using System.Reflection;
using System.Security.Claims;
using Bunit;
using Microsoft.AspNetCore.Components.Authorization;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using NSubstitute;
using ZB.MOM.WW.ScadaBridge.CentralUI.Auth;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Sites;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
using ZB.MOM.WW.ScadaBridge.Commons.Messages.DebugView;
using ZB.MOM.WW.ScadaBridge.Commons.Messages.Streaming;
using ZB.MOM.WW.ScadaBridge.Communication;
using ZB.MOM.WW.ScadaBridge.Communication.Grpc;
using DebugViewPage = ZB.MOM.WW.ScadaBridge.CentralUI.Components.Pages.Deployment.DebugView;

namespace ZB.MOM.WW.ScadaBridge.CentralUI.Tests.Deployment;

/// <summary>
/// Regression tests for arch-review 2026-08-19 P6-6. <c>Connect()</c> awaits
/// <c>StartStreamAsync</c> — which can take up to 30s — and then publishes the result into
/// <c>_session</c>. If the circuit was torn down inside that window, <c>Dispose()</c> had
/// already run, found <c>_session</c> still null and stopped nothing, so the just-created
/// session stayed registered in the singleton <see cref="DebugStreamService"/>. Its
/// keepalive renews registered sessions forever (the orphan reaper only collects
/// UNregistered ones), so the site subscription, the bridge actor and the dead circuit's
/// object graph were pinned until process restart. The fix publishes the session and
/// re-checks disposal under one lock, so exactly one side tears the session down.
/// </summary>
public class DebugViewConnectDisposeRaceTests : BunitContext
{
    /// <summary>
    /// A <see cref="DebugStreamService"/> whose start can be held open on demand, so the
    /// dispose-during-start window is deterministic rather than timing-dependent.
    /// </summary>
    private sealed class GatedDebugStreamService : DebugStreamService
    {
        private readonly TaskCompletionSource _gate = new(TaskCreationOptions.RunContinuationsAsynchronously);
        private readonly TaskCompletionSource _entered = new(TaskCreationOptions.RunContinuationsAsynchronously);
        private readonly List<string> _stopped = new();

        public GatedDebugStreamService(
            CommunicationService comms, IServiceProvider provider, SiteStreamGrpcClientFactory factory)
            : base(comms, provider, factory, NullLogger<DebugStreamService>.Instance)
        {
        }

        public string SessionId => "session-under-test";

        /// <summary>Completes once <see cref="StartStreamAsync"/> has been entered.</summary>
        public Task Entered => _entered.Task;

        /// <summary>Session ids passed to <see cref="StopStream"/>, in call order.</summary>
        public IReadOnlyList<string> Stopped
        {
            get { lock (_stopped) { return _stopped.ToList(); } }
        }

        public void ReleaseStart() => _gate.TrySetResult();

        public override async Task<DebugStreamSession> StartStreamAsync(
            int instanceId, Action<object> onEvent, Action onTerminated, CancellationToken ct = default)
        {
            _entered.TrySetResult();
            await _gate.Task;
            return new DebugStreamSession(
                SessionId,
                new DebugViewSnapshot(
                    "Inst-1",
                    Array.Empty<AttributeValueChanged>(),
                    Array.Empty<AlarmStateChanged>(),
                    DateTimeOffset.UtcNow));
        }

        public override void StopStream(string sessionId)
        {
            lock (_stopped) { _stopped.Add(sessionId); }
        }
    }

    private sealed class StubAuthStateProvider : AuthenticationStateProvider
    {
        private readonly AuthenticationState _state;
        public StubAuthStateProvider(AuthenticationState state) => _state = state;
        public override Task<AuthenticationState> GetAuthenticationStateAsync()
            => Task.FromResult(_state);
    }

    private (IRenderedComponent<DebugViewPage> Cut, GatedDebugStreamService Stream) RenderPage()
    {
        JSInterop.Mode = JSRuntimeMode.Loose;

        var repo = Substitute.For<ITemplateEngineRepository>();
        var siteRepo = Substitute.For<ISiteRepository>();
        siteRepo.GetAllSitesAsync().Returns(new List<Site>());
        Services.AddSingleton(repo);
        Services.AddSingleton(siteRepo);

        var comms = new CommunicationService(
            Options.Create(new CommunicationOptions()),
            NullLogger<CommunicationService>.Instance);
        Services.AddSingleton(comms);

        // An empty throwaway provider — the gated stub never calls into the base start
        // path, so nothing is resolved from it.
        var stream = new GatedDebugStreamService(
            comms,
            new ServiceCollection().BuildServiceProvider(),
            new SiteStreamGrpcClientFactory(NullLoggerFactory.Instance));
        Services.AddSingleton<DebugStreamService>(stream);

        var identity = new ClaimsIdentity(
            new[] { new Claim(ClaimTypes.Name, "deployer") }, "TestCookie");
        var stubAuth = new StubAuthStateProvider(
            new AuthenticationState(new ClaimsPrincipal(identity)));
        Services.AddSingleton<AuthenticationStateProvider>(stubAuth);
        Services.AddScoped(_ => new SiteScopeService(stubAuth));

        return (Render<DebugViewPage>(), stream);
    }

    private static void SetField(DebugViewPage page, string name, object value) =>
        typeof(DebugViewPage).GetField(name, BindingFlags.Instance | BindingFlags.NonPublic)!
            .SetValue(page, value);

    private static object? GetField(DebugViewPage page, string name) =>
        typeof(DebugViewPage).GetField(name, BindingFlags.Instance | BindingFlags.NonPublic)!
            .GetValue(page);

    /// <summary>
    /// Starts <c>Connect()</c> on the renderer's dispatcher (where it really runs) and hands
    /// back its task without awaiting it, so the test can act inside the start window.
    /// </summary>
    private static async Task<Task> StartConnectAsync(IRenderedComponent<DebugViewPage> cut)
    {
        var connect = typeof(DebugViewPage).GetMethod(
            "Connect", BindingFlags.Instance | BindingFlags.NonPublic)!;
        Task? task = null;
        await cut.InvokeAsync(() => { task = (Task)connect.Invoke(cut.Instance, null)!; });
        return task!;
    }

    [Fact]
    public async Task Connect_DisposedMidStart_StopsTheJustCreatedSession()
    {
        var (cut, stream) = RenderPage();
        SetField(cut.Instance, "_selectedSiteId", 1);
        SetField(cut.Instance, "_selectedInstanceId", 7);

        var connect = await StartConnectAsync(cut);
        await stream.Entered.WaitAsync(TimeSpan.FromSeconds(5));

        // The user navigates away while the start is still in flight. Dispose runs off the
        // renderer's thread, exactly as a circuit teardown can.
        cut.Instance.Dispose();

        stream.ReleaseStart();
        await connect.WaitAsync(TimeSpan.FromSeconds(10));

        Assert.Equal(new[] { stream.SessionId }, stream.Stopped);
        Assert.Null(GetField(cut.Instance, "_session"));
    }

    [Fact]
    public async Task Connect_ThenDispose_StopsTheSessionExactlyOnce()
    {
        var (cut, stream) = RenderPage();
        SetField(cut.Instance, "_selectedSiteId", 1);
        SetField(cut.Instance, "_selectedInstanceId", 7);

        // Normal path: the start completes while the component is very much alive.
        stream.ReleaseStart();
        var connect = await StartConnectAsync(cut);
        await connect.WaitAsync(TimeSpan.FromSeconds(10));

        Assert.Empty(stream.Stopped);
        Assert.NotNull(GetField(cut.Instance, "_session"));

        cut.Instance.Dispose();
        Assert.Equal(new[] { stream.SessionId }, stream.Stopped);

        // A second Dispose (bUnit tears the component down again at test end) must not
        // stop an already-released session a second time.
        cut.Instance.Dispose();
        Assert.Equal(new[] { stream.SessionId }, stream.Stopped);
    }

    [Fact]
    public async Task Disconnect_AfterConnect_StopsTheSessionOnceAndClearsTheSlot()
    {
        var (cut, stream) = RenderPage();
        SetField(cut.Instance, "_selectedSiteId", 1);
        SetField(cut.Instance, "_selectedInstanceId", 7);

        stream.ReleaseStart();
        var connect = await StartConnectAsync(cut);
        await connect.WaitAsync(TimeSpan.FromSeconds(10));

        var disconnect = typeof(DebugViewPage).GetMethod(
            "Disconnect", BindingFlags.Instance | BindingFlags.NonPublic)!;
        await cut.InvokeAsync(() => (Task)disconnect.Invoke(cut.Instance, null)!);

        Assert.Equal(new[] { stream.SessionId }, stream.Stopped);
        Assert.Null(GetField(cut.Instance, "_session"));

        // Dispose after an explicit disconnect has nothing left to stop.
        cut.Instance.Dispose();
        Assert.Equal(new[] { stream.SessionId }, stream.Stopped);
    }
}