using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.FOCAS;

namespace ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Tests;

/// <summary>
///     05/STAB-9 — the poll engine's <c>onError</c> sink must be wired to the driver health
///     surface: a poll-loop reader failure degrades health while preserving
///     <see cref="DriverHealth.LastSuccessfulRead"/>, and must never downgrade a pre-existing
///     <see cref="DriverState.Faulted"/>.
/// </summary>
[Trait("Category", "Unit")]
public sealed class FocasPollErrorHealthTests
{
    /// <summary>A poll reader failure degrades health, preserving the last successful read timestamp.</summary>
    [Fact]
    public async Task PollReaderFailure_DegradesHealth_PreservesLastSuccessfulRead()
    {
        var drv = new FocasDriver(new FocasDriverOptions
        {
            Devices = [new FocasDeviceOptions("focas://10.0.0.5:8193")],
            Probe = new FocasProbeOptions { Enabled = false },
        }, "focas-1", new FakeFocasClientFactory());
        await drv.InitializeAsync("{}", CancellationToken.None);

        var before = drv.GetHealth();
        before.State.ShouldBe(DriverState.Healthy);
        before.LastSuccessfulRead.ShouldNotBeNull();

        drv.HandlePollError(new InvalidOperationException("poll boom"));

        var after = drv.GetHealth();
        after.State.ShouldBe(DriverState.Degraded);
        after.LastSuccessfulRead.ShouldBe(before.LastSuccessfulRead);
        after.LastError.ShouldNotBeNull();
        after.LastError.ShouldContain("poll boom");
    }

    /// <summary>A poll reader failure never downgrades a pre-existing Faulted state.</summary>
    [Fact]
    public async Task PollReaderFailure_NeverDowngradesFaulted()
    {
        var drv = new FocasDriver(new FocasDriverOptions
        {
            Devices = [new FocasDeviceOptions("focas://10.0.0.5:8193")],
            // DeviceName "…:9999" is not in Devices → InitializeAsync fails fast → Faulted.
            RawTags = [FocasRawTags.Entry(new FocasTagDefinition("X", "focas://10.0.0.5:9999", "R100", FocasDataType.Byte))],
            Probe = new FocasProbeOptions { Enabled = false },
        }, "focas-1", new FakeFocasClientFactory());

        await Should.ThrowAsync<Exception>(() => drv.InitializeAsync("{}", CancellationToken.None));
        drv.GetHealth().State.ShouldBe(DriverState.Faulted);

        drv.HandlePollError(new InvalidOperationException("poll boom"));

        drv.GetHealth().State.ShouldBe(DriverState.Faulted);
    }

    /// <summary>
    ///     #740 review round 2 m3 — a poll failure carries the generation its batch STARTED under, so a batch that
    ///     began before a re-initialise cannot degrade the new generation. Positive control: a failure stamped with
    ///     the live generation (or unstamped) does degrade.
    /// </summary>
    [Fact]
    public async Task PollReaderFailure_from_a_previous_generation_does_not_degrade_the_new_one()
    {
        var drv = new FocasDriver(new FocasDriverOptions
        {
            Devices = [new FocasDeviceOptions("focas://10.0.0.5:8193")],
            Probe = new FocasProbeOptions { Enabled = false },
        }, "focas-1", new FakeFocasClientFactory());
        await drv.InitializeAsync("{}", CancellationToken.None);
        var oldGeneration = drv.LifecycleGeneration;
        await drv.InitializeAsync("{}", CancellationToken.None);

        var stale = new InvalidOperationException("old batch boom");
        stale.Data[FocasDriver.BatchGenerationKey] = oldGeneration;
        drv.HandlePollError(stale);
        drv.GetHealth().State.ShouldBe(DriverState.Healthy);

        var live = new InvalidOperationException("live batch boom");
        live.Data[FocasDriver.BatchGenerationKey] = drv.LifecycleGeneration;
        drv.HandlePollError(live);
        drv.GetHealth().State.ShouldBe(DriverState.Degraded);
    }
}