using System;

​

public class Program

{

  public static void Main()

  {

    new Multiple3Or5(3, 20).PrintOutput();

​

    Test3Next();

    Test5Next();

    TestNReached();

  }

​

  static void Test3Next()

  {

    var n3 = new Multiple3Or5(3, 20);

    Console.WriteLine(n3.GetNextNumber().Number == 5);

  }

​

  static void Test5Next()

  {

    var n5 = new Multiple3Or5(5, 20);

    Console.WriteLine(n5.GetNextNumber().Number == 6);

  }

​

  static void TestNReached()

  {

    var n3 = new Multiple3Or5(10, 10);

    Console.WriteLine(n3.GetNextNumber() == null);

  }

​

  class Multiple3Or5

  {

    public Multiple3Or5(int num, int n) { Number = num; N = n; }

    public int Number { get; private set; }

    private int N { get; set; }

​

    public void PrintOutput()

    {

      var next = GetNextNumber();

      if (next == null) return;

      Console.WriteLine(next.Number);

      next.PrintOutput();

    }

​

    public Multiple3Or5 GetNextNumber()

    {

      // can use class variable to avoid calculation again so we can move the PrintOutput out but for 3 and 5

      // we will have duplicate code. Can be separated into a class.

      int remainder3 = Number % 3;    

      int remainder5 = Number % 5;

​

      PrintOutput(remainder3, remainder5);    // this line is in the wrong func

​

      int nextNum = Number + ((3 - remainder3) > (5 - remainder5) ? (5 - remainder5) : (3 - remainder3));

      return (nextNum > N) ? null : new Multiple3Or5(nextNum, N);

    }

​

    private void PrintOutput(int r3, int r5)

    {

      if (r3 == 0 && r5 == 0)

        Console.WriteLine("FizzBuzz");

      else if (r3 == 0)

        Console.WriteLine("Fizz");

      else if (r5 == 0)

        Console.WriteLine("Buzz");

    }

  }

}