Better encapsulate PurchaseDownloadObserver.

Partial #696

Signed-off-by: Ross Goldberg <484615+rgoldberg@users.noreply.github.com>

.swiftlint.yml

@@ -41,3 +41,21 @@ file_types_order:
       [preview_provider],
       [library_content_provider],
     ]
+type_contents_order:
+  order:
+    [
+      [case],
+      [type_alias, associated_type],
+      [subtype],
+      [type_property],
+      [instance_property],
+      [ib_inspectable],
+      [ib_outlet],
+      [initializer],
+      [deinitializer],
+      [type_method],
+      [view_life_cycle_method],
+      [ib_action],
+      [other_method],
+      [subscript],
+    ]

Sources/mas/AppStore/PurchaseDownloadObserver.swift

@@ -7,23 +7,27 @@
 //
 
 import CommerceKit
+import PromiseKit
 import StoreFoundation
 
 private let downloadingPhase: Int64 = 0
 private let installingPhase: Int64 = 1
 private let downloadedPhase: Int64 = 5
 
-@objc
-class PurchaseDownloadObserver: NSObject, CKDownloadQueueObserver {
+class PurchaseDownloadObserver: CKDownloadQueueObserver {
     private let purchase: SSPurchase
-    var completionHandler: (() -> Void)?
-    var errorHandler: ((MASError) -> Void)?
+    private var completionHandler: (() -> Void)?
+    private var errorHandler: ((MASError) -> Void)?
     private var priorPhaseType: Int64?
 
     init(purchase: SSPurchase) {
         self.purchase = purchase
     }
 
+    deinit {
+        // do nothing
+    }
+
     func downloadQueue(_ queue: CKDownloadQueue, statusChangedFor download: SSDownload) {
         guard
             download.metadata.itemIdentifier == purchase.itemIdentifier,
@@ -82,7 +86,7 @@ class PurchaseDownloadObserver: NSObject, CKDownloadQueueObserver {
     }
 }
 
-struct ProgressState {
+private struct ProgressState {
     let percentComplete: Float
     let phase: String
 
@@ -92,7 +96,7 @@ struct ProgressState {
     }
 }
 
-func progress(_ state: ProgressState) {
+private func progress(_ state: ProgressState) {
     // Don't display the progress bar if we're not on a terminal
     guard isatty(fileno(stdout)) != 0 else {
         return
@@ -112,13 +116,13 @@ private extension SSDownload {
     }
 }
 
-extension SSDownloadStatus {
+private extension SSDownloadStatus {
     var progressState: ProgressState {
         ProgressState(percentComplete: percentComplete, phase: activePhase.phaseDescription)
     }
 }
 
-extension SSDownloadPhase {
+private extension SSDownloadPhase {
     var phaseDescription: String {
         switch phaseType {
         case downloadingPhase:
@@ -130,3 +134,17 @@ extension SSDownloadPhase {
         }
     }
 }
+
+extension PurchaseDownloadObserver {
+    func observeDownloadQueue(_ downloadQueue: CKDownloadQueue = CKDownloadQueue.shared()) -> Promise<Void> {
+        let observerID = downloadQueue.add(self)
+
+        return Promise<Void> { seal in
+            errorHandler = seal.reject
+            completionHandler = seal.fulfill_
+        }
+        .ensure {
+            downloadQueue.remove(observerID)
+        }
+    }
+}

Sources/mas/AppStore/SSPurchase.swift

@@ -75,17 +75,7 @@ extension SSPurchase {
                 }
         }
         .then { purchase in
-            let observer = PurchaseDownloadObserver(purchase: purchase)
-            let downloadQueue = CKDownloadQueue.shared()
-            let observerID = downloadQueue.add(observer)
-
-            return Promise<Void> { seal in
-                observer.errorHandler = seal.reject
-                observer.completionHandler = seal.fulfill_
-            }
-            .ensure {
-                downloadQueue.remove(observerID)
-            }
+            PurchaseDownloadObserver(purchase: purchase).observeDownloadQueue()
         }
     }
 }