/* list.h — intrusive circular doubly-linked list (header-only).
 *
 * Zero allocation: the node lives inside your struct. Recover the owner with
 * NAUT_CONTAINER_OF. This is the workhorse list for peer sets, freelists of
 * objects, timer wheels, etc.
 */
#ifndef NAUT_LIST_H
#define NAUT_LIST_H

#include "naut/common.h"

typedef struct naut_list {
    struct naut_list *prev;
    struct naut_list *next;
} naut_list;

NAUT_INLINE void naut_list_init(naut_list *l) { l->prev = l; l->next = l; }
NAUT_INLINE bool naut_list_empty(const naut_list *l) { return l->next == l; }

NAUT_INLINE void naut__link(naut_list *n, naut_list *p, naut_list *x) {
    n->prev = p; n->next = x; p->next = n; x->prev = n;
}

/* insert n at head / tail of list l */
NAUT_INLINE void naut_list_push_front(naut_list *l, naut_list *n) { naut__link(n, l, l->next); }
NAUT_INLINE void naut_list_push_back(naut_list *l, naut_list *n)  { naut__link(n, l->prev, l); }

NAUT_INLINE void naut_list_del(naut_list *n) {
    n->prev->next = n->next;
    n->next->prev = n->prev;
    n->prev = n->next = n;            /* safe to del again / detect detached */
}

NAUT_INLINE naut_list *naut_list_front(const naut_list *l) { return l->next; }
NAUT_INLINE naut_list *naut_list_back(const naut_list *l)  { return l->prev; }

#define naut_list_entry(ptr, type, member) NAUT_CONTAINER_OF(ptr, type, member)

#define naut_list_for_each(it, l) \
    for ((it) = (l)->next; (it) != (l); (it) = (it)->next)

/* safe against deletion of the current node */
#define naut_list_for_each_safe(it, tmp, l) \
    for ((it) = (l)->next, (tmp) = (it)->next; \
         (it) != (l); (it) = (tmp), (tmp) = (it)->next)

#endif /* NAUT_LIST_H */