)StatusCodes.BadSecurityChecksFailed));
        }

        [Test]
        public void InitializeServiceHostsThrowsForUnregisteredScheme()
        {
            using TestableStandardServer server = CreateServer();
            ApplicationConfiguration configuration = CreateConfiguration(
                "opc.https://localhost:62540/TestServer");
            var registry = new DefaultTransportBindingRegistry();

            InvalidOperationException ex = Assert.ThrowsAsync<InvalidOperationException>(
                async () => await server.InitializeAndDiscardServiceHostsAsync(configuration, registry)
                    .ConfigureAwait(false))!;

            Assert.That(ex.Message, Does.Contain("opc.https"));
            Assert.That(ex.Message, Does.Contain("AddHttpsTransport"));
        }

        [Test]
        public async Task InitializeServiceHostsUsesRegisteredFactoryAsync()
        {
            using TestableStandardServer server = CreateServer();
            ApplicationConfiguration configuration = CreateConfiguration(
                "opc.tcp://localhost:62541/TestServer");
            var registry = new DefaultTransportBindingRegistry();
            var factory = new FakeTcpListenerFactory();
            registry.RegisterListenerFactory(factory);

            await server.InitializeAndDiscardServiceHostsAsync(configuration, registry)
                .ConfigureAwait(false);

            Assert.That(factory.CreateServiceHostCallCount, Is.EqualTo(1));
        }

        private static ApplicationConfiguration CreateConfiguration(string endpointUrl)
        {
            return new ApplicationConfiguration
            {
                ApplicationName = "TestServer",
                ApplicationUri = "urn:localhost:UA:TestServer",
                ProductUri = "uri:opcfoundation.org:TestServer",
                ServerConfiguration = new ServerConfiguration
                {
                    BaseAddresses = [endpointUrl]
                }
            };
        }

        private sealed class FakeTcpListenerFactory : ITransportListenerFactory
        {
            public string UriScheme => Utils.UriSchemeOpcTcp;

            public int CreateServiceHostCallCount { get; private set; }

            public ITransportListener Create(ITelemetryContext telemetry)
            {
                throw new NotSupportedException();
            }

            public ValueTask<List<EndpointDescription>> CreateServiceHostAsync(
                ServerBase serverBase,
                IDictionary<string, ServiceHost> hosts,
                ApplicationConfiguration configuration,
                ArrayOf<string> baseAddresses,
                ApplicationDescription serverDescription,
                ArrayOf<ServerSecurityPolicy> securityPolicies,
                ICertificateRegistry serverCertificates,
                ICertificateValidatorEx clientCertificateValidator,
                CancellationToken ct = default)
            {
                CreateServiceHostCallCount++;
                return new ValueTask<List<EndpointDescription>>([]);
            }
        }
    }
}