using AVEVA.Historian.Client.Protocol;
using AVEVA.Historian.Client.Wcf;

namespace AVEVA.Historian.Client.Tests;

public sealed class WcfRuntimeParameterProtocolTests
{
    // GETRP pRequestBuff captured from the native client for GetRuntimeParameter("HistorianVersion")
    // via scripts/Capture-RuntimeParam.ps1 + instrument-wcf-writemessage:
    //   54 67 01 00         signature(0x6754) + version(1)
    //   01 00 00 00         name count = 1
    //   10 00 00 00         char count = 16
    //   UTF-16LE "HistorianVersion"
    private const string CaptureRequestHex =
        "54670100010000001000000048006900730074006F007200690061006E00560065007200730069006F006E00";

    // GETRP pResponseBuff captured from the paired GETRPResponse (instrument-wcf-readmessage):
    //   01 00               version = 1
    //   01 00 00 00         result count = 1
    //   43                  CRetVariant type 0x43 (VT_BSTR)
    //   1A 00               payload length = 26 (= charCount field + string bytes)
    //   0C 00               char count = 12
    //   UTF-16LE "20,0,000,000"
    private const string CaptureResponseHex =
        "010001000000431A000C00320030002C0030002C003000300030002C00300030003000";

    [Fact]
    public void SerializeRequestMatchesInstrumentedNativeRequestBuffer()
    {
        byte[] actual = HistorianRuntimeParameterProtocol.SerializeRequest("HistorianVersion");
        Assert.Equal(Convert.FromHexString(CaptureRequestHex), actual);
    }

    [Fact]
    public void ParseSingleStringResultReadsTheCapturedResponseValue()
    {
        byte[] response = Convert.FromHexString(CaptureResponseHex);
        string? value = HistorianRuntimeParameterProtocol.ParseSingleStringResult(response);
        Assert.Equal("20,0,000,000", value);
    }

    [Fact]
    public void ParseSingleStringResultReturnsNullForZeroResultCount()
    {
        // version(1) + result count(0)
        byte[] empty = [0x01, 0x00, 0x00, 0x00, 0x00, 0x00];
        Assert.Null(HistorianRuntimeParameterProtocol.ParseSingleStringResult(empty));
    }

    [Fact]
    public void ParseSingleStringResultThrowsForUncapturedVariantType()
    {
        // version(1) + count(1) + a non-string variant marker (0x03, VT_I4 — not captured).
        byte[] buffer = [0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x03, 0x04, 0x00, 0x00, 0x00, 0x00];
        Assert.Throws<ProtocolEvidenceMissingException>(
            () => HistorianRuntimeParameterProtocol.ParseSingleStringResult(buffer));
    }
}