New: App health displayed in UI

src/NzbDrone.Core/HealthCheck/Checks/UpdateCheck.cs

@@ -0,0 +1,51 @@
+using System;
+using System.IO;
+using NzbDrone.Common.Disk;
+using NzbDrone.Common.EnvironmentInfo;
+using NzbDrone.Core.Update;
+
+namespace NzbDrone.Core.HealthCheck.Checks
+{
+    public class UpdateCheck : IProvideHealthCheck
+    {
+        private readonly IDiskProvider _diskProvider;
+        private readonly IAppFolderInfo _appFolderInfo;
+        private readonly ICheckUpdateService _checkUpdateService;
+
+        public UpdateCheck(IDiskProvider diskProvider, IAppFolderInfo appFolderInfo, ICheckUpdateService checkUpdateService)
+        {
+            _diskProvider = diskProvider;
+            _appFolderInfo = appFolderInfo;
+            _checkUpdateService = checkUpdateService;
+        }
+
+
+        public HealthCheck Check()
+        {
+            if (OsInfo.IsWindows)
+            {
+                try
+                {
+                    var testPath = Path.Combine(_appFolderInfo.StartUpFolder, "drone_test.txt");
+                    _diskProvider.WriteAllText(testPath, DateTime.Now.ToString());
+                    _diskProvider.DeleteFile(testPath);
+                }
+                catch (Exception)
+                {
+                    return new HealthCheck(HealthCheckResultType.Error,
+                        "Unable to update, running from write-protected folder");
+                }
+            }
+
+            if (BuildInfo.BuildDateTime < DateTime.UtcNow.AddDays(-14))
+            {
+                if (_checkUpdateService.AvailableUpdate() != null)
+                {
+                    return new HealthCheck(HealthCheckResultType.Warning, "New update is available");
+                }
+            }
+
+            return null;
+        }
+    }
+}