From 5b18da4fe6c2b28f48f892f05953c6a9a22f52b8 Mon Sep 17 00:00:00 2001
From: Levitating Pineapple <noreply@levitatingpineapple.com>
Date: Fri, 16 Aug 2024 19:11:47 +0300
Subject: [PATCH] dual snapshot animation

---
 apps/ios/Shared/Model/ChatModel.swift        | 13 ++++----
 apps/ios/Shared/Views/Chat/ChatView.swift    | 23 ---------------
 apps/ios/Shared/Views/Chat/ReverseList.swift | 31 +++++++++++++++-----
 3 files changed, 30 insertions(+), 37 deletions(-)

diff --git a/apps/ios/Shared/Model/ChatModel.swift b/apps/ios/Shared/Model/ChatModel.swift
index ed3a5a3316..4b391b727e 100644
--- a/apps/ios/Shared/Model/ChatModel.swift
+++ b/apps/ios/Shared/Model/ChatModel.swift
@@ -450,13 +450,14 @@ final class ChatModel: ObservableObject {
             }
             return false
         } else {
-            var ci = cItem
-            if let status = chatItemStatuses.removeValue(forKey: ci.id), case .sndNew = ci.meta.itemStatus {
-                ci.meta.itemStatus = status
+            withConditionalAnimation(itemAnimation()) {
+                var ci = cItem
+                if let status = chatItemStatuses.removeValue(forKey: ci.id), case .sndNew = ci.meta.itemStatus {
+                    ci.meta.itemStatus = status
+                }
+                im.reversedChatItems.insert(ci, at: hasLiveDummy ? 1 : 0)
+                im.itemAdded = true
             }
-            if itemAnimation() != nil { FadeInChatItem.items.insert(ci.id) }
-            im.reversedChatItems.insert(ci, at: hasLiveDummy ? 1 : 0)
-            im.itemAdded = true
             return true
         }
 
diff --git a/apps/ios/Shared/Views/Chat/ChatView.swift b/apps/ios/Shared/Views/Chat/ChatView.swift
index 3b3962ccd5..655dd8aaed 100644
--- a/apps/ios/Shared/Views/Chat/ChatView.swift
+++ b/apps/ios/Shared/Views/Chat/ChatView.swift
@@ -413,7 +413,6 @@ struct ChatView: View {
                     revealedChatItem: $revealedChatItem,
                     selectedChatItems: $selectedChatItems
                 )
-                .modifier(FadeInChatItem(id: ci.id))
                 .onAppear {
                     floatingButtonModel.appeared(viewId: ci.viewId)
                 }
@@ -1551,28 +1550,6 @@ private func buildTheme() -> AppTheme {
     }
 }
 
-struct FadeInChatItem: ViewModifier {
-    static var items = Set<ChatItem.ID>()
-    private let chatItemId: ChatItem.ID
-    @State private var isVisible: Bool
-
-    init(id: ChatItem.ID) {
-        chatItemId = id
-        isVisible = !Self.items.contains(chatItemId)
-    }
-
-    func body(content: Content) -> some View {
-        content
-            .opacity(isVisible ? 1 : 0)
-            .onAppear {
-                if !isVisible {
-                    Self.items.remove(chatItemId)
-                    withAnimation(.easeInOut(duration: 0.5)) { isVisible = true }
-                }
-            }
-    }
-}
-
 struct ToggleNtfsButton: View {
     @ObservedObject var chat: Chat
 
diff --git a/apps/ios/Shared/Views/Chat/ReverseList.swift b/apps/ios/Shared/Views/Chat/ReverseList.swift
index 39a968f884..15bb31422b 100644
--- a/apps/ios/Shared/Views/Chat/ReverseList.swift
+++ b/apps/ios/Shared/Views/Chat/ReverseList.swift
@@ -171,17 +171,32 @@ struct ReverseList<Item: Identifiable & Hashable & Sendable, Content: View>: UIV
             Task { representer.scrollState = .atDestination }
         }
 
-        func update(items: Array<Item>) {
+        var updateInProgress = false
+
+        func update(items: [Item]) {
+            if updateInProgress { return }
+            let itemsAdded = items.count - itemCount
+            if itemsAdded > 0, itemCount != 0 {
+                updateInProgress = true
+                _update(items: Array(items[1...]), animated: false) {
+                    DispatchQueue.main.async {
+                        self._update(items: items, animated: true) {
+                            self.updateInProgress = false
+                        }
+                    }
+                }
+            } else {
+               _update(items: items, animated: false)
+            }
+            itemCount = items.count
+        }
+
+        func _update(items: Array<Item>, animated: Bool, completion: (() -> Void)? = nil) {
             var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
             snapshot.appendSections([.main])
             snapshot.appendItems(items)
-            dataSource.defaultRowAnimation = .none
-            let countChange = abs(items.count - itemCount)
-            dataSource.apply(snapshot, animatingDifferences:
-                countChange > 0 && // Avoid animating initial load
-                countChange < 5    // Avoid animating page loads
-            )
-            itemCount = items.count
+            dataSource.defaultRowAnimation = animated ? .top : .none
+            dataSource.apply(snapshot, animatingDifferences: animated, completion: completion)
         }
     }