From 491090e3739f2ed50c91051ebae330ec32422d00 Mon Sep 17 00:00:00 2001
From: Thomas Ricouard <ricouard77@gmail.com>
Date: Fri, 13 Sep 2024 11:27:01 +0200
Subject: [PATCH] New pending statuses behavior

---
 .../TimelineUnreadStatusesObserver.swift      |  5 +--
 .../Sources/Timeline/View/TimelineView.swift  |  3 +-
 .../Timeline/View/TimelineViewModel.swift     | 42 ++++++++++++-------
 3 files changed, 29 insertions(+), 21 deletions(-)

diff --git a/Packages/Timeline/Sources/Timeline/TimelineUnreadStatusesObserver.swift b/Packages/Timeline/Sources/Timeline/TimelineUnreadStatusesObserver.swift
index 726f12fd..7e4fb824 100644
--- a/Packages/Timeline/Sources/Timeline/TimelineUnreadStatusesObserver.swift
+++ b/Packages/Timeline/Sources/Timeline/TimelineUnreadStatusesObserver.swift
@@ -10,7 +10,6 @@ import SwiftUI
   var pendingStatusesCount: Int = 0
 
   var disableUpdate: Bool = false
-  var scrollToIndex: ((Int) -> Void)?
 
   var isLoadingNewStatuses: Bool = false
 
@@ -39,9 +38,7 @@ struct TimelineUnreadStatusesView: View {
 
   var body: some View {
     if observer.pendingStatusesCount > 0 || observer.isLoadingNewStatuses {
-      Button {
-        observer.scrollToIndex?(observer.pendingStatusesCount)
-      } label: {
+      Button { } label: {
         HStack(spacing: 8) {
           if observer.isLoadingNewStatuses {
             ProgressView()
diff --git a/Packages/Timeline/Sources/Timeline/View/TimelineView.swift b/Packages/Timeline/Sources/Timeline/View/TimelineView.swift
index e759d660..901b2164 100644
--- a/Packages/Timeline/Sources/Timeline/View/TimelineView.swift
+++ b/Packages/Timeline/Sources/Timeline/View/TimelineView.swift
@@ -99,8 +99,7 @@ public struct TimelineView: View {
       {
         collectionView.scrollToItem(at: .init(row: newValue, section: 0),
                                     at: .top,
-                                    animated: viewModel.scrollToIndexAnimated)
-        viewModel.scrollToIndexAnimated = false
+                                    animated: false)
         viewModel.scrollToIndex = nil
       }
     }
diff --git a/Packages/Timeline/Sources/Timeline/View/TimelineViewModel.swift b/Packages/Timeline/Sources/Timeline/View/TimelineViewModel.swift
index 5cc17771..bcf72575 100644
--- a/Packages/Timeline/Sources/Timeline/View/TimelineViewModel.swift
+++ b/Packages/Timeline/Sources/Timeline/View/TimelineViewModel.swift
@@ -80,13 +80,7 @@ import SwiftUI
     }
   }
 
-  var scrollToTopVisible: Bool = false {
-    didSet {
-      if scrollToTopVisible {
-        pendingStatusesObserver.pendingStatuses = []
-      }
-    }
-  }
+  var scrollToTopVisible: Bool = false
 
   var serverName: String {
     client?.server ?? "Error"
@@ -94,15 +88,10 @@ import SwiftUI
 
   var isTimelineVisible: Bool = false
   let pendingStatusesObserver: TimelineUnreadStatusesObserver = .init()
-  var scrollToIndexAnimated: Bool = false
   var marker: Marker.Content?
 
   init(statusFetcher: TimelineStatusFetching = TimelineStatusFetcher()) {
     self.statusFetcher = statusFetcher
-    pendingStatusesObserver.scrollToIndex = { [weak self] index in
-      self?.scrollToIndexAnimated = true
-      self?.scrollToIndex = index
-    }
   }
 
   private func fetchTag(id: String) async {
@@ -159,6 +148,12 @@ extension TimelineViewModel {
 extension TimelineViewModel: StatusesFetcher {
   func pullToRefresh() async {
     timelineTask?.cancel()
+    
+    if !pendingStatusesObserver.pendingStatuses.isEmpty {
+      await dequeuePendingStatuses()
+      return
+    }
+    
     if !timeline.supportNewestPagination || UserPreferences.shared.fastRefreshEnabled {
       await reset()
     }
@@ -245,7 +240,6 @@ extension TimelineViewModel: StatusesFetcher {
       {
         // Restore cache and scroll to latest seen status.
         statusesState = .display(statuses: statuses, nextPageState: .hasNextPage)
-        scrollToIndexAnimated = false
         scrollToIndex = index + 1
       } else {
         // Restore cache and scroll to top.
@@ -309,6 +303,23 @@ extension TimelineViewModel: StatusesFetcher {
     return newStatuses
   }
 
+  private func dequeuePendingStatuses() async {
+    canStreamEvents = false
+    pendingStatusesObserver.disableUpdate = true
+    let statuses = await datasource.getFiltered()
+    let newStatuses = pendingStatusesObserver.pendingStatuses.count + 1
+    statusesState = .display(statuses: statuses, nextPageState: .hasNextPage)
+    try? await Task.sleep(for: .milliseconds(0.005))
+    scrollToIndex = newStatuses
+    DispatchQueue.main.async { [weak self] in
+      self?.pendingStatusesObserver.disableUpdate = false
+      self?.canStreamEvents = true
+    }
+    if pendingStatusesObserver.pendingStatuses.count <= 2 {
+      pendingStatusesObserver.pendingStatuses = []
+    }
+  }
+  
   private func updateTimelineWithNewStatuses(_ newStatuses: [Status]) async {
     let topStatus = await datasource.getFiltered().first
     await datasource.insert(contentOf: newStatuses, at: 0)
@@ -332,7 +343,6 @@ extension TimelineViewModel: StatusesFetcher {
   private func updateTimelineWithScrollToTop(newStatuses: [Status], statuses: [Status], nextPageState: StatusesState.PagingState) {
     pendingStatusesObserver.disableUpdate = true
     statusesState = .display(statuses: statuses, nextPageState: nextPageState)
-    scrollToIndexAnimated = false
     scrollToIndex = newStatuses.count + 1
 
     DispatchQueue.main.async { [weak self] in
@@ -437,7 +447,9 @@ extension TimelineViewModel {
     await datasource.insert(event.status, at: 0)
     await cache()
     StatusDataControllerProvider.shared.updateDataControllers(for: [event.status], client: client)
-    await updateStatusesState()
+    if scrollToTopVisible, pendingStatusesObserver.pendingStatuses.isEmpty {
+      await updateStatusesState()
+    }
   }
 
   private func handleDeleteEvent(_ event: StreamEventDelete) async {