Wino-Mail/Wino.Mail.WinUI/Controls/ListView/WinoListView.cs

using System.Linq;
using System.Windows.Input;
using CommunityToolkit.WinUI;
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Wino.Core.Domain.Models.MailItem;
using Wino.Mail.ViewModels.Data;

namespace Wino.Mail.WinUI.Controls.ListView;

public partial class WinoListView : Microsoft.UI.Xaml.Controls.ListView
{
    private const string PART_ScrollViewer = "ScrollViewer";
    private ScrollViewer? internalScrollviewer;

    [GeneratedDependencyProperty]
    public partial bool IsThreadListView { get; set; }

    [GeneratedDependencyProperty]
    public partial ICommand? LoadMoreCommand { get; set; }

    protected override void OnApplyTemplate()
    {
        base.OnApplyTemplate();

        DragItemsStarting += ItemDragStarting;
        DragItemsStarting -= ItemDragStarting;

        internalScrollviewer = GetTemplateChild(PART_ScrollViewer) as ScrollViewer;

        if (internalScrollviewer == null) return;

        internalScrollviewer.ViewChanged -= InternalScrollVeiwerViewChanged;
        internalScrollviewer.ViewChanged += InternalScrollVeiwerViewChanged;
    }

    private void InternalScrollVeiwerViewChanged(object? sender, ScrollViewerViewChangedEventArgs e)
    {
        if (internalScrollviewer == null) return;

        // No need to raise init request if there are no items in the list.
        if (ItemsSource == null) return;

        double progress = internalScrollviewer.VerticalOffset / internalScrollviewer.ScrollableHeight;

        // Trigger when scrolled past 90% of total height
        if (progress >= 0.9)
        {
            bool canLoadMore = LoadMoreCommand?.CanExecute(null) ?? false;

            if (canLoadMore)
            {
                LoadMoreCommand?.Execute(null);
            }
        }
    }

    protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
    {
        base.PrepareContainerForItemOverride(element, item);

        // Ensure the container's selection state matches the model's state
        // This is crucial for virtualization scenarios where containers are recycled

        if (item is MailItemViewModel mailItemViewModel
            && element is WinoMailItemViewModelListViewItem container
            && container.Item != mailItemViewModel)
        {
            container.Item = mailItemViewModel;
            container.IsSelected = mailItemViewModel.IsSelected;
        }
        else if (item is ThreadMailItemViewModel threadMailItemViewModel
            && element is WinoThreadMailItemViewModelListViewItem threadContainer
            && threadContainer.Item != threadMailItemViewModel)
        {
            threadContainer.Item = threadMailItemViewModel;
            threadContainer.IsSelected = threadMailItemViewModel.IsSelected;
            threadContainer.IsThreadExpanded = threadMailItemViewModel.IsThreadExpanded;
        }
    }

    protected override void ClearContainerForItemOverride(DependencyObject element, object item)
    {
        base.ClearContainerForItemOverride(element, item);

        if (item is MailItemViewModel mailItemViewModel && element is WinoMailItemViewModelListViewItem container)
        {
            container.Item = null;
            container.IsSelected = false;
        }
        else if (item is ThreadMailItemViewModel threadMailItemViewModel && element is WinoThreadMailItemViewModelListViewItem threadContainer)
        {
            threadContainer.Item = null;
            threadContainer.IsSelected = false;
            threadContainer.IsThreadExpanded = false;
        }
    }

    public WinoMailItemViewModelListViewItem? GetMailItemContainer(MailItemViewModel mailItemViewModel)
    {
        foreach (var item in Items)
        {
            if (item is MailItemViewModel mailItem && mailItem.Id == mailItemViewModel.Id) return ContainerFromItem(mailItemViewModel) as WinoMailItemViewModelListViewItem;
            if (item is ThreadMailItemViewModel threadMailItem && threadMailItem.GetContainingIds().Contains(mailItemViewModel.MailCopy.UniqueId))
            {
                var threadContainer = ContainerFromItem(threadMailItem) as WinoThreadMailItemViewModelListViewItem;

                // Try to get the inner WinoListView.
                if (threadContainer != null)
                {
                    var innerListViewControl = threadContainer.GetWinoListViewControl();

                    return innerListViewControl?.ContainerFromItem(mailItemViewModel) as WinoMailItemViewModelListViewItem;
                }
            }
        }

        return null;
    }

    public WinoThreadMailItemViewModelListViewItem? GetThreadMailItemContainer(ThreadMailItemViewModel threadMailItemViewModel)
        => ContainerFromItem(threadMailItemViewModel) as WinoThreadMailItemViewModelListViewItem;

    public bool SelectMailItemContainer(MailItemViewModel mailItemViewModel)
    {
        WinoMailItemViewModelListViewItem? itemContainer = null;
        WinoThreadMailItemViewModelListViewItem? threadContainer = null;

        foreach (var item in Items)
        {
            if (item is MailItemViewModel mailItem && mailItem.Id == mailItemViewModel.Id)
            {
                itemContainer = ContainerFromItem(mailItemViewModel) as WinoMailItemViewModelListViewItem;

                break;
            }
            else if (item is ThreadMailItemViewModel threadMailItemViewModel && threadMailItemViewModel.HasUniqueId(mailItemViewModel.MailCopy.UniqueId))
            {
                threadContainer = ContainerFromItem(threadMailItemViewModel) as WinoThreadMailItemViewModelListViewItem;

                // Try to get the inner WinoListView.
                if (threadContainer != null)
                {
                    threadContainer.IsThreadExpanded = true;

                    var innerListViewControl = threadContainer.GetWinoListViewControl();

                    if (innerListViewControl != null)
                    {
                        itemContainer = innerListViewControl.ContainerFromItem(mailItemViewModel) as WinoMailItemViewModelListViewItem;
                    }
                }

                break;
            }
        }

        if (itemContainer != null)
        {
            itemContainer.IsSelected = true;
            return true;
        }
        else if (threadContainer != null)
        {
            return true;
        }

        return false;
    }

    public void ChangeSelectionMode(ListViewSelectionMode mode)
    {
        // Not only this control, but also all inner WinoListView controls should change the selection mode.
        // TODO: New threads added after this call won't have the correct selection mode.

        SelectionMode = mode;

        foreach (var item in Items)
        {
            if (item is ThreadMailItemViewModel)
            {
                var itemContainer = ContainerFromItem(item) as WinoThreadMailItemViewModelListViewItem;
                if (itemContainer != null)
                {
                    var innerListViewControl = itemContainer.GetWinoListViewControl();
                    innerListViewControl?.ChangeSelectionMode(mode);
                }
            }
        }
    }

    public void Cleanup()
    {
        DragItemsStarting -= ItemDragStarting;

        if (internalScrollviewer != null)
        {
            internalScrollviewer.ViewChanged -= InternalScrollVeiwerViewChanged;
        }
    }

    private void ItemDragStarting(object sender, DragItemsStartingEventArgs args)
    {
        // Dragging multiple mails from different accounts/folders are supported with the condition below:
        // All mails belongs to the drag will be matched on the dropped folder's account.
        // Meaning that if users drag 1 mail from Account A/Inbox and 1 mail from Account B/Inbox,
        // and drop to Account A/Inbox, the mail from Account B/Inbox will NOT be moved.

        if (IsThreadListView)
        {
            var allItems = args.Items.Cast<MailItemViewModel>();

            // Set native drag arg properties.
            var dragPackage = new MailDragPackage(allItems.Cast<IMailListItem>());

            args.Data.Properties.Add(nameof(MailDragPackage), dragPackage);
        }
        else
        {
            var dragPackage = new MailDragPackage(args.Items.Cast<IMailListItem>());

            args.Data.Properties.Add(nameof(MailDragPackage), dragPackage);
        }
    }
}