Add preference to use timeline marker API

Closes #40

Packages/Pachyderm/Sources/Pachyderm/Model/TimelineMarkers.swift

@@ -0,0 +1,40 @@
+//
+//  TimelineMarkers.swift
+//  Pachyderm
+//
+//  Created by Shadowfacts on 2/14/23.
+//
+
+import Foundation
+
+public struct TimelineMarkers: Decodable {
+    public let home: Marker?
+    public let notifications: Marker?
+    
+    public static func request(timelines: [Timeline]) -> Request<TimelineMarkers> {
+        return Request(method: .get, path: "/api/v1/markers", queryParameters: "timeline[]" => timelines.map(\.rawValue))
+    }
+    
+    public static func update(timeline: Timeline, lastReadID: String) -> Request<Empty> {
+        return Request(method: .post, path: "/api/v1/markers", body: ParametersBody([
+            "\(timeline.rawValue)[last_read_id]" => lastReadID,
+        ]))
+    }
+    
+    public enum Timeline: String {
+        case home
+        case notifications
+    }
+    
+    public struct Marker: Decodable {
+        public let lastReadID: String
+        public let version: Int
+        public let updatedAt: Date
+        
+        enum CodingKeys: String, CodingKey {
+            case lastReadID = "last_read_id"
+            case version
+            case updatedAt = "updated_at"
+        }
+    }
+}

Tusker/Preferences/Preferences.swift

@@ -75,6 +75,7 @@ class Preferences: Codable, ObservableObject {
         self.oppositeCollapseKeywords = try container.decodeIfPresent([String].self, forKey: .oppositeCollapseKeywords) ?? []
         self.confirmBeforeReblog = try container.decodeIfPresent(Bool.self, forKey: .confirmBeforeReblog) ?? false
         self.timelineStateRestoration = try container.decodeIfPresent(Bool.self, forKey: .timelineStateRestoration) ?? true
+        self.timelineSyncMode = try container.decodeIfPresent(TimelineSyncMode.self, forKey: .timelineSyncMode) ?? .icloud
         self.hideReblogsInTimelines = try container.decodeIfPresent(Bool.self, forKey: .hideReblogsInTimelines) ?? false
         self.hideRepliesInTimelines = try container.decodeIfPresent(Bool.self, forKey: .hideRepliesInTimelines) ?? false
         
@@ -127,6 +128,7 @@ class Preferences: Codable, ObservableObject {
         try container.encode(oppositeCollapseKeywords, forKey: .oppositeCollapseKeywords)
         try container.encode(confirmBeforeReblog, forKey: .confirmBeforeReblog)
         try container.encode(timelineStateRestoration, forKey: .timelineStateRestoration)
+        try container.encode(timelineSyncMode, forKey: .timelineSyncMode)
         try container.encode(hideReblogsInTimelines, forKey: .hideReblogsInTimelines)
         try container.encode(hideRepliesInTimelines, forKey: .hideRepliesInTimelines)
         
@@ -188,6 +190,7 @@ class Preferences: Codable, ObservableObject {
     @Published var oppositeCollapseKeywords: [String] = []
     @Published var confirmBeforeReblog = false
     @Published var timelineStateRestoration = true
+    @Published var timelineSyncMode = TimelineSyncMode.icloud
     @Published var hideReblogsInTimelines = false
     @Published var hideRepliesInTimelines = false
     
@@ -242,6 +245,7 @@ class Preferences: Codable, ObservableObject {
         case oppositeCollapseKeywords
         case confirmBeforeReblog
         case timelineStateRestoration
+        case timelineSyncMode
         case hideReblogsInTimelines
         case hideRepliesInTimelines
         
@@ -395,3 +399,10 @@ extension Preferences {
         }
     }
 }
+
+extension Preferences {
+    enum TimelineSyncMode: String, Codable {
+        case mastodon
+        case icloud
+    }
+}

Tusker/Screens/Preferences/BehaviorPrefsView.swift

@@ -37,8 +37,17 @@ struct BehaviorPrefsView: View {
             Toggle(isOn: $preferences.timelineStateRestoration) {
                 Text("Maintain Position Across App Launches")
             }
+            
+            Picker(selection: $preferences.timelineSyncMode) {
+                Text("iCloud").tag(Preferences.TimelineSyncMode.icloud)
+                Text("Mastodon").tag(Preferences.TimelineSyncMode.mastodon)
+            } label: {
+                Text("Sync Timeline Position via")
+            }
         } header: {
             Text("Timeline")
+        } footer: {
+            Text("Syncing via the Mastodon API can be more reliable than iCloud, but is not compatible with the Mastodon web interface.")
         }
         .appGroupedListRowBackground()
     }

Tusker/Screens/Timeline/TimelineViewController.swift

@@ -151,7 +151,8 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
         NotificationCenter.default.addObserver(self, selector: #selector(sceneDidEnterBackground), name: UIScene.didEnterBackgroundNotification, object: nil)
         NotificationCenter.default.publisher(for: .timelinePositionChanged)
             .filter { [unowned self] in
-                if let timelinePosition = $0.object as? TimelinePosition,
+                if Preferences.shared.timelineSyncMode == .icloud,
+                   let timelinePosition = $0.object as? TimelinePosition,
                    timelinePosition.accountID == self.mastodonController.accountInfo?.id,
                    timelinePosition.timeline == self.timeline {
                     return true
@@ -162,7 +163,7 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
             .debounce(for: .milliseconds(500), scheduler: DispatchQueue.main)
             .sink { [unowned self] _ in
                 Task {
-                    _ = await syncPositionIfNecessary(alwaysPrompt: true)
+                    _ = await syncPositionFromICloudIfNecessary(alwaysPrompt: true)
                 }
             }
             .store(in: &cancellables)
@@ -338,13 +339,33 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
         } else {
             fatalError()
         }
-        stateRestorationLogger.debug("TimelineViewController: saving state to persistent store with with centerID \(centerVisibleID)")
+        switch Preferences.shared.timelineSyncMode {
+        case .icloud:
+            stateRestorationLogger.debug("TimelineViewController: saving state to persistent store with with centerID \(centerVisibleID)")
             
-        let context = mastodonController.persistentContainer.viewContext
+            let context = mastodonController.persistentContainer.viewContext
-        let position = mastodonController.persistentContainer.getTimelinePosition(timeline: timeline) ?? TimelinePosition(timeline: timeline, account: accountInfo, context: context)
+            let position = mastodonController.persistentContainer.getTimelinePosition(timeline: timeline) ?? TimelinePosition(timeline: timeline, account: accountInfo, context: context)
-        position.statusIDs = ids
+            position.statusIDs = ids
-        position.centerStatusID = centerVisibleID
+            position.centerStatusID = centerVisibleID
-        mastodonController.persistentContainer.save(context: context)
+            mastodonController.persistentContainer.save(context: context)
+            
+        case .mastodon:
+            guard case .home = timeline else {
+                return
+            }
+            stateRestorationLogger.debug("TimelineViewController: updating timeline marker with last read ID \(centerVisibleID)")
+            Task {
+                do {
+                    let req = TimelineMarkers.update(timeline: .home, lastReadID: centerVisibleID)
+                    _ = try await mastodonController.run(req)
+                } catch {
+                    stateRestorationLogger.error("TimelineViewController: failed to update timeline marker: \(String(describing: error))")
+                    let event = Event(error: error)
+                    event.message = SentryMessage(formatted: "Failed to update timeline marker")
+                    SentrySDK.capture(event: event)
+                }
+            }
+        }
     }
     
     func stateRestorationActivity() -> NSUserActivity? {
@@ -359,17 +380,27 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
     
     func restoreState() async -> Bool {
         guard persistsState,
-              Preferences.shared.timelineStateRestoration,
+              Preferences.shared.timelineStateRestoration else {
-              let position = mastodonController.persistentContainer.getTimelinePosition(timeline: timeline) else {
             return false
         }
         loadViewIfNeeded()
         var loaded = false
         await controller.restoreInitial { @MainActor in
-            let hasStatusesToRestore = await loadStatusesToRestore(position: position)
+            switch Preferences.shared.timelineSyncMode {
-            if hasStatusesToRestore {
+            case .icloud:
-                applyItemsToRestore(position: position)
+                guard let position = mastodonController.persistentContainer.getTimelinePosition(timeline: timeline) else {
-                loaded = true
+                    return
+                }
+                let hasStatusesToRestore = await loadStatusesToRestore(position: position)
+                if hasStatusesToRestore {
+                    applyItemsToRestore(position: position)
+                    loaded = true
+                }
+            case .mastodon:
+                guard case .home = timeline else {
+                    return
+                }
+                loaded = await restoreStatusesFromMarkerPosition()
             }
         }
         return loaded
@@ -455,21 +486,8 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
         SentrySDK.addBreadcrumb(crumb)
         dataSource.apply(snapshot, animatingDifferences: false) {
             if let centerStatusID,
-               let index = statusIDs.firstIndex(of: centerStatusID),
+               let index = statusIDs.firstIndex(of: centerStatusID) {
-               let indexPath = self.dataSource.indexPath(for: items[index]) {
+                self.scrollToItem(item: items[index])
-                // it sometimes takes multiple attempts to convert on the right scroll position
-                // since we're dealing with a bunch of unmeasured cells, so just try a few times in a loop
-                var count = 0
-                while count < 5 {
-                    count += 1
-                    let origOffset = self.collectionView.contentOffset
-                    self.collectionView.layoutIfNeeded()
-                    self.collectionView.scrollToItem(at: indexPath, at: .centeredVertically, animated: false)
-                    let newOffset = self.collectionView.contentOffset
-                    if abs(origOffset.y - newOffset.y) <= 1 {
-                        break
-                    }
-                }
                 stateRestorationLogger.fault("TimelineViewController: restored statuses with center ID \(centerStatusID)")
             } else {
                 stateRestorationLogger.fault("TimelineViewController: restored statuses, but couldn't find center ID")
@@ -477,6 +495,57 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
         }
     }
     
+    @MainActor
+    private func restoreStatusesFromMarkerPosition() async -> Bool {
+        do {
+            let (marker, _) = try await mastodonController.run(TimelineMarkers.request(timelines: [.home]))
+            guard let home = marker.home else {
+                return false
+            }
+            async let status = try await mastodonController.run(Client.getStatus(id: home.lastReadID)).0
+            async let olderStatuses = try await mastodonController.run(Client.getStatuses(timeline: .home, range: .before(id: home.lastReadID, count: Self.pageSize))).0
+            
+            let allStatuses = try await [status] + olderStatuses
+            await mastodonController.persistentContainer.addAll(statuses: allStatuses)
+            
+            var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
+            snapshot.appendSections([.statuses])
+            let items = allStatuses.map { Item.status(id: $0.id, collapseState: .unknown, filterState: .unknown) }
+            snapshot.appendItems(items)
+            await dataSource.apply(snapshot, animatingDifferences: false)
+            collectionView.contentOffset = CGPoint(x: 0, y: -collectionView.adjustedContentInset.top)
+            
+            stateRestorationLogger.debug("TimelineViewController: restored from timeline marker with last read ID: \(home.lastReadID)")
+            
+            return true
+        } catch {
+            stateRestorationLogger.error("TimelineViewController: failed to load from timeline marker: \(String(describing: error))")
+            let event = Event(error: error)
+            event.message = SentryMessage(formatted: "Failed to load from timeline marker")
+            SentrySDK.capture(event: event)
+            return false
+        }
+    }
+    
+    private func scrollToItem(item: Item) {
+        guard let indexPath = dataSource.indexPath(for: item) else {
+            return
+        }
+        // it sometimes takes multiple attempts to convert on the right scroll position
+        // since we're dealing with a bunch of unmeasured cells, so just try a few times in a loop
+        var count = 0
+        while count < 5 {
+            count += 1
+            let origOffset = self.collectionView.contentOffset
+            self.collectionView.layoutIfNeeded()
+            self.collectionView.scrollToItem(at: indexPath, at: .centeredVertically, animated: false)
+            let newOffset = self.collectionView.contentOffset
+            if abs(origOffset.y - newOffset.y) <= 1 {
+                break
+            }
+        }
+    }
+    
     private func removeTimelineDescriptionCell() {
         var snapshot = dataSource.snapshot()
         snapshot.deleteItems([.publicTimelineDescription])
@@ -547,6 +616,15 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
     }
     
     func syncPositionIfNecessary(alwaysPrompt: Bool) async -> Bool {
+        switch Preferences.shared.timelineSyncMode {
+        case .icloud:
+            return await syncPositionFromICloudIfNecessary(alwaysPrompt: alwaysPrompt)
+        case .mastodon:
+            return await restoreStatusesFromMarkerPosition()
+        }
+    }
+    
+    private func syncPositionFromICloudIfNecessary(alwaysPrompt: Bool) async -> Bool {
         guard persistsState,
               let timelinePosition = mastodonController.persistentContainer.getTimelinePosition(timeline: timeline) else {
             return false