using System.Reflection;
using System.Security.Claims;
using Bunit;
using Microsoft.AspNetCore.Components.Authorization;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging.Abstractions;
using NSubstitute;
using ZB.MOM.WW.ScadaBridge.CentralUI.Auth;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Deployment;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
using ZB.MOM.WW.ScadaBridge.DeploymentManager;
using DeploymentsPage = ZB.MOM.WW.ScadaBridge.CentralUI.Components.Pages.Deployment.Deployments;

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

/// <summary>
/// Regression tests for deployment status push updates. Component-CentralUI "Real-Time Updates"
/// states deployment status transitions push to the UI immediately via SignalR
/// with no polling. The page previously ran a 10-second <c>Timer</c> that
/// reloaded every deployment record + instance map per tick. The fix removes
/// the timer and subscribes to <see cref="IDeploymentStatusNotifier"/>, which
/// <c>DeploymentService</c> raises on every deployment-record status write;
/// Blazor Server then pushes the re-render over its SignalR circuit.
///
/// <para>
/// The "did it reload?" assertions moved from <c>GetAllDeploymentRecordsAsync</c>
/// to <c>QueryDeploymentListPageAsync</c> when the page's read path went
/// server-paged (residual R3) — the push mechanism under test is unchanged, only
/// the query it drives.
/// </para>
/// </summary>
public class DeploymentsPushUpdateTests : BunitContext
{
    private IDeploymentManagerRepository _deployRepo = null!;
    private DeploymentStatusNotifier _notifier = null!;

    private void RegisterServices()
    {
        _deployRepo = Substitute.For<IDeploymentManagerRepository>();
        _notifier = new DeploymentStatusNotifier(NullLogger<DeploymentStatusNotifier>.Instance);

        _deployRepo.QueryDeploymentListPageAsync(
                Arg.Any<DeploymentListFilter>(), Arg.Any<int>(), Arg.Any<int>(), Arg.Any<CancellationToken>())
            .Returns(DeploymentListPage.Empty);
        _deployRepo.GetDeploymentStatusCountsAsync(
                Arg.Any<DeploymentListFilter>(), Arg.Any<CancellationToken>())
            .Returns(DeploymentStatusCounts.Empty);

        Services.AddSingleton(_deployRepo);
        Services.AddSingleton<IDeploymentStatusNotifier>(_notifier);

        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));
    }

    private sealed class StubAuthStateProvider : AuthenticationStateProvider
    {
        private readonly AuthenticationState _state;
        /// <summary>Initializes the provider with the authentication state it returns.</summary>
        /// <param name="state">The authentication state to return.</param>
        public StubAuthStateProvider(AuthenticationState state) => _state = state;
        /// <inheritdoc />
        public override Task<AuthenticationState> GetAuthenticationStateAsync()
            => Task.FromResult(_state);
    }

    /// <summary>Verifies that the Deployments page does not poll and has no refresh timer.</summary>
    [Fact]
    public void Deployments_DoesNotPoll_HasNoRefreshTimer()
    {
        // The 10-second polling Timer must be gone — push replaces polling.
        var timerField = typeof(DeploymentsPage).GetField(
            "_refreshTimer", BindingFlags.Instance | BindingFlags.NonPublic);

        Assert.Null(timerField);
    }

    /// <summary>Verifies that a deployment status change notification triggers a reload of the page.</summary>
    [Fact]
    public void Deployments_StatusChange_TriggersReload()
    {
        RegisterServices();
        var cut = Render<DeploymentsPage>();

        // Initial load: the paged query is issued once.
        _deployRepo.ClearReceivedCalls();

        // A deployment status write in DeploymentManager raises the notifier;
        // the page must reload in response (no polling timer involved).
        _notifier.NotifyStatusChanged(
            new DeploymentStatusChange("dep-1", 1, DeploymentStatus.Success));

        cut.WaitForAssertion(() =>
            _deployRepo.Received().QueryDeploymentListPageAsync(
                Arg.Any<DeploymentListFilter>(), Arg.Any<int>(), Arg.Any<int>(), Arg.Any<CancellationToken>()));
    }

    /// <summary>Verifies that disposing the page unsubscribes it from the status notifier.</summary>
    [Fact]
    public void Deployments_Dispose_UnsubscribesFromNotifier()
    {
        RegisterServices();
        var cut = Render<DeploymentsPage>();

        cut.Instance.Dispose();
        _deployRepo.ClearReceivedCalls();

        // After disposal, a status change must NOT touch the disposed component.
        _notifier.NotifyStatusChanged(
            new DeploymentStatusChange("dep-2", 1, DeploymentStatus.Failed));

        _deployRepo.DidNotReceive().QueryDeploymentListPageAsync(
            Arg.Any<DeploymentListFilter>(), Arg.Any<int>(), Arg.Any<int>(), Arg.Any<CancellationToken>());
    }

    /// <summary>
    /// Deferred-work register row 58: the notifier is a process SINGLETON that retains
    /// delegates targeting circuit-scoped components, so an un-detached handler leaks the
    /// whole component graph (and its circuit) for the process lifetime.
    /// <para>
    /// The sibling <see cref="Deployments_Dispose_UnsubscribesFromNotifier"/> pins the
    /// observable behaviour, but it is satisfied by the <c>_disposed</c> guard ALONE —
    /// delete the <c>-=</c> from <c>Dispose</c> and it still passes while the leak is
    /// wide open. This test pins the retention property structurally instead: the
    /// notifier's invocation list must actually shrink back to empty.
    /// </para>
    /// </summary>
    [Fact]
    public void Deployments_Dispose_ActuallyDetachesTheDelegate_NotJustGuardsIt()
    {
        RegisterServices();
        var cut = Render<DeploymentsPage>();

        Assert.Equal(1, SubscriberCount(_notifier));

        cut.Instance.Dispose();

        Assert.Equal(0, SubscriberCount(_notifier));
    }

    /// <summary>
    /// Reads the compiler-generated backing field of the field-like
    /// <c>StatusChanged</c> event and counts its invocation list. Reflection is the only
    /// way to observe retention — the notifier deliberately exposes no subscriber count,
    /// and a behavioural probe cannot distinguish "detached" from "attached but guarded".
    /// </summary>
    private static int SubscriberCount(DeploymentStatusNotifier notifier)
    {
        var field = typeof(DeploymentStatusNotifier).GetField(
            "StatusChanged", BindingFlags.Instance | BindingFlags.NonPublic);
        Assert.NotNull(field);

        var handlers = (Delegate?)field!.GetValue(notifier);
        return handlers?.GetInvocationList().Length ?? 0;
    }

    /// <summary>
    /// Deferred-work register row 58's TRIGGER, pinned: "a second page subscribes, or any
    /// subscriber lands without a matching <c>Dispose</c> unsubscribe". Row 58 is
    /// acceptable only while every subscriber detaches itself; a new page that subscribes
    /// and forgets is a silent circuit leak that no existing test would catch, because
    /// every other pin is written against the one known subscriber.
    /// <para>
    /// A source scan rather than reflection: the subscription is a <c>+=</c> operator
    /// inside a method body, which is not visible on the type's reflected surface.
    /// Mirrors the source-scan convention in <c>Commons.Tests/ArchitecturalConstraintTests</c>.
    /// </para>
    /// </summary>
    [Fact]
    public void EveryCentralUiSubscriberToTheNotifier_UnsubscribesAndIsDisposable()
    {
        var sourceDir = GetCentralUiSourceDirectory();
        var sourceFiles = Directory
            .GetFiles(sourceDir, "*.razor", SearchOption.AllDirectories)
            .Concat(Directory.GetFiles(sourceDir, "*.cs", SearchOption.AllDirectories))
            .Where(f => !f.Contains($"{Path.DirectorySeparatorChar}obj{Path.DirectorySeparatorChar}",
                            StringComparison.Ordinal)
                        && !f.Contains($"{Path.DirectorySeparatorChar}bin{Path.DirectorySeparatorChar}",
                            StringComparison.Ordinal));

        var subscribers = new List<string>();
        foreach (var file in sourceFiles)
        {
            var content = File.ReadAllText(file);
            if (!content.Contains("StatusChanged +=", StringComparison.Ordinal))
            {
                continue;
            }

            subscribers.Add(file);

            Assert.True(
                content.Contains("StatusChanged -=", StringComparison.Ordinal),
                $"{Path.GetFileName(file)} subscribes to IDeploymentStatusNotifier.StatusChanged but never "
                + "unsubscribes. The notifier is a singleton, so the delegate pins this circuit-scoped "
                + "component for the process lifetime (deferred-work register row 58).");

            Assert.True(
                content.Contains("IDisposable", StringComparison.Ordinal)
                || content.Contains("IAsyncDisposable", StringComparison.Ordinal),
                $"{Path.GetFileName(file)} subscribes to IDeploymentStatusNotifier.StatusChanged but does not "
                + "implement IDisposable/IAsyncDisposable, so its unsubscribe can never run.");
        }

        // Guard the guard: if the scan silently stops matching (file moved, API renamed)
        // the loop above would vacuously pass and the trigger would go unwatched.
        Assert.NotEmpty(subscribers);
    }

    /// <summary>Walks up from the test output directory to the CentralUI project source root.</summary>
    private static string GetCentralUiSourceDirectory()
    {
        var dir = new DirectoryInfo(AppContext.BaseDirectory);
        while (dir != null)
        {
            var candidate = Path.Combine(dir.FullName, "src", "ZB.MOM.WW.ScadaBridge.CentralUI");
            if (Directory.Exists(candidate))
            {
                return candidate;
            }

            dir = dir.Parent;
        }

        throw new InvalidOperationException("Could not locate the ZB.MOM.WW.ScadaBridge.CentralUI source directory.");
    }

    /// <summary>
    /// Regression test for the dispose race. The notifier is a process singleton:
    /// it can read its subscriber list and begin invoking
    /// <c>OnDeploymentStatusChanged</c> on the DeploymentManager thread an
    /// instant before the component is disposed. The handler must no-op against
    /// a disposed component rather than letting <c>InvokeAsync</c> throw an
    /// unobserved <see cref="ObjectDisposedException"/>.
    /// </summary>
    [Fact]
    public void Deployments_HasDisposalGuardField()
    {
        var field = typeof(DeploymentsPage).GetField(
            "_disposed", BindingFlags.Instance | BindingFlags.NonPublic);

        Assert.NotNull(field);
        Assert.Equal(typeof(bool), field!.FieldType);
    }

    /// <summary>Verifies that a status change delivered after disposal neither throws nor reloads the page.</summary>
    [Fact]
    public void Deployments_StatusChangeAfterDispose_DoesNotThrowOrReload()
    {
        RegisterServices();
        var cut = Render<DeploymentsPage>();
        var component = cut.Instance;

        component.Dispose();
        _deployRepo.ClearReceivedCalls();

        // Simulate the race: the notifier captured the handler before the
        // Dispose() unsubscribe and invokes it directly against the now-disposed
        // component. Pre-fix this dispatched InvokeAsync against a dead circuit
        // and threw ObjectDisposedException on a fire-and-forget task.
        var handler = typeof(DeploymentsPage).GetMethod(
            "OnDeploymentStatusChanged", BindingFlags.Instance | BindingFlags.NonPublic)!;

        var ex = Record.Exception(() => handler.Invoke(component,
            new object[] { new DeploymentStatusChange("dep-9", 1, DeploymentStatus.Success) }));

        Assert.Null(ex);
        // The guard short-circuits before any reload is attempted.
        _deployRepo.DidNotReceive().QueryDeploymentListPageAsync(
            Arg.Any<DeploymentListFilter>(), Arg.Any<int>(), Arg.Any<int>(), Arg.Any<CancellationToken>());
    }
}