/*
 * Copyright (c) 2016 Intel Corporation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @file
 *
 * @brief Header where single linked list utility code is found
 */

#ifndef __SLIST_H__
#define __SLIST_H__

#include <stddef.h>
#include <stdbool.h>

#ifdef __cplusplus
extern "C" {
#endif


struct _snode {
	struct _snode *next;
};

typedef struct _snode sys_snode_t;

struct _slist {
	sys_snode_t *head;
	sys_snode_t *tail;
};

typedef struct _slist sys_slist_t;

/**
 * @brief Provide the primitive to iterate on a list
 * Note: the loop is unsafe and thus __sn should not be removed
 *
 * User _MUST_ add the loop statement curly braces enclosing its own code:
 *
 *     SYS_SLIST_FOR_EACH_NODE(l, n) {
 *         <user code>
 *     }
 *
 * @param __sl A pointer on a sys_list_t to iterate on
 * @param __sn A sys_snode_t pointer to peek each node of the list
 */
#define SYS_SLIST_FOR_EACH_NODE(__sl, __sn)				\
	for (__sn = sys_slist_peek_head(__sl); __sn;			\
	     __sn = sys_slist_peek_next(__sn))

/**
 * @brief Provide the primitive to safely iterate on a list
 * Note: __sn can be removed, it will not break the loop.
 *
 * User _MUST_ add the loop statement curly braces enclosing its own code:
 *
 *     SYS_SLIST_FOR_EACH_NODE_SAFE(l, n, s) {
 *         <user code>
 *     }
 *
 * @param __sl A pointer on a sys_list_t to iterate on
 * @param __sn A sys_snode_t pointer to peek each node of the list
 * @param __sns A sys_snode_t pointer for the loop to run safely
 */
#define SYS_SLIST_FOR_EACH_NODE_SAFE(__sl, __sn, __sns)			\
	for (__sn = sys_slist_peek_head(__sl),				\
		     __sns = sys_slist_peek_next(__sn);			\
	     __sn; __sn = __sns,					\
		     __sns = sys_slist_peek_next(__sn))

/**
 * @brief Initialize a list
 *
 * @param list A pointer on the list to initialize
 */
static inline void sys_slist_init(sys_slist_t *list)
{
	list->head = NULL;
	list->tail = NULL;
}

#define SYS_SLIST_STATIC_INIT(ptr_to_list) {NULL, NULL}

/**
 * @brief Test if the given list is empty
 *
 * @param list A pointer on the list to test
 *
 * @return a boolean, true if it's empty, false otherwise
 */
static inline bool sys_slist_is_empty(sys_slist_t *list)
{
	return (!list->head);
}

/**
 * @brief Peek the first node from the list
 *
 * @param list A point on the list to peek the first node from
 *
 * @return A pointer on the first node of the list (or NULL if none)
 */
static inline sys_snode_t *sys_slist_peek_head(sys_slist_t *list)
{
	return list->head;
}

/**
 * @brief Peek the last node from the list
 *
 * @param list A point on the list to peek the last node from
 *
 * @return A pointer on the last node of the list (or NULL if none)
 */
static inline sys_snode_t *sys_slist_peek_tail(sys_slist_t *list)
{
	return list->tail;
}

/**
 * @brief Peek the next node from current node
 *
 * @param node A pointer on the node where to peek the next node
 *
 * @return a pointer on the next node (or NULL if none)
 */
static inline sys_snode_t *sys_slist_peek_next(sys_snode_t *node)
{
	return !node ? NULL : node->next;
}

/**
 * @brief Prepend a node to the given list
 *
 * @param list A pointer on the list to affect
 * @param node A pointer on the node to prepend
 */
static inline void sys_slist_prepend(sys_slist_t *list,
				     sys_snode_t *node)
{
	node->next = list->head;
	list->head = node;

	if (!list->tail) {
		list->tail = list->head;
	}
}

/**
 * @brief Append a node to the given list
 *
 * @param list A pointer on the list to affect
 * @param node A pointer on the node to append
 */
static inline void sys_slist_append(sys_slist_t *list,
				    sys_snode_t *node)
{
	node->next = NULL;

	if (!list->tail) {
		list->tail = node;
		list->head = node;
	} else {
		list->tail->next = node;
		list->tail = node;
	}
}

/**
 * @brief Append a list to the given list
 *
 * Append a singly-linked, NULL-terminated list consisting of nodes containing
 * the pointer to the next node as the first element of a node, to @a list.
 *
 * @param list A pointer on the list to affect
 * @param head A pointer to the first element of the list to append
 * @param tail A pointer to the last element of the list to append
 */
static inline void sys_slist_append_list(sys_slist_t *list,
					 void *head, void *tail)
{
	if (!list->tail) {
		list->head = (sys_snode_t *)head;
		list->tail = (sys_snode_t *)tail;
	} else {
		list->tail->next = (sys_snode_t *)head;
		list->tail = (sys_snode_t *)tail;
	}
}

/**
 * @brief merge two slists, appending the second one to the first
 *
 * When the operation is completed, the original list is empty.
 *
 * @param list A pointer on the list to affect
 * @param list_to_append A pointer to the list to append.
 */
static inline void sys_slist_merge_slist(sys_slist_t *list,
					 sys_slist_t *list_to_append)
{
	sys_slist_append_list(list, list_to_append->head,
				    list_to_append->tail);
	sys_slist_init(list);
}

/**
 * @brief Insert a node to the given list
 *
 * @param list A pointer on the list to affect
 * @param prev A pointer on the previous node
 * @param node A pointer on the node to insert
 */
static inline void sys_slist_insert(sys_slist_t *list,
				    sys_snode_t *prev,
				    sys_snode_t *node)
{
	if (!prev) {
		sys_slist_prepend(list, node);
	} else if (!prev->next) {
		sys_slist_append(list, node);
	} else {
		node->next = prev->next;
		prev->next = node;
	}
}

/**
 * @brief Fetch and remove the first node of the given list
 *
 * List must be known to be non-empty.
 *
 * @param list A pointer on the list to affect
 *
 * @return A pointer to the first node of the list
 */
static inline sys_snode_t *sys_slist_get_not_empty(sys_slist_t *list)
{
	sys_snode_t *node = list->head;

	list->head = node->next;
	if (list->tail == node) {
		list->tail = list->head;
	}

	return node;
}

/**
 * @brief Fetch and remove the first node of the given list
 *
 * @param list A pointer on the list to affect
 *
 * @return A pointer to the first node of the list (or NULL if empty)
 */
static inline sys_snode_t *sys_slist_get(sys_slist_t *list)
{
	return sys_slist_is_empty(list) ? NULL : sys_slist_get_not_empty(list);
}

/**
 * @brief Remove a node
 *
 * @param list A pointer on the list to affect
 * @param prev_node A pointer on the previous node
 *        (can be NULL, which means the node is the list's head)
 * @param node A pointer on the node to remove
 */
static inline void sys_slist_remove(sys_slist_t *list,
				    sys_snode_t *prev_node,
				    sys_snode_t *node)
{
	if (!prev_node) {
		list->head = node->next;

		/* Was node also the tail? */
		if (list->tail == node) {
			list->tail = list->head;
		}
	} else {
		prev_node->next = node->next;

		/* Was node the tail? */
		if (list->tail == node) {
			list->tail = prev_node;
		}
	}

	node->next = NULL;
}

/**
 * @brief Find and remove a node from a list
 *
 * @param list A pointer on the list to affect
 * @param node A pointer on the node to remove from the list
 */
static inline void sys_slist_find_and_remove(sys_slist_t *list,
					     sys_snode_t *node)
{
	sys_snode_t *prev = NULL;
	sys_snode_t *test;

	SYS_SLIST_FOR_EACH_NODE(list, test) {
		if (test == node) {
			sys_slist_remove(list, prev, node);
			break;
		}

		prev = test;
	}
}


#ifdef __cplusplus
}
#endif

#endif /* __SLIST_H__ */