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

namespace ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.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 TwinCATPollErrorHealthTests
{
    private const string Host = "ads://5.23.91.23.1.1:851";

    /// <summary>A poll reader failure degrades health, preserving the last successful read timestamp.</summary>
    [Fact]
    public async Task PollReaderFailure_DegradesHealth_PreservesLastSuccessfulRead()
    {
        var drv = new TwinCATDriver(new TwinCATDriverOptions
        {
            Devices = [new TwinCATDeviceOptions(Host)],
            Probe = new TwinCATProbeOptions { Enabled = false },
            EnableControllerBrowse = false,
        }, "twincat-1", new FakeTwinCATClientFactory());
        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 TwinCATDriver(new TwinCATDriverOptions
        {
            Devices = [new TwinCATDeviceOptions("not-a-valid-address")],
            Probe = new TwinCATProbeOptions { Enabled = false },
            EnableControllerBrowse = false,
        }, "twincat-1", new FakeTwinCATClientFactory());

        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);
    }
}