using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Runtime;

namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests.Runtime;

/// <summary>
///     Review 2026-10-21 G-3: <see cref="ReconnectSupervisor.ReportTransportFailure"/> allocated a
///     new <see cref="CancellationTokenSource"/> per recovery cycle and only the last one was ever
///     disposed. Each cycle now releases its own CTS when its loop exits, and
///     <see cref="ReconnectSupervisor.StopAsync"/> awaits the loop instead of blocking on it.
/// </summary>
public sealed class ReconnectSupervisorCycleCtsTests
{
    private const int WaitMs = 10_000;

    private static ReconnectOptions FastBackoff() =>
        new(InitialBackoffOverride: TimeSpan.FromMilliseconds(5), MaxBackoffOverride: TimeSpan.FromMilliseconds(20));

    /// <summary>Three completed cycles ⇒ three released CTSs; the in-flight one is not released early (positive control).</summary>
    [Fact]
    public async Task Every_completed_recovery_cycle_releases_its_own_cts()
    {
        var holdReopen = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
        var reopenEntered = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
        var hold = new[] { false }; // read on the recovery loop's thread, written here — Volatile both ways
        using var sup = new ReconnectSupervisor(
            reopen: async _ =>
            {
                if (Volatile.Read(ref hold[0]))
                {
                    reopenEntered.TrySetResult();
                    await holdReopen.Task;
                }
            },
            replay: _ => Task.CompletedTask,
            options: FastBackoff());

        for (var i = 0; i < 3; i++)
        {
            sup.ReportTransportFailure(new IOException($"drop {i}"));
            await sup.WaitForHealthyAsync(new CancellationTokenSource(WaitMs).Token);
        }
        await WaitUntilAsync(() => sup.CyclesReleased == 3, "each completed cycle must release its CTS");
        sup.CyclesStarted.ShouldBe(3);

        // Positive control: a cycle parked inside reopen still holds its CTS.
        Volatile.Write(ref hold[0], true);
        sup.ReportTransportFailure(new IOException("drop 3"));
        (await Task.WhenAny(reopenEntered.Task, Task.Delay(WaitMs))).ShouldBe(reopenEntered.Task);
        sup.CyclesStarted.ShouldBe(4);
        sup.CyclesReleased.ShouldBe(3, "an in-flight cycle's CTS is live until its loop exits");

        holdReopen.TrySetResult();
        await sup.WaitForHealthyAsync(new CancellationTokenSource(WaitMs).Token);
        await WaitUntilAsync(() => sup.CyclesReleased == 4, "the fourth cycle must release its CTS on exit");
    }

    /// <summary>StopAsync cancels a parked cycle, awaits its exit and releases its CTS without blocking.</summary>
    [Fact]
    public async Task StopAsync_cancels_the_in_flight_cycle_and_releases_its_cts()
    {
        var reopenEntered = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
        var sup = new ReconnectSupervisor(
            reopen: async ct =>
            {
                reopenEntered.TrySetResult();
                await Task.Delay(Timeout.Infinite, ct);
            },
            replay: _ => Task.CompletedTask,
            options: FastBackoff());

        sup.ReportTransportFailure(new IOException("drop"));
        (await Task.WhenAny(reopenEntered.Task, Task.Delay(WaitMs))).ShouldBe(reopenEntered.Task);

        var stop = sup.StopAsync();
        (await Task.WhenAny(stop, Task.Delay(WaitMs))).ShouldBe(stop, "StopAsync must cancel the parked reopen and return");
        sup.CyclesReleased.ShouldBe(1);
        await Should.NotThrowAsync(sup.StopAsync); // idempotent
        Should.NotThrow(sup.Dispose);
    }

    private static async Task WaitUntilAsync(Func<bool> condition, string because)
    {
        var deadline = DateTime.UtcNow.AddMilliseconds(WaitMs);
        while (!condition())
        {
            if (DateTime.UtcNow > deadline) throw new ShouldAssertException(because);
            await Task.Delay(10);
        }
    }
}