namespace AcDream.Core.Net.Packets;

/// <summary>
/// Builds retail's connection-level disconnect packet.
/// </summary>
/// <remarks>
/// <c>ClientNet::LogOffServer</c> at <c>0x00543EF0</c> creates the
/// <c>0x8000</c> optional header and sends it through
/// <c>SharedNet::SendOptionalHeader</c> at <c>0x00543160</c>. That path
/// zero-initializes the packet sequence and copies the receiver's network id
/// and iteration into the fixed header. The disconnect is cleartext and has
/// no body.
/// </remarks>
public static class TransportDisconnect
{
    public static byte[] Build(ushort networkId, ushort iteration)
    {
        var header = new PacketHeader
        {
            Sequence = 0,
            Flags = PacketHeaderFlags.Disconnect,
            Id = networkId,
            Iteration = iteration,
        };

        return PacketCodec.Encode(
            header,
            ReadOnlySpan<byte>.Empty,
            outboundIsaac: null);
    }
}