Actually don't purge old persistent history

Closes #480

Tusker.xcodeproj/project.pbxproj

@@ -259,6 +259,7 @@
 		D6A6C10F25B62D2400298D0F /* DiskCache.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6A6C10E25B62D2400298D0F /* DiskCache.swift */; };
 		D6A6C11525B62E9700298D0F /* CacheExpiry.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6A6C11425B62E9700298D0F /* CacheExpiry.swift */; };
 		D6A6C11B25B63CEE00298D0F /* MemoryCache.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6A6C11A25B63CEE00298D0F /* MemoryCache.swift */; };
+		D6A8D7A52C14DB280007B285 /* PersistentHistoryTokenStore.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6A8D7A42C14DB280007B285 /* PersistentHistoryTokenStore.swift */; };
 		D6AC956723C4347E008C9946 /* MainSceneDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6AC956623C4347E008C9946 /* MainSceneDelegate.swift */; };
 		D6ADB6E828E8C878009924AB /* PublicTimelineDescriptionCollectionViewCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6ADB6E728E8C878009924AB /* PublicTimelineDescriptionCollectionViewCell.swift */; };
 		D6ADB6EA28E91C30009924AB /* TimelineStatusCollectionViewCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6ADB6E928E91C30009924AB /* TimelineStatusCollectionViewCell.swift */; };
@@ -687,6 +688,7 @@
 		D6A6C10E25B62D2400298D0F /* DiskCache.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DiskCache.swift; sourceTree = "<group>"; };
 		D6A6C11425B62E9700298D0F /* CacheExpiry.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CacheExpiry.swift; sourceTree = "<group>"; };
 		D6A6C11A25B63CEE00298D0F /* MemoryCache.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MemoryCache.swift; sourceTree = "<group>"; };
+		D6A8D7A42C14DB280007B285 /* PersistentHistoryTokenStore.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PersistentHistoryTokenStore.swift; sourceTree = "<group>"; };
 		D6A9E04F29F8917500BEDC7E /* MatchedGeometryPresentation */ = {isa = PBXFileReference; lastKnownFileType = wrapper; path = MatchedGeometryPresentation; sourceTree = "<group>"; };
 		D6AC956623C4347E008C9946 /* MainSceneDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MainSceneDelegate.swift; sourceTree = "<group>"; };
 		D6ADB6E728E8C878009924AB /* PublicTimelineDescriptionCollectionViewCell.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PublicTimelineDescriptionCollectionViewCell.swift; sourceTree = "<group>"; };
@@ -1051,6 +1053,7 @@
 				D608470E2A245D1F00C17380 /* ActiveInstance.swift */,
 				D60E2F2D244248BF005F8713 /* MastodonCachePersistentStore.swift */,
 				D6B936702829F72900237D0E /* NSManagedObjectContext+Helpers.swift */,
+				D6A8D7A42C14DB280007B285 /* PersistentHistoryTokenStore.swift */,
 			);
 			path = CoreData;
 			sourceTree = "<group>";
@@ -2412,6 +2415,7 @@
 				D68A76E829527884001DA1B3 /* PinnedTimelinesView.swift in Sources */,
 				D690797324A4EF9700023A34 /* UIBezierPath+Helpers.swift in Sources */,
 				D6D12B5A292D684600D528E1 /* AccountListViewController.swift in Sources */,
+				D6A8D7A52C14DB280007B285 /* PersistentHistoryTokenStore.swift in Sources */,
 				D693DE5723FE1A6A0061E07D /* EnhancedNavigationViewController.swift in Sources */,
 				D646DCDC2A081CF10059ECEB /* StatusUpdatedNotificationCollectionViewCell.swift in Sources */,
 			);

Tusker/CoreData/MastodonCachePersistentStore.swift

@@ -48,8 +48,6 @@ class MastodonCachePersistentStore: NSPersistentCloudKitContainer {
         return context
     }()
     
-    private var lastRemoteChangeToken: NSPersistentHistoryToken?
-    
     // TODO: consider sending managed objects through this to avoid re-fetching things unnecessarily
     // would need to audit existing uses to make sure everything happens on the main thread
     // and when updating things on the background context would need to switch to main, refetch, and then publish
@@ -190,9 +188,11 @@ class MastodonCachePersistentStore: NSPersistentCloudKitContainer {
         viewContext.mergePolicy = NSMergePolicy.mergeByPropertyObjectTrump
         viewContext.name = "View"
         
+        if accountInfo != nil {
             NotificationCenter.default.addObserver(self, selector: #selector(managedObjectsDidChange), name: .NSManagedObjectContextObjectsDidChange, object: viewContext)
             NotificationCenter.default.addObserver(self, selector: #selector(remoteChanges), name: .NSPersistentStoreRemoteChange, object: persistentStoreCoordinator)
         }
+    }
     
     func save(context: NSManagedObjectContext) {
         guard context.hasChanges else {
@@ -521,22 +521,48 @@ class MastodonCachePersistentStore: NSPersistentCloudKitContainer {
     }
     
     @objc private func remoteChanges(_ notification: Foundation.Notification) {
-        guard let token = notification.userInfo?[NSPersistentHistoryTokenKey] as? NSPersistentHistoryToken else {
+        guard let accountInfo,
+              let token = notification.userInfo?[NSPersistentHistoryTokenKey] as? NSPersistentHistoryToken else {
             return
         }
-        remoteChangesBackgroundContext.perform {
+        PersistentHistoryTokenStore.token(for: accountInfo) { lastToken in
+            self.remoteChangesBackgroundContext.perform {
                 defer {
-                self.lastRemoteChangeToken = token
+                    PersistentHistoryTokenStore.setToken(token, for: accountInfo)
                 }
-            let req = NSPersistentHistoryChangeRequest.fetchHistory(after: self.lastRemoteChangeToken)
-            if let result = try? self.remoteChangesBackgroundContext.execute(req) as? NSPersistentHistoryResult,
-               let transactions = result.result as? [NSPersistentHistoryTransaction],
-               !transactions.isEmpty {
+                let transactions: [NSPersistentHistoryTransaction]
+                do {
+                    let req = NSPersistentHistoryChangeRequest.fetchHistory(after: lastToken)
+                    if let result = try self.remoteChangesBackgroundContext.execute(req) as? NSPersistentHistoryResult {
+                        transactions = result.result as? [NSPersistentHistoryTransaction] ?? []
+                    } else {
+                        logger.error("Unexpectedly non-NSPersistentHistoryResult")
+                        return
+                    }
+                } catch {
+                    logger.error("Unable to fetch persistent history results: \(String(describing: error), privacy: .public)")
+                    return
+                }
+                if !transactions.isEmpty {
+                    self.processPersistentHistoryTransactions(transactions)
+                }
+                
+                // NB: We deliberately do not purge old persistent history.
+                // Doing so causes the CoreData+CloudKit integration to replay all of
+                // the server's changes on initialization, which takes a long time
+                // and produces a bunch of intermediate UI updates we don't want.
+            }
+        }
+    }
+    
+    private func processPersistentHistoryTransactions(_ transactions: [NSPersistentHistoryTransaction]) {
+        logger.info("Processing \(transactions.count) persistent history transactions")
         var changedHashtags = false
         var changedInstances = false
         var changedTimelinePositions = Set<NSManagedObjectID>()
         var changedAccountPrefs = false
         outer: for transaction in transactions {
+            logger.info("Processing \(transaction.changes?.count ?? 0) changes in transaction")
             for change in transaction.changes ?? [] {
                 if change.changedObjectID.entity.name == "SavedHashtag" {
                     changedHashtags = true
@@ -574,8 +600,6 @@ class MastodonCachePersistentStore: NSPersistentCloudKitContainer {
             }
         }
     }
-        }
-    }
     
 }
 

Tusker/CoreData/PersistentHistoryTokenStore.swift

@@ -0,0 +1,47 @@
+//
+//  PersistentHistoryTokenStore.swift
+//  Tusker
+//
+//  Created by Shadowfacts on 6/8/24.
+//  Copyright © 2024 Shadowfacts. All rights reserved.
+//
+
+import Foundation
+import CoreData
+import UserAccounts
+
+struct PersistentHistoryTokenStore {
+    private static let queue = DispatchQueue(label: "PersistentHistoryTokenStore")
+    
+    private static var tokens: [String: NSPersistentHistoryToken] = (try? load()) ?? [:]
+    
+    private static let applicationSupportDirectory = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask).first!
+    private static let storeURL = applicationSupportDirectory.appendingPathComponent("PersistentHistoryTokenStore.plist")
+    
+    private static func load() throws -> [String: NSPersistentHistoryToken]? {
+        let data = try Data(contentsOf: storeURL)
+        let unarchived = try NSKeyedUnarchiver.unarchivedObject(ofClasses: [NSDictionary.self, NSString.self, NSPersistentHistoryToken.self], from: data)
+        return unarchived as? [String: NSPersistentHistoryToken]
+    }
+    
+    private static func save() throws {
+        let data = try NSKeyedArchiver.archivedData(withRootObject: tokens as [NSString: NSPersistentHistoryToken], requiringSecureCoding: true)
+        try data.write(to: PersistentHistoryTokenStore.storeURL)
+    }
+
+    static func token(for account: UserAccountInfo, completion: @escaping (NSPersistentHistoryToken?) -> Void) {
+        queue.async {
+            completion(tokens[account.id])
+        }
+    }
+    
+    static func setToken(_ token: NSPersistentHistoryToken, for account: UserAccountInfo) {
+        queue.async {
+            tokens[account.id] = token
+            try? save()
+        }
+    }
+    
+    private init() {}
+
+}

Tusker/Screens/Main/MainSplitViewController.swift

@@ -188,28 +188,28 @@ class MainSplitViewController: UISplitViewController {
     }
     
     @objc func handleSidebarCommandTimelines() {
-        sidebar.select(item: .tab(.timelines), animated: false)
         select(newItem: .tab(.timelines), oldItem: sidebar.selectedItem)
+        sidebar.select(item: .tab(.timelines), animated: false)
     }
     
     @objc func handleSidebarCommandNotifications() {
-        sidebar.select(item: .tab(.notifications), animated: false)
         select(newItem: .tab(.notifications), oldItem: sidebar.selectedItem)
+        sidebar.select(item: .tab(.notifications), animated: false)
     }
     
     @objc func handleSidebarCommandExplore() {
-        sidebar.select(item: .tab(.explore), animated: false)
         select(newItem: .tab(.explore), oldItem: sidebar.selectedItem)
+        sidebar.select(item: .tab(.explore), animated: false)
     }
     
     @objc func handleSidebarCommandBookmarks() {
-        sidebar.select(item: .bookmarks, animated: false)
         select(newItem: .bookmarks, oldItem: sidebar.selectedItem)
+        sidebar.select(item: .bookmarks, animated: false)
     }
     
     @objc func handleSidebarCommandMyProfile() {
-        sidebar.select(item: .tab(.myProfile), animated: false)
         select(newItem: .tab(.myProfile), oldItem: sidebar.selectedItem)
+        sidebar.select(item: .tab(.myProfile), animated: false)
     }
     
     @objc private func sidebarTapped() {

Tusker/Views/Status/StatusCollectionViewCell.swift

@@ -256,6 +256,7 @@ extension StatusCollectionViewCell {
                 view.backgroundColor = .tintColor.withAlphaComponent(0.5)
                 view.layer.cornerRadius = 2.5
                 view.layer.maskedCorners = [.layerMinXMaxYCorner, .layerMaxXMaxYCorner]
+                view.layer.zPosition = -1
                 prevThreadLinkView = view
                 contentView.addSubview(view)
                 NSLayoutConstraint.activate([
@@ -278,6 +279,7 @@ extension StatusCollectionViewCell {
                 view.backgroundColor = .tintColor.withAlphaComponent(0.5)
                 view.layer.cornerRadius = 2.5
                 view.layer.maskedCorners = [.layerMinXMinYCorner, .layerMaxXMinYCorner]
+                view.layer.zPosition = -1
                 nextThreadLinkView = view
                 contentView.addSubview(view)
                 let bottomConstraint = view.bottomAnchor.constraint(equalTo: contentView.bottomAnchor)