#ifndef __NICKEL_LINKEDLIST_H_
#define __NICKEL_LINKEDLIST_H_

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

#ifdef __cplusplus
extern "C" {
#endif

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

// sentinel type structure for head + count
typedef struct ni_list {
  ni_list_node head;
  size_t count;
} ni_list;

// convenience ptr wrapper struct for a 'generic' list of pointers to things
typedef struct ni_list_ptr {
    ni_list_node link;
    void* ptr;
} ni_list_ptr;

// List functions
void ni_list__init(ni_list* l);
bool ni_list__is_empty(ni_list* l);

void ni_list__insert_after(ni_list* l, ni_list_node* entry, ni_list_node* n);
void ni_list__insert_before(ni_list* l, ni_list_node* entry, ni_list_node* n);

void ni_list__push_front(ni_list* l, ni_list_node* n);
void ni_list__push_back(ni_list* l, ni_list_node* n);

void ni_list__remove(ni_list* l, ni_list_node* n);

static inline ni_list_node* ni_list__get_front(ni_list* l) {
    // if l is_empty() front == NULL else return the first actual data baring node
    return ni_list__is_empty(l) ? NULL : l->head.next;
}

static inline ni_list_node* ni_list__get_back(ni_list* l) {
    // if l is_empty() front == NULL else return the last node in the list
    return ni_list__is_empty(l) ? NULL : l->head.prev;
}

/* Iter Helpers */

// helper macro for element traversal, ordering of operations may cause seg faults
// generally just don't remove 'it', this causes it->next on the next loop to segfault
#define NI_LIST__FOREACH(lptr) \
    for (ni_list_node* it = (lptr)->head.next; it != &(lptr)->head; it = it->next)

// helper macro for element traversal, that also makes a copy of it in tmp
// useful for removing/moving the current node (it)
#define NI_LIST_FOREACH_SAFE(tmp, lptr) \
    for (ni_list_node* it = (lptr)->head.next, *tmp = it->next; \
        it != &(lptr)->head; \
        it = tmp, tmp = it-> next)

// create a pointer to struct that contains a ni_list_node member
// since we know the structure size at compile time we can do some math
// to retreive the base address of the structure that contains our list node.
#define NI_LIST_CONTAINER_OF(ptr, type, member) \
    ((type*)((uint8_t*)(ptr) - offsetof(type, member)))

#ifdef __cplusplus
}
#endif

#endif	/* __NICKEL_LINKEDLIST_H_ */