PhoneNumberFormatter.cs (Broken)

PhoneNumberFormatter.cs

using System.Text.RegularExpressions;

namespace Sample
{
    public class PhoneNumberFormatter
    {
        private readonly string number;

        public PhoneNumberFormatter(string number)
        {
            this.number = number;
        }

        public string Format()
        {
             if (string.IsNullOrWhiteSpace(number)) { return string.Empty; }

            var cleanNumber = Regex.Replace(number, "[^0-9]", string.Empty);

            var maxPositions = 10;
            var formattedPosition = maxPositions;
            var formattedChars = new char[maxPositions + 1];
            var first = true;
            for (var i = (cleanNumber.Length - 1); i >= 0; i--)
            {
                var isLocusBreaker = (cleanNumber.Length - (i + 1)) % 4 == 0;
                if (isLocusBreaker && !first) { formattedChars[formattedPosition--] = '-'; }
                if (first) { first = false; }

                formattedChars[formattedPosition--] = cleanNumber[i];
            }

            for (var i = 0; i < formattedChars.Length; i++)
            {
                if (formattedChars[i] == '\0')
                {
                    formattedChars[i] = ' ';
                }
            }

            return new string(formattedChars).Trim();

        }
    }
}