Displays progress when downloading/refreshing apps

Refactors download/refresh steps into separate Operation subclasses

AltStore/Operations/DownloadAppOperation.swift

@@ -0,0 +1,65 @@
+//
+//  DownloadAppOperation.swift
+//  AltStore
+//
+//  Created by Riley Testut on 6/10/19.
+//  Copyright © 2019 Riley Testut. All rights reserved.
+//
+
+import Foundation
+import Roxas
+
+import AltSign
+
+@objc(DownloadAppOperation)
+class DownloadAppOperation: ResultOperation<InstalledApp>
+{
+    let app: App
+    private let downloadURL: URL
+    private let ipaURL: URL
+    
+    private let session = URLSession(configuration: .default)
+    
+    init(app: App)
+    {
+        self.app = app
+        self.downloadURL = app.downloadURL
+        self.ipaURL = InstalledApp.ipaURL(for: app)
+        
+        super.init()
+        
+        self.progress.totalUnitCount = 1
+    }
+    
+    override func main()
+    {
+        super.main()
+        
+        let downloadTask = self.session.downloadTask(with: self.downloadURL) { (fileURL, response, error) in
+            do
+            {
+                let (fileURL, _) = try Result((fileURL, response), error).get()
+                
+                try FileManager.default.copyItem(at: fileURL, to: self.ipaURL, shouldReplace: true)
+
+                DatabaseManager.shared.persistentContainer.performBackgroundTask { (context) in
+                    let app = context.object(with: self.app.objectID) as! App
+                    
+                    let installedApp = InstalledApp(app: app,
+                                                    bundleIdentifier: app.identifier,
+                                                    expirationDate: Date(),
+                                                    context: context)
+                    
+                    self.finish(.success(installedApp))
+                }
+            }
+            catch let error
+            {
+                self.finish(.failure(error))
+            }
+        }
+        
+        self.progress.addChild(downloadTask.progress, withPendingUnitCount: 1)
+        downloadTask.resume()
+    }
+}