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using System.Linq;
using System.Threading.Tasks;

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

using AwesomeAssertions;

using ICSharpCode.ILSpy;
using ICSharpCode.ILSpy.AppEnv;
using ICSharpCode.ILSpy.Languages;

using NUnit.Framework;

namespace ICSharpCode.ILSpy.Tests;

[TestFixture]
public class LanguageVersionPersistenceTests
{
	[AvaloniaTest]
	public async Task Switching_Away_From_And_Back_To_A_Versioned_Language_Restores_The_Version()
	{
		// Regression: selecting C# x.y, switching to a language with no versions (IL), then back to
		// C# must restore x.y in the version combo. The toolbar's version ComboBox is bound TwoWay
		// to LanguageService.CurrentVersion; when the language flips, its ItemsSource swaps to the
		// new (empty) language first and writes a null selection back, so the outgoing version has
		// to be stashed before that happens or the restore reads back null.
		var (window, _) = await TestHarness.BootAsync();
		var toolbar = await window.WaitForComponent<MainToolBar>();

		var languageCombo = toolbar.GetVisualDescendants().OfType<ComboBox>()
			.Single(c => c.Name == "LanguageComboBox");
		var versionCombo = toolbar.GetVisualDescendants().OfType<ComboBox>()
			.Single(c => c.Name == "LanguageVersionComboBox");

		var languageService = AppComposition.Current.GetExport<LanguageService>();
		var csharp = languageService.Languages.Single(l => l.Name == "C#");
		var noVersionLanguage = languageService.Languages.First(l => !l.HasLanguageVersions);

		// Start on C# and pick a version that is NOT the default latest, so a reset is detectable.
		languageCombo.SelectedItem = csharp;
		Dispatcher.UIThread.RunJobs();
		var chosen = csharp.LanguageVersions.First();
		chosen.Should().NotBe(csharp.LanguageVersions.Last(), "the test needs a non-default version");
		versionCombo.SelectedItem = chosen;
		Dispatcher.UIThread.RunJobs();
		languageService.CurrentVersion.Should().Be(chosen);

		// Flip to a language with no versions, then back to C#.
		languageCombo.SelectedItem = noVersionLanguage;
		Dispatcher.UIThread.RunJobs();
		languageCombo.SelectedItem = csharp;
		Dispatcher.UIThread.RunJobs();

		languageService.CurrentVersion.Should().Be(chosen,
			"switching away from C# and back must restore the previously selected C# version");
		versionCombo.SelectedItem.Should().Be(chosen,
			"the version ComboBox must reflect the restored version");
	}
}