using System;

public abstract class ShoppingCartBase

{

    private string customerEmail;

    private decimal orderTotal;

    protected string GetUserEmail()

    {

        return this.customerEmail;

    }

​

    protected decimal CalculateTotal()

    {

        return this.orderTotal;

    }

​

    public void Checkout(string customerEmail, decimal orderTotal)

    {

        this.customerEmail = customerEmail;

        this.orderTotal = orderTotal;

    }

}

​

public interface IPaymentProcessor

{

    bool PayOnline(decimal totalAmount);

}

​

public class PaymentProcessor : IPaymentProcessor

{

    private Random random = new Random();

    public bool PayOnline(decimal totalAmount)

    {

        var randomNumber = random.Next(1, 100);

        var paymentSucceeds = randomNumber % 2 == 0;

        var paymentMessage = paymentSucceeds ? "succeeded" : "failed";

        Console.WriteLine($"Payment processor: payment of {totalAmount} {paymentMessage}");

        return paymentSucceeds;

    }

}

​

public interface IEmailServer

{

    void SendEmail(string to, string message);

}

​

public class EmailServer : IEmailServer

{

    public void SendEmail(string to, string message)

    {

        Console.WriteLine($"Email server: sending email to '{to}' with message: {message}");

    }

}

​

public class ShoppingCart : ShoppingCartBase

{

    private readonly IPaymentProcessor paymentProcessor;

    private readonly IEmailServer emailServer;

    public ShoppingCart(IPaymentProcessor paymentProcessor, IEmailServer emailServer)

    {

        this.paymentProcessor = paymentProcessor;

        this.emailServer = emailServer;

    }

    public bool PlaceOrder()

    {

        // calculate totals

        var orderTotal = CalculateTotal();

        // pay online

        var paymentSucceeded = this.paymentProcessor.PayOnline(orderTotal);

        // send confirmation email

        this.emailServer.SendEmail(GetUserEmail(), paymentSucceeded ? "order succesfully placed" : "online payment failed, your order wasn't placed");

        return paymentSucceeded;

    }

}

​

public class Program

{

    public static void Main()

    {

        var paymentProcessor = new PaymentProcessor();

        var emailServer = new EmailServer();

        var shoppingCart = new ShoppingCart(paymentProcessor, emailServer);

        shoppingCart.Checkout("user@gmail.com", 200);

        shoppingCart.PlaceOrder();

    }

}