/*
 * Copyright (c) 2019 ETH Zürich, Educational Development and Technology (LET)
 *
 * 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.Linq;
using System.Threading.Tasks;
using SafeExamBrowser.Contracts.Lockdown;
using SafeExamBrowser.Contracts.Logging;

namespace SafeExamBrowser.Lockdown
{
	public class AutoRestoreMechanism : IAutoRestoreMechanism
	{
		private readonly object @lock = new object();

		private IFeatureConfigurationBackup backup;
		private ILogger logger;
		private bool running;
		private int timeout_ms;

		public AutoRestoreMechanism(IFeatureConfigurationBackup backup, ILogger logger, 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.timeout_ms = timeout_ms;
		}

		public void Start()
		{
			lock (@lock)
			{
				if (!running)
				{
					running = true;
					Task.Run(new Action(RestoreAll));
					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 RestoreAll()
		{
			var configurations = backup.GetAllConfigurations();

			if (!configurations.Any())
			{
				running = false;
				logger.Info("Nothing to restore, stopped auto-restore mechanism.");

				return;
			}

			logger.Info($"Attempting to restore {configurations.Count} items...");

			foreach (var configuration in configurations)
			{
				var success = configuration.Restore();

				if (success)
				{
					backup.Delete(configuration);
				}
				else
				{
					logger.Warn($"Failed to restore {configuration}!");
				}

				lock (@lock)
				{
					if (!running)
					{
						logger.Info("Auto-restore mechanism was aborted.");

						return;
					}
				}
			}

			Task.Delay(timeout_ms).ContinueWith((_) => RestoreAll());
		}
	}
}