Restore SEBPatch

SafeExamBrowser.Core/OperationModel/OperationSequence.cs

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+/*
+ * 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 System.Linq;
+using SafeExamBrowser.Core.Contracts.OperationModel;
+using SafeExamBrowser.Core.Contracts.OperationModel.Events;
+using SafeExamBrowser.Logging.Contracts;
+
+namespace SafeExamBrowser.Core.OperationModel
+{
+	/// <summary>
+	/// Default implementation of the <see cref="IOperationSequence"/>.
+	/// </summary>
+	public class OperationSequence : IOperationSequence
+	{
+		protected ILogger logger;
+		protected Queue<IOperation> operations = new Queue<IOperation>();
+		protected Stack<IOperation> stack = new Stack<IOperation>();
+
+		public event ActionRequiredEventHandler ActionRequired
+		{
+			add { operations.ForEach(o => o.ActionRequired += value); }
+			remove { operations.ForEach(o => o.ActionRequired -= value); }
+		}
+
+		public event ProgressChangedEventHandler ProgressChanged;
+
+		public event StatusChangedEventHandler StatusChanged
+		{
+			add { operations.ForEach(o => o.StatusChanged += value); }
+			remove { operations.ForEach(o => o.StatusChanged -= value); }
+		}
+
+		public OperationSequence(ILogger logger, Queue<IOperation> operations)
+		{
+			this.logger = logger;
+			this.operations = new Queue<IOperation>(operations);
+		}
+
+		public virtual OperationResult TryPerform()
+		{
+			var result = OperationResult.Failed;
+
+			try
+			{
+				Initialize();
+				result = Perform();
+
+				if (result != OperationResult.Success)
+				{
+					Revert(true);
+				}
+			}
+			catch (Exception e)
+			{
+				logger.Error("Failed to perform operations!", e);
+			}
+
+			return result;
+		}
+
+		public virtual OperationResult TryRevert()
+		{
+			var result = OperationResult.Failed;
+
+			try
+			{
+				Initialize(true);
+				result = Revert();
+			}
+			catch (Exception e)
+			{
+				logger.Error("Failed to revert operations!", e);
+			}
+
+			return result;
+		}
+
+		protected virtual void Initialize(bool indeterminate = false)
+		{
+			if (indeterminate)
+			{
+				UpdateProgress(new ProgressChangedEventArgs { IsIndeterminate = true });
+			}
+			else
+			{
+				UpdateProgress(new ProgressChangedEventArgs { CurrentValue = 0, MaxValue = operations.Count });
+			}
+		}
+
+		protected virtual OperationResult Perform()
+		{
+			foreach (var operation in operations)
+			{
+				var result = OperationResult.Failed;
+
+				stack.Push(operation);
+
+				try
+				{
+					result = operation.Perform();
+				}
+				catch (Exception e)
+				{
+					logger.Error($"Caught unexpected exception while performing operation '{operation.GetType().Name}'!", e);
+				}
+
+				if (result != OperationResult.Success)
+				{
+					return result;
+				}
+
+				UpdateProgress(new ProgressChangedEventArgs { Progress = true });
+			}
+
+			return OperationResult.Success;
+		}
+
+		protected virtual OperationResult Revert(bool regress = false)
+		{
+			var success = true;
+
+			while (stack.Any())
+			{
+				var operation = stack.Pop();
+
+				try
+				{
+					var result = operation.Revert();
+
+					if (result != OperationResult.Success)
+					{
+						success = false;
+					}
+				}
+				catch (Exception e)
+				{
+					logger.Error($"Caught unexpected exception while reverting operation '{operation.GetType().Name}'!", e);
+					success = false;
+				}
+
+				if (regress)
+				{
+					UpdateProgress(new ProgressChangedEventArgs { Regress = true });
+				}
+			}
+
+			return success ? OperationResult.Success : OperationResult.Failed;
+		}
+
+		protected void UpdateProgress(ProgressChangedEventArgs args)
+		{
+			ProgressChanged?.Invoke(args);
+		}
+	}
+}