#include <stdlib.h>
#include "stack.h"

//TODO: grundlegende Stackfunktionen implementieren:
/*  * `push`: legt ein Element oben auf den Stack,
    * `pop`: entfernt das oberste Element,
    * `top`: liefert das oberste Element zurück,
    * `clearStack`: gibt den gesamten Speicher frei. */

// Pushes data as pointer onto the stack.
StackNode *push(StackNode *stack, void *data)
{
	StackNode* stacknew = malloc(sizeof(StackNode));

	stacknew->value = data;
	stacknew->prev = stack;

	return stacknew;
}

// Deletes the top element of the stack (latest added element) and releases its memory. (Pointer to data has to be
// freed by caller.)
StackNode *pop(StackNode *stack)
{
	StackNode *ptr = stack->prev;

	free(stack);
	return ptr;
}

// Returns the data of the top element.
void *top(StackNode *stack)
{

    return stack->value;

}

// Clears stack and releases all memory.
void clearStack(StackNode *stack)
{
    StackNode *ptr = stack;

    while (ptr != NULL) {

        StackNode *prev = ptr->prev;

        free(ptr->value);
        free(ptr);

        ptr = prev;
    }
}