#include <stdlib.h>

#include "abac_stack.h"
#include "abac_util.h"

abac_stack_t *abac_stack_new(void) {
    abac_stack_t *ret = abac_xmalloc(sizeof(abac_stack_t));
    ret->elts = NULL;
    ret->size = 0;
    return ret;
}

/* push only if it is not in there still */
int abac_stack_unique_push(abac_stack_t *stack, void *elt) {
    if(!stack) return 0; 

    void *cur;
    abac_stack_foreach(stack, cur,
        if(cur == elt)
            return 0;
        );
    abac_stack_push(stack,elt);
    return 1;
}

void abac_stack_push(abac_stack_t *stack, void *elt) {
    abac_stack_element_t *new_element = abac_xmalloc(sizeof(abac_stack_element_t));

    new_element->ptr = elt;
    DL_APPEND(stack->elts, new_element);
    ++stack->size;
}

void *abac_stack_pop(abac_stack_t *stack) {
    abac_stack_element_t *cur;
    void *ret;
   
    if(!stack) return NULL;

    if(stack->size>0) {
        cur=stack->elts;
        ret=cur->ptr;
        DL_DELETE(stack->elts, cur);
        free(cur);
        --stack->size;
        return ret;
    }
    // reutrn false if we don't
    return NULL;
}

int abac_stack_size(abac_stack_t *stack) {
    if(stack) return stack->size;
    return 0;
}

void abac_stack_free(abac_stack_t *stack) {
    abac_stack_element_t *elt, *tmp;

    if(!stack) return; 

    // free everthing in the stack
    DL_FOREACH_SAFE(stack->elts, elt, tmp) {
        DL_DELETE(stack->elts, elt);
        free(elt);
    }

    // free the list
    free(stack);
}