using System.Text;
using Sick.Tim781s.Colab.Helpers;

namespace Sick.Tim781s.Colab.Commands;

/// <summary>
/// Command to read a value from the scanner (sRN - Read by Name)
/// </summary>
public sealed class ReadCommand : CommandBase
{
    public ReadCommand(string variableName) 
        : base($"sRN {variableName}")
    {
        VariableName = variableName;
    }

    public string VariableName { get; }

    public string? ReplyValue { get; private set; }
    
    public byte[]? RawReplyData { get; private set; }

    public override bool ProcessReply(ReadOnlyMemory<byte> replyData)
    {
        // Store raw reply data for binary parsing
        RawReplyData = replyData.ToArray();
        
        // Parse reply: "sAN <variableName> <value>" or "sRA <variableName> <value>"
        // For binary data, only the header is ASCII, the rest is binary
        // Try to find where ASCII header ends
        var asciiHeaderEnd = -1;
        for (int i = 0; i < replyData.Length && i < 100; i++)
        {
            if (replyData.Span[i] == 0 || replyData.Span[i] > 127)
            {
                // Found non-ASCII byte, header ends here
                asciiHeaderEnd = i;
                break;
            }
        }
        
        // If we found where ASCII ends, only decode that part
        var headerLength = asciiHeaderEnd > 0 ? asciiHeaderEnd : Math.Min(replyData.Length, 100);
        var replyString = Encoding.ASCII.GetString(replyData.Span.Slice(0, headerLength));
        
        // Check if reply starts with "sAN" (Answer) or "sRA" (Read Answer)
        if (!replyString.StartsWith("sAN", StringComparison.Ordinal) && 
            !replyString.StartsWith("sRA", StringComparison.Ordinal))
        {
            WasSuccessful = false;
            return false;
        }

        // Extract value after variable name
        var parts = replyString.Split(' ', StringSplitOptions.RemoveEmptyEntries);
        if (parts.Length >= 2 && parts[1] == VariableName)
        {
            // For binary data, ReplyValue will contain ASCII header only
            // The actual binary data is in RawReplyData
            if (parts.Length >= 3)
            {
                ReplyValue = string.Join(" ", parts.Skip(2));
            }
            else
            {
                // Binary data follows immediately after header
                ReplyValue = string.Empty;
            }
            WasSuccessful = true;
            return true;
        }

        WasSuccessful = false;
        return false;
    }
}