fix #46 Reload index cache when the file changed in index directories

Wox.Plugin.SystemPlugins/Program/FileChangeWatcher.cs

@@ -0,0 +1,56 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using Wox.Infrastructure.Storage.UserSettings;
+
+namespace Wox.Plugin.SystemPlugins.Program
+{
+    internal class FileChangeWatcher
+    {
+        private static bool isIndexing = false;
+        private static List<string> watchedPath = new List<string>(); 
+
+        public static void AddWatch(string path, bool includingSubDirectory = true)
+        {
+            if (watchedPath.Contains(path)) return;
+            if (!Directory.Exists(path))
+            {
+                Debug.WriteLine(string.Format("FileChangeWatcher: {0} doesn't exist", path),"WoxDebug");
+                return;
+            }
+
+            watchedPath.Add(path);
+            foreach (string fileType in UserSettingStorage.Instance.ProgramSuffixes.Split(';'))
+            {
+                FileSystemWatcher watcher = new FileSystemWatcher
+                {
+                    Path = path,
+                    IncludeSubdirectories = includingSubDirectory,
+                    Filter = string.Format("*.{0}", fileType),
+                    EnableRaisingEvents = true
+                };
+                watcher.Changed += FileChanged;
+                watcher.Created += FileChanged;
+                watcher.Deleted += FileChanged;
+                watcher.Renamed += FileChanged;
+            }
+        }
+
+        private static void FileChanged(object source, FileSystemEventArgs e)
+        {
+            if (!isIndexing)
+            {
+                ThreadPool.QueueUserWorkItem(o =>
+                {
+                    Programs.IndexPrograms();
+                    isIndexing = false;
+                });
+            }
+        }
+ 
+    }
+}