namespace AccountSample
{
	// Methodless roles
	public interface TransferMoneySink
	{
	}
 
 
	// Methodfull roles
	public interface TransferMoneySource
	{
	}
 
	public static class TransferMoneySourceTraits
	{
		public static void TransferFrom(this TransferMoneySource self, TransferMoneySink recipient, double amount)
		{
			Account self_ = self as Account;
			Account recipient_ = recipient as Account;
 
			// Selfcontained readable and testable algorithm
 
			if (self_ != null && recipient_ != null)
			{
				self_.Withdraw(amount);
				self_.Log("Withdrawing " + amount);
				recipient_.Deposit(amount);
				recipient_.Log("Depositing " + amount);
			}
		}
	}
 
 
	// Context object
	public class TransferMoneyContext
	{
		// Properties for accesing the concrete objects relevant in this context through their methodless roles
		public TransferMoneySource Source { get; private set; }
		public TransferMoneySink Sink { get; private set; }
		public double Amount { get; private set; }
 
		public TransferMoneyContext()
		{
			// logic for retrieving source and sink accounts
		}
 
		public TransferMoneyContext(TransferMoneySource source, TransferMoneySink sink, double amount)
		{
			Source = source;
			Sink = sink;
			Amount = amount;
		}
 
		public void Doit()
		{
			Source.TransferFrom(Sink, Amount);
			// Alternatively the context could be passed to the source and sink object.
		}
	}
 
 
	// Abstract domain object
	public abstract class Account
	{
		public abstract void Withdraw(double amount);
		public abstract void Deposit(double amount);
		public abstract void Log(string message);
	}
 
	// Concrete domain object
	public class SavingsAccount : Account, TransferMoneySource, TransferMoneySink
	{
		private double balance;
 
		public SavingsAccount()
		{
			balance = 10000;
		}
 
		public override void Withdraw(double amount)
		{
			balance -= amount;
		}
 
		public override void Deposit(double amount)
		{
			balance += amount;
		}
 
		public override void Log(string message)
		{
			Console.WriteLine(message);
		}
 
		public override string ToString()
		{
			return "Balance " + balance;
 
		}
	}
 
 
 
	// Test app
	public class Program
	{
		public static void Main(string[] args)
		{
			SavingsAccount src = new SavingsAccount();
			SavingsAccount snk = new SavingsAccount();
 
			Console.WriteLine("Before:");
			Console.WriteLine("Src:" + src);
			Console.WriteLine("Snk:" + snk);
 
			Console.WriteLine("Run transfer:");
			new TransferMoneyContext(src, snk, 1000).Doit();
 
			Console.WriteLine("After:");
			Console.WriteLine("Src:" + src);
			Console.WriteLine("Snk:" + snk);
 
			Console.ReadLine();
		}
	}
 
}