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

namespace Sick.SafetyScanners.Cola2.Commands;

/// <summary>
/// Command to request the latest telegram (measurement data) from the sensor via TCP
/// Variable index: 179 + channel_index (179 for channel 0, 180 for channel 1, etc.)
/// </summary>
public sealed class LatestTelegramVariableCommand : CommandBase
{
    private readonly ushort _variableIndex;
    private readonly ParseData _dataParser;
    private UdpScanData? _scanData;
    
    /// <summary>
    /// Creates a new LatestTelegramVariableCommand
    /// </summary>
    /// <param name="channelIndex">Channel index (0-3), defaults to 0</param>
    public LatestTelegramVariableCommand(sbyte channelIndex = 0)
        : base(0x52, 0x49) // 'R' and 'I' in ASCII (Read by Index)
    {
        if (channelIndex < 0 || channelIndex > 3)
        {
            throw new ArgumentOutOfRangeException(nameof(channelIndex), 
                "Channel index must be between 0 and 3");
        }
        
        // Variable index: 179 + channel_index
        _variableIndex = (ushort)(179 + channelIndex);
        _dataParser = new ParseData();
    }
    
    public ushort VariableIndex => _variableIndex;
    
    public override bool CanBeExecutedWithoutSessionId => true;
    
    /// <summary>
    /// Gets the parsed scan data after the command has been executed successfully
    /// </summary>
    public UdpScanData? ScanData => _scanData;
    
    protected override ReadOnlyMemory<byte> AddTelegramData()
    {
        var data = new byte[2];
        var span = data.AsSpan();
        
        // Variable index (2 bytes, little endian)
        ReadWriteHelper.WriteUint16LittleEndian(span, 0, _variableIndex);
        
        return data;
    }
    
    protected override bool ProcessReplyInternal(ReadOnlyMemory<byte> replyData, 
        byte replyCommandType, byte replyCommandMode)
    {
        // Reply should be 'R' (0x52) and 'A' (0x41) for Acknowledge
        if ((replyCommandType == 0x52 && replyCommandMode == 0x41) ||
            (replyCommandType == 'R' && replyCommandMode == 'A'))
        {
            try
            {
                // Parse the TCP sequence data
                // The replyData contains the measurement data payload
                var packetBuffer = new PacketBuffer(replyData.ToArray(), replyData.Length);
                _scanData = _dataParser.ParseTcpSequence(packetBuffer);
                return true;
            }
            catch (Exception)
            {
                // Parsing failed
                return false;
            }
        }
        
        return false;
    }
}