using InnovEnergy.Lib.Protocols.Modbus.Protocol.Frames.Accessors;

namespace InnovEnergy.Lib.Protocols.Modbus.Tcp;

internal readonly struct MbapHeader 
{
    public const Int32 Size = 6;

    public ArraySegment<Byte> Data { get; }

    public MbWord Id          => Data.WordAt(0);
    public MbWord Protocol    => Data.WordAt(2);
    public MbWord FrameLength => Data.WordAt(4);

    public MbapHeader(UInt16 transactionId, Int32 frameLength)
    {
        Data = new ArraySegment<Byte>(new Byte[Size]);

        Id.Set(transactionId);
        FrameLength.Set(frameLength);
    }

    public MbapHeader(Byte[] data) : this(new ArraySegment<Byte>(data))
    { }

    public MbapHeader(ArraySegment<Byte> data) 
    {
        Data = data;

        if (data.Count != Size)
            throw new ArgumentOutOfRangeException($"Expecting an array exactly {Size} bytes long!");

        if (Protocol != 0)
            throw new ArgumentException($"Protocol {Protocol} not supported!", nameof(Protocol));
    }
}