using Avalonia.Input;
using Avalonia.Headless;
using Avalonia;
using System.Reflection;
using System.Runtime.ExceptionServices;
using AtomUI.Controls;
using Avalonia.Collections;
using Avalonia.Controls;
using Avalonia.Threading;
using Avalonia.VisualTree;
using Shouldly;
using Xunit;
using AtomTreeView = AtomUI.Desktop.Controls.TreeView;
using AtomTreeViewItem = AtomUI.Desktop.Controls.TreeViewItem;

namespace AtomUI.Desktop.Controls.Tests.TreeView;

public class TreeViewDragDropTests
{
    static TreeViewDragDropTests()
    {
        AvaloniaTestApp.EnsureInitialized();
    }

    [Fact]
    public void ItemsSource_Root_Drop_Reorders_Source_Collection()
    {
        var first  = new TreeItemNode { Header = "first" };
        var second = new TreeItemNode { Header = "second" };
        var third  = new TreeItemNode { Header = "third" };
        var source = new AvaloniaList<ITreeItemNode> { first, second, third };
        var droppedCount = 0;
        var treeView = new AtomTreeView
        {
            IsShowEmptyIndicator = false,
            ItemsSource          = source
        };
        treeView.ItemDropped += (_, _) => droppedCount++;

        ShowInWindow(treeView, () =>
        {
            var secondContainer = FindContainerForNode(treeView, second)!;

            Should.NotThrow(() => PerformDrop(treeView, secondContainer, new DropTargetInfo
            {
                IsRoot = true,
                Index  = 0
            }));

            source.ShouldBe([second, first, third]);
            droppedCount.ShouldBe(1);
        });
    }

    [Fact]
    public void ItemsSource_Child_Drop_Moves_Node_Between_Children_And_Updates_Parent()
    {
        var childA = new TreeItemNode { Header = "child A" };
        var childB = new TreeItemNode { Header = "child B" };
        var parentA = new TreeItemNode
        {
            Header     = "parent A",
            IsExpanded = true,
            Children   = [childA]
        };
        var parentB = new TreeItemNode
        {
            Header     = "parent B",
            IsExpanded = true,
            Children   = [childB]
        };
        var source = new AvaloniaList<ITreeItemNode> { parentA, parentB };
        var droppedCount = 0;
        var treeView = new AtomTreeView
        {
            IsShowEmptyIndicator = false,
            ItemsSource          = source
        };
        treeView.ItemDropped += (_, _) => droppedCount++;

        ShowInWindow(treeView, () =>
        {
            RunDispatcherJobsUntil(() =>
                FindContainerForNode(treeView, childA) is not null &&
                FindContainerForNode(treeView, parentB) is not null);
            var childAContainer = FindContainerForNode(treeView, childA)!;
            var parentBContainer = FindContainerForNode(treeView, parentB)!;

            Should.NotThrow(() => PerformDrop(treeView, childAContainer, new DropTargetInfo
            {
                TargetTreeItem = parentBContainer,
                Index          = 1,
                IsRoot         = false
            }));

            parentA.Children.ShouldBeEmpty();
            parentB.Children.ShouldBe([childB, childA]);
            childA.ParentNode.ShouldBeSameAs(parentB);
            droppedCount.ShouldBe(1);
        });
        var draggedContainer = new AtomTreeViewItem { Header = "dragged" };
        var targetContainer = new AtomTreeViewItem { Header = "target", IsExpanded = true };
        var containerTree = new AtomTreeView { Width = 300, Height = 250 };
        containerTree.Items.Add(draggedContainer);
        containerTree.Items.Add(targetContainer);
        var window = new Avalonia.Controls.Window { Width = 420, Height = 320, Content = containerTree };
        var callbackCount = 0;
        containerTree.ItemDropped += (_, _) =>
        {
            targetContainer.Items.ShouldContain(draggedContainer,
                "ItemDropped must expose an already committed insertion");
            ++callbackCount;
            window.Close();
        };
        try
        {
            window.Show();
            Dispatcher.UIThread.RunJobs();
            Should.NotThrow(() => PerformDrop(containerTree, draggedContainer,
                new DropTargetInfo { TargetTreeItem = targetContainer, Index = 0 }));
            callbackCount.ShouldBe(1);
            targetContainer.Items.ShouldContain(draggedContainer);
            containerTree.Items.ShouldNotContain(draggedContainer);
        }
        finally
        {
            window.Close();
        }
    }

    [Fact]
    public void Root_Drop_Order_And_Synchronous_Drag_Callback_Closure_Are_Safe()
    {
        var first  = new TreeItemNode { Header = "first" };
        var second = new TreeItemNode { Header = "second" };
        var third  = new TreeItemNode { Header = "third" };
        var fourth = new TreeItemNode { Header = "fourth" };
        var source = new AvaloniaList<ITreeItemNode> { first, second, third, fourth };
        var treeView = new AtomTreeView
        {
            IsShowEmptyIndicator = false,
            ItemsSource          = source
        };

        ShowInWindow(treeView, () =>
        {
            var thirdContainer = FindContainerForNode(treeView, third)!;

            Should.NotThrow(() => PerformDrop(treeView, thirdContainer, new DropTargetInfo
            {
                IsRoot = true,
                Index  = 1
            }));

            source.ShouldBe([first, third, second, fourth]);
        });
        var liveTree = new AtomTreeView
        {
            Width = 300, Height = 250, IsDraggable = true, IsShowEmptyIndicator = false,
            ItemsSource = new ITreeItemNode[] { new TreeItemNode { Header = "first" }, new TreeItemNode { Header = "second" } }
        };
        var window = new Avalonia.Controls.Window { Width = 420, Height = 320, Content = liveTree };
        var started = 0;
        var completed = 0;
        liveTree.ItemDragStarted += (_, _) => { ++started; window.Close(); };
        liveTree.ItemDragCompleted += (_, _) => ++completed;
        try
        {
            window.Show();
            Dispatcher.UIThread.RunJobs();
            var item = liveTree.ContainerFromIndex(0).ShouldBeOfType<AtomTreeViewItem>();
            var header = item.GetVisualDescendants().OfType<TreeViewItemHeader>().First();
            var point = header.TranslatePoint(new Point(30, header.Bounds.Height / 2), window).ShouldNotBeNull();
            window.MouseMove(point);
            window.MouseDown(point, MouseButton.Left);
            Should.NotThrow(() => window.MouseMove(point + new Vector(40, 0), RawInputModifiers.LeftMouseButton));
            Dispatcher.UIThread.RunJobs();
            started.ShouldBe(1);
            completed.ShouldBe(1);
            liveTree.IsDragging.ShouldBeFalse();
            item.IsDragging.ShouldBeFalse();
        }
        finally
        {
            window.Close();
        }
        var leaveTree = new AtomTreeView
        {
            Width = 300, Height = 250, IsDraggable = true, IsShowEmptyIndicator = false,
            ItemsSource = new ITreeItemNode[] { new TreeItemNode { Header = "first" }, new TreeItemNode { Header = "second" } }
        };
        var leaveWindow = new Avalonia.Controls.Window { Width = 420, Height = 320, Content = leaveTree };
        var leaveCount = 0;
        leaveTree.ItemDragLeave += (_, _) => { ++leaveCount; leaveWindow.Close(); };
        leaveTree.ItemDragEnter += (_, args) => args.DraggedViewItem.ShouldNotBeNull();
        try
        {
            leaveWindow.Show();
            Dispatcher.UIThread.RunJobs();
            var sourceContainer = leaveTree.ContainerFromIndex(0).ShouldBeOfType<AtomTreeViewItem>();
            var destination = leaveTree.ContainerFromIndex(1).ShouldBeOfType<AtomTreeViewItem>();
            var header = destination.GetVisualDescendants().OfType<TreeViewItemHeader>().First();
            var point = header.TranslatePoint(new Point(30, header.Bounds.Height / 2), leaveTree).ShouldNotBeNull();
            leaveTree.GetNodeByPosition(point).ShouldBeSameAs(destination);
            SetPrivateField(leaveTree, "_beingDraggedTreeItem", sourceContainer);
            SetPrivateField(leaveTree, "_currentDragOver", sourceContainer);
            leaveTree.IsDragging = true;
            sourceContainer.IsDragOver = true;
            try
            {
                typeof(AtomTreeView).GetMethod("SetupDragOver", BindingFlags.Instance | BindingFlags.NonPublic)!
                    .Invoke(leaveTree, new object[] { point });
            }
            catch (TargetInvocationException ex) when (ex.InnerException is not null)
            {
                ExceptionDispatchInfo.Capture(ex.InnerException).Throw();
            }
            leaveCount.ShouldBe(1);
            leaveTree.IsDragging.ShouldBeFalse();
            sourceContainer.IsDragOver.ShouldBeFalse();
            destination.IsDragOver.ShouldBeFalse();
        }
        finally
        {
            leaveWindow.Close();
        }
    }

    [Fact]
    public void ItemsSource_Drop_Preserves_Selected_And_Checked_Node_State()
    {
        var first  = new TreeItemNode { Header = "first" };
        var second = new TreeItemNode { Header = "second" };
        var third  = new TreeItemNode { Header = "third" };
        var source = new AvaloniaList<ITreeItemNode> { first, second, third };
        var treeView = new AtomTreeView
        {
            IsShowEmptyIndicator = false,
            ItemsSource          = source,
            SelectionMode        = SelectionMode.Multiple,
            ToggleType           = ItemToggleType.CheckBox
        };

        ShowInWindow(treeView, () =>
        {
            treeView.SelectedItems.Add(second);
            treeView.CheckedItems.Add(second);
            Dispatcher.UIThread.RunJobs();
            var secondContainer = FindContainerForNode(treeView, second)!;

            Should.NotThrow(() => PerformDrop(treeView, secondContainer, new DropTargetInfo
            {
                IsRoot = true,
                Index  = 3
            }));

            source.ShouldBe([first, third, second]);
            treeView.SelectedItems.Contains(second).ShouldBeTrue();
            treeView.CheckedItems.Contains(second).ShouldBeTrue();
        });
    }

    [Fact]
    public void Immutable_ItemsSource_Drop_Cancels_Without_Throwing_Or_Raising_Dropped()
    {
        var first  = new TreeItemNode { Header = "first" };
        var second = new TreeItemNode { Header = "second" };
        var source = new ITreeItemNode[] { first, second };
        var droppedCount = 0;
        var treeView = new AtomTreeView
        {
            IsShowEmptyIndicator = false,
            ItemsSource          = source
        };
        treeView.ItemDropped += (_, _) => droppedCount++;

        ShowInWindow(treeView, () =>
        {
            var secondContainer = FindContainerForNode(treeView, second)!;

            Should.NotThrow(() => PerformDrop(treeView, secondContainer, new DropTargetInfo
            {
                IsRoot = true,
                Index  = 0
            }));

            source.ShouldBe([first, second]);
            droppedCount.ShouldBe(0);
        });
    }

    private static void PerformDrop(AtomTreeView treeView, AtomTreeViewItem source, DropTargetInfo targetInfo)
    {
        SetPrivateField(treeView, "_beingDraggedTreeItem", source);
        SetPrivateField(treeView, "_dropTargetInfo", targetInfo);

        try
        {
            typeof(AtomTreeView)
                .GetMethod("PerformDropOperation", BindingFlags.Instance | BindingFlags.NonPublic)!
                .Invoke(treeView, null);
        }
        catch (TargetInvocationException ex) when (ex.InnerException is not null)
        {
            ExceptionDispatchInfo.Capture(ex.InnerException).Throw();
        }
    }

    private static void SetPrivateField(AtomTreeView treeView, string fieldName, object? value)
    {
        typeof(AtomTreeView)
            .GetField(fieldName, BindingFlags.Instance | BindingFlags.NonPublic)!
            .SetValue(treeView, value);
    }

    private static AtomTreeViewItem? FindContainerForNode(Control root, ITreeItemNode node)
    {
        return root.GetVisualDescendants()
                   .OfType<AtomTreeViewItem>()
                   .FirstOrDefault(item => ReferenceEquals(item.Header, node));
    }

    private static void ShowInWindow(Control content, Action assertion)
    {
        var window = new Avalonia.Controls.Window
        {
            Width   = 420,
            Height  = 320,
            Content = content
        };

        try
        {
            window.Show();
            Dispatcher.UIThread.RunJobs();
            assertion();
        }
        finally
        {
            window.Close();
        }
    }

    private static void RunDispatcherJobsUntil(Func<bool> condition, int maxPasses = 128)
    {
        for (var i = 0; i < maxPasses; i++)
        {
            Dispatcher.UIThread.RunJobs();
            if (condition())
            {
                return;
            }
        }
    }
}