//
// Copyright 2016 Garrett D'Amore <garrett@damore.org>
//
// This software is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt).  A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//

#include <stdlib.h>
#include <string.h>

#include "core/nng_impl.h"

// Linked list implementation.  We implement a doubly linked list.
// Using pointer arithmetic, we can operate as a list of "anything".

#define NODE(list, item) \
	(nni_list_node *) (void *) (((char *) item) + list->ll_offset)
#define ITEM(list, node) \
	(void *) (((char *) node) - list->ll_offset)

void
nni_list_init_offset(nni_list *list, size_t offset)
{
	list->ll_offset = offset;
	list->ll_head.ln_next = &list->ll_head;
	list->ll_head.ln_prev = &list->ll_head;
}


void *
nni_list_first(const nni_list *list)
{
	nni_list_node *node = list->ll_head.ln_next;

	if (node == &list->ll_head) {
		return (NULL);
	}
	return (ITEM(list, node));
}


void *
nni_list_last(const nni_list *list)
{
	nni_list_node *node = list->ll_head.ln_prev;

	if (node == &list->ll_head) {
		return (NULL);
	}
	return (ITEM(list, node));
}


void
nni_list_append(nni_list *list, void *item)
{
	nni_list_node *node = NODE(list, item);

	if ((node->ln_next != NULL) || (node->ln_prev != NULL)) {
		nni_panic("appending node already on a list or not inited");
	}
	node->ln_prev = list->ll_head.ln_prev;
	node->ln_next = &list->ll_head;
	node->ln_next->ln_prev = node;
	node->ln_prev->ln_next = node;
}


void
nni_list_prepend(nni_list *list, void *item)
{
	nni_list_node *node = NODE(list, item);

	if ((node->ln_next != NULL) || (node->ln_prev != NULL)) {
		nni_panic("prepending node already on a list or not inited");
	}
	node->ln_next = list->ll_head.ln_next;
	node->ln_prev = &list->ll_head;
	node->ln_next->ln_prev = node;
	node->ln_prev->ln_next = node;
}


void *
nni_list_next(const nni_list *list, void *item)
{
	nni_list_node *node = NODE(list, item);

	if ((node = node->ln_next) == &list->ll_head) {
		return (NULL);
	}
	return (ITEM(list, node));
}


void *
nni_list_prev(const nni_list *list, void *item)
{
	nni_list_node *node = NODE(list, item);

	if ((node = node->ln_prev) == &list->ll_head) {
		return (NULL);
	}
	return (ITEM(list, node));
}


void
nni_list_remove(nni_list *list, void *item)
{
	nni_list_node *node = NODE(list, item);

	node->ln_prev->ln_next = node->ln_next;
	node->ln_next->ln_prev = node->ln_prev;
	node->ln_next = NULL;
	node->ln_prev = NULL;
}