using System.Buffers.Binary;
using System.Text;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport.Cip;
using ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport.Logix;
using ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport.Tests.Captures;
namespace ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport.Tests.Logix;

public sealed class SymbolObjectServicesTests
{
    private static readonly string[] ExpectedNames =
        ["Motor_Run", "Line1_Count", "Pump_1_Speed", "TestArray", "TestString", "TestSINT", "TestBOOL", "TestREAL", "TestDINT"];

    [Fact]
    public void Request_matches_capture()
    {
        // libplctag requests attributes 2,7,8,1 in that order -- same as the brief; no change needed.
        var cap = CaptureFile.CipPayload(CaptureFile.Load("logix-tags-listing.hex").First(f => f.FromClient));
        SymbolObjectServices.GetInstanceAttributeList(null, 0).ShouldBe(cap);
    }

    [Fact]
    public void Request_with_program_scope_and_start_instance() =>
        Convert.ToHexString(SymbolObjectServices.GetInstanceAttributeList("Main", 0x0102)).ShouldBe(
            "550A" + "910C" + Convert.ToHexString(Encoding.ASCII.GetBytes("Program:Main"))
            + "206B2500" + "0201" + "0400" + "0200" + "0700" + "0800" + "0100");

    [Fact]
    public void Captured_reply_entries_have_the_decoder_layout()
    {
        var reply = CipReply.Parse(CaptureFile.CipPayload(CaptureFile.Load("logix-tags-listing.hex").First(f => !f.FromClient)));
        var (entries, last, more) = SymbolObjectServices.ParseListingReply(reply);
        more.ShouldBeFalse();
        last.ShouldBe(9u);

        var names = new List<string>();
        var pos = 0;
        uint expectedInstance = 1;
        while (pos < entries.Length)
        {
            BinaryPrimitives.ReadUInt32LittleEndian(entries.AsSpan(pos)).ShouldBe(expectedInstance++);
            var nameLen = BinaryPrimitives.ReadUInt16LittleEndian(entries.AsSpan(pos + 20));
            names.Add(Encoding.ASCII.GetString(entries, pos + 22, nameLen));
            pos += 22 + nameLen;
        }
        names.ShouldBe(ExpectedNames);
    }

    [Fact]
    public void More_flag_follows_status_0x06()
    {
        var entry = Convert.FromHexString("05000000" + "C400" + "0400" + "00000000" + "00000000" + "00000000" + "0100" + "41");
        var reply = new CipReply(0x55, 0x06, [], entry);
        var (entries, last, more) = SymbolObjectServices.ParseListingReply(reply);
        more.ShouldBeTrue(); last.ShouldBe(5u); entries.ShouldBe(entry);
    }

    [Fact]
    public void MaxInstance_is_the_highest_in_the_page_whatever_its_order()
    {
        static string Entry(uint i) => BitConverter.ToString(BitConverter.GetBytes(i)).Replace("-", "")
            + "C400" + "0400" + "00000000" + "00000000" + "00000000" + "0100" + "41";
        var entries = Convert.FromHexString(Entry(9) + Entry(3) + Entry(5));
        var (_, max, more) = SymbolObjectServices.ParseListingReply(new CipReply(0x55, 0x06, [], entries));
        more.ShouldBeTrue();
        max.ShouldBe(9u);
    }

    [Fact]
    public void Failure_status_throws() =>
        Should.Throw<AbTransportException>(() =>
            SymbolObjectServices.ParseListingReply(new CipReply(0x55, 0x04, [], ReadOnlyMemory<byte>.Empty)));

    [Fact]
    public void Start_instance_above_16_bits_uses_32_bit_segment() =>
        Convert.ToHexString(SymbolObjectServices.GetInstanceAttributeList(null, 0x12345)).ShouldBe(
            "5504" + "206B" + "2600" + "45230100" + "0400" + "0200" + "0700" + "0800" + "0100");

    [Fact]
    public void More_with_no_entries_throws() =>
        Should.Throw<AbTransportException>(() =>
            SymbolObjectServices.ParseListingReply(new CipReply(0x55, 0x06, [], ReadOnlyMemory<byte>.Empty)))
            .Status.ShouldBe(AbStatus.BadReply);
}