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

using Avalonia.Headless.NUnit;

using AwesomeAssertions;

using ICSharpCode.ILSpyX;

using ICSharpCode.ILSpy.AppEnv;

using NUnit.Framework;

namespace ICSharpCode.ILSpy.Tests;

/// <summary>
/// The target-framework override lets the user hint the TFM used to resolve an assembly's
/// references instead of the one detected from its TargetFrameworkAttribute. These tests pin
/// the load-bearing behaviour: the override wins over detection, survives the assembly-list
/// XML round-trip, defaults to null for assemblies persisted without it, and is carried across
/// a reload (which is how a runtime change re-resolves against the new framework).
/// </summary>
[TestFixture]
public class TargetFrameworkOverrideTests
{
	static AssemblyListManager Manager => AppComposition.Current.GetExport<SettingsService>().AssemblyListManager;

	[AvaloniaTest]
	public async Task Override_Wins_Over_Detected_Tfm_Even_After_Detection_Cached()
	{
		var list = Manager.CreateList("tfm-override-" + Guid.NewGuid().ToString("N"));
		var asm = list.OpenAssembly(FixtureAssembly.Emit("TfmOverrideFixture"));

		// Force detection to run and cache its result first, so the test also proves the override
		// takes precedence over an already-cached detected value.
		var detected = await asm.GetTargetFrameworkIdAsync();
		asm.TargetFrameworkIdOverride = ".NETFramework,Version=v4.7.2";

		(await asm.GetTargetFrameworkIdAsync()).Should().Be(".NETFramework,Version=v4.7.2");
		detected.Should().NotBe(".NETFramework,Version=v4.7.2",
			"the fixture is not a .NET Framework 4.7.2 assembly; the override is what changes the result");
	}

	[AvaloniaTest]
	public void Override_Survives_SaveAsXml_Roundtrip()
	{
		var list = Manager.CreateList("tfm-roundtrip-" + Guid.NewGuid().ToString("N"));
		var asm = list.OpenAssembly(FixtureAssembly.Emit("TfmRoundtripFixture"));
		asm.TargetFrameworkIdOverride = ".NETCoreApp,Version=v6.0";

		var reloaded = new AssemblyList(Manager, list.SaveAsXml());

		reloaded.GetAssemblies().Should().ContainSingle()
			.Which.TargetFrameworkIdOverride.Should().Be(".NETCoreApp,Version=v6.0");
	}

	[AvaloniaTest]
	public void Assembly_Without_Override_Persists_No_Attribute_And_Loads_Null()
	{
		var list = Manager.CreateList("tfm-noattr-" + Guid.NewGuid().ToString("N"));
		list.OpenAssembly(FixtureAssembly.Emit("TfmNoAttrFixture"));

		var xml = list.SaveAsXml();
		xml.Elements("Assembly").Should().OnlyContain(e => e.Attribute("TargetFramework") == null,
			"no attribute is written when there is no override (backward-compatible XML)");

		var reloaded = new AssemblyList(Manager, xml);
		reloaded.GetAssemblies().Should().ContainSingle()
			.Which.TargetFrameworkIdOverride.Should().BeNull();
	}

	[AvaloniaTest]
	[TestCase("")]
	[TestCase("   ")]
	public async Task Blank_Override_Normalizes_To_Null_And_Falls_Back_To_Detected(string blank)
	{
		var list = Manager.CreateList("tfm-blank-" + Guid.NewGuid().ToString("N"));
		var asm = list.OpenAssembly(FixtureAssembly.Emit("TfmBlankFixture"));
		var detected = await asm.GetTargetFrameworkIdAsync();

		// A blank/whitespace override must not suppress detection with an empty effective TFM.
		asm.TargetFrameworkIdOverride = blank;

		asm.TargetFrameworkIdOverride.Should().BeNull();
		(await asm.GetTargetFrameworkIdAsync()).Should().Be(detected);
	}

	[AvaloniaTest]
	public void Override_Is_Trimmed()
	{
		var list = Manager.CreateList("tfm-trim-" + Guid.NewGuid().ToString("N"));
		var asm = list.OpenAssembly(FixtureAssembly.Emit("TfmTrimFixture"));

		asm.TargetFrameworkIdOverride = "  .NETCoreApp,Version=v8.0  ";

		asm.TargetFrameworkIdOverride.Should().Be(".NETCoreApp,Version=v8.0");
	}

	[AvaloniaTest]
	public async Task Blank_TargetFramework_Attribute_In_Xml_Loads_As_Null()
	{
		// A hand-edited assembly-list XML may carry TargetFramework="". Loading it must behave
		// like no override at all, not pin the effective TFM to an empty string.
		var list = Manager.CreateList("tfm-blankxml-" + Guid.NewGuid().ToString("N"));
		var asm = list.OpenAssembly(FixtureAssembly.Emit("TfmBlankXmlFixture"));
		var xml = list.SaveAsXml();
		xml.Elements("Assembly").Single().SetAttributeValue("TargetFramework", "");

		var reloaded = new AssemblyList(Manager, xml);
		var loaded = reloaded.GetAssemblies().Should().ContainSingle().Subject;

		loaded.TargetFrameworkIdOverride.Should().BeNull();
		(await loaded.GetTargetFrameworkIdAsync()).Should().Be(await asm.GetTargetFrameworkIdAsync());
	}

	[AvaloniaTest]
	public void ReloadAssembly_Carries_Override_To_New_Instance()
	{
		var list = Manager.CreateList("tfm-reload-" + Guid.NewGuid().ToString("N"));
		var asm = list.OpenAssembly(FixtureAssembly.Emit("TfmReloadFixture"));
		asm.TargetFrameworkIdOverride = ".NETStandard,Version=v2.0";

		var reloaded = list.ReloadAssembly(asm);

		((object?)reloaded).Should().NotBeNull();
		reloaded!.Should().NotBeSameAs(asm);
		reloaded.TargetFrameworkIdOverride.Should().Be(".NETStandard,Version=v2.0");
	}
}