Restructuring the project, first steps.

src/GreenshotPlugin/Core/Cache.cs

@@ -0,0 +1,214 @@
+/*
+ * Greenshot - a free and open source screenshot tool
+ * Copyright (C) 2007-2021 Thomas Braun, Jens Klingen, Robin Krom
+ * 
+ * For more information see: http://getgreenshot.org/
+ * The Greenshot project is hosted on GitHub https://github.com/greenshot/greenshot
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 1 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+using System;
+using System.Collections.Generic;
+using System.Timers;
+using log4net;
+
+namespace GreenshotPlugin.Core {
+	/// <summary>
+	/// Cache class 
+	/// </summary>
+	/// <typeparam name="TK">Type of key</typeparam>
+	/// <typeparam name="TV">Type of value</typeparam>
+	public class Cache<TK, TV> {
+		private static readonly ILog Log = LogManager.GetLogger(typeof(Cache<TK, TV>));
+		private readonly IDictionary<TK, TV> _internalCache = new Dictionary<TK, TV>();
+		private readonly object _lockObject = new object();
+		private readonly int _secondsToExpire = 10;
+		private readonly CacheObjectExpired _expiredCallback;
+		public delegate void CacheObjectExpired(TK key, TV cacheValue);
+
+		/// <summary>
+		/// Initialize the cache
+		/// </summary>
+		public Cache() {
+		}
+		/// <summary>
+		/// Initialize the cache
+		/// </summary>
+		/// <param name="expiredCallback"></param>
+		public Cache(CacheObjectExpired expiredCallback) : this() {
+			_expiredCallback = expiredCallback;
+		}
+
+		/// <summary>
+		/// Initialize the cache with a expire setting
+		/// </summary>
+		/// <param name="secondsToExpire"></param>
+		public Cache(int secondsToExpire) : this() {
+			_secondsToExpire = secondsToExpire;
+		}
+
+		/// <summary>
+		/// Initialize the cache with a expire setting
+		/// </summary>
+		/// <param name="secondsToExpire"></param>
+		/// <param name="expiredCallback"></param>
+		public Cache(int secondsToExpire, CacheObjectExpired expiredCallback) : this(expiredCallback) {
+			_secondsToExpire = secondsToExpire;
+		}
+
+		/// <summary>
+		/// Enumerable for the values in the cache
+		/// </summary>
+		public IEnumerable<TV> Elements {
+			get {
+				List<TV> elements = new List<TV>();
+
+				lock (_lockObject)
+				{
+					foreach (TV element in _internalCache.Values) {
+						elements.Add(element);
+					}
+				}
+				foreach (TV element in elements) {
+					yield return element;
+				}
+			}
+		}
+
+		/// <summary>
+		/// Get the value by key from the cache
+		/// </summary>
+		/// <param name="key"></param>
+		/// <returns></returns>
+		public TV this[TK key] {
+			get {
+				TV result = default;
+				lock (_lockObject) {
+					if (_internalCache.ContainsKey(key)) {
+						result = _internalCache[key];
+					}
+				}
+				return result;
+			}
+		}
+
+		/// <summary>
+		/// Contains
+		/// </summary>
+		/// <param name="key"></param>
+		/// <returns>true if the cache contains the key</returns>
+		public bool Contains(TK key)
+		{
+			lock (_lockObject)
+			{
+				return _internalCache.ContainsKey(key);
+			}
+		}
+
+		/// <summary>
+		/// Add a value to the cache
+		/// </summary>
+		/// <param name="key"></param>
+		/// <param name="value"></param>
+		public void Add(TK key, TV value) {
+			Add(key, value, null);
+		}
+
+		/// <summary>
+		/// Add a value to the cache
+		/// </summary>
+		/// <param name="key"></param>
+		/// <param name="value"></param>
+		/// <param name="secondsToExpire">optional value for the seconds to expire</param>
+		public void Add(TK key, TV value, int? secondsToExpire) {
+			lock (_lockObject) {
+				var cachedItem = new CachedItem(key, value, secondsToExpire ?? _secondsToExpire);
+				cachedItem.Expired += delegate(TK cacheKey, TV cacheValue) {
+					if (_internalCache.ContainsKey(cacheKey)) {
+						Log.DebugFormat("Expiring object with Key: {0}", cacheKey);
+						_expiredCallback?.Invoke(cacheKey, cacheValue);
+						Remove(cacheKey);
+					} else {
+						Log.DebugFormat("Expired old object with Key: {0}", cacheKey);
+					}
+				};
+
+				if (_internalCache.ContainsKey(key)) {
+					_internalCache[key] = value;
+					Log.DebugFormat("Updated item with Key: {0}", key);
+				} else {
+					_internalCache.Add(key, cachedItem);
+					Log.DebugFormat("Added item with Key: {0}", key);
+				}
+			}
+		}
+
+		/// <summary>
+		/// Remove item from cache
+		/// </summary>
+		/// <param name="key"></param>
+		public void Remove(TK key) {
+			lock (_lockObject) {
+				if (!_internalCache.ContainsKey(key)) {
+					throw new ApplicationException($"An object with key ‘{key}’ does not exists in cache");
+				}
+				_internalCache.Remove(key);
+				Log.DebugFormat("Removed item with Key: {0}", key);
+			}
+		}
+
+		/// <summary>
+		/// A cache item
+		/// </summary>
+		private class CachedItem {
+			public event CacheObjectExpired Expired;
+			private readonly int _secondsToExpire;
+			private readonly Timer _timerEvent;
+
+			public CachedItem(TK key, TV item, int secondsToExpire) {
+				if (key == null) {
+					throw new ArgumentNullException(nameof(key));
+				}
+				Key = key;
+				Item = item;
+				_secondsToExpire = secondsToExpire;
+				if (secondsToExpire <= 0)
+				{
+					return;
+				}
+				_timerEvent = new Timer(secondsToExpire * 1000) { AutoReset = false };
+				_timerEvent.Elapsed += timerEvent_Elapsed;
+				_timerEvent.Start();
+			}
+
+			private void ExpireNow() {
+				_timerEvent.Stop();
+				if (_secondsToExpire > 0) {
+					Expired?.Invoke(Key, Item);
+				}
+			}
+
+			private void timerEvent_Elapsed(object sender, ElapsedEventArgs e) {
+				ExpireNow();
+			}
+
+			public TK Key { get; private set; }
+			public TV Item { get; private set; }
+
+			public static implicit operator TV(CachedItem a) {
+				return a.Item;
+			}
+		}
+	}
+}