/**
 * llist.h
 * Copyright (c) 2022 Jon Santmyer <jon@jonsantmyer.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */

#ifndef LINKED_LIST_H
#define LINKED_LIST_H 1

#include <stddef.h>

/*List member structs must begin with this struct as the first member*/
struct llist_header
{
    struct llist_header *prev, *next;
};

/*Marks an unknown-state llist header as a single member circular list*/
static inline void __llist_setup(struct llist_header *head)
{
    head->prev = head->next = head;
}
#define llist_setup(head) __llist_setup((struct llist_header*)(head))

/*Fits a new node between prev and next*/
static inline void __llist_add(struct llist_header *new, struct llist_header *prev, struct llist_header *next)
{
    new->prev = prev;
    new->next = next;
    prev->next = new;
    next->prev = new;
}

#define llist_append(head, new) __llist_add(\
        (struct llist_header*)(new), \
        (struct llist_header*)(head), \
        (struct llist_header*)(head->next))
#define llist_prepend(head, new) __llist_add(\
        (struct llist_header*)(new), \
        (struct llist_header*)(head->prev), \
        (struct llist_header*)(head))

/*Seperates a node from prev and next, marking the removed as memberless*/
static inline void __llist_del(struct llist_header *node, struct llist_header *prev, struct llist_header *next)
{
    prev->next = node->next;
    next->prev = node->prev;
    node->prev = node->next = NULL;
}
#define llist_del(node) __llist_del(\
        (struct llist_header*)(node), \
        (struct llist_header*)(node->prev), \
        (struct llist_header*)(node->next))

/*Returns the list header i elements ahead of head*/
static inline struct llist_header *__llist_traverse(struct llist_header *head, size_t i)
{
    if(head == NULL) return NULL;
    for(; i != 0 && head != NULL; head = head->next, i--);
    return head;
}
#define llist_traverse(head, i) __list_traverse((struct llist_header*)(head), i)

/*Returns how many jumps forwards it takes to reach find*/
static inline int __llist_at(struct llist_header *head, struct llist_header *find)
{
    if(head == NULL) return -1;
    int r = 1;
    for(
            struct llist_header *node = head->next; 
            node != head; 
            node = node->next, r++) {
        if(node == find) return ++r;
    }
    return -1;
}
#define llist_at(head, find) __llist_at(\
        (struct llist_header*)(head), \
        (struct llist_header*)(find))

/*Define for easily looping through a llist*/
#define llist_foreach(node, head) \
    for(struct llist_header *node = head->next; node != head; node = node->next)

#endif