using Sick.SafetyScanners.DataStructures;
using Sick.SafetyScanners.Helpers;
using System.Text;

namespace Sick.SafetyScanners.DataProcessing;

/// <summary>
/// Parser for OrderNumber response from COLA2 variable command
/// Thread-safe implementation
/// </summary>
public sealed class ParseOrderNumber
{
    /// <summary>
    /// Parses the order number from a TCP sequence (COLA2 response)
    /// Matches: ParseOrderNumber::parseTCPSequence in C++
    /// </summary>
    public OrderNumber ParseTcpSequence(PacketBuffer buffer)
    {
        var span = buffer.GetBufferSpan();
        return new OrderNumber
        {
            Number = ReadOrderNumber(span)
        };
    }
    
    /// <summary>
    /// Reads order number from buffer
    /// Matches: ParseOrderNumber::readOrderNumber in C++
    /// </summary>
    private string ReadOrderNumber(ReadOnlySpan<byte> span)
    {
        ushort stringLength = ReadWriteHelper.ReadUint16LittleEndian(span, 0);
        
        var numberBuilder = new StringBuilder(stringLength);
        for (ushort i = 0; i < stringLength; i++)
        {
            ushort ch = ReadWriteHelper.ReadUint8(span, 2 + i);
            numberBuilder.Append((char)ch);
        }
        
        return numberBuilder.ToString();
    }
}