// *********************************************************
// Implementation file StackP.cpp for the ADT stack.
// Pointer-based implementation.
// *********************************************************
#include "StackP.h"  // header file
#include <cstddef>   // for NULL
#include <cassert>   // for assert

Stack::Stack() : top(NULL)
{
}  // end default constructor

Stack::Stack(const Stack& aStack)
{
   if (aStack.top == NULL)
      top = NULL;  // original list is empty

   else
   {  // copy first node
      top = new StackNode(aStack.top->item);

      // copy rest of list
      StackNode *newNode = top;    // new list pointer
      for (StackNode *origNode = aStack.top->next;
                      origNode != NULL;
                      origNode = origNode->next)
      {  
         newNode->next = new StackNode(origNode->item->clone());
         newNode = newNode->next;
      }  // end for

   }  // end if
}  // end copy constructor

Stack::~Stack()
{
   popAll();
   // Assertion: top == NULL
}  // end destructor

bool Stack::isEmpty() const
{
   return top == NULL;
}  // end isEmpty

void Stack::push(Object* newItem)
{
   // create a new node
   StackNode *newNode = new StackNode(newItem,top);
   top = newNode;
}  // end push

Object* Stack::pop() throw(StackException)
{
   if (isEmpty())
      throw StackException("StackException: stack empty on pop");
   else
   {  // stack is not empty; delete top
      StackNode *tempNode = top;
      top = top->next;
      // return deleted node to system
      Object* item = tempNode->item;
      delete tempNode;
      return item;
   }  // end if
}  // end pop

void Stack::popAll()
{
   while (!isEmpty())
   {  // stack is not empty; retrieve and delete top
      delete pop();
   }  // end if
}  // end pop

const Object* Stack::peek() const throw(StackException)
{
   if (isEmpty())
      throw StackException("StackException: stack empty on getTop");
   else
      // stack is not empty; retrieve top
      return top->item;
}  // end getTop
// End of implementation file.