Restore SEBPatch

SafeExamBrowser.Lockdown/AutoRestoreMechanism.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 System.Threading.Tasks;
+using SafeExamBrowser.Lockdown.Contracts;
+using SafeExamBrowser.Logging.Contracts;
+
+namespace SafeExamBrowser.Lockdown
+{
+	public class AutoRestoreMechanism : IAutoRestoreMechanism
+	{
+		private readonly object @lock = new object();
+
+		private IFeatureConfigurationBackup backup;
+		private ILogger logger;
+		private ISystemConfigurationUpdate systemConfigurationUpdate;
+		private bool running;
+		private int timeout_ms;
+
+		public AutoRestoreMechanism(
+			IFeatureConfigurationBackup backup,
+			ILogger logger,
+			ISystemConfigurationUpdate systemConfigurationUpdate,
+			int timeout_ms)
+		{
+			if (timeout_ms < 0)
+			{
+				throw new ArgumentException("Must be 0 or greater!", nameof(timeout_ms));
+			}
+
+			this.backup = backup;
+			this.logger = logger;
+			this.systemConfigurationUpdate = systemConfigurationUpdate;
+			this.timeout_ms = timeout_ms;
+		}
+
+		public void Start()
+		{
+			lock (@lock)
+			{
+				if (!running)
+				{
+					running = true;
+					Task.Run(new Action(AutoRestore));
+					logger.Info("Started auto-restore mechanism.");
+				}
+				else
+				{
+					logger.Info("Auto-restore mechanism is already running.");
+				}
+			}
+		}
+
+		public void Stop()
+		{
+			lock (@lock)
+			{
+				if (running)
+				{
+					running = false;
+					logger.Info("Stopped auto-restore mechanism.");
+				}
+				else
+				{
+					logger.Info("Auto-restore mechanism is not running.");
+				}
+			}
+		}
+
+		private void AutoRestore()
+		{
+			if (IsStopped())
+			{
+				return;
+			}
+
+			var configurations = backup.GetAllConfigurations();
+
+			if (configurations.Any())
+			{
+				var success = TryRestoreAll(configurations);
+
+				if (success == true)
+				{
+					systemConfigurationUpdate.ExecuteAsync();
+				}
+				else if (success == false)
+				{
+					Task.Delay(timeout_ms).ContinueWith((_) => AutoRestore());
+				}
+				else
+				{
+					logger.Info("Auto-restore mechanism was aborted.");
+				}
+			}
+			else
+			{
+				lock (@lock)
+				{
+					running = false;
+					logger.Info("Nothing to restore, stopped auto-restore mechanism.");
+				}
+			}
+		}
+
+		private bool IsStopped()
+		{
+			lock (@lock)
+			{
+				return !running;
+			}
+		}
+
+		private bool? TryRestoreAll(IList<IFeatureConfiguration> configurations)
+		{
+			var restored = 0;
+
+			logger.Info($"Attempting to restore {configurations.Count} items...");
+
+			foreach (var configuration in configurations)
+			{
+				var success = TryRestore(configuration);
+
+				if (success)
+				{
+					restored++;
+				}
+
+				if (IsStopped())
+				{
+					return null;
+				}
+			}
+
+			logger.Info($"Restored {restored} of {configurations.Count} items.");
+
+			return restored == configurations.Count;
+		}
+
+		private bool TryRestore(IFeatureConfiguration configuration)
+		{
+			var success = configuration.Restore();
+
+			if (success)
+			{
+				backup.Delete(configuration);
+			}
+			else
+			{
+				logger.Warn($"Failed to restore {configuration}!");
+			}
+
+			return success;
+		}
+	}
+}