Retrieve directory listing information from FTP

FTPHelper.cs

using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Net;
using System.Text.RegularExpressions;

namespace FTPHelper
{
    public class FTPItem
    {
        public char[] Permissions { get; set; }
        public int Size { get; set; }
        public DateTime LastModified { get; set; }
        public string Name { get; set; }
        public string FullPath { get; set; }

        public override string ToString()
        {
            return Name;
        }
    }

    public class FTPDirectory : FTPItem
    {
        public FTPDirectory(FTPItem item)
        {
            Permissions = item.Permissions;
            Size = item.Size;
            LastModified = item.LastModified;
            Name = item.Name;
            FullPath = item.FullPath;
        }

        public Lazy<List<FTPItem>> SubItems { get; set; }
    }

    public class FTPFile : FTPItem
    {
        public FTPFile(FTPItem item)
        {
            Permissions = item.Permissions;
            Size = item.Size;
            LastModified = item.LastModified;
            Name = item.Name;
            FullPath = item.FullPath;
        }
    }

    public class FTPClient
    {
        private string address;
        private string username;
        private string password;

        public FTPClient(string address, string username, string password)
        {
            this.address = address.StartsWith("ftp://", StringComparison.OrdinalIgnoreCase) ? address : $"ftp://{address}";
            this.username = username;
            this.password = password;
        }

        public List<FTPItem> RetrieveDirectoryListingsFromFTP(string startingPath = null)
        {
            List<FTPItem> results = new List<FTPItem>();
            string path = !string.IsNullOrEmpty(startingPath) ? startingPath.Replace(" ", "%20") : address;
            path = !path.StartsWith(address) ? $"{address}/{path}" : path;

            FtpWebRequest request = (FtpWebRequest)WebRequest.Create(path);
            request.Method = WebRequestMethods.Ftp.ListDirectoryDetails;
            request.Credentials = new NetworkCredential(username, password);
            request.KeepAlive = false;
            request.UseBinary = true;
            request.UsePassive = true;

            Regex directoryListingRegex = new Regex(@"^([d-])((?:[rwxt-]{3}){3})\s+\d{1,}\s+.*?(\d{1,})\s+(\w+)\s+(\d{1,2})\s+(\d{4})?(\d{1,2}:\d{2})?\s+(.+?)\s?$",
                                    RegexOptions.Compiled | RegexOptions.Multiline | RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhitespace);

            using (FtpWebResponse response = (FtpWebResponse)request.GetResponse())
            {
                using (Stream responseStream = response.GetResponseStream())
                {
                    using (StreamReader reader = new StreamReader(responseStream))
                    {
                        string line;
                        while ((line = reader.ReadLine()) != null)
                        {
                            Match match = directoryListingRegex.Match(line);

                            FTPItem item = new FTPItem
                            {
                                Permissions = match.Groups[2].Value.ToArray(),
                                Size = int.Parse(match.Groups[3].Value),
                                LastModified = DateTime.ParseExact($"{match.Groups[4]} {match.Groups[5]} {match.Groups[6]} {match.Groups[7]}",
                                                    $"MMM dd {(match.Groups[6].Value != "" ? "yyyy" : "")} {(match.Groups[7].Value != "" ? "HH:mm" : "")}",
                                                    CultureInfo.InvariantCulture, DateTimeStyles.AdjustToUniversal | DateTimeStyles.AssumeUniversal),
                                Name = match.Groups[8].Value,
                                FullPath = $"{path}/{match.Groups[8].Value.Replace(" ", "%20")}",
                            };

                            if (match.Groups[1].Value == "d")
                            {
                                FTPDirectory dir = new FTPDirectory(item);
                                dir.SubItems = new Lazy<List<FTPItem>>(() => RetrieveDirectoryListingsFromFTP(dir.FullPath));
                                results.Add(dir);
                            }
                            else
                            {
                                FTPFile file = new FTPFile(item);
                                results.Add(file);
                            }
                        }
                    }
                }
            }

            return results;
        }
    }
}