using System;
 
namespace DoFactory.GangOfFour.Proxy.RealWorld
{
  /// 

  /// MainApp startup class for Real-World 
  /// Proxy Design Pattern.
  /// 

  class MainApp
  {
	/// 

	/// Entry point into console application.
	/// 

    static void Main()
    {
      // Create math proxy
      MathProxy proxy = new MathProxy();

      // Do the math
      Console.WriteLine("4 + 2 = " + proxy.Add(4, 2));
      Console.WriteLine("4 - 2 = " + proxy.Sub(4, 2));
      Console.WriteLine("4 * 2 = " + proxy.Mul(4, 2));
      Console.WriteLine("4 / 2 = " + proxy.Div(4, 2));
 
      // Wait for user
      Console.ReadKey();
    }
  }
 
  /// 

  /// The 'Subject interface
  /// 
  public interface IMath
  {
    double Add(double x, double y);
    double Sub(double x, double y);
    double Mul(double x, double y);
    double Div(double x, double y);
  }
 
  /// 

  /// The 'RealSubject' class
  /// 
  class Math : IMath
  {
    public double Add(double x, double y) { return x + y; }
    public double Sub(double x, double y) { return x - y; }
    public double Mul(double x, double y) { return x * y; }
    public double Div(double x, double y) { return x / y; }
  }
 
  /// 

  /// The 'Proxy Object' class
  /// 
  class MathProxy : IMath
  {
    private Math _math = new Math();
 
    public double Add(double x, double y)
    {
      return _math.Add(x, y);
    }
    public double Sub(double x, double y)
    {
      return _math.Sub(x, y);
    }
    public double Mul(double x, double y)
    {
      return _math.Mul(x, y);
    }
    public double Div(double x, double y)
    {
      return _math.Div(x, y);
    }
  }
}