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

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

    if (newNode == NULL)
    {
        return stack;
    }

    newNode->data = data;
    newNode->next = stack;

    return newNode;
}

// 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 *nextNode = NULL;

    if (stack != NULL)
    {
        nextNode = stack->next;
        free(stack);
    }

    return nextNode;
}

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

    if (stack != NULL)
    {
        data = stack->data;
    }

    return data;
}

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

    while (currentNode != NULL)
    {
        nextNode = currentNode->next;
        free(currentNode);
        currentNode = nextNode;
    }
}