using System.Text.Json;
using AcDream.Core.Plugins;
using AcDream.Core.Selection;
using AcDream.Plugin.Abstractions;

namespace AcDream.Core.Tests.Plugins;

public sealed class PluginSessionTests
{
    [Fact]
    public void AbsentAllowListLoadsEveryDiscoveredPlugin()
    {
        using var temporary = new TemporaryDirectory();
        InstallFixture(temporary.Path, "alpha", "acdream.test.alpha");
        InstallFixture(temporary.Path, "beta", "acdream.test.beta");
        var statuses = new List<PluginSessionStatus>();
        var plugins = new PluginSession(new StubHost(), statuses.Add);

        plugins.Start([temporary.Path], allowList: null);

        Assert.Equal(2, plugins.LoadedCount);
        Assert.Equal(
            ["acdream.test.alpha", "acdream.test.beta"],
            plugins.LoadedPluginIds);
        Assert.All(
            statuses,
            status => Assert.Equal(PluginSessionStatusKind.Loaded, status.Kind));
        ReleaseAndCollect(plugins);
    }

    [Fact]
    public void AllowListIsCaseInsensitiveAndOneFailureDoesNotBlockAnotherPlugin()
    {
        using var temporary = new TemporaryDirectory();
        InstallFixture(temporary.Path, "good", "acdream.test.good");
        InstallBroken(temporary.Path, "broken", "acdream.test.broken");
        var statuses = new List<PluginSessionStatus>();
        var plugins = new PluginSession(new StubHost(), statuses.Add);

        plugins.Start(
            [temporary.Path],
            [
                "ACDREAM.TEST.BROKEN",
                "ACDREAM.TEST.GOOD",
                "acdream.test.missing",
            ]);

        Assert.Equal(["acdream.test.good"], plugins.LoadedPluginIds);
        Assert.Equal(
            [
                ("ACDREAM.TEST.BROKEN", PluginSessionStatusKind.Failed),
                ("acdream.test.good", PluginSessionStatusKind.Loaded),
                ("acdream.test.missing", PluginSessionStatusKind.Failed),
            ],
            statuses.Select(static status => (status.Plugin, status.Kind)));
        Assert.All(
            statuses.Where(static status => status.Kind == PluginSessionStatusKind.Failed),
            status => Assert.False(string.IsNullOrWhiteSpace(status.Error)));
        ReleaseAndCollect(plugins);
    }

    [Fact]
    public void ExplicitEmptyAllowListLoadsNothing()
    {
        using var temporary = new TemporaryDirectory();
        InstallFixture(temporary.Path, "fixture", "acdream.test.fixture");
        var statuses = new List<PluginSessionStatus>();
        using var plugins = new PluginSession(new StubHost(), statuses.Add);

        plugins.Start([temporary.Path], []);

        Assert.Equal(0, plugins.LoadedCount);
        Assert.Empty(statuses);
    }

    private static void ReleaseAndCollect(PluginSession plugins)
    {
        IReadOnlyList<WeakReference> contexts =
            plugins.CaptureLoadContextWeakReferences();
        plugins.Dispose();
        for (int attempt = 0;
             attempt < 10 && contexts.Any(static context => context.IsAlive);
             attempt++)
        {
            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();
        }
        Assert.All(contexts, static context => Assert.False(context.IsAlive));
    }

    private static void InstallFixture(string root, string folder, string id)
    {
        string source = FixturePluginPath();
        Assert.True(File.Exists(source), $"fixture DLL not found: {source}");
        string pluginDirectory = Path.Combine(root, folder);
        Directory.CreateDirectory(pluginDirectory);
        string fileName = Path.GetFileName(source);
        File.Copy(source, Path.Combine(pluginDirectory, fileName));
        WriteManifest(pluginDirectory, id, fileName);
    }

    private static void InstallBroken(string root, string folder, string id)
    {
        string pluginDirectory = Path.Combine(root, folder);
        Directory.CreateDirectory(pluginDirectory);
        WriteManifest(pluginDirectory, id, "missing.dll");
    }

    private static void WriteManifest(
        string directory,
        string id,
        string entryDll) =>
        File.WriteAllText(
            Path.Combine(directory, "plugin.json"),
            JsonSerializer.Serialize(new
            {
                id,
                displayName = id,
                version = "1.0.0",
                entryDll,
                apiVersion = 1,
            }));

    private static string FixturePluginPath()
    {
        string configuration = new DirectoryInfo(AppContext.BaseDirectory)
            .Parent!.Name;
        string root = FindRepoRoot(AppContext.BaseDirectory);
        return Path.Combine(
            root,
            "tests",
            "AcDream.Core.Tests.Fixtures.HelloPlugin",
            "bin",
            configuration,
            "net10.0",
            "AcDream.Core.Tests.Fixtures.HelloPlugin.dll");
    }

    private static string FindRepoRoot(string start)
    {
        DirectoryInfo? directory = new(start);
        while (directory is not null
            && !File.Exists(Path.Combine(directory.FullName, "AcDream.slnx")))
        {
            directory = directory.Parent;
        }
        return directory?.FullName
            ?? throw new InvalidOperationException("Repository root not found.");
    }

    private sealed class StubHost : IPluginHost
    {
        public bool HasUi => false;
        public IPluginLogger Log { get; } = new StubLogger();
        public IGameState State { get; } = new StubState();
        public IEvents Events { get; } = new StubEvents();
        public ISelectionService Selection { get; } = new SelectionState();
        public IUiRegistry Ui => NoOpUiRegistry.Instance;
    }

    private sealed class StubLogger : IPluginLogger
    {
        public void Info(string message) { }
        public void Warn(string message) { }
        public void Error(string message, Exception? exception = null) { }
    }

    private sealed class StubState : IGameState
    {
        public IReadOnlyList<WorldEntitySnapshot> Entities => [];
    }

    private sealed class StubEvents : IEvents
    {
        public event Action<WorldEntitySnapshot> EntitySpawned
        {
            add { }
            remove { }
        }
    }

    private sealed class TemporaryDirectory : IDisposable
    {
        internal TemporaryDirectory()
        {
            Path = System.IO.Path.Combine(
                System.IO.Path.GetTempPath(),
                $"acdream-plugin-session-{Guid.NewGuid():N}");
            Directory.CreateDirectory(Path);
        }

        internal string Path { get; }

        public void Dispose()
        {
            if (Directory.Exists(Path))
                Directory.Delete(Path, recursive: true);
        }
    }
}