Restore SEBPatch

SafeExamBrowser.Proctoring/ScreenProctoring/Buffer.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.Logging.Contracts;
+using SafeExamBrowser.Proctoring.ScreenProctoring.Data;
+using SafeExamBrowser.Proctoring.ScreenProctoring.Imaging;
+
+namespace SafeExamBrowser.Proctoring.ScreenProctoring
+{
+	internal class Buffer
+	{
+		private readonly object @lock = new object();
+
+		private readonly List<(MetaData metaData, DateTime schedule, ScreenShot screenShot)> list;
+		private readonly ILogger logger;
+
+		internal int Count
+		{
+			get
+			{
+				lock (@lock)
+				{
+					return list.Count;
+				}
+			}
+		}
+
+		internal Buffer(ILogger logger)
+		{
+			this.list = new List<(MetaData, DateTime, ScreenShot)>();
+			this.logger = logger;
+		}
+
+		internal bool Any()
+		{
+			lock (@lock)
+			{
+				return list.Any();
+			}
+		}
+
+		internal void Dequeue()
+		{
+			lock (@lock)
+			{
+				if (list.Any())
+				{
+					var (_, schedule, screenShot) = list.First();
+
+					list.RemoveAt(0);
+					logger.Debug($"Removed data for '{screenShot.CaptureTime:HH:mm:ss} -> {schedule:HH:mm:ss}', {Count} item(s) remaining.");
+				}
+			}
+		}
+
+		internal void Enqueue(MetaData metaData, DateTime schedule, ScreenShot screenShot)
+		{
+			lock (@lock)
+			{
+				list.Add((metaData, schedule, screenShot));
+				list.Sort((a, b) => DateTime.Compare(a.schedule, b.schedule));
+
+				logger.Debug($"Buffered data for '{screenShot.CaptureTime:HH:mm:ss} -> {schedule:HH:mm:ss}', now holding {Count} item(s).");
+			}
+		}
+
+		internal bool TryPeek(out MetaData metaData, out DateTime schedule, out ScreenShot screenShot)
+		{
+			lock (@lock)
+			{
+				metaData = default;
+				schedule = default;
+				screenShot = default;
+
+				if (list.Any())
+				{
+					(metaData, schedule, screenShot) = list.First();
+				}
+
+				return metaData != default && screenShot != default;
+			}
+		}
+	}
+}