/*
 * stack.c
 */
#include "stack.h"
sPtr SCreate(CompareFuncT cf){
  sPtr s = malloc(sizeof(struct Stack));
  s->top = NULL;
  s->bottom = NULL;
  s->cf = cf;
  s->size = 0;
  return s;
}
void SDestroy(sPtr s){
  if (s->size == 0){
    free(s);
    return;
  }
  while (s->size != 0)
    SPop(s);
  free(s);
  return;
}
int SPush(sPtr s, void *data){
  if (data == NULL)
    return 1;
  sNode *new = malloc(sizeof(sNode));
  new->data = data;
  new->next = NULL;
  new->rc = 0;
  if (s->size == 0){
    s->top = new;
    s->bottom = new;
    s->size++;
    return 0;
  }
  new->next = s->top;
  s->top = new;
  s->size++;
  return 0;
}
void *SPop(sPtr s){
  if (s->size == 0)
    return NULL;
  sNode *pop = s->top;
  if (pop->rc > 0)
    return NULL;
  void *data = pop->data;
  s->top = pop->next;
  free(pop);
  return data;
}
int SDelete(sPtr s, void *data){
  if (s->size == 0)
    return 1;
  sNode *i = s->top;
  int cr = s->cf(data, i->data);
  if (cr == 0){
    sNode *delete = i;
    i = i->next;
    s->top = i;
    free(delete);
    s->size--;
    return 0;
  }
  while (i->next != NULL){
    sNode *next = i->next;
    cr = s->cf(data, next->data);
    if (cr == 0){
      if (next->rc > 0)
        return 2;
      i->next = next->next;
      free(next);
      s->size--;
      return 0;
    }
    i = i->next;
  }
  return 1;
}
siPtr SCreateIterator(sPtr s){
  siPtr si = malloc(sizeof(struct StackIterator));
  si->ptr = s->top;
  si->ptr->rc++;
  return si;
}
void SDestroyIterator(siPtr si){
  if (si->ptr != NULL)
    si->ptr->rc--;
  free(si);
}
void *SAdvanceIterator(siPtr si){
  if (si->ptr == NULL)
    return NULL;
  void *data = si->ptr->data;
  si->ptr->rc--;
  si->ptr = si->ptr->next;
  if (si->ptr != NULL)
    si->ptr->rc++;
  return data;
}