// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

using Avalonia.Controls;
using Avalonia.Controls.Primitives;
using Avalonia.Headless;
using Avalonia.Headless.NUnit;
using Avalonia.Input;
using Avalonia.Threading;
using Avalonia.VisualTree;

using AwesomeAssertions;

using ICSharpCode.ILSpyX.TreeView;

using ICSharpCode.ILSpy.Controls.TreeView;

using NUnit.Framework;

namespace ICSharpCode.ILSpy.Tests.Controls;

[TestFixture]
public class SharpTreeViewTests
{
	sealed class TestNode : SharpTreeNode
	{
		readonly string text;
		public TestNode(string text, params TestNode[] children)
		{
			this.text = text;
			foreach (var child in children)
				Children.Add(child);
		}
		public override object Text => text;
	}

	static (Window window, SharpTreeView tree, TestNode root) Host()
	{
		var b1 = new TestNode("B1");
		var b = new TestNode("B", b1);
		var root = new TestNode("root", new TestNode("A"), b, new TestNode("C"));
		var tree = new SharpTreeView { ShowRoot = false, Root = root };
		var window = new Window { Content = tree, Width = 300, Height = 400 };
		window.Show();
		Dispatcher.UIThread.RunJobs();
		return (window, tree, root);
	}

	[AvaloniaTest]
	public void Flattens_Visible_Nodes_And_Expand_Collapse_Updates_Row_Count()
	{
		var (_, tree, root) = Host();
		var b = (TestNode)root.Children[1];

		tree.ItemCount.Should().Be(3, "A, B (collapsed), C are the visible top-level rows");

		b.IsExpanded = true;
		Dispatcher.UIThread.RunJobs();
		tree.ItemCount.Should().Be(4, "expanding B reveals B1");

		b.IsExpanded = false;
		Dispatcher.UIThread.RunJobs();
		tree.ItemCount.Should().Be(3, "collapsing B hides B1 again");
	}

	[AvaloniaTest]
	public void Shift_Down_Extends_And_Shift_Up_Shrinks_From_The_Anchor()
	{
		// The whole reason for the rewrite: native ListBox anchor selection both extends AND
		// shrinks a shift-range -- the thing ProDataGrid's additive SetRowsSelection could not do.
		var nodes = Enumerable.Range(0, 5).Select(i => new TestNode(((char)('A' + i)).ToString())).ToArray();
		var root = new TestNode("root", nodes);
		var tree = new SharpTreeView { ShowRoot = false, Root = root };
		var window = new Window { Content = tree, Width = 300, Height = 400 };
		window.Show();
		Dispatcher.UIThread.RunJobs();

		tree.SelectedItem = nodes[0];
		Dispatcher.UIThread.RunJobs();
		(tree.ContainerFromItem(nodes[0]))?.Focus();
		Dispatcher.UIThread.RunJobs();

		window.KeyPress(Key.Down, RawInputModifiers.Shift, PhysicalKey.ArrowDown, null);
		Dispatcher.UIThread.RunJobs();
		window.KeyPress(Key.Down, RawInputModifiers.Shift, PhysicalKey.ArrowDown, null);
		Dispatcher.UIThread.RunJobs();
		tree.SelectedItems!.Cast<SharpTreeNode>().Should()
			.BeEquivalentTo(new[] { nodes[0], nodes[1], nodes[2] }, "Shift+Down twice extends A..C");

		window.KeyPress(Key.Up, RawInputModifiers.Shift, PhysicalKey.ArrowUp, null);
		Dispatcher.UIThread.RunJobs();
		tree.SelectedItems!.Cast<SharpTreeNode>().Should()
			.BeEquivalentTo(new[] { nodes[0], nodes[1] }, "Shift+Up shrinks the range back toward the anchor (A,B)");
	}

	[AvaloniaTest]
	public void Type_Ahead_Jumps_To_The_Visible_Node_Matching_The_Typed_Prefix()
	{
		var apple = new TestNode("Apple");
		var banana = new TestNode("Banana");
		var cherry = new TestNode("Cherry");
		var cranberry = new TestNode("Cranberry");
		var root = new TestNode("root", apple, banana, cherry, cranberry);
		var tree = new SharpTreeView { ShowRoot = false, Root = root };
		var window = new Window { Content = tree, Width = 300, Height = 400 };
		window.Show();
		Dispatcher.UIThread.RunJobs();

		// "cra": 'c' lands on Cherry, 'r' has to search forward to Cranberry, 'a' stays.
		foreach (char ch in "cra")
		{
			tree.RaiseEvent(new TextInputEventArgs {
				RoutedEvent = InputElement.TextInputEvent,
				Text = ch.ToString(),
				Source = tree,
			});
			Dispatcher.UIThread.RunJobs();
		}

		tree.SelectedItem.Should().BeSameAs(cranberry, "type-ahead refines forward to the Cr* match");
	}

	[AvaloniaTest]
	public void Selecting_A_Row_Sets_The_Node_IsSelected()
	{
		var (_, tree, root) = Host();
		var a = (TestNode)root.Children[0];
		var c = (TestNode)root.Children[2];

		tree.SelectedItem = a;
		Dispatcher.UIThread.RunJobs();
		a.IsSelected.Should().BeTrue();

		tree.SelectedItem = c;
		Dispatcher.UIThread.RunJobs();
		c.IsSelected.Should().BeTrue();
		a.IsSelected.Should().BeFalse("moving the selection clears the old node's flag");
	}

	/// <summary>The number of rows the flattener should expose for a tree rooted in
	/// <paramref name="root"/> when the root itself is not shown.</summary>
	static int VisibleRowCount(SharpTreeNode root)
	{
		int count = 0;
		void Walk(SharpTreeNode node)
		{
			foreach (SharpTreeNode child in node.Children)
			{
				if (child.IsHidden)
					continue;
				count++;
				if (child.IsExpanded)
					Walk(child);
			}
		}
		Walk(root);
		return count;
	}

	static void AssertEveryRowResolves(SharpTreeView tree, SharpTreeNode root, string because)
	{
		tree.UpdateLayout();
		Dispatcher.UIThread.RunJobs();
		int expected = VisibleRowCount(root);
		tree.ItemCount.Should().Be(expected, because);
		for (int i = 0; i < expected; i++)
			tree.ItemsView[i].Should().NotBeNull($"row {i} must resolve after {because}");
	}

	/// <summary>
	/// Collapsing and removing nodes above a scrolled viewport shrinks the flattened list under
	/// the virtualizing panel's realized index range. The panel must not be left indexing rows
	/// that no longer exist.
	/// </summary>
	[AvaloniaTest]
	public void Shrinking_The_Tree_Above_A_Scrolled_Viewport_Keeps_Every_Row_Resolvable()
	{
		var groups = Enumerable.Range(0, 200)
			.Select(i => new TestNode($"g{i}", Enumerable.Range(0, 5)
				.Select(j => new TestNode($"g{i}_{j}")).ToArray()))
			.ToArray();
		var root = new TestNode("root", groups);
		var tree = new SharpTreeView { ShowRoot = false, Root = root };
		var window = new Window { Content = tree, Width = 300, Height = 400 };
		window.Show();
		Dispatcher.UIThread.RunJobs();

		foreach (var group in groups)
			group.IsExpanded = true;
		AssertEveryRowResolves(tree, root, "expanding every group");
		tree.GetRealizedContainers().Count().Should()
			.BeLessThan(tree.ItemCount, "the panel must be virtualizing, or this test proves nothing");

		// Park the realized range far from index 0, with a live selection inside it.
		tree.SelectedItem = groups[^1].Children[^1];
		tree.ScrollIntoView(tree.ItemCount - 1);
		AssertEveryRowResolves(tree, root, "scrolling to the last row");

		for (int i = 0; i < 190; i++)
			groups[i].IsExpanded = false;
		AssertEveryRowResolves(tree, root, "collapsing 190 groups above the viewport");

		for (int i = 0; i < 150; i++)
			root.Children.RemoveAt(0);
		AssertEveryRowResolves(tree, root, "removing 150 groups above the viewport");

		tree.ScrollIntoView(0);
		AssertEveryRowResolves(tree, root, "scrolling back to the top");
	}

	/// <summary>
	/// A lazily loaded node replaces its placeholder with real children while the tree is
	/// scrolled: the row count grows and shrinks in the same gesture.
	/// </summary>
	[AvaloniaTest]
	public void Lazy_Loading_Under_A_Scrolled_Viewport_Keeps_Every_Row_Resolvable()
	{
		var lazy = Enumerable.Range(0, 100).Select(i => new LazyNode($"l{i}", 7)).ToArray();
		var root = new TestNode("root");
		foreach (var node in lazy)
			root.Children.Add(node);
		var tree = new SharpTreeView { ShowRoot = false, Root = root };
		var window = new Window { Content = tree, Width = 300, Height = 400 };
		window.Show();
		Dispatcher.UIThread.RunJobs();

		AssertEveryRowResolves(tree, root, "the initial collapsed list");

		tree.ScrollIntoView(tree.ItemCount - 1);
		AssertEveryRowResolves(tree, root, "scrolling to the last row");

		foreach (var node in lazy)
		{
			node.IsExpanded = true;
			AssertEveryRowResolves(tree, root, $"lazily expanding {node.Text}");
		}

		foreach (var node in lazy)
			node.ReloadChildren();
		AssertEveryRowResolves(tree, root, "reloading every lazy subtree in place");
	}

	sealed class LazyNode : SharpTreeNode
	{
		readonly string text;
		readonly int childCount;
		public LazyNode(string text, int childCount)
		{
			this.text = text;
			this.childCount = childCount;
			LazyLoading = true;
		}
		public override object Text => text;
		protected override void LoadChildren()
		{
			for (int i = 0; i < childCount; i++)
				Children.Add(new TestNode($"{text}_{i}"));
		}
	}

	[AvaloniaTest]
	public void Moving_An_Expanded_Node_Reorders_The_Rendered_Rows()
	{
		var (_, tree, root) = Host();
		var b = (TestNode)root.Children[1];
		b.IsExpanded = true;
		Dispatcher.UIThread.RunJobs();
		RenderedRows(tree).Should().Equal("A", "B", "B1", "C");

		// B carries B1 with it: the run [B, B1] moves past C.
		root.Children.Move(1, 2);
		Dispatcher.UIThread.RunJobs();

		RenderedRows(tree).Should().Equal("A", "C", "B", "B1");
	}

	/// <summary>Builds <paramref name="rootCount"/> top-level rows in a viewport too short to show
	/// them all, with one expandable node, so an expansion has somewhere to scroll.</summary>
	static (Window window, SharpTreeView tree, ScrollViewer scrollViewer, TestNode[] nodes) ShortViewport(
		int rootCount, int expandableIndex, int childCount)
	{
		var nodes = Enumerable.Range(0, rootCount)
			.Select(i => i == expandableIndex
				? new TestNode($"N{i}", Enumerable.Range(0, childCount)
					.Select(c => new TestNode($"N{i}.{c}")).ToArray())
				: new TestNode($"N{i}"))
			.ToArray();
		var root = new TestNode("root", nodes);
		var tree = new SharpTreeView { ShowRoot = false, Root = root };
		var window = new Window { Content = tree, Width = 300, Height = 180 };
		window.Show();
		Dispatcher.UIThread.RunJobs();
		return (window, tree, tree.GetVisualDescendants().OfType<ScrollViewer>().First(), nodes);
	}

	/// <summary>Expands a node the way a user does, with Right on its focused row.</summary>
	static void PressRightOn(Window window, SharpTreeView tree, SharpTreeNode node)
	{
		tree.SelectedItem = node;
		Dispatcher.UIThread.RunJobs();
		tree.ContainerFromItem(node)?.Focus();
		Dispatcher.UIThread.RunJobs();
		window.KeyPress(Key.Right, RawInputModifiers.None, PhysicalKey.ArrowRight, null);
		Dispatcher.UIThread.RunJobs();
	}

	[AvaloniaTest]
	public void Expanding_A_Node_Scrolls_Children_That_Do_Not_Fit_Into_View()
	{
		var (window, tree, scrollViewer, nodes) = ShortViewport(rootCount: 15, expandableIndex: 5, childCount: 5);
		var parent = nodes[5];
		scrollViewer.Offset.Y.Should().Be(0, "nothing has moved the viewport yet");

		PressRightOn(window, tree, parent);

		tree.IsNodeFullyVisible(parent.Children[^1])
			.Should().BeTrue("the expansion reveals children below the viewport, so the view scrolls to show them");
		tree.IsNodeFullyVisible(parent)
			.Should().BeTrue("the scroll is bounded by the expanded node: it never leaves the viewport");
	}

	[AvaloniaTest]
	public void Expanding_A_Node_Whose_Children_Already_Fit_Leaves_The_Viewport_Alone()
	{
		var (window, tree, scrollViewer, nodes) = ShortViewport(rootCount: 15, expandableIndex: 1, childCount: 2);
		var parent = nodes[1];

		PressRightOn(window, tree, parent);

		scrollViewer.Offset.Y.Should().Be(0, "the children fit below the node, so there is nothing to scroll to");
		tree.IsNodeFullyVisible(parent.Children[^1]).Should().BeTrue();
	}

	[AvaloniaTest]
	public void Expanding_A_Node_With_More_Children_Than_Fit_Keeps_The_Node_Visible()
	{
		var (window, tree, _, nodes) = ShortViewport(rootCount: 15, expandableIndex: 5, childCount: 30);
		var parent = nodes[5];

		PressRightOn(window, tree, parent);

		tree.IsNodeFullyVisible(parent)
			.Should().BeTrue("showing every child would push the node off the top, so the scroll stops at the node");
		tree.IsNodeFullyVisible(parent.Children[0])
			.Should().BeTrue("as many children as fit are shown below it");
	}

	[AvaloniaTest]
	public async Task Clicking_The_Expander_Scrolls_The_Children_Into_View()
	{
		// The mouse path never passes through SharpTreeView: the row template's toggle writes
		// IsExpanded straight to the node, so the reveal hangs off the toggle's Click.
		var (window, tree, _, nodes) = ShortViewport(rootCount: 15, expandableIndex: 5, childCount: 5);
		var parent = nodes[5];

		await window.ClickAsync(() => tree.ContainerFromItem(parent)?.GetVisualDescendants()
			.OfType<ToggleButton>().FirstOrDefault(b => b.Name == "PART_Expander"));
		Dispatcher.UIThread.RunJobs();

		parent.IsExpanded.Should().BeTrue("precondition: the click toggled the node open");
		tree.IsNodeFullyVisible(parent.Children[^1])
			.Should().BeTrue("a click on the expander reveals the children, just as the keyboard does");
	}

	[AvaloniaTest]
	public void Expanding_A_Node_In_Code_Does_Not_Move_The_Viewport()
	{
		// Revealing a node expands its ancestors first (ScrollIntoNodeView, TreeSelectionBinder)
		// and positions the viewport itself afterwards; a scroll per ancestor would fight that.
		var (_, _, scrollViewer, nodes) = ShortViewport(rootCount: 15, expandableIndex: 5, childCount: 5);

		nodes[5].IsExpanded = true;
		Dispatcher.UIThread.RunJobs();

		scrollViewer.Offset.Y.Should().Be(0, "only a user gesture reveals the children");
	}

	static List<string> RenderedRows(SharpTreeView tree)
	{
		var rows = new List<string>();
		for (int i = 0; i < tree.ItemCount; i++)
		{
			var container = tree.ContainerFromIndex(i);
			rows.Add((container?.DataContext as SharpTreeNode)?.Text?.ToString() ?? "<unrealized>");
		}
		return rows;
	}
}