4. Fake Text Markup Language

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





namespace FTML_TryWithRegex
{
    class Program
    {
        static void Main()
        {
            string revTag = @"<rev>(?<group>[^<]*)</rev>";
            string upper = @"<upper>(?<group>[^<]*)</upper>";
            string lower = @"<lower>(?<group>[^<]*)</lower>";
            string toggle = @"<toggle>(?<group>[^<]*)</toggle>";
            string delTag = @"<del>(?<group>[^<]*)</del>";
            // ReadInput();
            StringBuilder readInput = new StringBuilder();
            ReadAllFTML(readInput);
            string input = readInput.ToString();


            int maches = -1;
            while (maches != 0)
            {
                int revCount = Regex.Matches(input, revTag).Count;
                if (revCount > 0)
                {
                    input = Regex.Replace(input, revTag, (m => Reverse(m.Groups["group"].Value)));
                }
                int upperCount = Regex.Matches(input, upper).Count;
                if (upperCount > 0)
                {
                    input = Regex.Replace(input, upper, (m => m.Groups["group"].Value.ToUpper()));
                }
                int lowerCount = Regex.Matches(input, lower).Count;
                if (lowerCount > 0)
                {
                    input = Regex.Replace(input, lower, (m => m.Groups["group"].Value.ToLower()));
                }
                int toggleCount = Regex.Matches(input, toggle).Count;
                if (toggleCount > 0)
                {
                    input = Regex.Replace(input, toggle, (m => Toggle(m.Groups["group"].Value)));
                }

                int delCount = Regex.Matches(input, delTag).Count;
                if (delCount > 0)
                {
                    input = Regex.Replace(input, delTag, string.Empty);
                }

                maches = delCount + lowerCount + upperCount + toggleCount + revCount;
            }
            Console.Write(input);
        }


        private static string Toggle(string p)
        {
            StringBuilder result = new StringBuilder();
            for (int i = 0; i < p.Length; i++)
            {
                if (p[i] >= 'A' && p[i] <= 'Z')
                {
                    result.Append(p[i].ToString().ToLower());
                }
                else if (p[i] >= 'a' && p[i] <= 'z')
                {
                    result.Append(p[i].ToString().ToUpper());
                }
                else
                {
                    result.Append(p[i]);
                }
            }
            return result.ToString();
        }

        private static void ReadAllFTML(StringBuilder readInput)
        {
            if (File.Exists(@"C:\Users\Admin\Desktop\Test.txt"))
            {

                Console.SetIn(new StreamReader(@"C:\Users\Admin\Desktop\Test.txt"));

            }


            int length = int.Parse(Console.ReadLine());
            for (int i = 0; i < length; i++)
            {
                readInput.AppendLine(Console.ReadLine());
            }
        }
        private static void ReadInput()
        {
            if (File.Exists("test.txt"))
            {
                Console.SetIn(new StreamReader("test.txt"));
            }
        }
        private static string Reverse(string p)
        {
            Stack<char> toRev = new Stack<char>();
            StringBuilder result = new StringBuilder();


            foreach (char item in p)
            {
                if (item != '\r')
                {
                    toRev.Push(item);

                }


            }
            foreach (var item in toRev)
            {
                result.Append(item);
            }
            return result.ToString();
        }
    }
}