/*
 * Copyright (c) 2024 ETH Zürich, IT Services
 * 
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

using System;
using System.Collections.Generic;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Moq;
using SafeExamBrowser.Configuration.Contracts;
using SafeExamBrowser.Configuration.Contracts.Cryptography;
using SafeExamBrowser.Core.Contracts.OperationModel;
using SafeExamBrowser.Core.Contracts.OperationModel.Events;
using SafeExamBrowser.Logging.Contracts;
using SafeExamBrowser.Runtime.Operations;
using SafeExamBrowser.Runtime.Operations.Events;
using SafeExamBrowser.Server.Contracts;
using SafeExamBrowser.Server.Contracts.Data;
using SafeExamBrowser.Settings;
using SafeExamBrowser.Settings.Server;
using SafeExamBrowser.SystemComponents.Contracts;

namespace SafeExamBrowser.Runtime.UnitTests.Operations
{
	[TestClass]
	public class ServerOperationTests
	{
		private SessionContext context;
		private Mock<IFileSystem> fileSystem;
		private Mock<ILogger> logger;
		private Mock<IServerProxy> server;
		private Mock<IConfigurationRepository> configuration;

		private ServerOperation sut;

		[TestInitialize]
		public void Initialize()
		{
			configuration = new Mock<IConfigurationRepository>();
			context = new SessionContext();
			fileSystem = new Mock<IFileSystem>();
			logger = new Mock<ILogger>();
			server = new Mock<IServerProxy>();

			context.Current = new SessionConfiguration();
			context.Current.AppConfig = new AppConfig();
			context.Current.Settings = new AppSettings();
			context.Next = new SessionConfiguration();
			context.Next.AppConfig = new AppConfig();
			context.Next.Settings = new AppSettings();

			sut = new ServerOperation(new string[0], configuration.Object, fileSystem.Object, logger.Object, context, server.Object);
		}

		[TestMethod]
		public void Perform_MustCorrectlyInitializeServerSession()
		{
			var connect = 0;
			var connection = new ConnectionInfo { Api = "some API", ConnectionToken = "some token", Oauth2Token = "some OAuth2 token" };
			var counter = 0;
			var delete = 0;
			var exam = new Exam { Id = "some id", LmsName = "some LMS", Name = "some name", Url = "some URL" };
			var examSelection = 0;
			var examSettings = new AppSettings();
			var getConfiguration = 0;
			var getConnection = 0;
			var getExams = 0;
			var initialize = 0;
			var initialSettings = context.Next.Settings;
			var serverSettings = context.Next.Settings.Server;

			configuration
				.Setup(c => c.TryLoadSettings(It.IsAny<Uri>(), out examSettings, It.IsAny<PasswordParameters>()))
				.Returns(LoadStatus.Success);
			context.Next.Settings.SessionMode = SessionMode.Server;
			fileSystem.Setup(f => f.Delete(It.IsAny<string>())).Callback(() => delete = ++counter);
			server.Setup(s => s.Connect()).Returns(new ServerResponse(true)).Callback(() => connect = ++counter);
			server.Setup(s => s.Initialize(It.IsAny<ServerSettings>())).Callback(() => initialize = ++counter);
			server.Setup(s => s.GetConnectionInfo()).Returns(connection).Callback(() => getConnection = ++counter);
			server.Setup(s => s.SendSelectedExam(It.IsAny<Exam>())).Returns(new ServerResponse<string>(true, default));
			server
				.Setup(s => s.GetAvailableExams(It.IsAny<string>()))
				.Returns(new ServerResponse<IEnumerable<Exam>>(true, default(IEnumerable<Exam>)))
				.Callback(() => getExams = ++counter);
			server
				.Setup(s => s.GetConfigurationFor(It.IsAny<Exam>()))
				.Returns(new ServerResponse<Uri>(true, new Uri("file:///configuration.seb")))
				.Callback(() => getConfiguration = ++counter);
			sut.ActionRequired += (args) =>
			{
				if (args is ExamSelectionEventArgs e)
				{
					e.Success = true;
					e.SelectedExam = exam;
					examSelection = ++counter;
				}
			};

			var result = sut.Perform();

			fileSystem.Verify(f => f.Delete(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.Connect(), Times.Once);
			server.Verify(s => s.Initialize(It.IsAny<ServerSettings>()), Times.Once);
			server.Verify(s => s.GetAvailableExams(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.GetConfigurationFor(It.Is<Exam>(e => e == exam)), Times.Once);
			server.Verify(s => s.GetConnectionInfo(), Times.Once);
			server.Verify(s => s.SendSelectedExam(It.Is<Exam>(e => e == exam)), Times.Once);

			Assert.AreEqual(1, initialize);
			Assert.AreEqual(2, connect);
			Assert.AreEqual(3, getExams);
			Assert.AreEqual(4, examSelection);
			Assert.AreEqual(5, getConfiguration);
			Assert.AreEqual(6, getConnection);
			Assert.AreEqual(7, delete);
			Assert.AreEqual(connection.Api, context.Next.AppConfig.ServerApi);
			Assert.AreEqual(connection.ConnectionToken, context.Next.AppConfig.ServerConnectionToken);
			Assert.AreEqual(connection.Oauth2Token, context.Next.AppConfig.ServerOauth2Token);
			Assert.AreEqual(exam.Id, context.Next.AppConfig.ServerExamId);
			Assert.AreEqual(exam.Url, context.Next.Settings.Browser.StartUrl);
			Assert.AreSame(examSettings, context.Next.Settings);
			Assert.AreSame(serverSettings, context.Next.Settings.Server);
			Assert.AreNotSame(initialSettings, context.Next.Settings);
			Assert.AreEqual(OperationResult.Success, result);
			Assert.AreEqual(SessionMode.Server, context.Next.Settings.SessionMode);
		}

		[TestMethod]
		public void Perform_MustFailIfSettingsCouldNotBeLoaded()
		{
			var connection = new ConnectionInfo { Api = "some API", ConnectionToken = "some token", Oauth2Token = "some OAuth2 token" };
			var exam = new Exam { Id = "some id", LmsName = "some LMS", Name = "some name", Url = "some URL" };
			var examSettings = new AppSettings();
			var initialSettings = context.Next.Settings;

			configuration.Setup(c => c.TryLoadSettings(It.IsAny<Uri>(), out examSettings, It.IsAny<PasswordParameters>())).Returns(LoadStatus.UnexpectedError);
			context.Next.Settings.SessionMode = SessionMode.Server;
			server.Setup(s => s.Connect()).Returns(new ServerResponse(true));
			server.Setup(s => s.Initialize(It.IsAny<ServerSettings>()));
			server.Setup(s => s.GetConnectionInfo()).Returns(connection);
			server.Setup(s => s.GetAvailableExams(It.IsAny<string>())).Returns(new ServerResponse<IEnumerable<Exam>>(true, default(IEnumerable<Exam>)));
			server.Setup(s => s.GetConfigurationFor(It.IsAny<Exam>())).Returns(new ServerResponse<Uri>(true, new Uri("file:///configuration.seb")));
			sut.ActionRequired += (args) =>
			{
				if (args is ExamSelectionEventArgs e)
				{
					e.Success = true;
					e.SelectedExam = exam;
				}
			};

			var result = sut.Perform();

			fileSystem.Verify(f => f.Delete(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.Connect(), Times.Once);
			server.Verify(s => s.Initialize(It.IsAny<ServerSettings>()), Times.Once);
			server.Verify(s => s.GetAvailableExams(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.GetConfigurationFor(It.Is<Exam>(e => e == exam)), Times.Once);
			server.Verify(s => s.GetConnectionInfo(), Times.Once);

			Assert.AreNotEqual(connection.Api, context.Next.AppConfig.ServerApi);
			Assert.AreNotEqual(connection.ConnectionToken, context.Next.AppConfig.ServerConnectionToken);
			Assert.AreNotEqual(connection.Oauth2Token, context.Next.AppConfig.ServerOauth2Token);
			Assert.AreNotEqual(exam.Id, context.Next.AppConfig.ServerExamId);
			Assert.AreNotEqual(exam.Url, context.Next.Settings.Browser.StartUrl);
			Assert.AreNotSame(examSettings, context.Next.Settings);
			Assert.AreSame(initialSettings, context.Next.Settings);
			Assert.AreEqual(OperationResult.Failed, result);
			Assert.AreEqual(SessionMode.Server, context.Next.Settings.SessionMode);
		}

		[TestMethod]
		public void Perform_MustCorrectlyAbort()
		{
			var connection = new ConnectionInfo { Api = "some API", ConnectionToken = "some token", Oauth2Token = "some OAuth2 token" };
			var exam = new Exam { Id = "some id", LmsName = "some LMS", Name = "some name", Url = "some URL" };
			var examSettings = new AppSettings();
			var messageShown = false;

			configuration.Setup(c => c.TryLoadSettings(It.IsAny<Uri>(), out examSettings, It.IsAny<PasswordParameters>())).Returns(LoadStatus.Success);
			context.Next.Settings.SessionMode = SessionMode.Server;
			server.Setup(s => s.Connect()).Returns(new ServerResponse(true));
			server.Setup(s => s.Initialize(It.IsAny<ServerSettings>()));
			server.Setup(s => s.GetConnectionInfo()).Returns(connection);
			server.Setup(s => s.GetAvailableExams(It.IsAny<string>())).Returns(new ServerResponse<IEnumerable<Exam>>(true, default(IEnumerable<Exam>)));
			server.Setup(s => s.GetConfigurationFor(It.IsAny<Exam>())).Returns(new ServerResponse<Uri>(false, default(Uri)));
			sut.ActionRequired += (args) =>
			{
				if (args is ExamSelectionEventArgs e)
				{
					e.Success = true;
					e.SelectedExam = exam;
				}

				if (args is ServerFailureEventArgs s)
				{
					s.Abort = true;
					messageShown = true;
				}
			};

			var result = sut.Perform();

			fileSystem.Verify(f => f.Delete(It.IsAny<string>()), Times.Never);
			server.Verify(s => s.Connect(), Times.Once);
			server.Verify(s => s.Initialize(It.IsAny<ServerSettings>()), Times.Once);
			server.Verify(s => s.GetAvailableExams(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.GetConfigurationFor(It.Is<Exam>(e => e == exam)), Times.Once);
			server.Verify(s => s.GetConnectionInfo(), Times.Never);

			Assert.IsTrue(messageShown);
			Assert.AreEqual(OperationResult.Aborted, result);
		}

		[TestMethod]
		public void Perform_MustCorrectlyFallback()
		{
			var connection = new ConnectionInfo { Api = "some API", ConnectionToken = "some token", Oauth2Token = "some OAuth2 token" };
			var exam = new Exam { Id = "some id", LmsName = "some LMS", Name = "some name", Url = "some URL" };
			var examSettings = new AppSettings();
			var messageShown = false;

			configuration.Setup(c => c.TryLoadSettings(It.IsAny<Uri>(), out examSettings, It.IsAny<PasswordParameters>())).Returns(LoadStatus.Success);
			context.Next.Settings.SessionMode = SessionMode.Server;
			server.Setup(s => s.Connect()).Returns(new ServerResponse(true));
			server.Setup(s => s.Initialize(It.IsAny<ServerSettings>()));
			server.Setup(s => s.GetConnectionInfo()).Returns(connection);
			server.Setup(s => s.GetAvailableExams(It.IsAny<string>())).Returns(new ServerResponse<IEnumerable<Exam>>(true, default(IEnumerable<Exam>)));
			server.Setup(s => s.GetConfigurationFor(It.IsAny<Exam>())).Returns(new ServerResponse<Uri>(false, default(Uri)));
			sut.ActionRequired += (args) =>
			{
				if (args is ExamSelectionEventArgs e)
				{
					e.Success = true;
					e.SelectedExam = exam;
				}

				if (args is ServerFailureEventArgs s)
				{
					s.Fallback = true;
					messageShown = true;
				}
			};

			var result = sut.Perform();

			fileSystem.Verify(f => f.Delete(It.IsAny<string>()), Times.Never);
			server.Verify(s => s.Connect(), Times.Once);
			server.Verify(s => s.Initialize(It.IsAny<ServerSettings>()), Times.Once);
			server.Verify(s => s.GetAvailableExams(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.GetConfigurationFor(It.Is<Exam>(e => e == exam)), Times.Once);
			server.Verify(s => s.GetConnectionInfo(), Times.Never);

			Assert.IsTrue(messageShown);
			Assert.AreEqual(SessionMode.Normal, context.Next.Settings.SessionMode);
			Assert.AreEqual(OperationResult.Success, result);
		}

		[TestMethod]
		public void Perform_MustAutomaticallySelectExam()
		{
			var connection = new ConnectionInfo { Api = "some API", ConnectionToken = "some token", Oauth2Token = "some OAuth2 token" };
			var exam = new Exam { Id = "some id", LmsName = "some LMS", Name = "some name", Url = "some URL" };
			var examSettings = new AppSettings();
			var serverSettings = context.Next.Settings.Server;

			configuration.Setup(c => c.TryLoadSettings(It.IsAny<Uri>(), out examSettings, It.IsAny<PasswordParameters>())).Returns(LoadStatus.Success);
			context.Next.Settings.SessionMode = SessionMode.Server;
			context.Next.Settings.Server.ExamId = "some id";
			fileSystem.Setup(f => f.Delete(It.IsAny<string>()));
			server.Setup(s => s.Connect()).Returns(new ServerResponse(true));
			server.Setup(s => s.Initialize(It.IsAny<ServerSettings>()));
			server.Setup(s => s.GetConnectionInfo()).Returns(connection);
			server.Setup(s => s.GetAvailableExams(It.IsAny<string>())).Returns(new ServerResponse<IEnumerable<Exam>>(true, new[] { exam }));
			server.Setup(s => s.GetConfigurationFor(It.IsAny<Exam>())).Returns(new ServerResponse<Uri>(true, new Uri("file:///configuration.seb")));
			server.Setup(s => s.SendSelectedExam(It.IsAny<Exam>())).Returns(new ServerResponse<string>(true, default));
			sut.ActionRequired += (args) => Assert.Fail();

			var result = sut.Perform();

			fileSystem.Verify(f => f.Delete(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.Connect(), Times.Once);
			server.Verify(s => s.Initialize(It.IsAny<ServerSettings>()), Times.Once);
			server.Verify(s => s.GetAvailableExams(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.GetConfigurationFor(It.Is<Exam>(e => e == exam)), Times.Once);
			server.Verify(s => s.GetConnectionInfo(), Times.Once);
			server.Verify(s => s.SendSelectedExam(It.Is<Exam>(e => e == exam)), Times.Once);

			Assert.AreEqual(OperationResult.Success, result);
		}

		[TestMethod]
		public void Perform_MustDoNothingIfNormalSession()
		{
			var initialSettings = context.Next.Settings;

			context.Next.Settings.SessionMode = SessionMode.Normal;
			sut.ActionRequired += (_) => Assert.Fail();

			var result = sut.Perform();

			configuration.VerifyNoOtherCalls();
			fileSystem.VerifyNoOtherCalls();
			server.VerifyNoOtherCalls();

			Assert.AreSame(initialSettings, context.Next.Settings);
			Assert.AreEqual(SessionMode.Normal, context.Next.Settings.SessionMode);
			Assert.AreEqual(OperationResult.Success, result);
		}

		[TestMethod]
		public void Repeat_MustCorrectlyInitializeServerSession()
		{
			var connect = 0;
			var connection = new ConnectionInfo { Api = "some API", ConnectionToken = "some token", Oauth2Token = "some OAuth2 token" };
			var counter = 0;
			var delete = 0;
			var exam = new Exam { Id = "some id", LmsName = "some LMS", Name = "some name", Url = "some URL" };
			var examSelection = 0;
			var examSettings = new AppSettings();
			var getConfiguration = 0;
			var getConnection = 0;
			var getExams = 0;
			var initialize = 0;
			var initialSettings = context.Next.Settings;
			var serverSettings = context.Next.Settings.Server;

			configuration
				.Setup(c => c.TryLoadSettings(It.IsAny<Uri>(), out examSettings, It.IsAny<PasswordParameters>()))
				.Returns(LoadStatus.Success);
			context.Next.Settings.SessionMode = SessionMode.Server;
			fileSystem.Setup(f => f.Delete(It.IsAny<string>())).Callback(() => delete = ++counter);
			server.Setup(s => s.Connect()).Returns(new ServerResponse(true)).Callback(() => connect = ++counter);
			server.Setup(s => s.Initialize(It.IsAny<ServerSettings>())).Callback(() => initialize = ++counter);
			server.Setup(s => s.GetConnectionInfo()).Returns(connection).Callback(() => getConnection = ++counter);
			server.Setup(s => s.SendSelectedExam(It.IsAny<Exam>())).Returns(new ServerResponse<string>(true, default));
			server
				.Setup(s => s.GetAvailableExams(It.IsAny<string>()))
				.Returns(new ServerResponse<IEnumerable<Exam>>(true, default(IEnumerable<Exam>)))
				.Callback(() => getExams = ++counter);
			server
				.Setup(s => s.GetConfigurationFor(It.IsAny<Exam>()))
				.Returns(new ServerResponse<Uri>(true, new Uri("file:///configuration.seb")))
				.Callback(() => getConfiguration = ++counter);
			sut.ActionRequired += (args) =>
			{
				if (args is ExamSelectionEventArgs e)
				{
					e.Success = true;
					e.SelectedExam = exam;
					examSelection = ++counter;
				}
			};

			var result = sut.Repeat();

			fileSystem.Verify(f => f.Delete(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.Connect(), Times.Once);
			server.Verify(s => s.Initialize(It.IsAny<ServerSettings>()), Times.Once);
			server.Verify(s => s.GetAvailableExams(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.GetConfigurationFor(It.Is<Exam>(e => e == exam)), Times.Once);
			server.Verify(s => s.GetConnectionInfo(), Times.Once);
			server.Verify(s => s.SendSelectedExam(It.Is<Exam>(e => e == exam)), Times.Once);

			Assert.AreEqual(1, initialize);
			Assert.AreEqual(2, connect);
			Assert.AreEqual(3, getExams);
			Assert.AreEqual(4, examSelection);
			Assert.AreEqual(5, getConfiguration);
			Assert.AreEqual(6, getConnection);
			Assert.AreEqual(7, delete);
			Assert.AreEqual(connection.Api, context.Next.AppConfig.ServerApi);
			Assert.AreEqual(connection.ConnectionToken, context.Next.AppConfig.ServerConnectionToken);
			Assert.AreEqual(connection.Oauth2Token, context.Next.AppConfig.ServerOauth2Token);
			Assert.AreEqual(exam.Id, context.Next.AppConfig.ServerExamId);
			Assert.AreEqual(exam.Url, context.Next.Settings.Browser.StartUrl);
			Assert.AreSame(examSettings, context.Next.Settings);
			Assert.AreSame(serverSettings, context.Next.Settings.Server);
			Assert.AreNotSame(initialSettings, context.Next.Settings);
			Assert.AreEqual(OperationResult.Success, result);
			Assert.AreEqual(SessionMode.Server, context.Next.Settings.SessionMode);
		}

		[TestMethod]
		public void Repeat_MustFailIfSettingsCouldNotBeLoaded()
		{
			var connection = new ConnectionInfo { Api = "some API", ConnectionToken = "some token", Oauth2Token = "some OAuth2 token" };
			var exam = new Exam { Id = "some id", LmsName = "some LMS", Name = "some name", Url = "some URL" };
			var examSettings = new AppSettings();
			var initialSettings = context.Next.Settings;

			configuration.Setup(c => c.TryLoadSettings(It.IsAny<Uri>(), out examSettings, It.IsAny<PasswordParameters>())).Returns(LoadStatus.UnexpectedError);
			context.Next.Settings.SessionMode = SessionMode.Server;
			server.Setup(s => s.Connect()).Returns(new ServerResponse(true));
			server.Setup(s => s.Initialize(It.IsAny<ServerSettings>()));
			server.Setup(s => s.GetConnectionInfo()).Returns(connection);
			server.Setup(s => s.GetAvailableExams(It.IsAny<string>())).Returns(new ServerResponse<IEnumerable<Exam>>(true, default(IEnumerable<Exam>)));
			server.Setup(s => s.GetConfigurationFor(It.IsAny<Exam>())).Returns(new ServerResponse<Uri>(true, new Uri("file:///configuration.seb")));
			sut.ActionRequired += (args) =>
			{
				if (args is ExamSelectionEventArgs e)
				{
					e.Success = true;
					e.SelectedExam = exam;
				}
			};

			var result = sut.Repeat();

			fileSystem.Verify(f => f.Delete(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.Connect(), Times.Once);
			server.Verify(s => s.Initialize(It.IsAny<ServerSettings>()), Times.Once);
			server.Verify(s => s.GetAvailableExams(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.GetConfigurationFor(It.Is<Exam>(e => e == exam)), Times.Once);
			server.Verify(s => s.GetConnectionInfo(), Times.Once);

			Assert.AreNotEqual(connection.Api, context.Next.AppConfig.ServerApi);
			Assert.AreNotEqual(connection.ConnectionToken, context.Next.AppConfig.ServerConnectionToken);
			Assert.AreNotEqual(connection.Oauth2Token, context.Next.AppConfig.ServerOauth2Token);
			Assert.AreNotEqual(exam.Id, context.Next.AppConfig.ServerExamId);
			Assert.AreNotEqual(exam.Url, context.Next.Settings.Browser.StartUrl);
			Assert.AreNotSame(examSettings, context.Next.Settings);
			Assert.AreSame(initialSettings, context.Next.Settings);
			Assert.AreEqual(OperationResult.Failed, result);
			Assert.AreEqual(SessionMode.Server, context.Next.Settings.SessionMode);
		}

		[TestMethod]
		public void Repeat_MustCorrectlyAbort()
		{
			var connection = new ConnectionInfo { Api = "some API", ConnectionToken = "some token", Oauth2Token = "some OAuth2 token" };
			var exam = new Exam { Id = "some id", LmsName = "some LMS", Name = "some name", Url = "some URL" };
			var examSettings = new AppSettings();
			var messageShown = false;

			configuration.Setup(c => c.TryLoadSettings(It.IsAny<Uri>(), out examSettings, It.IsAny<PasswordParameters>())).Returns(LoadStatus.Success);
			context.Next.Settings.SessionMode = SessionMode.Server;
			server.Setup(s => s.Connect()).Returns(new ServerResponse(true));
			server.Setup(s => s.Initialize(It.IsAny<ServerSettings>()));
			server.Setup(s => s.GetConnectionInfo()).Returns(connection);
			server.Setup(s => s.GetAvailableExams(It.IsAny<string>())).Returns(new ServerResponse<IEnumerable<Exam>>(true, default(IEnumerable<Exam>)));
			server.Setup(s => s.GetConfigurationFor(It.IsAny<Exam>())).Returns(new ServerResponse<Uri>(false, default(Uri)));
			sut.ActionRequired += (args) =>
			{
				if (args is ExamSelectionEventArgs e)
				{
					e.Success = true;
					e.SelectedExam = exam;
				}

				if (args is ServerFailureEventArgs s)
				{
					s.Abort = true;
					messageShown = true;
				}
			};

			var result = sut.Repeat();

			fileSystem.Verify(f => f.Delete(It.IsAny<string>()), Times.Never);
			server.Verify(s => s.Connect(), Times.Once);
			server.Verify(s => s.Initialize(It.IsAny<ServerSettings>()), Times.Once);
			server.Verify(s => s.GetAvailableExams(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.GetConfigurationFor(It.Is<Exam>(e => e == exam)), Times.Once);
			server.Verify(s => s.GetConnectionInfo(), Times.Never);

			Assert.IsTrue(messageShown);
			Assert.AreEqual(OperationResult.Aborted, result);
		}

		[TestMethod]
		public void Repeat_MustCorrectlyFallback()
		{
			var connection = new ConnectionInfo { Api = "some API", ConnectionToken = "some token", Oauth2Token = "some OAuth2 token" };
			var exam = new Exam { Id = "some id", LmsName = "some LMS", Name = "some name", Url = "some URL" };
			var examSettings = new AppSettings();
			var messageShown = false;

			configuration.Setup(c => c.TryLoadSettings(It.IsAny<Uri>(), out examSettings, It.IsAny<PasswordParameters>())).Returns(LoadStatus.Success);
			context.Next.Settings.SessionMode = SessionMode.Server;
			server.Setup(s => s.Connect()).Returns(new ServerResponse(true));
			server.Setup(s => s.Initialize(It.IsAny<ServerSettings>()));
			server.Setup(s => s.GetConnectionInfo()).Returns(connection);
			server.Setup(s => s.GetAvailableExams(It.IsAny<string>())).Returns(new ServerResponse<IEnumerable<Exam>>(true, default(IEnumerable<Exam>)));
			server.Setup(s => s.GetConfigurationFor(It.IsAny<Exam>())).Returns(new ServerResponse<Uri>(false, default(Uri)));
			sut.ActionRequired += (args) =>
			{
				if (args is ExamSelectionEventArgs e)
				{
					e.Success = true;
					e.SelectedExam = exam;
				}

				if (args is ServerFailureEventArgs s)
				{
					s.Fallback = true;
					messageShown = true;
				}
			};

			var result = sut.Repeat();

			fileSystem.Verify(f => f.Delete(It.IsAny<string>()), Times.Never);
			server.Verify(s => s.Connect(), Times.Once);
			server.Verify(s => s.Initialize(It.IsAny<ServerSettings>()), Times.Once);
			server.Verify(s => s.GetAvailableExams(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.GetConfigurationFor(It.Is<Exam>(e => e == exam)), Times.Once);
			server.Verify(s => s.GetConnectionInfo(), Times.Never);

			Assert.IsTrue(messageShown);
			Assert.AreEqual(SessionMode.Normal, context.Next.Settings.SessionMode);
			Assert.AreEqual(OperationResult.Success, result);
		}

		[TestMethod]
		public void Repeat_MustAutomaticallySelectExam()
		{
			var connection = new ConnectionInfo { Api = "some API", ConnectionToken = "some token", Oauth2Token = "some OAuth2 token" };
			var exam = new Exam { Id = "some id", LmsName = "some LMS", Name = "some name", Url = "some URL" };
			var examSettings = new AppSettings();
			var serverSettings = context.Next.Settings.Server;

			configuration.Setup(c => c.TryLoadSettings(It.IsAny<Uri>(), out examSettings, It.IsAny<PasswordParameters>())).Returns(LoadStatus.Success);
			context.Next.Settings.SessionMode = SessionMode.Server;
			context.Next.Settings.Server.ExamId = "some id";
			fileSystem.Setup(f => f.Delete(It.IsAny<string>()));
			server.Setup(s => s.Connect()).Returns(new ServerResponse(true));
			server.Setup(s => s.Initialize(It.IsAny<ServerSettings>()));
			server.Setup(s => s.GetConnectionInfo()).Returns(connection);
			server.Setup(s => s.GetAvailableExams(It.IsAny<string>())).Returns(new ServerResponse<IEnumerable<Exam>>(true, new[] { exam }));
			server.Setup(s => s.GetConfigurationFor(It.IsAny<Exam>())).Returns(new ServerResponse<Uri>(true, new Uri("file:///configuration.seb")));
			server.Setup(s => s.SendSelectedExam(It.IsAny<Exam>())).Returns(new ServerResponse<string>(true, default));
			sut.ActionRequired += (args) => Assert.Fail();

			var result = sut.Repeat();

			fileSystem.Verify(f => f.Delete(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.Connect(), Times.Once);
			server.Verify(s => s.Initialize(It.IsAny<ServerSettings>()), Times.Once);
			server.Verify(s => s.GetAvailableExams(It.IsAny<string>()), Times.Once);
			server.Verify(s => s.GetConfigurationFor(It.Is<Exam>(e => e == exam)), Times.Once);
			server.Verify(s => s.GetConnectionInfo(), Times.Once);
			server.Verify(s => s.SendSelectedExam(It.Is<Exam>(e => e == exam)), Times.Once);

			Assert.AreEqual(OperationResult.Success, result);
		}

		[TestMethod]
		public void Repeat_MustNotAllowToReconfigureServerSession()
		{
			var args = default(ActionRequiredEventArgs);

			context.Current.AppConfig.ServerApi = "api";
			context.Current.AppConfig.ServerConnectionToken = "token";
			context.Current.AppConfig.ServerExamId = "id";
			context.Current.AppConfig.ServerOauth2Token = "oauth2";
			context.Current.Settings.SessionMode = SessionMode.Server;
			context.Next.Settings.SessionMode = SessionMode.Server;

			sut.ActionRequired += (a) =>
			{
				args = a;
			};

			var result = sut.Repeat();

			configuration.VerifyNoOtherCalls();
			fileSystem.VerifyNoOtherCalls();
			server.VerifyNoOtherCalls();

			Assert.IsNull(context.Next.AppConfig.ServerApi);
			Assert.IsNull(context.Next.AppConfig.ServerConnectionToken);
			Assert.IsNull(context.Next.AppConfig.ServerOauth2Token);
			Assert.IsInstanceOfType(args, typeof(MessageEventArgs));
			Assert.AreEqual(OperationResult.Aborted, result);
		}

		[TestMethod]
		public void Repeat_MustDoNothingIfNormalSession()
		{
			var initialSettings = context.Next.Settings;

			context.Current.Settings.SessionMode = SessionMode.Normal;
			context.Next.Settings.SessionMode = SessionMode.Normal;
			sut.ActionRequired += (_) => Assert.Fail();

			var result = sut.Repeat();

			configuration.VerifyNoOtherCalls();
			fileSystem.VerifyNoOtherCalls();
			server.VerifyNoOtherCalls();

			Assert.AreSame(initialSettings, context.Next.Settings);
			Assert.AreEqual(SessionMode.Normal, context.Next.Settings.SessionMode);
			Assert.AreEqual(OperationResult.Success, result);
		}

		[TestMethod]
		public void Revert_MustDisconnectFromServerWhenSessionRunning()
		{
			context.Current.Settings.SessionMode = SessionMode.Server;
			context.Next = default;
			server.Setup(s => s.Disconnect()).Returns(new ServerResponse(true));

			var result = sut.Revert();

			fileSystem.VerifyNoOtherCalls();
			server.Verify(s => s.Disconnect(), Times.Once);

			Assert.AreEqual(OperationResult.Success, result);
		}

		[TestMethod]
		public void Revert_MustDisconnectFromServerWhenSessionStartFailed()
		{
			context.Current = default;
			context.Next.Settings.SessionMode = SessionMode.Server;
			server.Setup(s => s.Disconnect()).Returns(new ServerResponse(true));

			var result = sut.Revert();

			fileSystem.VerifyNoOtherCalls();
			server.Verify(s => s.Disconnect(), Times.Once);

			Assert.AreEqual(OperationResult.Success, result);
		}

		[TestMethod]
		public void Revert_MustFailWhenDisconnectionUnsuccesful()
		{
			context.Current.Settings.SessionMode = SessionMode.Server;
			server.Setup(s => s.Disconnect()).Returns(new ServerResponse(false));

			var result = sut.Revert();

			fileSystem.VerifyNoOtherCalls();
			server.Verify(s => s.Disconnect(), Times.Once);

			Assert.AreEqual(OperationResult.Failed, result);
		}

		[TestMethod]
		public void Revert_MustDoNothingIfNormalSession()
		{
			context.Current.Settings.SessionMode = SessionMode.Normal;
			sut.ActionRequired += (_) => Assert.Fail();

			var result = sut.Revert();

			configuration.VerifyNoOtherCalls();
			fileSystem.VerifyNoOtherCalls();
			server.VerifyNoOtherCalls();

			Assert.AreEqual(OperationResult.Success, result);
		}
	}
}