From 804fdb439deb999006c973c036c145ad8d00b524 Mon Sep 17 00:00:00 2001
From: Shadowfacts <me@shadowfacts.net>
Date: Sun, 6 Feb 2022 10:19:38 -0500
Subject: [PATCH] Fix offscreen row pruning removing all rows from profile
 statuses

---
 .../ProfileStatusesViewController.swift       |  2 ++
 ...fableTimelineLikeTableViewController.swift | 28 ++++++-------------
 2 files changed, 11 insertions(+), 19 deletions(-)

diff --git a/Tusker/Screens/Profile/ProfileStatusesViewController.swift b/Tusker/Screens/Profile/ProfileStatusesViewController.swift
index e8d48df7..85aa1681 100644
--- a/Tusker/Screens/Profile/ProfileStatusesViewController.swift
+++ b/Tusker/Screens/Profile/ProfileStatusesViewController.swift
@@ -52,6 +52,8 @@ class ProfileStatusesViewController: DiffableTimelineLikeTableViewController<Pro
         return NSLocalizedString("Refresh Statuses", comment: "refresh statuses command discoverability title")
     }
     
+    // MARK: - DiffableTimelineLikeTableViewController
+    
     override func cellProvider(_ tableView: UITableView, _ indexPath: IndexPath, _ item: Item) -> UITableViewCell? {
         let cell = tableView.dequeueReusableCell(withIdentifier: "statusCell", for: indexPath) as! TimelineStatusTableViewCell
         
diff --git a/Tusker/Screens/Utilities/DiffableTimelineLikeTableViewController.swift b/Tusker/Screens/Utilities/DiffableTimelineLikeTableViewController.swift
index d73ae518..4d4551fc 100644
--- a/Tusker/Screens/Utilities/DiffableTimelineLikeTableViewController.swift
+++ b/Tusker/Screens/Utilities/DiffableTimelineLikeTableViewController.swift
@@ -67,8 +67,7 @@ class DiffableTimelineLikeTableViewController<Section: Hashable & CaseIterable,
     }
     
     private func pruneOffscreenRows() {
-        guard let lastVisibleRow = lastLastVisibleRow,
-              lastVisibleRow.section < tableView.numberOfSections else {
+        guard let lastVisibleRow = tableView.indexPathsForVisibleRows?.last else {
             return
         }
         
@@ -77,33 +76,24 @@ class DiffableTimelineLikeTableViewController<Section: Hashable & CaseIterable,
         let lastVisibleRowSection = snapshot.sectionIdentifiers[lastVisibleRow.section]
         
         let contentSections = snapshot.sectionIdentifiers.filter { timelineContentSections().contains($0) }
+        let contentSectionIndices = contentSections.compactMap(snapshot.indexOfSection(_:))
+        let maxContentSectionIndex = contentSectionIndices.max()!
         
-        guard let lastVisibleContentSectionIndex = contentSections.lastIndex(of: lastVisibleRowSection) else {
+        if lastVisibleRow.section < maxContentSectionIndex {
             return
-        }
-        
-        if lastVisibleContentSectionIndex < contentSections.count - 1 {
-            // there are more content sections below the current last visible one
-            
-            let sectionsToRemove = contentSections[lastVisibleContentSectionIndex...]
-            snapshot.deleteSections(Array(sectionsToRemove))
-            
-            let itemsToRemove = sectionsToRemove.filter {
-                snapshot.indexOfSection($0) != nil
-            }.flatMap(snapshot.itemIdentifiers(inSection:))
-            willRemoveItems(itemsToRemove)
-        } else if lastVisibleContentSectionIndex == contentSections.count - 1 {
+        } else if lastVisibleRow.section == maxContentSectionIndex {
             let items = snapshot.itemIdentifiers(inSection: lastVisibleRowSection)
             
-            if lastVisibleRow.row < items.count - pageSize {
-                let itemsToRemove = Array(items.suffix(pageSize))
+            let numberOfPagesToPrune = (items.count - lastVisibleRow.row - 1) / pageSize
+            if numberOfPagesToPrune > 0 {
+                let itemsToRemove = Array(items.suffix(numberOfPagesToPrune * pageSize))
                 snapshot.deleteItems(itemsToRemove)
-                
                 willRemoveItems(itemsToRemove)
             } else {
                 return
             }
         } else {
+            // unreachable
             return
         }