using System;
using System.Buffers.Binary;
using AVEVA.Historian.Client.Wcf;
using Xunit;

namespace AVEVA.Historian.Client.Tests;

/// <summary>
/// Golden-byte coverage for the 2023 R2 gRPC event-SEND registration buffers, pinned against a live
/// native capture (<c>capture-send-event</c> scenario, 2026-06-23). The send itself rides
/// <c>HistoryService.AddStreamValues</c> with the same "OS" buffer the WCF path uses
/// (<see cref="HistorianEventWriteProtocol"/>, already golden-tested in
/// <c>WcfEventWriteProtocolTests</c>); what is gRPC-specific is the CM_EVENT registration the event
/// connection performs first (RegisterTags + the 86-byte gRPC EnsureTags). These fixtures are the raw
/// bytes the native client sent on the wire — they carry no identity (CM_EVENT / "AnE Event" /
/// constant tag + event-type GUIDs / a registration FILETIME).
/// </summary>
public class GrpcEventSendProtocolTests
{
    // GrpcHistoryClient.RegisterTags.tagInfos captured from the native event connection: the packet
    // header 50 67 02 00 + count(1) + the 16-byte CM_EVENT tag GUID.
    private const string CapturedRegisterTagsHex =
        "506702000100000045813b35f05d464da253871aef49b321";

    // GrpcHistoryClient.EnsureTags.tagInfos captured from the native event connection (86 bytes): the
    // 8-byte EnsureTags header + CM_EVENT CTagMetadata + a registration FILETIME + the …e01f2f27
    // event-type GUID.
    private const string CapturedEnsureTagsHex =
        "4e670300010000000386000545813b35f05d464da253871aef49b321090800434d5f4556454e54090900416e45204576656e7402020100000001000000004e18d6bd4503dd0142ae595fb63b604791a5ab0be01f2f27";

    [Fact]
    public void BuildRegisterCmEventInputBuffer_MatchesNativeGrpcCapture()
    {
        byte[] expected = Convert.FromHexString(CapturedRegisterTagsHex);
        byte[] actual = HistorianEventRegistrationProtocol.BuildRegisterCmEventInputBuffer();
        Assert.Equal(expected, actual);
    }

    [Fact]
    public void SerializeCmEventEnsureTagsGrpc_MatchesNativeGrpcCapture()
    {
        byte[] expected = Convert.FromHexString(CapturedEnsureTagsHex);
        Assert.Equal(86, expected.Length);

        // The only run-varying field is the registration FILETIME (the 8 bytes immediately before the
        // trailing 16-byte event-type GUID). Feed the captured time back so the comparison is exact.
        long filetime = BinaryPrimitives.ReadInt64LittleEndian(expected.AsSpan(expected.Length - 24, 8));
        DateTime createdUtc = DateTime.FromFileTimeUtc(filetime);

        byte[] actual = HistorianAddTagsProtocol.SerializeCmEventEnsureTagsGrpc(createdUtc);
        Assert.Equal(expected, actual);
    }
}