clear cache and open file on iOS

src/iOS/Services/DeviceActionService.cs

@@ -1,6 +1,8 @@
 using System;
 using Bit.App.Abstractions;
 using UIKit;
+using Foundation;
+using System.IO;
 
 namespace Bit.iOS.Services
 {
@@ -14,12 +16,63 @@ namespace Bit.iOS.Services
 
         public bool OpenFile(byte[] fileData, string id, string fileName)
         {
-            return true;
+            var filePath = Path.Combine(GetTempPath(), fileName);
+            File.WriteAllBytes(filePath, fileData);
+            var url = NSUrl.FromFilename(filePath);
+            var viewer = UIDocumentInteractionController.FromUrl(url);
+            var controller = GetVisibleViewController();
+            return viewer.PresentOpenInMenu(controller.View.Frame, controller.View, true);
         }
 
         public bool CanOpenFile(string fileName)
         {
+            // Not sure of a way to check this ahead of time on iOS
             return true;
         }
+
+        public void ClearCache()
+        {
+            var url = new NSUrl(GetTempPath());
+            NSError error;
+            var tmpFiles = NSFileManager.DefaultManager.GetDirectoryContent(url, null,
+                NSDirectoryEnumerationOptions.SkipsHiddenFiles, out error);
+            if(error == null && tmpFiles.Length > 0)
+            {
+                foreach(var item in tmpFiles)
+                {
+                    NSError itemError;
+                    NSFileManager.DefaultManager.Remove(item, out itemError);
+                }
+            }
+        }
+
+        private UIViewController GetVisibleViewController(UIViewController controller = null)
+        {
+            controller = controller ?? UIApplication.SharedApplication.KeyWindow.RootViewController;
+            if(controller.PresentedViewController == null)
+            {
+                return controller;
+            }
+
+            if(controller.PresentedViewController is UINavigationController)
+            {
+                return ((UINavigationController)controller.PresentedViewController).VisibleViewController;
+            }
+
+            if(controller.PresentedViewController is UITabBarController)
+            {
+                return ((UITabBarController)controller.PresentedViewController).SelectedViewController;
+            }
+
+            return GetVisibleViewController(controller.PresentedViewController);
+        }
+
+        // ref:  //https://developer.xamarin.com/guides/ios/application_fundamentals/working_with_the_file_system/
+        public string GetTempPath()
+        {
+            var documents = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
+            var tmp = Path.Combine(documents, "..", "tmp");
+            return tmp;
+        }
     }
 }