02. Song Encryption-Programming Fundamentals Final Exam Prep

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

namespace _02._Song_Encryption
{
    class Program
    {
        static void Main(string[] args)
        {
            string pattern = @"^([A-Z]{1}[a-z]+([ |']*[a-z]*)*):([A-Z]+( ?[A-Z]?)+)$";
            string input;
            while ((input = Console.ReadLine()) != "end")
            {
                Match match = Regex.Match(input, pattern);
                if (!match.Success)
                {
                    Console.WriteLine("Invalid input!");
                }
                else
                {
                    int key = match.Groups[1].Length;

                    string artist = match.Groups[1].Value;
                    StringBuilder matches = new StringBuilder();
                    matches.Append(match.Groups[1]);
                    matches.Append('@');
                    matches.Append(match.Groups[3]);
                    StringBuilder encryptedArtistSong = new StringBuilder();
                    foreach (char item in matches.ToString())
                    {

                        if (!(item == ' ' || item == '\'' || item == '@'))
                        {
                            char newChar = ' ';
                            if (char.IsUpper(item) && ((int)item + key) <= 90)
                            {
                                newChar = (char)((int)item + key);

                            }
                            else if (char.IsUpper(item) && ((int)item + key) > 90)
                            {
                                newChar = (char)((int)item + key - 90 + 64);
                            }
                            else if (char.IsLower(item) && ((int)item + key) <= 122)
                            {
                                newChar = (char)((int)item + key);

                            }
                            else if (char.IsLower(item) && ((int)item + key) > 122)
                            {
                                newChar = (char)((int)item + key - 122 + 96);
                            }
                            encryptedArtistSong.Append(newChar);
                        }
                        else
                        {
                            encryptedArtistSong.Append(item);
                        }

                    }
                    Console.WriteLine($"Successful encryption: {encryptedArtistSong}");

                }
            }
        }
    }
}