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

namespace ZB.MOM.WW.OtOpcUa.Driver.S7.Tests;

/// <summary>
///     Unit-level coverage for the <c>DriverHealth.Diagnostics</c> dictionary the S7 driver
///     exposes through <see cref="S7Driver.GetHealth"/>. Wire-level reads of
///     <c>S7.NegotiatedPduSize</c> against a real handshake live in the Snap7 integration
///     suite (where the simulator negotiates a fixed 240-byte PDU); this suite covers the
///     before-connect / after-shutdown contract on the same key without booting a fixture.
/// </summary>
[Trait("Category", "Unit")]
public sealed class S7DriverDiagnosticsTests
{
    [Fact]
    public void NegotiatedPduSize_diagnostics_key_starts_at_zero_before_initialize()
    {
        // Before InitializeAsync the driver hasn't talked to a PLC, so the negotiated PDU
        // is unknown. We surface 0 (rather than omitting the key) so the Admin UI driver-
        // diagnostics panel can render a stable row even pre-connect — operators see "0"
        // and immediately know the driver hasn't completed a handshake yet.
        using var drv = new S7Driver(new S7DriverOptions { Host = "192.0.2.1" }, "s7-pre-init");

        var health = drv.GetHealth();
        // Pre-init the driver's state is Unknown and Diagnostics is null (the empty dict);
        // the field-backed counter is what we directly assert here.
        drv.NegotiatedPduSize.ShouldBe(0);
        // The DriverHealth surface should also be safe to consume.
        health.DiagnosticsOrEmpty.ContainsKey("S7.NegotiatedPduSize").ShouldBeFalse(
            "pre-init Diagnostics is null and DiagnosticsOrEmpty returns the empty dict");
    }

    [Fact]
    public async Task NegotiatedPduSize_resets_to_zero_after_shutdown()
    {
        // Even when InitializeAsync fails (unreachable host), the field must remain at 0
        // so a subsequent ShutdownAsync doesn't carry a stale value forward into the next
        // re-init attempt. RFC 5737 documentation IP guarantees a fast TCP timeout.
        var opts = new S7DriverOptions { Host = "192.0.2.1", Timeout = TimeSpan.FromMilliseconds(250) };
        using var drv = new S7Driver(opts, "s7-shutdown");

        await Should.ThrowAsync<Exception>(async () =>
            await drv.InitializeAsync("{}", TestContext.Current.CancellationToken));

        // The Faulted path in InitializeAsync's catch block doesn't touch _negotiatedPduSize
        // (we never reached the post-OpenAsync capture) so it should still be 0.
        drv.NegotiatedPduSize.ShouldBe(0);

        await drv.ShutdownAsync(TestContext.Current.CancellationToken);
        drv.NegotiatedPduSize.ShouldBe(0, "ShutdownAsync must zero the negotiated PDU snapshot");
    }
}