/** @file StackP.cpp */

#include <cstddef>   // for NULL
#include <new>       // for bad_alloc
#include "C6-StackP.h"  // header file

using namespace std;

Stack::Stack() : topPtr(NULL)
{
}

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

  else{
    // copy first node
    topPtr = new StackNode;
    topPtr->item = aStack.topPtr->item;

    // copy rest of list
    StackNode *newPtr = topPtr;    // new list pointer
    for (StackNode *origPtr = aStack.topPtr->next;
	 origPtr != NULL;
	 origPtr = origPtr->next){
      newPtr->next = new StackNode;
      newPtr = newPtr->next;
      newPtr->item = origPtr->item;
    }
    
    newPtr->next = NULL;
  }
}

Stack::~Stack()
{
  // pop until stack is empty
  while (!isEmpty())
    pop();
  // Assertion: topPtr == NULL
}

bool Stack::isEmpty() const
{
  return topPtr == NULL;
}

void Stack::push(const StackItemType& newItem)
            throw(StackException)
{
  // create a new node
  try{
    StackNode *newPtr = new StackNode;
    
    // set data portion  of new node
    newPtr->item = newItem;
    
    // insert the new node
    newPtr->next = topPtr;
    topPtr = newPtr;
  }
  catch (bad_alloc e){
    throw StackException("StackException: push cannot allocate memory.");
  }
}

void Stack::pop() throw(StackException)
{
  if (isEmpty())
    throw StackException("StackException: stack empty on pop");
  else{
    // stack is not empty; delete top
    StackNode *temp = topPtr;
    topPtr = topPtr->next;
    // return deleted node to system
    temp->next = NULL;  // safeguard
    delete temp;
  }
}

void Stack::pop(StackItemType& stackTop) throw(StackException)
{
  if (isEmpty())
    throw StackException("StackException: stack empty on pop");
  else{
    // stack is not empty; retrieve and delete top
    stackTop = topPtr->item;
    StackNode *temp = topPtr;
    topPtr = topPtr->next;
    
    // return deleted node to system
    temp->next = NULL;  // safeguard
    delete temp;
  }
}

void Stack::getTop(StackItemType& stackTop) const throw(StackException)
{
  if (isEmpty())
    throw StackException("StackException: stack empty on getTop");
  else
    // stack is not empty; retrieve top
    stackTop = topPtr->item;
}