Decode cloth data from https://santatracker.google.com/santaselfie.html

SantaDecode.cs

string[] sprayNames = new[]
{
    "red", "orange", "yellow", "green", "cyan", "purple", "pink", "blue"
};
string[] decorationNames = new[]
{
    "snowman", "bauble", "bow", "holly"
};
char[] charMap = new []{'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};


string RleDecode(string input)
{
    string rleString = string.Empty;
    var numMatches = Regex.Matches(input, "([0-9]+)");
    var charMatches = Regex.Matches(input, "([A-Za-z])");
    Debug.Assert(numMatches.Count == charMatches.Count);
    for (int s = 0; s < charMatches.Count; s++)
    {
        char c = charMatches[s].Groups[0].Value[0];
        for (int n = 0; n < int.Parse(numMatches[s].Groups[0].Value); n++)
        {
            rleString += c;
        }
    }
    return rleString;
}

int[] Base52Decode(string input)
{
    int[] output = new int[input.Length];
    for (int i = 0; i < output.Length; i++)
    {
        output[i] = Array.IndexOf(charMap, input[i]);
    }
    return output;
}

void Main()
{
    var input = "1B2G2B5G10B3G1B2G2B2G1B2G3B1G1B2G5B3G3B1G2B6G1B2G7B1G3B5G1B1G2B2G1B2G5B2G2B5G4B2G1B3G4B2G3B4G2B2G5B2G1B1G7B3G1B3G6B1G7B9G5B3G5B1G1B5G1B2G4B5G3B1G1I2G1B1G3B1G1B7G3B8G5B7G4B8G1B1G5B2G7B7G1B4G3B1G6B8G1B1G1B3G9B2G1B1G1B10G2B2G4B3G1B3G1B7G2B1G2B1A2B2G1B6G1B6G1B1G2B1A2B6G2B3G1B1G1B2G1B2G1B1A13G1B4G4B1A8G1B5G1B5G1B2A3B6G1B10G1B2A3B15G2B3A1G4B13G1B4A1G1B2G1B11G2B5A2B2G1B1G1B9G7A14B9A1B2G15B2G2B2G2B2G2B3G1B3G2B2G1B3G1B1G";

    string rleString = RleDecode(input);
    Console.Out.WriteLine(rleString);
    if (rleString.Length != 645)
    {
        Console.Out.WriteLine("length should be 645");
    }
        
    int[] output = Base52Decode(rleString);
    //Console.Out.WriteLine(output);
    
    for (int i = 0; i < output.Length; i++)
    {
        var point = new ClothPoint(output[i]);
        Console.Out.Write($"{i} - {output[i]}");
        if (!point.Draw())
        {
            Console.Out.WriteLine($" - hidden");
            continue;
        }
        if (point.IsPlain())
        {
            Console.Out.WriteLine($" - plain");
            continue; // wont be anything else
        }
        
        var spray = point.Spray();
        if (spray != null)
        {
            Console.Out.Write($" - {sprayNames[spray.Value]} spray ({spray})");
        }
        
        var decoration = point.Decoration();
        if (decoration != null)
        {
            Console.Out.Write($" - {decorationNames[decoration.Value]} decoration ({decoration})");
        }
        Console.Out.WriteLine();
    }
}

struct ClothPoint
{
    private readonly int m_value;
    
    public ClothPoint(int value)
    {
        m_value = value;
    }
    
    public bool IsPlain() => m_value == 1;
    
    public bool Draw() => 0 < m_value;
    public int? Spray() 
    {
        var sprayValue = (int)Math.Floor((decimal)(m_value - 1) / 5); // hmm decimal. most precice floor
        if (sprayValue == 0) return null;
        return sprayValue-1;
    }
    public int? Decoration() 
    {
        var decorationValue = (m_value - 1) % 5;
        if (decorationValue == 0) return null;
        return decorationValue-1;
    }
}