namespace Finance.Utilities;
public static class StringExtensions
{
    public static string MaskSensitiveData(this string input)
    {
        if (string.IsNullOrEmpty(input) || input.Length <= 4)
        {
            return input;
        }
        string result = "";
        int maskLength = input.Length - 4;
        // Manually build the string using basic loops and concatenation
        for (int i = 0; i < input.Length; i++)
        {
            if (i < maskLength)
            {
                result += "*";
            }
            else
            {
                result += input[i];
            }
        }
        
        return result;
    }
}