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

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);
    }

    [Fact]
    public void GraphicalKindSet_RegistersRenderPackAndWithdrawsBeforeUnload()
    {
        using var temporary = new TemporaryDirectory();
        InstallFixture(
            temporary.Path,
            "render",
            "acdream.test.render",
            [PluginKind.RenderPack]);
        var statuses = new List<PluginSessionStatus>();
        var registry = new RecordingRenderPackRegistry();
        var plugins = new PluginSession(
            new StubHost(),
            statuses.Add,
            registry,
            [PluginKind.Gameplay, PluginKind.RenderPack]);

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

        Assert.Equal(1, plugins.LoadedCount);
        Assert.Equal(1, registry.ActiveCount);
        Assert.Equal("acdream.test.noop-pack", registry.Descriptor?.Id);
        IReadOnlyList<WeakReference> contexts =
            plugins.CaptureLoadContextWeakReferences();
        plugins.Dispose();
        Assert.Equal(0, registry.ActiveCount);
        Collect(contexts);
    }

    [Fact]
    public void GameplayOnlyHost_SkipsUnrequestedRenderPackBeforeDllProbe()
    {
        using var temporary = new TemporaryDirectory();
        InstallBroken(
            temporary.Path,
            "render",
            "acdream.test.render",
            [PluginKind.RenderPack]);
        var statuses = new List<PluginSessionStatus>();
        using var plugins = new PluginSession(new StubHost(), statuses.Add);

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

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

    [Fact]
    public void RenderPackRegisterFailure_WithdrawsPartialRegistrationBeforeUnload()
    {
        using var temporary = new TemporaryDirectory();
        InstallFixture(
            temporary.Path,
            "render",
            "acdream.test.render",
            [PluginKind.RenderPack]);
        File.WriteAllText(
            Path.Combine(temporary.Path, "render", "throw-after-render-register"),
            string.Empty);
        var registry = new RecordingRenderPackRegistry();
        var statuses = new List<PluginSessionStatus>();
        var plugins = new PluginSession(
            new StubHost(),
            statuses.Add,
            registry,
            [PluginKind.Gameplay, PluginKind.RenderPack]);

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

        Assert.Equal(0, plugins.LoadedCount);
        Assert.Equal(0, registry.ActiveCount);
        PluginSessionStatus status = Assert.Single(statuses);
        Assert.Equal(PluginSessionStatusKind.Failed, status.Kind);
        Assert.Contains("failed after publishing", status.Error);
        IReadOnlyList<WeakReference> contexts =
            plugins.CaptureLoadContextWeakReferences();
        plugins.Dispose();
        Collect(contexts);
    }

    [Fact]
    public void GameplayOnlyHost_ExplicitRenderPackReportsKindWithoutDllProbe()
    {
        using var temporary = new TemporaryDirectory();
        InstallBroken(
            temporary.Path,
            "render",
            "acdream.test.render",
            [PluginKind.RenderPack]);
        var statuses = new List<PluginSessionStatus>();
        using var plugins = new PluginSession(new StubHost(), statuses.Add);

        plugins.Start([temporary.Path], ["acdream.test.render"]);

        PluginSessionStatus status = Assert.Single(statuses);
        Assert.Equal(PluginSessionStatusKind.Failed, status.Kind);
        Assert.Contains("does not support", status.Error);
        Assert.DoesNotContain("entry dll", status.Error);
        Assert.Empty(plugins.CaptureLoadContextWeakReferences());
    }

    private static void ReleaseAndCollect(PluginSession plugins)
    {
        IReadOnlyList<WeakReference> contexts =
            plugins.CaptureLoadContextWeakReferences();
        plugins.Dispose();
        Collect(contexts);
    }

    private static void Collect(IReadOnlyList<WeakReference> contexts)
    {
        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)
        => InstallFixture(root, folder, id, kinds: null);

    private static void InstallFixture(
        string root,
        string folder,
        string id,
        IReadOnlyList<PluginKind>? kinds)
    {
        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, kinds);
    }

    private static void InstallBroken(
        string root,
        string folder,
        string id,
        IReadOnlyList<PluginKind>? kinds = null)
    {
        string pluginDirectory = Path.Combine(root, folder);
        Directory.CreateDirectory(pluginDirectory);
        WriteManifest(pluginDirectory, id, "missing.dll", kinds);
    }

    private static void WriteManifest(
        string directory,
        string id,
        string entryDll,
        IReadOnlyList<PluginKind>? kinds = null) =>
        File.WriteAllText(
            Path.Combine(directory, "plugin.json"),
            JsonSerializer.Serialize(new
            {
                id,
                displayName = id,
                version = "1.0.0",
                entryDll,
                apiVersion = 1,
                kinds = kinds?.Select(static kind => kind.ToString()),
            }));

    private sealed class RecordingRenderPackRegistry : IRenderPackRegistry
    {
        private readonly List<Registration> _registrations = [];

        internal int ActiveCount => _registrations.Count;
        internal RenderPackDescriptor? Descriptor { get; private set; }

        public IDisposable Register(
            RenderPackDescriptor descriptor,
            IRenderPackAssets assets)
        {
            Descriptor = descriptor;
            var registration = new Registration(this, assets);
            _registrations.Add(registration);
            return registration;
        }

        private void Remove(Registration registration) =>
            _registrations.Remove(registration);

        private sealed class Registration(
            RecordingRenderPackRegistry owner,
            IRenderPackAssets assets) : IDisposable
        {
            private RecordingRenderPackRegistry? _owner = owner;
            private IRenderPackAssets? _assets = assets;

            public void Dispose()
            {
                RecordingRenderPackRegistry? current =
                    Interlocked.Exchange(ref _owner, null);
                _assets = null;
                current?.Remove(this);
            }
        }
    }

    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;
        public IAutomationSurface Automation => NoOpAutomationSurface.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 { }
        }

        public event Action<double> Tick
        {
            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);
        }
    }
}