//Define the Pattern Interface and Handler Objects.

//Define the IVisitor interface to be used as the "blueprint" for the main application classes.
//This interface defines the Visit() method, which accepts the object to be visited as a parameter.
public interface IVisitor
{
void Visit(Element element);
}

//The PrintVisitor class (object) invokes the Accept() method on the class (object) to be visited.
//The visited class, in turn, invokes the Visit() method on the PrintVisitor class.
//The Visit() method contains the process (code) that needs to be executed against the visited class (object) each time the object is visited.
public class PrintVisitor : IVisitor
{
public void Print(Element element)
{
element.Accept(this);
if (element.Child != null)
{
Console.Write(" [");
Print(element.Child);
}

if (element.Next != null)
{
Print(element.Next);
Console.Write("] ");
}
}

public void Visit(Element element)
{
Console.Write(" {0}", element.Weight);
}
}

//The StructureVisitor class (object) invokes the Accept() method on the class (object) to be visited.
//The visited class, in turn, invokes the Visit() method on the StructureVisitor class.
//The Visit() method contains the process (code) that needs to be executed against the visited class (object) each time the object is visited.
public class StructureVisitor : IVisitor
{
public int Lab { get; set; }
public int Test { get; set; }

public void VisitAllLabTest(Element element)
{
element.Accept(this);
if (element.Child != null)
{
VisitAllLabTest(element.Child.Next);
}

if (element.Next != null)
{
VisitAllLabTest(element.Next);
}
}

public void Visit(Element element)
{
if ((element.GetType() == typeof(MidTerm) || element.GetType() == typeof(Exam)) && element.Child == null)
{
Test += element.Weight;
return;
}

if (element.GetType() == typeof(Lab))
{
Lab += element.Weight;
return;
}

if (element.GetType() == typeof(Test))
{
Test += element.Weight;
}
}
}