From eac5a4c9a6a3e0b146c99e576f7e47e60cc2bedd Mon Sep 17 00:00:00 2001
From: Shadowfacts <me@shadowfacts.net>
Date: Sun, 7 May 2023 19:46:15 -0400
Subject: [PATCH] Fix notifications scrolling to top when refreshing

---
 .../NotificationsCollectionViewController.swift  | 16 ++++++++++++++++
 .../TimelineLikeCollectionViewController.swift   |  1 +
 2 files changed, 17 insertions(+)

diff --git a/Tusker/Screens/Notifications/NotificationsCollectionViewController.swift b/Tusker/Screens/Notifications/NotificationsCollectionViewController.swift
index 7a5cd270..051eafb6 100644
--- a/Tusker/Screens/Notifications/NotificationsCollectionViewController.swift
+++ b/Tusker/Screens/Notifications/NotificationsCollectionViewController.swift
@@ -355,8 +355,24 @@ extension NotificationsCollectionViewController {
     }
     
     func handlePrependItems(_ timelineItems: [NotificationGroup]) async {
+        let topItem = dataSource.snapshot().itemIdentifiers(inSection: .notifications).first
+        
         // we always replace all, because new items are merged with existing ones
         await handleReplaceAllItems(timelineItems)
+        
+        // preserve the scroll position
+        // todo: this won't work for cmd+r when not at top
+        if let topID = topItem?.group?.notifications.first?.id {
+            // the exact item may have changed, due to merging
+            let newTopGroup = timelineItems.first {
+                $0.notifications.contains {
+                    $0.id == topID
+                }
+            }!
+            if let newTopIndexPath = dataSource.indexPath(for: .group(newTopGroup)) {
+                collectionView.scrollToItem(at: newTopIndexPath, at: .top, animated: false)
+            }
+        }
     }
     
     func loadOlder() async throws -> [NotificationGroup] {
diff --git a/Tusker/Screens/Utilities/TimelineLikeCollectionViewController.swift b/Tusker/Screens/Utilities/TimelineLikeCollectionViewController.swift
index 36f1536e..f7754539 100644
--- a/Tusker/Screens/Utilities/TimelineLikeCollectionViewController.swift
+++ b/Tusker/Screens/Utilities/TimelineLikeCollectionViewController.swift
@@ -153,6 +153,7 @@ extension TimelineLikeCollectionViewController {
         }
         await apply(snapshot, animatingDifferences: false)
         
+        // todo: this won't work for cmd+r when not at top
         if let first,
            let indexPath = dataSource.indexPath(for: first) {
             // TODO: i can't tell if this actually works or not