animateTo method

Implementation

Future<void> animateTo(
  ChatItemId itemId, {
  ChatItem? item,
  ChatItemQuote? reply,
  ChatItemQuote? forward,
  bool ignoreElements = false,
  bool offsetBasedOnBottom = true,
  bool addToHistory = true,
  double offset = 50,
}) async {
  final ChatItem? original = reply?.original ?? forward?.original ?? item;
  final ChatItemId animateTo = original?.id ?? itemId;

  final int index = elements.values.toList().indexWhere((e) {
    return e.id.id == animateTo ||
        (e is ChatForwardElement &&
            (e.forwards.any((e1) => e1.value.id == animateTo) ||
                e.note.value?.value.id == animateTo));
  });

  // If [original] is within the [elements], then just [animateToIndex].
  if (index != -1 && !ignoreElements) {
    _highlight(elements.values.elementAt(index).id);

    if (listController.hasClients) {
      await listController.sliverController.animateToIndex(
        index,
        offsetBasedOnBottom: offsetBasedOnBottom,
        offset: offset,
        duration: 200.milliseconds,
        curve: Curves.ease,
      );
    } else {
      initIndex = index;
    }

    // And add the transition to the [history].
    if (addToHistory && item != null) {
      this.addToHistory(item);
    }
  } else {
    if (original != null) {
      final ListElementId elementId = ListElementId(original.at, original.id);
      final ListElementId? lastId =
          elements.values
              .lastWhereOrNull(
                (e) =>
                    e is ChatMessageElement ||
                    e is ChatInfoElement ||
                    e is ChatCallElement ||
                    e is ChatForwardElement,
              )
              ?.id;

      // If the [original] is placed before the first item, then animate to top,
      // or otherwise to bottom.
      if (lastId != null && elementId.compareTo(lastId) == 1) {
        if (_topLoader == null) {
          _topLoader = LoaderElement.top();
          elements[_topLoader!.id] = _topLoader!;
        }

        SchedulerBinding.instance.addPostFrameCallback((_) async {
          _ignorePositionChanges = true;
          await listController.sliverController.animateToIndex(
            elements.length - 1,
            offsetBasedOnBottom: true,
            offset: 0,
            duration: 300.milliseconds,
            curve: Curves.ease,
          );
          _ignorePositionChanges = false;
        });
      } else {
        if (_bottomLoader == null) {
          _bottomLoader = LoaderElement.bottom();
          elements[_bottomLoader!.id] = _bottomLoader!;
        }

        SchedulerBinding.instance.addPostFrameCallback((_) async {
          _ignorePositionChanges = true;
          await listController.sliverController.animateToIndex(
            0,
            offsetBasedOnBottom: true,
            offset: 0,
            duration: 300.milliseconds,
            curve: Curves.ease,
          );
          _ignorePositionChanges = false;
        });
      }
    }

    // And then try to fetch the items.
    try {
      await _fetchItemsAround(
        itemId,
        reply: reply?.original?.id,
        forward: forward?.original?.id,
      );

      final int index = elements.values.toList().indexWhere((e) {
        return e.id.id == animateTo ||
            (e is ChatForwardElement &&
                (e.forwards.any((e1) => e1.value.id == animateTo) ||
                    e.note.value?.value.id == animateTo));
      });

      if (index != -1) {
        // [FlutterListView] ignores the [initIndex], if it is 0.
        if (index == 0) {
          initIndex = 1;
          initOffset = -5000;
        } else {
          initIndex = index;
          initOffset = offset;
        }

        _highlight(elements.values.elementAt(index).id);

        if (addToHistory && item != null) {
          this.addToHistory(item);
        }
      }
    } finally {
      SchedulerBinding.instance.addPostFrameCallback((_) {
        // Stop the animation, if any.
        listController.jumpTo(listController.offset);

        // Ensure [FlutterListView] has correct index and offset.
        listController.sliverController.jumpToIndex(
          initIndex,
          offset: initOffset,
          offsetBasedOnBottom: offsetBasedOnBottom,
        );

        _ignorePositionChanges = false;

        elements.remove(_topLoader?.id);
        elements.remove(_bottomLoader?.id);
        _topLoader = null;
        _bottomLoader = null;
      });
    }
  }
}