using System;

// Program.cs
namespace Calculator
{
    public class Program
    {
        static void Main(string[] args)
        {
            Application app = new Application();
            app.Run();
        }
    }
}

// Application.cs
namespace Calculator
{
    public class Application
    {
        private const string AppTitle = "Mini Calculator";
        
        public void Run()
        {
            Console.Title = AppTitle;

            Console.WriteLine("###############");
            Console.WriteLine(AppTitle);
            Console.WriteLine("###############\n");

            string s;
            
            do
            {
                var userInputs = Input();
                var result = Calculate(userInputs);
                OutputResult(result);

                Console.WriteLine("Do you like to solve another arithmetical problem? (y/n)");
                s = Console.ReadLine().Trim().ToLower();
            } while (s.StartsWith("y"));

            Console.WriteLine("\nPress any key to exit...");
            Console.ReadKey();
        }
        
        public class UserInputs
        {
             public double Number1 { get; set; }
             public double Number2 { get; set; }
             public int Operator { get; set; }
        }

        public static UserInputs Input()
        {
            Console.WriteLine("Please enter your first number: ");
            double number1 = double.Parse(Console.ReadLine());
            Console.WriteLine($"You chose: {number1}");

            Console.WriteLine("Please enter your second number: ");
            double number2 = double.Parse(Console.ReadLine());
            Console.WriteLine($"You chose: {number2}");

            Console.WriteLine("Choose your operator by number and hit enter:");
            Console.WriteLine("> 1.) Addition");
            Console.WriteLine("> 2.) Subtraction");
            Console.WriteLine("> 3.) Multiplication");
            Console.WriteLine("> 4.) Division");

            int op = 0;
                
            while (true)
            {
                op = int.Parse(Console.ReadLine());
                Console.WriteLine($"You chose: {op}");

                if (op < 1 || op > 4)
                {
                    Console.WriteLine("Your input is invalid. Try again, with numerals 1 - 4.");
                    continue;
                }
                    
                break;
            }
                
            return new UserInputs() { Number1 = number1, Number2 = number2, Operator = op };
        }
        
        public double Calculate(UserInputs userInputs)
        {
            double result = 0;

            switch (userInputs.Operator)
            {
                case 1:
                    result = Calculation.Addition(userInputs.Number1, userInputs.Number2);
                    break;
                case 2:
                    result = Calculation.Subtraction(userInputs.Number1, userInputs.Number2);
                    break;
                case 3:
                    result = Calculation.Multiplication(userInputs.Number1, userInputs.Number2);
                    break;
                case 4:
                    result = Calculation.Division(userInputs.Number1, userInputs.Number2);
                    break;
            }
            
            return result;
        }
        
        public void OutputResult(double result)
        {
            Console.WriteLine($"Result: {result}");
        }
    }
} 

// Calculation.cs
namespace Calculator
{
    public static class Calculation
    {
        public static double Addition(double x, double y)
        {
            return x + y;
        }

        public static double Subtraction(double x, double y)
        {
            return x - y;
        }

        public static double Multiplication(double x, double y)
        {
            return x * y;
        }

        public static double Division(double x, double y)
        {
            return x / y;
        }
    }
}