using System;
using System.Collections.Generic;
using System.Text;
using System.Linq;

using System.Text.RegularExpressions;
using System.IO;

namespace Hoge
{
    public class Test
    {
        class Reader
        {
            TextReader reader;
            string cache;

            public Reader(TextReader reader) { this.reader = reader; }

            /// <summary>
            /// 次の行を返す
            /// </summary>
            public string ReadLine() { cache = reader.ReadLine(); return cache; }

            /// <summary>
            /// 今の行を返す
            /// </summary>
            public string PeekLine() { return cache; }
        }

        IEnumerable<Folder> Folders(Reader sr)
        {
            var str = sr.ReadLine();

            while (str != null)
            {
                if (IsSubFolder(str))
                {
                    //いきなりサブフォルダはない
                    throw new Exception();
                }
                else
                {
                    yield return new Folder(str, SubFolders(sr));
                    str = sr.PeekLine();
                }
            }
        }

        IEnumerable<SubFolder> SubFolders(Reader sr)
        {
            while (true)
            {
                var str = sr.ReadLine();

                if (str == null) yield break;

                if (IsSubFolder(str))
                {
                    yield return new SubFolder(SubFolderName(str));
                }
                else
                {
                    yield break;
                }
            }
        }

        bool IsSubFolder(string s)
        {
            return s.StartsWith("..");
        }

        string SubFolderName(string s)
        {
            return s.Substring(2);
        }

        class Folder
        {
            public string Name;

            public Folder(string name, IEnumerable<SubFolder> subFolders)
            {
                this.Name = name;
                SubFolders = subFolders;
            }
            public IEnumerable<SubFolder> SubFolders;
        }

        class SubFolder
        {
            public string Name;
            public SubFolder(string name)
            {
                this.Name = name;
            }
        }


        public static void Do()
        {
            var text =
@"folder1
..subfolder1
folder2
..subfolder1
..subfolder2";

            var sr = new StringReader(text);

            var folders = new Test().Folders(new Reader(sr));


            foreach (var f in folders)
            {
                Console.WriteLine(f.Name);

                //fを取り出しているのにSubFoldersを列挙しないと、無限ループに突入する
                foreach (var s in f.SubFolders)
                {
                    Console.WriteLine(s.Name);
                }
            }
        }
    }
}