using System.IO;
using System.Reflection;
using Xunit;

namespace Recordingtest.Architecture.Tests;

/// <summary>
/// Enforces the 3-tier separation rule from CLAUDE.md §8.1:
///
///   Generic   → no SUT assembly references at all
///   HmEG-aware → HmEG.dll only, no per-app assembly
///   App-specific → anything (not checked here; not referenced by this project)
///
/// These tests walk <see cref="Assembly.GetReferencedAssemblies"/> on each
/// compiled output and fail if a forbidden reference appears. The test
/// project itself does NOT reference any Sut/* project, so a physical build
/// error would catch accidental upward references even before these tests
/// run — this file is the explicit contract.
/// </summary>
public class DependencyGraphTests
{
    private static readonly string[] ForbiddenAppAssemblies =
    {
        "Editor03.PluginInterface",
        "Editor02.HmEGAppManager",
        "EditorCore",
    };

    private const string HmegAssembly = "HmEG";

    private static readonly string[] GenericAssemblies =
    {
        "Recordingtest.Bridge.Abstractions",
        "Recordingtest.Recorder",
        "Recordingtest.Player",
        "Recordingtest.Normalizer",
        "Recordingtest.DiffReporter",
        "Recordingtest.Runner",
        "Recordingtest.SutProber",
    };

    private static readonly string[] HmegAwareAssemblies =
    {
        "Recordingtest.Hmeg.Bridge",
        "Recordingtest.Hmeg.Catalog",
        "Recordingtest.Hmeg.Bridge.Client",
    };

    [Theory]
    [InlineData("Recordingtest.Bridge.Abstractions")]
    [InlineData("Recordingtest.Recorder")]
    [InlineData("Recordingtest.Player")]
    [InlineData("Recordingtest.Normalizer")]
    [InlineData("Recordingtest.DiffReporter")]
    [InlineData("Recordingtest.Runner")]
    [InlineData("Recordingtest.SutProber")]
    public void Generic_Tier_Does_Not_Reference_Hmeg_Or_AppAssemblies(string assemblyName)
    {
        var refs = LoadReferences(assemblyName);
        Assert.DoesNotContain(HmegAssembly, refs);
        foreach (var app in ForbiddenAppAssemblies)
        {
            Assert.DoesNotContain(app, refs);
        }
    }

    [Theory]
    [InlineData("Recordingtest.Hmeg.Bridge")]
    [InlineData("Recordingtest.Hmeg.Catalog")]
    [InlineData("Recordingtest.Hmeg.Bridge.Client")]
    public void HmegAware_Tier_Does_Not_Reference_AppAssemblies(string assemblyName)
    {
        var refs = LoadReferences(assemblyName);
        foreach (var app in ForbiddenAppAssemblies)
        {
            Assert.DoesNotContain(app, refs);
        }
    }

    [Fact]
    public void Hmeg_Bridge_References_HmEG_Dll()
    {
        // HmEG-aware tier is expected to reference HmEG.dll. This is the
        // positive check that pairs with the App-specific forbidden list.
        var refs = LoadReferences("Recordingtest.Hmeg.Bridge");
        Assert.Contains(HmegAssembly, refs);
    }

    private static IReadOnlySet<string> LoadReferences(string assemblyName)
    {
        // Locate the assembly via a type we know belongs to it. Each tier
        // member has at least one public type; we use GenericAssemblies/
        // HmegAwareAssemblies as lookups by name.
        Assembly? asm = null;
        foreach (var loaded in AppDomain.CurrentDomain.GetAssemblies())
        {
            if (loaded.GetName().Name == assemblyName)
            {
                asm = loaded;
                break;
            }
        }
        if (asm is null)
        {
            // Force-load by trying to resolve a type: the test project has a
            // ProjectReference to the target, so the binary is next to ours.
            var dir = Path.GetDirectoryName(typeof(DependencyGraphTests).Assembly.Location)!;
            var path = Path.Combine(dir, assemblyName + ".dll");
            asm = Assembly.LoadFrom(path);
        }
        return new HashSet<string>(
            asm.GetReferencedAssemblies().Select(n => n.Name ?? string.Empty),
            StringComparer.Ordinal);
    }
}