internal void KeyDown()

in src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs [418:550]
119 lines of code
29 McCabe index (conditional complexity)

        internal void KeyDown(IMenuItem? item, KeyEventArgs e)
        {
            switch (e.Key)
            {
                case Key.Up:
                case Key.Down:
                    {
                        if (item?.IsTopLevel == true && item.HasSubMenu)
                        {
                            if (!item.IsSubMenuOpen)
                            {
                                Open(item, true);
                            }
                            else
                            {
                                item.MoveSelection(NavigationDirection.First, true);
                            }

                            e.Handled = true;
                        }
                        else
                        {
                            goto default;
                        }
                        break;
                    }

                case Key.Left:
                    {
                        if (item is { IsSubMenuOpen: true, SelectedItem: null })
                        {
                            item.Close();
                        }
                        else if (item?.Parent is IMenuItem { IsTopLevel: false, IsSubMenuOpen: true } parent)
                        {
                            parent.Close();
                            parent.Focus();
                            e.Handled = true;
                        }
                        else
                        {
                            goto default;
                        }
                        break;
                    }

                case Key.Right:
                    {
                        if (item != null && !item.IsTopLevel && item.HasSubMenu)
                        {
                            Open(item, true);
                            e.Handled = true;
                        }
                        else
                        {
                            goto default;
                        }
                        break;
                    }

                case Key.Enter:
                    {
                        if (item != null)
                        {
                            if (!item.HasSubMenu)
                            {
                                Click(item);
                            }
                            else
                            {
                                Open(item, true);
                            }

                            e.Handled = true;
                        }
                        break;
                    }

                case Key.Escape:
                    {
                        if (item?.Parent is IMenuElement parent)
                        {
                            parent.Close();
                            parent.Focus();
                        }
                        else
                        {
                            Menu!.Close();
                        }

                        e.Handled = true;
                        break;
                    }

                default:
                    {
                        var direction = e.Key.ToNavigationDirection();

                        if (direction?.IsDirectional() == true)
                        {
                            if (item == null && _isContextMenu)
                            {
                                if (Menu!.MoveSelection(direction.Value, true) == true)
                                {
                                    e.Handled = true;
                                }
                            }
                            else if (item?.Parent?.MoveSelection(direction.Value, true) == true)
                            {
                                // If the parent is an IMenu which successfully moved its selection,
                                // and the current menu is open then close the current menu and open the
                                // new menu.
                                if (item.IsSubMenuOpen &&
                                    item.Parent is IMenu &&
                                    item.Parent.SelectedItem is object &&
                                    item.Parent.SelectedItem != item)
                                {
                                    item.Close();
                                    Open(item.Parent.SelectedItem, true);
                                }
                                e.Handled = true;
                            }
                        }

                        break;
                    }
            }

            if (!e.Handled && item?.Parent is IMenuItem parentItem)
            {
                KeyDown(parentItem, e);
            }
        }