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

static int growStack (stack *);

int initStack (stack **inst) {

  *inst = calloc (1, sizeof(stack));
  (*inst)->items = calloc (DEFAULT_SIZE_STACK, sizeof(void *));
  
  (*inst)->size = DEFAULT_SIZE_STACK;
  
  return 0;
}

int destroyStack(stack **inst) {

  free ((*inst)->items);  
  free (*inst);
  *inst = NULL;

  return 0;
}


int pushStack (stack *inst, void *item) {

  if (!inst) return -1;
  if (!item) return -1;
  
  if (inst->count == inst->size)
    growStack(inst);

  inst->items[inst->count++] = item;

  return 0;
}


int popStack (stack *inst, void **item) {

  if (!inst) return -1;
  if (!item) return -1;
  if (!inst->count) return -1;

  *item = inst->items[inst->count-1];
  inst->count--;
  
  return 0;
}

int peek (stack *inst, void **item) {

  if (!inst) return -1;
  if (!item) return -1;
  if (!inst->count) return -1;

  *item = inst->items[inst->count-1];

  return 0;
}


static int growStack (stack *inst) {

 void **newItems;

  if (!inst)
    return -1;
 
  newItems = realloc(inst->items, GROWTH_STACK * inst->size);
  inst->size *= GROWTH_STACK;
                            
  inst->items = newItems;
  
  return 0;
                            
}