lmxopcua/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Mqtt.Tests/MqttWriteEncoderTests.cs

using System.Text;
using Google.Protobuf;
using Org.Eclipse.Tahu.Protobuf;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.Mqtt.Sparkplug;
using TahuDataType = Org.Eclipse.Tahu.Protobuf.DataType;

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

/// <summary>
///     Unit tests for <see cref="MqttWriteEncoder"/> — the pure half of MQTT write-through (Gitea #508):
///     what a write encodes to, and which writes are refused before anything reaches a broker.
/// </summary>
[Trait("Category", "Unit")]
public sealed class MqttWriteEncoderTests
{
    private static MqttTagDefinition Plain(
        string? writeTopic,
        MqttPayloadFormat format = MqttPayloadFormat.Scalar,
        DriverDataType dataType = DriverDataType.Float64)
        => new(
            Name: "Plant/Mqtt/dev1/Setpoint",
            Topic: "factory/oven/temp",
            PayloadFormat: format,
            JsonPath: "$",
            DataType: dataType,
            Qos: null,
            RetainSeed: true,
            WriteTopic: writeTopic);

    private static MqttTagDefinition Sparkplug(
        string? deviceId,
        DriverDataType dataType = DriverDataType.Float64,
        string metricName = "Speed")
        => new(
            Name: "Plant/Mqtt/dev1/Speed",
            Topic: "",
            PayloadFormat: MqttPayloadFormat.Json,
            JsonPath: "$",
            DataType: dataType,
            Qos: null,
            RetainSeed: true,
            GroupId: "OtOpcUaSim",
            EdgeNodeId: "EdgeA",
            DeviceId: deviceId,
            MetricName: metricName);

    // ---- The refusal that is the whole point of the feature -------------------------------------

    [Fact]
    public void A_plain_tag_with_no_write_topic_is_refused_rather_than_published_nowhere()
    {
        // Before #508 there was no IWritable at all — honest read-only. The one outcome that would be
        // WORSE is a node that accepts a write, reports Good and publishes nothing. So this must be a
        // refusal, and specifically the "no destination" one, which the driver maps to BadNotWritable.
        var error = MqttWriteEncoder.TryEncode(MqttMode.Plain, Plain(writeTopic: null), 42.5, out var encoded);

        error.ShouldBe(MqttWriteEncodeError.NoWriteDestination);
        encoded.Topic.ShouldBeNull();
        encoded.Payload.ShouldBeNull();
    }

    [Theory]
    [InlineData("")]
    [InlineData("   ")]
    public void A_blank_write_topic_is_treated_as_absent(string writeTopic)
        => MqttWriteEncoder.TryEncode(MqttMode.Plain, Plain(writeTopic), 1, out _)
            .ShouldBe(MqttWriteEncodeError.NoWriteDestination);

    [Fact]
    public void A_sparkplug_tag_with_an_incomplete_tuple_has_no_command_address()
    {
        // A Sparkplug tag's command address IS its binding tuple, so an incomplete one is the same
        // failure as a missing write topic, not a different kind.
        var def = Sparkplug(deviceId: null) with { MetricName = null };

        MqttWriteEncoder.TryEncode(MqttMode.SparkplugB, def, 1.0, out _)
            .ShouldBe(MqttWriteEncodeError.NoWriteDestination);
    }

    // ---- Plain encoding --------------------------------------------------------------------------

    [Fact]
    public void Plain_publishes_to_the_write_topic_not_the_read_topic()
    {
        // The two-field split is the point: publishing a command onto the tag's own read topic would
        // echo back and read as a confirmed device value.
        var def = Plain("factory/oven/temp/set");

        MqttWriteEncoder.TryEncode(MqttMode.Plain, def, 42.5, out var encoded)
            .ShouldBe(MqttWriteEncodeError.None);

        encoded.Topic.ShouldBe("factory/oven/temp/set");
        encoded.Topic.ShouldNotBe(def.Topic);
    }

    [Theory]
    [InlineData(MqttPayloadFormat.Scalar)]
    [InlineData(MqttPayloadFormat.Raw)]
    public void Scalar_and_raw_encode_the_value_as_utf8_text(MqttPayloadFormat format)
    {
        MqttWriteEncoder.TryEncode(MqttMode.Plain, Plain("t/set", format), 42.5, out var encoded)
            .ShouldBe(MqttWriteEncodeError.None);

        Encoding.UTF8.GetString(encoded.Payload).ShouldBe("42.5");
    }

    [Fact]
    public void Numbers_are_encoded_with_the_invariant_culture()
    {
        // A comma decimal separator would publish a number the device cannot parse — and it would only
        // reproduce on a host with a European locale, which is the worst kind of bug to chase.
        var previous = Thread.CurrentThread.CurrentCulture;
        Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("de-DE");
        try
        {
            MqttWriteEncoder.TryEncode(MqttMode.Plain, Plain("t/set"), 42.5, out var encoded)
                .ShouldBe(MqttWriteEncodeError.None);

            Encoding.UTF8.GetString(encoded.Payload).ShouldBe("42.5");
        }
        finally
        {
            Thread.CurrentThread.CurrentCulture = previous;
        }
    }

    [Fact]
    public void Json_encodes_a_bare_json_literal()
    {
        MqttWriteEncoder.TryEncode(
                MqttMode.Plain, Plain("t/set", MqttPayloadFormat.Json), 42.5, out var encoded)
            .ShouldBe(MqttWriteEncodeError.None);

        Encoding.UTF8.GetString(encoded.Payload).ShouldBe("42.5");
    }

    [Fact]
    public void Json_quotes_a_string_value()
        => Encoding.UTF8.GetString(
                EncodeOrThrow(MqttMode.Plain, Plain("t/set", MqttPayloadFormat.Json, DriverDataType.String), "on"))
            .ShouldBe("\"on\"");

    [Fact]
    public void A_null_value_is_refused()
        // A zero-length MQTT payload is a legitimate clear-the-retained-message instruction — an
        // entirely different operation. Encoding null as "no bytes" would conflate the two.
        => MqttWriteEncoder.TryEncode(MqttMode.Plain, Plain("t/set"), null, out _)
            .ShouldBe(MqttWriteEncodeError.ValueNotRepresentable);

    // ---- Sparkplug command encoding ---------------------------------------------------------------

    [Fact]
    public void A_device_metric_encodes_as_a_DCMD_addressed_to_that_device()
    {
        // Addressing a device metric with NCMD would command the NODE, which does not own it.
        MqttWriteEncoder.TryEncode(MqttMode.SparkplugB, Sparkplug("Filler1"), 12.5, out var encoded)
            .ShouldBe(MqttWriteEncodeError.None);

        encoded.Topic.ShouldBe("spBv1.0/OtOpcUaSim/DCMD/EdgeA/Filler1");
    }

    [Fact]
    public void An_edge_node_metric_encodes_as_an_NCMD()
        => EncodeTopic(MqttMode.SparkplugB, Sparkplug(deviceId: null))
            .ShouldBe("spBv1.0/OtOpcUaSim/NCMD/EdgeA");

    [Fact]
    public void The_command_carries_the_metric_by_name_with_an_explicit_datatype()
    {
        // By NAME, never by alias: an alias may be reused for a different metric across a rebirth.
        // Datatype explicitly, because a node that treats it as ambiguous drops the command SILENTLY —
        // the exact failure mode this feature must not have.
        var bytes = EncodeOrThrow(MqttMode.SparkplugB, Sparkplug("Filler1"), 12.5);
        var payload = Payload.Parser.ParseFrom(bytes);

        payload.Metrics.Count.ShouldBe(1);
        var metric = payload.Metrics[0];
        metric.Name.ShouldBe("Speed");
        metric.Alias.ShouldBe(0ul);
        metric.Datatype.ShouldBe((uint)TahuDataType.Double);
        metric.DoubleValue.ShouldBe(12.5);
        metric.Timestamp.ShouldBeGreaterThan(0ul);
        payload.Timestamp.ShouldBeGreaterThan(0ul);
    }

    [Fact]
    public void The_command_carries_no_sequence_number()
    {
        // seq belongs to the messages an edge node itself publishes. A strict node validating a
        // host-supplied one against its own counter would have grounds to reject the command.
        var payload = Payload.Parser.ParseFrom(EncodeOrThrow(MqttMode.SparkplugB, Sparkplug("Filler1"), 1.0));

        payload.HasSeq.ShouldBeFalse();
    }

    [Theory]
    [InlineData(DriverDataType.Boolean, true, (uint)TahuDataType.Boolean)]
    [InlineData(DriverDataType.Int32, 7, (uint)TahuDataType.Int32)]
    [InlineData(DriverDataType.Int64, 7L, (uint)TahuDataType.Int64)]
    [InlineData(DriverDataType.UInt32, 7, (uint)TahuDataType.Uint32)]
    [InlineData(DriverDataType.Float32, 1.5f, (uint)TahuDataType.Float)]
    [InlineData(DriverDataType.String, "x", (uint)TahuDataType.String)]
    public void The_declared_data_type_selects_the_wire_datatype(
        DriverDataType dataType, object value, uint expectedWireType)
    {
        var payload = Payload.Parser.ParseFrom(
            EncodeOrThrow(MqttMode.SparkplugB, Sparkplug("Filler1", dataType), value));

        payload.Metrics[0].Datatype.ShouldBe(expectedWireType);
    }

    [Fact]
    public void An_unrepresentable_value_is_refused_rather_than_coerced()
        // "not-a-number" into a Float64 tag must not silently become 0 on a live plant.
        => MqttWriteEncoder.TryEncode(MqttMode.SparkplugB, Sparkplug("Filler1"), "not-a-number", out _)
            .ShouldBe(MqttWriteEncodeError.ValueNotRepresentable);

    [Fact]
    public void A_type_with_no_command_encoding_is_refused_rather_than_stringified()
        // Reference has no Sparkplug wire representation. Falling back to String would put a value on
        // the wire that is not what the tag's type says it is.
        => MqttWriteEncoder.TryEncode(
                MqttMode.SparkplugB, Sparkplug("Filler1", DriverDataType.Reference), "ref", out _)
            .ShouldBe(MqttWriteEncodeError.UnsupportedDataType);

    [Fact]
    public void The_mode_decides_the_shape_not_the_blob()
    {
        // A tag can legitimately carry both shapes' keys (the editor preserves unknown keys across a
        // retype), so sniffing would make one authored tag mean two different things.
        var both = Sparkplug("Filler1") with { WriteTopic = "plain/set" };

        EncodeTopic(MqttMode.Plain, both).ShouldBe("plain/set");
        EncodeTopic(MqttMode.SparkplugB, both).ShouldBe("spBv1.0/OtOpcUaSim/DCMD/EdgeA/Filler1");
    }

    private static string EncodeTopic(MqttMode mode, MqttTagDefinition def)
    {
        MqttWriteEncoder.TryEncode(mode, def, 1.0, out var encoded).ShouldBe(MqttWriteEncodeError.None);
        return encoded.Topic;
    }

    private static byte[] EncodeOrThrow(MqttMode mode, MqttTagDefinition def, object value)
    {
        MqttWriteEncoder.TryEncode(mode, def, value, out var encoded).ShouldBe(MqttWriteEncodeError.None);
        return encoded.Payload;
    }
}