#include "Stack.h"

Stack::Stack() {
	myCount = 0;
}

Stack::Node::Node(const Item& item, Node* next) {
	myItem = item;
	myNext = next;
}

Stack::Node::Node(const Item& item) {
	myItem = item;
	myNext = NULL;
}

Stack::~Stack() {
//	Node* ptr = NULL;
//	while (true) {
//		ptr = myTop;
//		if (ptr == NULL) break;
//		myTop = myTop->myNext;
//		delete ptr;
//	
//	}
	delete myTop;
	myTop = NULL;
}

//Stack::Node::~Node() {
////	delete myNext;
////	myNext = NULL;
//}

void Stack::push(const Item& newItem) {
	myTop = new Node(newItem, myTop);
	myCount++;
}

Item Stack::getTop() const {
	if ( isEmpty() ) {
		throw std::underflow_error("Stack::getTop(): stack is empty");
	}
	return myTop->myItem;
}

Item Stack::pop() {
	if ( isEmpty() ) {
		throw std::underflow_error("Stack::pop(): stack is empty");
	}
	Item result = myTop->myItem;
	Node* nPtr = myTop;
	myTop = myTop->myNext;
	nPtr->myNext = NULL;
	delete nPtr;
	myCount--;
	return result;
}