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

namespace Sick.SafetyScanners.DataProcessing;

/// <summary>
/// Parser for UserName response from COLA2 variable command
/// Thread-safe implementation
/// </summary>
public sealed class ParseUserName
{
    /// <summary>
    /// Parses the user name from a TCP sequence (COLA2 response)
    /// Matches: ParseUserNameData::parseTCPSequence in C++
    /// </summary>
    public UserName ParseTcpSequence(PacketBuffer buffer)
    {
        var span = buffer.GetBufferSpan();
        return new UserName
        {
            VersionCVersion = ReadVersionIndicator(span),
            VersionMajorVersionNumber = ReadMajorNumber(span),
            VersionMinorVersionNumber = ReadMinorNumber(span),
            VersionReleaseNumber = ReadReleaseNumber(span),
            NameLength = ReadNameLength(span),
            Name = ReadUserName(span)
        };
    }
    
    /// <summary>
    /// Matches: ParseUserNameData::readVersionIndicator in C++
    /// </summary>
    private string ReadVersionIndicator(ReadOnlySpan<byte> span)
    {
        byte ch = ReadWriteHelper.ReadUint8(span, 0);
        return ((char)ch).ToString();
    }
    
    /// <summary>
    /// Matches: ParseUserNameData::readMajorNumber in C++
    /// </summary>
    private byte ReadMajorNumber(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint8(span, 1);
    }
    
    /// <summary>
    /// Matches: ParseUserNameData::readMinorNumber in C++
    /// </summary>
    private byte ReadMinorNumber(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint8(span, 2);
    }
    
    /// <summary>
    /// Matches: ParseUserNameData::readReleaseNumber in C++
    /// </summary>
    private byte ReadReleaseNumber(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint8(span, 3);
    }
    
    /// <summary>
    /// Matches: ParseUserNameData::readNameLength in C++
    /// </summary>
    private uint ReadNameLength(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint32LittleEndian(span, 4);
    }
    
    /// <summary>
    /// Matches: ParseUserNameData::readUserName in C++
    /// </summary>
    private string ReadUserName(ReadOnlySpan<byte> span)
    {
        uint nameLength = ReadWriteHelper.ReadUint32LittleEndian(span, 4);
        
        var nameBuilder = new StringBuilder((int)nameLength);
        for (uint i = 0; i < nameLength; i++)
        {
            byte ch = ReadWriteHelper.ReadUint8(span, 8 + (int)i);
            nameBuilder.Append((char)ch);
        }
        
        return nameBuilder.ToString();
    }
}