Add upgrade check.

Wox/Update/UpdateChecker.cs

@@ -0,0 +1,96 @@
+using System;
+using System.Collections.Generic;
+using System.Configuration;
+using System.IO;
+using System.Linq;
+using System.Net;
+using System.Text;
+using Newtonsoft.Json;
+using Wox.Helper;
+using Wox.Infrastructure;
+
+namespace Wox.Update
+{
+    public class UpdateChecker
+    {
+        private string updateURL = "https://api.getwox.com/release/latest/";
+
+        /// <summary>
+        /// If new release is available, then return the new release
+        /// otherwise, return null
+        /// </summary>
+        /// <returns></returns>
+        public Release CheckUpgrade()
+        {
+            Release release = null;
+            HttpWebResponse response = HttpRequest.CreateGetHttpResponse(updateURL, HttpProxy.Instance);
+            Stream s = response.GetResponseStream();
+            if (s != null)
+            {
+                StreamReader reader = new StreamReader(s, Encoding.UTF8);
+                string json = reader.ReadToEnd();
+                try
+                {
+                    release = JsonConvert.DeserializeObject<Release>(json);
+                }
+                catch
+                {
+                    return null;
+                }
+            }
+
+            if (!IsNewerThanCurrent(release))
+            {
+                return null;
+            }
+
+            return release;
+        }
+
+        private bool IsNewerThanCurrent(Release release)
+        {
+            if (release == null) return false;
+
+            string currentVersion = ConfigurationManager.AppSettings["version"];
+            return CompareVersion(release.version, currentVersion) > 0;
+        }
+
+        /// <summary>
+        /// if version1 > version2 return 1 
+        /// else -1 
+        /// </summary>
+        /// <param name="version1"></param>
+        /// <param name="version2"></param>
+        /// <returns></returns>
+        private int CompareVersion(string version1, string version2)
+        {
+            if (version1 == version2) return 0;
+            if (string.IsNullOrEmpty(version1) || string.IsNullOrEmpty(version2)) return 0;
+
+            //semantic version, e.g. 1.1.0
+            List<int> version1List = version1.Split('.').Select(int.Parse).ToList();
+            List<int> version2List = version2.Split('.').Select(int.Parse).ToList();
+
+            if (version1List[0] > version2List[0])
+            {
+                return 1;
+            }
+            else if (version1List[0] == version2List[0])
+            {
+                if (version1List[1] > version2List[1])
+                {
+                    return 1;
+                }
+                else if (version1List[1] == version2List[1])
+                {
+                    if (version1List[2] > version2List[2])
+                    {
+                        return 1;
+                    }
+                }
+            }
+
+            return -1;
+        }
+    }
+}