Finished the job but idk why the tests are failing.Have to troubleshoot

Author: E-m-i-n-e-n-c-e

lib/model/message_list.dart

@@ -167,7 +167,8 @@ mixin _MessageSequence {
   /// before, between, or after the messages.
   ///
   /// This information is completely derived from [messages] and
-  /// the flags [haveOldest], [fetchingOlder] and [fetchOlderCoolingDown].
+  /// the flags [haveOldest], [fetchingOlder] and [fetchOlderCoolingDown]
+  /// and [haveNewest], [fetchingNewer] and [fetchNewerCoolingDown].
   /// It exists as an optimization, to memoize that computation.
   final QueueList<MessageListItem> items = QueueList();
 
@@ -476,16 +477,20 @@ bool _sameDay(DateTime date1, DateTime date2) {
 ///  * Add listeners with [addListener].
 ///  * Fetch messages with [fetchInitial].  When the fetch completes, this object
 ///    will notify its listeners (as it will any other time the data changes.)
-///  * Fetch more messages as needed with [fetchOlder].
+///  * Fetch more messages as needed with [fetchOlder] or [fetchNewer].
 ///  * On reassemble, call [reassemble].
 ///  * When the object will no longer be used, call [dispose] to free
 ///    resources on the [PerAccountStore].
 class MessageListView with ChangeNotifier, _MessageSequence {
-  MessageListView._({required this.store, required this.narrow});
+  MessageListView._({required this.store, required this.narrow, this.anchorMessageId});
 
+  // Anchor message ID is used to fetch messages from a specific point in the list.
+  // It is set when the user navigates to a message list page with a specific anchor message.
+  int? anchorMessageId;
+  int? get anchorIndex => anchorMessageId != null ? findItemWithMessageId(anchorMessageId!) : null;
   factory MessageListView.init(
-      {required PerAccountStore store, required Narrow narrow}) {
-    final view = MessageListView._(store: store, narrow: narrow);
+      {required PerAccountStore store, required Narrow narrow, int? anchorMessageId}) {
+    final view = MessageListView._(store: store, narrow: narrow, anchorMessageId: anchorMessageId);
     store.registerMessageList(view);
     return view;
   }
@@ -564,15 +569,13 @@ class MessageListView with ChangeNotifier, _MessageSequence {
     }
   }
 
-  /// The message ID to use as an anchor when fetching messages.
-  /// If null, the latest messages will be fetched.
-  int? anchorMessageId;
+
 
   /// Fetch messages, starting from scratch.
   Future<void> fetchInitial() async {
     // TODO(#80): fetch from anchor firstUnread, instead of newest
 
-    assert(!fetched && !haveOldest && !fetchingOlder && !fetchOlderCoolingDown);
+    assert(!fetched && !haveOldest && !fetchingOlder && !fetchOlderCoolingDown && !fetchingNewer && !fetchNewerCoolingDown && !haveNewest);
     assert(messages.isEmpty && contents.isEmpty);
     // TODO schedule all this in another isolate
     final generation = this.generation;
@@ -585,9 +588,11 @@ class MessageListView with ChangeNotifier, _MessageSequence {
         ? kMessageListFetchBatchSize ~/ 2  // Fetch messages before and after anchor
         : kMessageListFetchBatchSize,      // Fetch only older messages when no anchor
       numAfter: anchorMessageId != null
-        ? kMessageListFetchBatchSize ~/ 2  // Fetch messages before and after anchor
-        : 0,                               // Don't fetch newer messages when no anchor
+        ? kMessageListFetchBatchSize ~/2 // Fetch messages before and after anchor
+        : 0,                          // Don't fetch newer messages when no anchor
     );
+    anchorMessageId ??= result.messages.last.id;
+
     if (this.generation > generation) return;
     store.reconcileMessages(result.messages);
     store.recentSenders.handleMessages(result.messages); // TODO(#824)
@@ -598,16 +603,11 @@ class MessageListView with ChangeNotifier, _MessageSequence {
     }
     _fetched = true;
     _haveOldest = result.foundOldest;
+    _haveNewest = result.foundNewest;
     _updateEndMarkers();
     notifyListeners();
   }
 
-  /// Initialize the view with a specific anchor message.
-  void setAnchorMessage(int messageId) {
-    anchorMessageId = messageId;
-    _reset();
-    fetchInitial();
-  }
 
   /// Fetch the next batch of older messages, if applicable.
   Future<void> fetchOlder() async {
@@ -720,8 +720,7 @@ class MessageListView with ChangeNotifier, _MessageSequence {
 
       _insertAllMessages(messages.length, fetchedMessages);
 
-      // No foundNewest in API, assume we're caught up if we get fewer messages
-      _haveNewest = result.messages.length < kMessageListFetchBatchSize;
+      _haveNewest = result.foundNewest;
 
     } finally {
       if (this.generation == generation) {

lib/widgets/message_list.dart

@@ -182,12 +182,12 @@ abstract class MessageListPageState {
 }
 
 class MessageListPage extends StatefulWidget {
-  const MessageListPage({super.key, required this.initNarrow});
-
+  const MessageListPage({super.key, required this.initNarrow, this.anchorMessageId});
+  final int? anchorMessageId;
   static Route<void> buildRoute({int? accountId, BuildContext? context,
-      required Narrow narrow}) {
+      required Narrow narrow, int? anchorMessageId}) {
     return MaterialAccountWidgetRoute(accountId: accountId, context: context,
-      page: MessageListPage(initNarrow: narrow));
+      page: MessageListPage(initNarrow: narrow, anchorMessageId: anchorMessageId));
   }
 
   /// The [MessageListPageState] above this context in the tree.
@@ -302,7 +302,7 @@ class _MessageListPageState extends State<MessageListPage> implements MessageLis
               removeBottom: ComposeBox.hasComposeBox(narrow),
 
               child: Expanded(
-                child: MessageList(narrow: narrow, onNarrowChanged: _narrowChanged))),
+                child: MessageList(narrow: narrow, onNarrowChanged: _narrowChanged, anchorMessageId: widget.anchorMessageId))),
             if (ComposeBox.hasComposeBox(narrow))
               ComposeBox(key: _composeBoxKey, narrow: narrow)
           ]))));
@@ -443,11 +443,11 @@ const _kShortMessageHeight = 80;
 const kFetchMessagesBufferPixels = (kMessageListFetchBatchSize / 2) * _kShortMessageHeight;
 
 class MessageList extends StatefulWidget {
-  const MessageList({super.key, required this.narrow, required this.onNarrowChanged});
+  const MessageList({super.key, required this.narrow, required this.onNarrowChanged, this.anchorMessageId});
 
   final Narrow narrow;
   final void Function(Narrow newNarrow) onNarrowChanged;
-
+  final int? anchorMessageId;
   @override
   State<StatefulWidget> createState() => _MessageListState();
 }
@@ -456,6 +456,8 @@ class _MessageListState extends State<MessageList> with PerAccountStoreAwareStat
   MessageListView? model;
   final ScrollController scrollController = ScrollController();
   final ValueNotifier<bool> _scrollToBottomVisibleValue = ValueNotifier<bool>(false);
+  List<MessageListItem> newItems = [];
+  List<MessageListItem> oldItems = [];
 
   @override
   void initState() {
@@ -476,10 +478,14 @@ class _MessageListState extends State<MessageList> with PerAccountStoreAwareStat
     super.dispose();
   }
 
-  void _initModel(PerAccountStore store) {
-    model = MessageListView.init(store: store, narrow: widget.narrow);
+  void _initModel(PerAccountStore store) async{
+    model = MessageListView.init(store: store, narrow: widget.narrow, anchorMessageId: widget.anchorMessageId);
     model!.addListener(_modelChanged);
-    model!.fetchInitial();
+    await model!.fetchInitial();
+    setState(() {
+      oldItems = model!.items.sublist(0, model!.anchorIndex!+1);
+      newItems = model!.items.sublist(model!.anchorIndex!+1, model!.items.length);
+    });
   }
 
   void _modelChanged() {
@@ -488,10 +494,54 @@ class _MessageListState extends State<MessageList> with PerAccountStoreAwareStat
       // [PropagateMode.changeAll] or [PropagateMode.changeLater].
       widget.onNarrowChanged(model!.narrow);
     }
+
+    final previousLength = oldItems.length + newItems.length;
+
     setState(() {
+      oldItems = model!.items.sublist(0, model!.anchorIndex!+1);
+      newItems = model!.items.sublist(model!.anchorIndex!+1, model!.items.length);
       // The actual state lives in the [MessageListView] model.
       // This method was called because that just changed.
     });
+
+
+    // Auto-scroll when new messages arrive if we're already near the bottom
+    if (model!.items.length > previousLength && // New messages were added
+        scrollController.hasClients) {
+      // Use post-frame callback to ensure scroll metrics are up to date
+      WidgetsBinding.instance.addPostFrameCallback((_) async {
+        // This is to prevent auto-scrolling when fetching newer messages
+        if(model!.fetchingNewer || model!.fetchingOlder || model!.fetchNewerCoolingDown || model!.fetchOlderCoolingDown || !model!.haveNewest ){
+          return;
+        }
+
+        final viewportDimension = scrollController.position.viewportDimension;
+        final maxScrollExtent = scrollController.position.maxScrollExtent;
+        final currentScroll = scrollController.position.pixels;
+
+        // If we're within 300px of the bottommost viewport, auto-scroll
+        if (maxScrollExtent - currentScroll - viewportDimension < 300) {
+
+        final distance = scrollController.position.pixels;
+        final durationMsAtSpeedLimit = (1000 * distance / 8000).ceil();
+        final durationMs = max(300, durationMsAtSpeedLimit);
+
+        await scrollController.animateTo(
+            scrollController.position.maxScrollExtent,
+            duration: Duration(milliseconds: durationMs),
+            curve: Curves.ease);
+
+
+
+        if (scrollController.position.pixels + 40 < scrollController.position.maxScrollExtent ) {
+          await scrollController.animateTo(
+            scrollController.position.maxScrollExtent,
+            duration: Duration(milliseconds: durationMs),
+              curve: Curves.ease);
+          }
+        }
+      });
+    }
   }
 
   void _handleScrollMetrics(ScrollMetrics scrollMetrics) {
@@ -510,6 +560,11 @@ class _MessageListState extends State<MessageList> with PerAccountStoreAwareStat
       //   still not yet updated to account for the newly-added messages.
       model?.fetchOlder();
     }
+
+    // Check for fetching newer messages when near the bottom
+    if (scrollMetrics.extentAfter < kFetchMessagesBufferPixels) {
+      model?.fetchNewer();
+    }
   }
 
   void _scrollChanged() {
@@ -562,7 +617,8 @@ class _MessageListState extends State<MessageList> with PerAccountStoreAwareStat
   }
 
   Widget _buildListView(BuildContext context) {
-    final length = model!.items.length;
+    final length = oldItems.length;
+    final newLength = newItems.length;
     const centerSliverKey = ValueKey('center sliver');
 
     Widget sliver = SliverStickyHeaderList(
@@ -587,22 +643,32 @@ class _MessageListState extends State<MessageList> with PerAccountStoreAwareStat
           final valueKey = key as ValueKey<int>;
           final index = model!.findItemWithMessageId(valueKey.value);
           if (index == -1) return null;
-          return length - 1 - (index - 3);
+          return length - 1 - index;
         },
-        childCount: length + 3,
+        childCount: length,
         (context, i) {
-          // To reinforce that the end of the feed has been reached:
-          //   https://chat.zulip.org/#narrow/stream/243-mobile-team/topic/flutter.3A.20Mark-as-read/near/1680603
-          if (i == 0) return const SizedBox(height: 36);
-
-          if (i == 1) return MarkAsReadWidget(narrow: widget.narrow);
-
-          if (i == 2) return TypingStatusWidget(narrow: widget.narrow);
-
-          final data = model!.items[length - 1 - (i - 3)];
+          final data = oldItems[length - 1 - i];
           return _buildItem(data, i);
         }));
 
+    Widget newMessagesSliver = SliverStickyHeaderList(
+      headerPlacement: HeaderPlacement.scrollingStart,
+      delegate: SliverChildBuilderDelegate(
+        findChildIndexCallback: (Key key) {
+          final valueKey = key as ValueKey<int>;
+          final index = model!.findItemWithMessageId(valueKey.value);
+          if (index == -1) return null;
+          return index-3;
+        },
+        childCount: newLength+3,
+        (context, i) {
+          if (i == newLength) return TypingStatusWidget(narrow: widget.narrow);
+          if (i == newLength+1) return MarkAsReadWidget(narrow: widget.narrow);
+          if (i == newLength+2) return const SizedBox(height: 36);
+          final data = newItems[i];
+          return _buildItem(data, i-newLength);
+        }));
+
     if (!ComposeBox.hasComposeBox(widget.narrow)) {
       // TODO(#311) If we have a bottom nav, it will pad the bottom
       //   inset, and this shouldn't be necessary
@@ -623,16 +689,16 @@ class _MessageListState extends State<MessageList> with PerAccountStoreAwareStat
 
       controller: scrollController,
       semanticChildCount: length + 2,
-      anchor: 1.0,
+      anchor: 0.85,
       center: centerSliverKey,
 
       slivers: [
-        sliver,
-
-        // This is a trivial placeholder that occupies no space.  Its purpose is
-        // to have the key that's passed to [ScrollView.center], and so to cause
-        // the above [SliverStickyHeaderList] to run from bottom to top.
+        sliver,  // Main message list (grows upward)
+        // Center point - everything before this grows up, everything after grows down
         const SliverToBoxAdapter(key: centerSliverKey),
+        // Static widgets and new messages (will grow downward)
+        newMessagesSliver,  // New messages list (will grow downward)
+
       ]);
   }
 
@@ -674,14 +740,28 @@ class ScrollToBottomButton extends StatelessWidget {
   final ValueNotifier<bool> visibleValue;
   final ScrollController scrollController;
 
-  Future<void> _navigateToBottom() {
+  Future<void> _navigateToBottom() async {
+    // Calculate initial scroll parameters
     final distance = scrollController.position.pixels;
     final durationMsAtSpeedLimit = (1000 * distance / 8000).ceil();
     final durationMs = max(300, durationMsAtSpeedLimit);
-    return scrollController.animateTo(
-      0,
+
+    // Do a single scroll attempt with a completion check
+    await scrollController.animateTo(
+      scrollController.position.maxScrollExtent,
       duration: Duration(milliseconds: durationMs),
       curve: Curves.ease);
+    var count =1;
+    // Check if we actually reached bottom, if not try again
+    // This handles cases where content was loaded during scroll
+    while (scrollController.position.pixels + 40 < scrollController.position.maxScrollExtent) {
+      await scrollController.animateTo(
+        scrollController.position.maxScrollExtent,
+        duration: const Duration(milliseconds: 300),
+        curve: Curves.ease);
+      count++;
+    }
+    print("count: $count");
   }
 
   @override
@@ -728,6 +808,7 @@ class _TypingStatusWidgetState extends State<TypingStatusWidget> with PerAccount
   }
 
   void _modelChanged() {
+
     setState(() {
       // The actual state lives in [model].
       // This method was called because that just changed.
@@ -1358,11 +1439,9 @@ class MessageWithPossibleSender extends StatelessWidget {
               selfUserId: store.selfUserId),
           };
           Navigator.push(context,
-            MessageListPage.buildRoute(context: context, narrow: narrow));
-          final messageListState = context.findAncestorStateOfType<_MessageListState>();
-          if (messageListState != null) {
-            messageListState.model?.setAnchorMessage(message.id);
-          }
+            MessageListPage.buildRoute(context: context, narrow: narrow, anchorMessageId: message.id));
+
+
         }
       },
       child: Padding(