Persist timeline state using CoreData, rather than NSUserActivity

This allows persisting state for all the primary timelines, and across
all accounts.

Closes #297
Closes #293

Tusker.xcodeproj/project.pbxproj

@@ -305,6 +305,7 @@
 		D6D4DDE5212518A200E1C4BB /* TuskerTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D4DDE4212518A200E1C4BB /* TuskerTests.swift */; };
 		D6D4DDF0212518A200E1C4BB /* TuskerUITests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D4DDEF212518A200E1C4BB /* TuskerUITests.swift */; };
 		D6D706A029466649000827ED /* ScrollingSegmentedControl.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D7069F29466649000827ED /* ScrollingSegmentedControl.swift */; };
+		D6D706A72948D4D0000827ED /* TimlineState.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D706A62948D4D0000827ED /* TimlineState.swift */; };
 		D6DD2A3F273C1F4900386A6C /* ComposeAttachmentImage.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6DD2A3E273C1F4900386A6C /* ComposeAttachmentImage.swift */; };
 		D6DD2A45273D6C5700386A6C /* GIFImageView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6DD2A44273D6C5700386A6C /* GIFImageView.swift */; };
 		D6DD353D22F28CD000A9563A /* ContentWarningCopyMode.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6DD353C22F28CD000A9563A /* ContentWarningCopyMode.swift */; };
@@ -698,6 +699,7 @@
 		D6D4DDEF212518A200E1C4BB /* TuskerUITests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TuskerUITests.swift; sourceTree = "<group>"; };
 		D6D4DDF1212518A200E1C4BB /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		D6D7069F29466649000827ED /* ScrollingSegmentedControl.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ScrollingSegmentedControl.swift; sourceTree = "<group>"; };
+		D6D706A62948D4D0000827ED /* TimlineState.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TimlineState.swift; sourceTree = "<group>"; };
 		D6DD2A3E273C1F4900386A6C /* ComposeAttachmentImage.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ComposeAttachmentImage.swift; sourceTree = "<group>"; };
 		D6DD2A44273D6C5700386A6C /* GIFImageView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GIFImageView.swift; sourceTree = "<group>"; };
 		D6DD353C22F28CD000A9563A /* ContentWarningCopyMode.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ContentWarningCopyMode.swift; sourceTree = "<group>"; };
@@ -933,6 +935,7 @@
 				D61F75932936F0DA00C0B37F /* FollowedHashtag.swift */,
 				D61F759A29384F9C00C0B37F /* FilterMO.swift */,
 				D61F75AA293AF11400C0B37F /* FilterKeywordMO.swift */,
+				D6D706A62948D4D0000827ED /* TimlineState.swift */,
 				D60E2F2D244248BF005F8713 /* MastodonCachePersistentStore.swift */,
 				D6B936702829F72900237D0E /* NSManagedObjectContext+Helpers.swift */,
 			);
@@ -2071,6 +2074,7 @@
 				D6114E1327F89B440080E273 /* TrendingLinkTableViewCell.swift in Sources */,
 				D6262C9A28D01C4B00390C1F /* LoadingTableViewCell.swift in Sources */,
 				D68C2AE325869BAB00548EFF /* AuxiliarySceneDelegate.swift in Sources */,
+				D6D706A72948D4D0000827ED /* TimlineState.swift in Sources */,
 				D66C900B28DAB7FD00217BF2 /* TimelineViewController.swift in Sources */,
 				D61F758D2933C69C00C0B37F /* StatusUpdatedNotificationTableViewCell.swift in Sources */,
 				D6AEBB432321685E00E5038B /* OpenInSafariActivity.swift in Sources */,

Tusker/CoreData/MastodonCachePersistentStore.swift

@@ -355,6 +355,15 @@ class MastodonCachePersistentStore: NSPersistentContainer {
         }
     }
     
+    func getTimelineState(timeline: Timeline) -> TimelineState? {
+        do {
+            let req = TimelineState.fetchRequest(timeline: timeline)
+            return try viewContext.fetch(req).first
+        } catch {
+            return nil
+        }
+    }
+    
     @objc private func managedObjectsDidChange(_ notification: Foundation.Notification) {
         let changes = hasChangedSavedHashtagsOrInstances(notification)
         if changes.hashtags {

Tusker/CoreData/StatusMO.swift

@@ -18,6 +18,12 @@ public final class StatusMO: NSManagedObject, StatusProtocol {
         return NSFetchRequest<StatusMO>(entityName: "Status")
     }
     
+    @nonobjc public class func fetchRequest(id: String) -> NSFetchRequest<StatusMO> {
+        let req = Self.fetchRequest()
+        req.predicate = NSPredicate(format: "id = %@", id)
+        return req
+    }
+    
     @NSManaged public var applicationName: String?
     @NSManaged private var attachmentsData: Data?
     @NSManaged private var bookmarkedInternal: Bool

Tusker/CoreData/TimlineState.swift

@@ -0,0 +1,89 @@
+//
+//  TimlineState.swift
+//  Tusker
+//
+//  Created by Shadowfacts on 12/13/22.
+//  Copyright © 2022 Shadowfacts. All rights reserved.
+//
+
+import Foundation
+import CoreData
+import Pachyderm
+
+@objc(TimelineState)
+public final class TimelineState: NSManagedObject {
+    
+    @nonobjc public class func fetchRequest(timeline: Timeline) -> NSFetchRequest<TimelineState> {
+        let req = NSFetchRequest<TimelineState>(entityName: "TimelineState")
+        req.predicate = NSPredicate(format: "timelineKind = %@", toTimelineKind(timeline))
+        return req
+    }
+    
+    @NSManaged private var timelineKind: String
+    @NSManaged public var centerStatusID: String?
+    @NSManaged private var statuses: NSOrderedSet
+    
+    var timeline: Timeline {
+        get { fromTimelineKind(timelineKind) }
+        set { timelineKind = toTimelineKind(newValue) }
+    }
+    
+    var statusMOs: [StatusMO] {
+        statuses.array as! [StatusMO]
+    }
+    
+    convenience init(timeline: Timeline, context: NSManagedObjectContext) {
+        self.init(context: context)
+        self.timeline = timeline
+    }
+    
+    func setStatuses(_ statusIDs: [String]) {
+        let context = managedObjectContext!
+        // todo: this feels really inefficient, but I'm not sure if it's better or worse than doing a single "id IN %@" fetch and sorting after
+        let mos = statusIDs.compactMap { try? context.fetch(StatusMO.fetchRequest(id: $0)).first }
+        self.statuses = NSOrderedSet(array: mos)
+    }
+    
+}
+
+// blergh, this is the simplest way of getting the Timeline into a format that A) CoreData can handle and B) is usable in the predicate
+private func toTimelineKind(_ timeline: Timeline) -> String {
+    switch timeline {
+    case .home:
+        return "home"
+    case .public(local: true):
+        return "local"
+    case .public(local: false):
+        return "federated"
+    case .direct:
+        return "direct"
+    case .tag(hashtag: let name):
+        return "hashtag:\(name)"
+    case .list(id: let id):
+        return "list:\(id)"
+    }
+}
+
+private func fromTimelineKind(_ kind: String) -> Timeline {
+    if kind == "home" {
+        return .home
+    } else if kind == "local" {
+        return .public(local: true)
+    } else if kind == "federated" {
+        return .public(local: false)
+    } else if kind == "direct" {
+        return .direct
+    } else if kind.starts(with: "hashtag:") {
+        return .tag(hashtag: String(trimmingPrefix("hashtag:", of: kind)))
+    } else if kind.starts(with: "list:") {
+        return .list(id: String(trimmingPrefix("list:", of: kind)))
+    } else {
+        fatalError("invalid timeline kind \(kind)")
+    }
+}
+
+// replace with Collection.trimmingPrefix
+@available(iOS, obsoleted: 16.0)
+private func trimmingPrefix(_ prefix: String, of str: String) -> Substring {
+    return str[str.index(str.startIndex, offsetBy: prefix.count)...]
+}

Tusker/CoreData/Tusker.xcdatamodeld/Tusker.xcdatamodel/contents

@@ -105,10 +105,16 @@
         <attribute name="visibilityString" attributeType="String"/>
         <relationship name="account" optional="YES" maxCount="1" deletionRule="Nullify" destinationEntity="Account" inverseName="statuses" inverseEntity="Account"/>
         <relationship name="reblog" optional="YES" maxCount="1" deletionRule="Nullify" destinationEntity="Status"/>
+        <relationship name="timelines" optional="YES" toMany="YES" deletionRule="Nullify" destinationEntity="TimelineState" inverseName="statuses" inverseEntity="TimelineState"/>
         <uniquenessConstraints>
             <uniquenessConstraint>
                 <constraint value="id"/>
             </uniquenessConstraint>
         </uniquenessConstraints>
     </entity>
+    <entity name="TimelineState" representedClassName="TimelineState" syncable="YES">
+        <attribute name="centerStatusID" optional="YES" attributeType="String"/>
+        <attribute name="timelineKind" attributeType="String" valueTransformerName="pachydermTimeline" customClassName="Tusker.TimelineContainer"/>
+        <relationship name="statuses" toMany="YES" deletionRule="Nullify" ordered="YES" destinationEntity="Status" inverseName="timelines" inverseEntity="Status"/>
+    </entity>
 </model>

Tusker/Screens/Timeline/TimelineViewController.swift

@@ -15,6 +15,8 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
     weak var mastodonController: MastodonController!
     let filterer: Filterer
     
+    var persistsState = false
+    
     private(set) var controller: TimelineLikeController<TimelineItem>!
     let confirmLoadMore = PassthroughSubject<Void, Never>()
     // stored separately because i don't want to query the snapshot every time the user scrolls
@@ -196,7 +198,7 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
         }
         
         if case .notLoadedInitial = controller.state {
-            if doRestore() {
+            if restoreState() {
                 Task {
                     await checkPresent(jumpImmediately: false)
                 }
@@ -227,22 +229,23 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
         super.viewDidDisappear(animated)
         
         disappearedAt = Date()
+        saveState()
     }
     
-    func stateRestorationActivity() -> NSUserActivity? {
+    private func saveState() {
-        guard isViewLoaded else {
+        guard isViewLoaded,
-            return nil
+              persistsState else {
+            return
         }
         let visible = collectionView.indexPathsForVisibleItems.sorted()
         let snapshot = dataSource.snapshot()
         let visibleRect = CGRect(origin: collectionView.contentOffset, size: collectionView.bounds.size)
         let midPoint = CGPoint(x: visibleRect.midX, y: visibleRect.midY)
-        guard let currentAccountID = mastodonController.accountInfo?.id,
+        guard !visible.isEmpty,
-              !visible.isEmpty,
               let statusesSection = snapshot.sectionIdentifiers.firstIndex(of: .statuses),
               let rawCenterVisible = collectionView.indexPathForItem(at: midPoint),
               let centerVisible = visible.first(where: { $0.section == statusesSection && $0 >= rawCenterVisible }) else {
-            return nil
+            return
         }
         let allItems = snapshot.itemIdentifiers(inSection: .statuses)
         
@@ -282,44 +285,40 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
         } else {
             fatalError()
         }
-        stateRestorationLogger.debug("TimelineViewController: creating state restoration activity with topID \(centerVisibleID)")
+        stateRestorationLogger.debug("TimelineViewController: saving state to persistent store with with centerID \(centerVisibleID)")
         
+        let state = mastodonController.persistentContainer.getTimelineState(timeline: timeline) ?? TimelineState(timeline: timeline, context: mastodonController.persistentContainer.viewContext)
+        state.setStatuses(ids)
+        state.centerStatusID = centerVisibleID
+        mastodonController.persistentContainer.save(context: mastodonController.persistentContainer.viewContext)
+    }
+    
+    func stateRestorationActivity() -> NSUserActivity? {
+        guard isViewLoaded,
+              let currentAccountID = mastodonController.accountInfo?.id else {
+            return nil
+        }
         let activity = UserActivityManager.showTimelineActivity(timeline: timeline, accountID: currentAccountID)!
-        activity.addUserInfoEntries(from: [
-            "statusIDs": ids,
-            "centerID": centerVisibleID,
-        ])
         activity.isEligibleForPrediction = false
         return activity
     }
     
-    func restoreActivity(_ activity: NSUserActivity) {
+    private func restoreState() -> Bool {
-        self.activityToRestore = activity
+        guard persistsState,
-    }
+              Preferences.shared.timelineStateRestoration,
-    
+              let state = mastodonController.persistentContainer.getTimelineState(timeline: timeline) else {
-    private func doRestore() -> Bool {
-        guard let activity = activityToRestore,
-              Preferences.shared.timelineStateRestoration else {
-            return false
-        }
-        guard let statusIDs = activity.userInfo?["statusIDs"] as? [String] else {
-            stateRestorationLogger.fault("TimelineViewController: activity missing statusIDs")
-            return false
-        }
-        activityToRestore = nil
-        let existingStatuses = statusIDs.filter { mastodonController.persistentContainer.status(for: $0) != nil }
-        guard !existingStatuses.isEmpty else {
             return false
         }
+        let statusIDs = state.statusMOs.map(\.id)
         loadViewIfNeeded()
         controller.restoreInitial {
             var snapshot = dataSource.snapshot()
             snapshot.appendSections([.statuses])
-            let items = existingStatuses.map { Item.status(id: $0, collapseState: .unknown, filterState: .unknown) }
+            let items = statusIDs.map { Item.status(id: $0, collapseState: .unknown, filterState: .unknown) }
             snapshot.appendItems(items, toSection: .statuses)
             dataSource.apply(snapshot, animatingDifferences: false) {
-                if let centerID = activity.userInfo?["centerID"] as? String ?? activity.userInfo?["topID"] as? String,
+                if let centerID = state.centerStatusID,
-                   let index = existingStatuses.firstIndex(of: centerID),
+                   let index = statusIDs.firstIndex(of: centerID),
                    let indexPath = self.dataSource.indexPath(for: 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
@@ -400,6 +399,7 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
             return
         }
         disappearedAt = Date()
+        saveState()
     }
     
     @objc func refresh() {

Tusker/Screens/Timeline/TimelinesPageViewController.swift

@@ -22,12 +22,15 @@ class TimelinesPageViewController: SegmentedPageViewController<TimelinesPageView
         
         let home = TimelineViewController(for: .home, mastodonController: mastodonController)
         home.title = homeTitle
+        home.persistsState = true
         
         let federated = TimelineViewController(for: .public(local: false), mastodonController: mastodonController)
         federated.title = federatedTitle
+        federated.persistsState = true
         
         let local = TimelineViewController(for: .public(local: true), mastodonController: mastodonController)
         local.title = localTitle
+        local.persistsState = true
         
         super.init(pages: [
             (.home, "Home", home),
@@ -83,9 +86,6 @@ class TimelinesPageViewController: SegmentedPageViewController<TimelinesPageView
             return
         }
         selectPage(page, animated: false)
-        // can't use currentIndex here because the view isn't loaded yet, and so the page wasn't actually updated by the selectPage call
-        let timelineVC = pageControllers[pages.firstIndex(of: page)!] as! TimelineViewController
-        timelineVC.restoreActivity(activity)
     }
     
     @objc private func filtersPressed() {