using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Driver.AbCip;

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

/// <summary>
///     Array element stride. Seen live on a production CompactLogix: reading
///     <c>Program:UN01_Press._ModeNames</c> (<c>STR0016[32]</c>, 4 elements requested) returned an
///     80-byte buffer with libplctag's <c>ElementSize</c> unset; the driver strode 88 bytes (built-in
///     STRING) and the read failed <c>ErrorOutOfBounds</c>. The real values were
///     "undefined" / "Production" / "Maintenance" / "Manual" at a 20-byte stride.
/// </summary>
[Trait("Category", "Unit")]
public sealed class AbCipArrayStrideTests
{
    /// <summary>A user string type's stride comes from the buffer, not the built-in STRING size.</summary>
    [Fact]
    public void User_string_array_strides_by_buffer_size_over_count()
    {
        LibplctagTagRuntime.ResolveArrayStride(null, bufferSize: 80, count: 4, AbCipDataType.String).ShouldBe(20);
    }

    /// <summary>The built-in STRING still strides 88.</summary>
    [Fact]
    public void Builtin_STRING_array_strides_88()
    {
        LibplctagTagRuntime.ResolveArrayStride(null, bufferSize: 3 * 88, count: 3, AbCipDataType.String).ShouldBe(88);
    }

    /// <summary>libplctag's own element size wins when it is populated.</summary>
    [Fact]
    public void Reported_element_size_wins()
    {
        LibplctagTagRuntime.ResolveArrayStride(4, bufferSize: 80, count: 4, AbCipDataType.DInt).ShouldBe(4);
    }

    /// <summary>An empty or uneven buffer falls back to the static per-type size.</summary>
    [Fact]
    public void Empty_or_uneven_buffer_falls_back_to_the_type_size()
    {
        LibplctagTagRuntime.ResolveArrayStride(null, bufferSize: 0, count: 4, AbCipDataType.Real).ShouldBe(4);
        LibplctagTagRuntime.ResolveArrayStride(null, bufferSize: 81, count: 4, AbCipDataType.String).ShouldBe(88);
    }
}