using System;

using System.Collections.Generic;

public class ClientApp

    {

        public static void Main()

        {

            OrderingFascade of = new OrderingFascade();

            of.PlaceOrder(12, 22.50);

        }

    }

​

    public class OrderingFascade

    {

        private Accounting acct = new Accounting();

        private Warehouse wh = new Warehouse();

​

        public int PlaceOrder(int productId, double amt)

        {

            var orderId = -1;

​

            if (productId > 0 && amt > 0)

            {                

                if (wh.IsInInventory(productId))

                {

                    orderId = (int)Math.Round(Math.PI * DateTime.Now.Second, 0);                    

                    if (!acct.ProcessPayment(amt, orderId))

                    {

                        throw new Exception($"Payment for order {orderId} failed.");

                    }

                } else

                {

                    throw new Exception($"Product {productId} is out of stock.");

                }

            }

​

            return orderId;

        }

    }

​

    public class Accounting

    {

        public bool ProcessPayment(double amt, int orderId)

        {

            if (orderId > 0 && amt > 0)

            {

                return true;

            } else

            {

                return false;

            }

        }

    }

​

    public class Warehouse

    {

        public bool IsInInventory(int productId)

        {

            if (productId > 10)

            {

                return true;

            } else

            {

                return false;

            }

        }

    }  

​

​