using Sick.SafetyScanners.DataStructures;
using Sick.SafetyScanners.Helpers;

namespace Sick.SafetyScanners.DataProcessing;

/// <summary>
/// Parser for MonitoringCaseData response from COLA2 variable command
/// Thread-safe implementation
/// </summary>
public sealed class ParseMonitoringCaseData
{
    /// <summary>
    /// Parses the monitoring case data from a TCP sequence (COLA2 response)
    /// Matches: ParseMonitoringCaseData::parseTCPSequence in C++
    /// </summary>
    public MonitoringCaseData ParseTcpSequence(PacketBuffer buffer)
    {
        var span = buffer.GetBufferSpan();
        bool valid = IsValid(span);
        
        if (!valid)
        {
            return new MonitoringCaseData
            {
                IsValid = false
            };
        }
        
        var indices = new List<ushort>(8);
        var fieldsValid = new List<bool>(8);
        
        for (int i = 0; i < 8; i++)
        {
            indices.Add(ReadFieldIndex(span, i));
            fieldsValid.Add(ReadFieldValid(span, i));
        }
        
        return new MonitoringCaseData
        {
            IsValid = true,
            MonitoringCaseNumber = ReadMonitoringCaseNumber(span),
            FieldIndices = indices,
            FieldsValid = fieldsValid
        };
    }
    
    /// <summary>
    /// Matches: ParseMonitoringCaseData::isValid in C++
    /// </summary>
    private bool IsValid(ReadOnlySpan<byte> span)
    {
        byte byteValue = ReadWriteHelper.ReadUint8(span, 0);
        return byteValue == 'R' || byteValue == 'Y';
    }
    
    /// <summary>
    /// Matches: ParseMonitoringCaseData::readMonitoringCaseNumber in C++
    /// </summary>
    private ushort ReadMonitoringCaseNumber(ReadOnlySpan<byte> span)
    {
        return ReadWriteHelper.ReadUint16LittleEndian(span, 6);
    }
    
    /// <summary>
    /// Matches: ParseMonitoringCaseData::readFieldIndex in C++
    /// </summary>
    private ushort ReadFieldIndex(ReadOnlySpan<byte> span, int index)
    {
        return ReadWriteHelper.ReadUint16LittleEndian(span, 158 + (index * 4));
    }
    
    /// <summary>
    /// Matches: ParseMonitoringCaseData::readFieldValid in C++
    /// </summary>
    private bool ReadFieldValid(ReadOnlySpan<byte> span, int index)
    {
        byte byteValue = ReadWriteHelper.ReadUint8(span, 157 + (index * 4));
        return (byteValue & (0x01 << 0)) != 0;
    }
}