using Google.Protobuf;
using Google.Protobuf.WellKnownTypes;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.Protos.Telemetry.V1;
using ZB.MOM.WW.OtOpcUa.ControlPlane.Telemetry;
using ZB.MOM.WW.OtOpcUa.ControlPlane.Tests.Telemetry.Pre847;

namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Tests.Telemetry;

/// <summary>
///     Mixed-version wire tests for <c>DriverHealth.reporting_node_id</c> (proto field 15, added by lmxopcua#847;
///     tests lmxopcua#851). A rolling upgrade runs old and new nodes against old and new centrals, so the field
///     must cross the wire in all three directions: new→new round-trips, old→new parses as ABSENT (not an empty
///     node id), and new→old is ignored as an unknown field without disturbing the rest of the message. "Old" is
///     the frozen pre-#847 schema in <c>Protos/telemetry_pre847.proto</c> — a real generated parser/serializer, not
///     a hand-built byte string.
/// </summary>
[Trait("Category", "Unit")]
public sealed class DriverHealthReportingNodeWireTests
{
    private static readonly DateTime PublishedUtc = new(2026, 11, 11, 12, 0, 0, DateTimeKind.Utc);
    private static readonly DateTime LastReadUtc = new(2026, 11, 11, 11, 59, 30, DateTimeKind.Utc);

    private static DriverHealth NewHealth(string? reportingNodeId)
    {
        var msg = new DriverHealth
        {
            ClusterId = "MAIN",
            DriverInstanceId = "drv-1",
            State = "Faulted",
            LastSuccessfulReadUtc = Timestamp.FromDateTime(LastReadUtc),
            LastError = "timeout",
            ErrorCount5Min = 4,
            PublishedUtc = Timestamp.FromDateTime(PublishedUtc),
            HasDiagnostics = true,
        };
        msg.Diagnostics["pdu"] = "480";
        if (reportingNodeId is not null) msg.ReportingNodeId = reportingNodeId;
        return msg;
    }

    [Fact]
    public void New_sender_to_new_receiver_round_trips_the_reporting_node_id()
    {
        var bytes = NewHealth("central-1").ToByteArray();

        var parsed = DriverHealth.Parser.ParseFrom(bytes);
        parsed.HasReportingNodeId.ShouldBeTrue();

        var e = TelemetryProtoMapCentral.ToHealth(parsed);
        e.ReportingNodeId.ShouldBe("central-1");
        e.DriverInstanceId.ShouldBe("drv-1");
        e.State.ShouldBe("Faulted");
        e.PublishedUtc.ShouldBe(PublishedUtc);
    }

    [Fact]
    public void New_sender_without_a_node_id_omits_field_15_and_maps_to_null()
    {
        // A harness / node with no role info leaves the field unset: it must not appear on the wire at all, so an
        // explicit "" would not be confused with "absent" either way.
        var msg = NewHealth(reportingNodeId: null);
        msg.HasReportingNodeId.ShouldBeFalse();

        var e = TelemetryProtoMapCentral.ToHealth(DriverHealth.Parser.ParseFrom(msg.ToByteArray()));
        e.ReportingNodeId.ShouldBeNull();
    }

    [Fact]
    public void Old_sender_to_new_receiver_parses_as_absent_node_id_and_keeps_every_other_field()
    {
        var old = new DriverHealthPre847
        {
            ClusterId = "MAIN",
            DriverInstanceId = "drv-1",
            State = "Healthy",
            LastSuccessfulReadUtc = Timestamp.FromDateTime(LastReadUtc),
            ErrorCount5Min = 0,
            PublishedUtc = Timestamp.FromDateTime(PublishedUtc),
            RediscoveryReason = "schema changed",
            HasDiagnostics = true,
        };
        old.Diagnostics["pdu"] = "240";

        var parsed = DriverHealth.Parser.ParseFrom(old.ToByteArray());

        // Explicit presence: absent, NOT the proto3 default "" — central keys the snapshot under the
        // driver-only (unlabelled) node and the AdminUI renders it as a pre-#847 row.
        parsed.HasReportingNodeId.ShouldBeFalse();
        var e = TelemetryProtoMapCentral.ToHealth(parsed);
        e.ReportingNodeId.ShouldBeNull();
        e.ClusterId.ShouldBe("MAIN");
        e.DriverInstanceId.ShouldBe("drv-1");
        e.State.ShouldBe("Healthy");
        e.LastSuccessfulReadUtc.ShouldBe(LastReadUtc);
        e.LastError.ShouldBeNull();
        e.PublishedUtc.ShouldBe(PublishedUtc);
        e.RediscoveryReason.ShouldBe("schema changed");
        e.Diagnostics.ShouldNotBeNull();
        e.Diagnostics!["pdu"].ShouldBe("240");
    }

    [Fact]
    public void New_sender_to_old_receiver_ignores_field_15_and_keeps_every_other_field()
    {
        var bytes = NewHealth("central-2").ToByteArray();

        // An old central's parser: field 15 is unknown to it. It must neither throw nor shift any known field.
        var old = DriverHealthPre847.Parser.ParseFrom(bytes);

        old.ClusterId.ShouldBe("MAIN");
        old.DriverInstanceId.ShouldBe("drv-1");
        old.State.ShouldBe("Faulted");
        old.LastSuccessfulReadUtc.ToDateTime().ShouldBe(LastReadUtc);
        old.LastError.ShouldBe("timeout");
        old.ErrorCount5Min.ShouldBe(4);
        old.PublishedUtc.ToDateTime().ShouldBe(PublishedUtc);
        old.HasDiagnostics.ShouldBeTrue();
        old.Diagnostics["pdu"].ShouldBe("480");

        // The old parser keeps field 15 as an unknown field rather than corrupting it: re-serialised by an old
        // process, a new reader still recovers the node id.
        DriverHealth.Parser.ParseFrom(old.ToByteArray()).ReportingNodeId.ShouldBe("central-2");
    }
}