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

namespace Sick.SafetyScanners.DataProcessing;

/// <summary>
/// Parser for FieldHeaderData response from COLA2 variable command
/// Thread-safe implementation
/// </summary>
public sealed class ParseFieldHeaderData
{
    /// <summary>
    /// Parses the field header data from a TCP sequence (COLA2 response)
    /// Matches: ParseFieldHeaderData::parseTCPSequence in C++
    /// </summary>
    public FieldData ParseTcpSequence(PacketBuffer buffer)
    {
        var span = buffer.GetBufferSpan();
        bool valid = IsValid(span);
        
        if (!valid)
        {
            return new FieldData
            {
                IsValid = false
            };
        }
        
        SetFieldType(span, out bool isWarningField, out bool isProtectiveField);
        ushort setIndex = ReadSetIndex(span);
        uint nameLength = ReadNameLength(span);
        
        return new FieldData
        {
            IsValid = true,
            VersionCVersion = ReadVersionIndicator(span),
            VersionMajorVersionNumber = ReadMajorNumber(span),
            VersionMinorVersionNumber = ReadMinorNumber(span),
            VersionReleaseNumber = ReadReleaseNumber(span),
            IsDefined = ReadIsDefined(span),
            EvalMethod = ReadEvalMethod(span),
            MultiSampling = ReadMultiSampling(span),
            ObjectResolution = ReadObjectResolution(span),
            FieldSetIndex = setIndex,
            NameLength = nameLength,
            FieldName = ReadFieldName(span, nameLength),
            IsWarningField = isWarningField,
            IsProtectiveField = isProtectiveField
        };
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::isValid in C++
    /// </summary>
    private bool IsValid(ReadOnlySpan<byte> span)
    {
        byte byteValue = ReadWriteHelper.ReadUint8(span, 0);
        return byteValue == 'R' || byteValue == 'Y';
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::setFieldType in C++
    /// </summary>
    private void SetFieldType(ReadOnlySpan<byte> span, out bool isWarningField, out bool isProtectiveField)
    {
        byte fieldType = ReadEvalMethod(span);
        isWarningField = false;
        isProtectiveField = false;
        if (fieldType == 4 || fieldType == 14)
        {
            isProtectiveField = true;
        }
        else if (fieldType == 5 || fieldType == 15)
        {
            isWarningField = true;
        }
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::readVersionIndicator in C++
    /// </summary>
    private string ReadVersionIndicator(ReadOnlySpan<byte> span)
    {
        byte ch = ReadWriteHelper.ReadUint8(span, 0);
        return ((char)ch).ToString();
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::readMajorNumber in C++
    /// </summary>
    private byte ReadMajorNumber(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint8(span, 1);
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::readMinorNumber in C++
    /// </summary>
    private byte ReadMinorNumber(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint8(span, 2);
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::readReleaseNumber in C++
    /// </summary>
    private byte ReadReleaseNumber(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint8(span, 3);
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::readIsDefined in C++
    /// </summary>
    private bool ReadIsDefined(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint8(span, 72) != 0;
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::readEvalMethod in C++
    /// </summary>
    private byte ReadEvalMethod(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint8(span, 73);
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::readMultiSampling in C++
    /// </summary>
    private ushort ReadMultiSampling(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint16LittleEndian(span, 74);
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::readObjectResolution in C++
    /// </summary>
    private ushort ReadObjectResolution(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint16LittleEndian(span, 78);
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::readSetIndex in C++
    /// </summary>
    private ushort ReadSetIndex(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint16LittleEndian(span, 82);
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::readNameLength in C++
    /// </summary>
    private uint ReadNameLength(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint32LittleEndian(span, 84);
    }
    
    /// <summary>
    /// Matches: ParseFieldHeaderData::readFieldName in C++
    /// </summary>
    private string ReadFieldName(ReadOnlySpan<byte> span, uint nameLength)
    {
        var nameBuilder = new StringBuilder((int)nameLength);
        for (uint i = 0; i < nameLength; i++)
        {
            byte ch = ReadWriteHelper.ReadUint8(span, 88 + (int)i);
            nameBuilder.Append((char)ch);
        }
        
        return nameBuilder.ToString();
    }
}