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

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

/// <summary>
///     Decodes a captured <c>@tags</c> Symbol Object response, byte for byte as libplctag handed
///     it back — the evidence for the entry layout, rather than another statement of it.
/// </summary>
/// <remarks>
///     <para>
///         Every other decoder test builds its own input, so the builder and the decoder can share
///         a wrong assumption and still agree. They did: both padded each entry to an even length,
///         and a controller pads nothing (Gitea #468).
///     </para>
///     <para>
///         This capture came off the AbCip integration fixture — libplctag's <c>ab_server</c>,
///         patched to serve the Symbol Object listing (see the fixture's
///         <c>Docker/patches/</c>) — and the same server's replies are read correctly by
///         libplctag's own <c>list_tags_logix</c> client. That client is the reference
///         implementation exercised against real Logix hardware, so its agreement is what makes
///         this sample evidence about controllers and not merely about our fixture.
///     </para>
///     <para>
///         Re-capture with <c>plc_tag_create("…&amp;name=@tags")</c> against the fixture and dump
///         <c>plc_tag_get_uint8</c> across <c>plc_tag_get_size</c> if the fixture's tag set changes.
///     </para>
/// </remarks>
[Trait("Category", "Unit")]
public sealed class CipSymbolObjectWireCaptureTests
{
    /// <summary>
    ///     The nine tags the <c>controllogix</c> fixture profile serves, in wire order. 281 bytes.
    /// </summary>
    private const string CapturedTagsReply =
        "01000000C120010001000000000000000000000009004D6F746F725F52756E" +
        "02000000C42004000100000000000000000000000B004C696E65315F436F756E74" +
        "03000000CA2004000100000000000000000000000C0050756D705F315F5370656564" +
        "04000000C42004001000000000000000000000000900546573744172726179" +
        "05000000D02058000100000000000000000000000A0054657374537472696E67" +
        "06000000C220010001000000000000000000000008005465737453494E54" +
        "07000000C1200100010000000000000000000000080054657374424F4F4C" +
        "08000000CA2004000100000000000000000000000800546573745245414C" +
        "09000000C420040001000000000000000000000008005465737444494E54";

    private static byte[] Capture() => Convert.FromHexString(CapturedTagsReply);

    /// <summary>The capture is the length the entry layout predicts — no padding anywhere.</summary>
    /// <remarks>
    ///     Nine entries of 22 header bytes plus their name lengths
    ///     (9 + 11 + 12 + 9 + 10 + 8 + 8 + 8 + 8 = 83) come to 281. An even-padded stream would be
    ///     285, so the length alone falsifies the old assumption.
    /// </remarks>
    [Fact]
    public void The_capture_is_packed_with_no_padding_between_entries()
    {
        Capture().Length.ShouldBe((9 * 22) + 83);
    }

    /// <summary>Every tag the fixture serves comes back, in wire order.</summary>
    /// <remarks>
    ///     The first entry's name is 9 bytes, so the second entry begins at offset 31 — an odd
    ///     offset. Under the old even-alignment step the decoder read <c>Motor_Run</c> and then
    ///     lost all eight tags behind it.
    /// </remarks>
    [Fact]
    public void Every_captured_symbol_decodes_in_wire_order()
    {
        var tags = CipSymbolObjectDecoder.Decode(Capture()).ToList();

        tags.Select(t => t.Name).ShouldBe([
            "Motor_Run",
            "Line1_Count",
            "Pump_1_Speed",
            "TestArray",
            "TestString",
            "TestSINT",
            "TestBOOL",
            "TestREAL",
            "TestDINT",
        ]);
    }

    /// <summary>Types survive the array-dimension bits a real symbol type carries.</summary>
    /// <remarks>
    ///     Each captured symbol type is <c>0x20xx</c>, not <c>0x00xx</c>: bits 13-14 hold the array
    ///     dimension count. Only the low 12 bits are the CIP type code, and reading the word whole
    ///     would classify every one of these as an unknown type.
    /// </remarks>
    [Fact]
    public void Captured_symbol_types_map_through_the_dimension_bits()
    {
        var tags = CipSymbolObjectDecoder.Decode(Capture()).ToList();

        tags.Single(t => t.Name == "Motor_Run").DataType.ShouldBe(AbCipDataType.Bool);
        tags.Single(t => t.Name == "Line1_Count").DataType.ShouldBe(AbCipDataType.DInt);
        tags.Single(t => t.Name == "Pump_1_Speed").DataType.ShouldBe(AbCipDataType.Real);
        tags.Single(t => t.Name == "TestString").DataType.ShouldBe(AbCipDataType.String);
        tags.Single(t => t.Name == "TestSINT").DataType.ShouldBe(AbCipDataType.SInt);
    }

    /// <summary>
    ///     <c>ab_server</c> marks every symbol as a one-dimensional array (a scalar is
    ///     <c>[1]</c>); only <c>TestArray</c> has more than one element. A 1-element, 1-D entry is
    ///     treated as a scalar, so the fixture's scalars do not browse as 1-element arrays — a
    ///     real controller sets no dimension bits on a scalar at all
    ///     (<see cref="CipSymbolObjectRealControllerCaptureTests"/>).
    /// </summary>
    [Fact]
    public void Only_the_multi_element_capture_entry_is_an_array()
    {
        var tags = CipSymbolObjectDecoder.Decode(Capture()).ToList();

        var array = tags.Single(t => t.Name == "TestArray");
        array.IsArray.ShouldBeTrue();
        array.ElementCount.ShouldBe(16);
        tags.Where(t => t.Name != "TestArray").ShouldAllBe(t => !t.IsArray && t.ElementCount == 1);
    }

    /// <summary>None of the captured symbols is misread as a system tag or a structure.</summary>
    /// <remarks>
    ///     The dimension bits sit next to the flags the decoder tests for, so a mask that is one
    ///     bit wide in the wrong place would show up as a plain DINT being reported as a UDT — and
    ///     a UDT is fanned out into member tags, so the error would not stay quiet.
    /// </remarks>
    [Fact]
    public void No_captured_symbol_is_misread_as_a_system_tag_or_a_structure()
    {
        var tags = CipSymbolObjectDecoder.Decode(Capture()).ToList();

        tags.ShouldAllBe(t => !t.IsSystemTag);
        tags.ShouldAllBe(t => t.DataType != AbCipDataType.Structure);
        tags.ShouldAllBe(t => t.TemplateInstanceId == null);
    }
}