Mark notifications on Mastodon web frontend as read once displayed

Fixes #357

Tusker/Screens/Notifications/NotificationsCollectionViewController.swift

@@ -12,6 +12,9 @@ import Combine
 #if canImport(Sentry)
 import Sentry
 #endif
+import OSLog
+
+private let logger = Logger(subsystem: Bundle.main.bundleIdentifier!, category: "NotificationsCVC")
 
 class NotificationsCollectionViewController: UIViewController, TimelineLikeCollectionViewController, CollectionViewController {
     
@@ -32,6 +35,9 @@ class NotificationsCollectionViewController: UIViewController, TimelineLikeColle
     private var newer: RequestRange?
     private var older: RequestRange?
     
+    var updatesNotificationsMarker: Bool = false
+    private var newestDisplayedNotification: Item?
+    
     init(allowedTypes: [Pachyderm.Notification.Kind], mastodonController: MastodonController) {
         self.allowedTypes = allowedTypes
         self.mastodonController = mastodonController
@@ -205,6 +211,12 @@ class NotificationsCollectionViewController: UIViewController, TimelineLikeColle
         }
     }
     
+    override func viewWillDisappear(_ animated: Bool) {
+        super.viewWillDisappear(animated)
+        
+        updateNotificationsMarkerIfNecessary()
+    }
+    
     @objc func refresh() {
         Task { @MainActor in
             if case .notLoadedInitial = controller.state {
@@ -311,6 +323,23 @@ class NotificationsCollectionViewController: UIViewController, TimelineLikeColle
         await apply(snapshot, animatingDifferences: true)
     }
     
+    private func updateNotificationsMarkerIfNecessary() {
+        guard updatesNotificationsMarker,
+              case let .group(group, _, _) = newestDisplayedNotification,
+              let notification = group.notifications.first else {
+            return
+        }
+        logger.debug("Updating notifications marker with \(notification.id)")
+        Task {
+            let req = TimelineMarkers.update(timeline: .notifications, lastReadID: notification.id)
+            do {
+                _ = try await mastodonController.run(req)
+            } catch {
+                logger.error("Failed to update notifications marker: \(String(describing: error))")
+            }
+        }
+    }
+    
 }
 
 extension NotificationsCollectionViewController {
@@ -545,6 +574,21 @@ extension NotificationsCollectionViewController: UICollectionViewDelegate {
         guard case .notifications = dataSource.sectionIdentifier(for: indexPath.section) else {
             return
         }
+        
+        if updatesNotificationsMarker {
+            let shouldUpdateNewestDisplayedNotification: Bool
+            if let newestDisplayedNotification,
+               let currentNewestIndexPath = dataSource.indexPath(for: newestDisplayedNotification) {
+                shouldUpdateNewestDisplayedNotification = indexPath < currentNewestIndexPath
+            } else {
+                shouldUpdateNewestDisplayedNotification = true
+            }
+            if shouldUpdateNewestDisplayedNotification,
+               let item = dataSource.itemIdentifier(for: indexPath) {
+                newestDisplayedNotification = item
+            }
+        }
+        
         let itemsInSection = collectionView.numberOfItems(inSection: indexPath.section)
         if indexPath.row == itemsInSection - 1 {
             Task {
@@ -765,3 +809,9 @@ extension NotificationsCollectionViewController: StatusBarTappableViewController
         return .stop
     }
 }
+
+extension NotificationsCollectionViewController: BackgroundableViewController {
+    func sceneDidEnterBackground() {
+        updateNotificationsMarkerIfNecessary()
+    }
+}

Tusker/Screens/Notifications/NotificationsPageViewController.swift

@@ -24,6 +24,7 @@ class NotificationsPageViewController: SegmentedPageViewController<Notifications
             let vc = NotificationsCollectionViewController(allowedTypes: page.allowedTypes, mastodonController: mastodonController)
             vc.title = page.title
             vc.userActivity = page.userActivity(accountID: mastodonController.accountInfo!.id)
+            vc.updatesNotificationsMarker = page == .all
             return vc
         }