Clean up ActionNotificationGroupTableViewCell avatar fetching code

Tusker/Caching/ImageCache.swift

@@ -78,6 +78,14 @@ class ImageCache {
         }
     }
     
+    func get(_ url: URL, loadOriginal: Bool = false) async -> (Data?, UIImage?) {
+        return await withCheckedContinuation { continuation in
+            _ = get(url, loadOriginal: loadOriginal) { data, image in
+                continuation.resume(returning: (data, image))
+            }
+        }
+    }
+    
     func fetchIfNotCached(_ url: URL) {
         // if caching is disabled, don't bother fetching since nothing will be done with the result
         guard !ImageCache.disableCaching else { return }

Tusker/Views/Notifications/ActionNotificationGroupTableViewCell.swift

@@ -25,7 +25,6 @@ class ActionNotificationGroupTableViewCell: UITableViewCell {
     var group: NotificationGroup!
     var statusID: String!
     
-    private var avatarRequests = [String: ImageCache.Request]()
     private var updateTimestampWorkItem: DispatchWorkItem?
     private var isGrayscale = false
     
@@ -47,7 +46,9 @@ class ActionNotificationGroupTableViewCell: UITableViewCell {
         }
         
         if isGrayscale != Preferences.shared.grayscaleImages {
-            updateGrayscaleableUI()
+            Task {
+                await updateGrayscaleableUI()
+            }
         }
     }
     
@@ -78,29 +79,11 @@ class ActionNotificationGroupTableViewCell: UITableViewCell {
         
         actionAvatarStackView.arrangedSubviews.forEach { $0.removeFromSuperview() }
         var imageViews = [UIImageView]()
-        for account in people {
+        for _ in people {
             let imageView = UIImageView()
             imageView.translatesAutoresizingMaskIntoConstraints = false
             imageView.layer.masksToBounds = true
             imageView.layer.cornerRadius = Preferences.shared.avatarStyle.cornerRadiusFraction * 30
-            if let avatarURL = account.avatar {
-                avatarRequests[account.id] = ImageCache.avatars.get(avatarURL) { [weak self] (_, image) in
-                    guard let self = self else { return }
-                    guard let image = image,
-                          self.group.id == group.id,
-                          let transformedImage = ImageGrayscalifier.convertIfNecessary(url: avatarURL, image: image) else {
-                        DispatchQueue.main.async {
-                            self.avatarRequests.removeValue(forKey: account.id)
-                        }
-                        return
-                    }
-                    
-                    DispatchQueue.main.async {
-                        self.avatarRequests.removeValue(forKey: account.id)
-                        imageView.image = transformedImage
-                    }
-                }
-            }
             actionAvatarStackView.addArrangedSubview(imageView)
             imageViews.append(imageView)
             
@@ -115,6 +98,10 @@ class ActionNotificationGroupTableViewCell: UITableViewCell {
         }
         NSLayoutConstraint.activate(imageViews.map { $0.widthAnchor.constraint(equalTo: $0.heightAnchor) })
         
+        Task {
+            await updateGrayscaleableUI()
+        }
+
         updateTimestamp()
         actionLabel.setEmojis(pairs: people.map { ($0.displayOrUserName, $0.emojis) }, identifier: group.id)
         
@@ -122,36 +109,29 @@ class ActionNotificationGroupTableViewCell: UITableViewCell {
         statusContentLabel.text = try! doc.text()
     }
     
-    private func updateGrayscaleableUI() {
+    @MainActor
+    private func updateGrayscaleableUI() async {
         let people = group.notifications.compactMap { mastodonController.persistentContainer.account(for: $0.account.id) }
         let groupID = group.id
         
         for (index, account) in people.enumerated() {
             guard actionAvatarStackView.arrangedSubviews.count > index,
-                  let imageView = actionAvatarStackView.arrangedSubviews[index] as? UIImageView else {
+                  let imageView = actionAvatarStackView.arrangedSubviews[index] as? UIImageView,
+                  let avatarURL = account.avatar else {
                 continue
             }
             
-            if let avatarURL = account.avatar {
+            Task {
-                avatarRequests[account.id] = ImageCache.avatars.get(avatarURL) { [weak self] (_, image) in
+                let (_, image) = await ImageCache.avatars.get(avatarURL)
-                    guard let self = self else { return }
                 guard let image = image,
                       self.group.id == groupID,
                       let transformedImage = ImageGrayscalifier.convertIfNecessary(url: avatarURL, image: image) else {
-                        DispatchQueue.main.async {
-                            self.avatarRequests.removeValue(forKey: account.id)
-                        }
                     return
                 }
-                    
-                    DispatchQueue.main.async {
-                        self.avatarRequests.removeValue(forKey: account.id)
                 imageView.image = transformedImage
             }
         }
     }
-        }
-    }
     
     private func updateTimestamp() {
         guard let notification = group.notifications.first else {
@@ -217,7 +197,6 @@ class ActionNotificationGroupTableViewCell: UITableViewCell {
     override func prepareForReuse() {
         super.prepareForReuse()
         
-        avatarRequests.values.forEach { $0.cancel() }
         updateTimestampWorkItem?.cancel()
         updateTimestampWorkItem = nil
     }