#include <stdio.h>
#include <string.h>
#include <assert.h>

typedef struct _list
{
	int index;
	int prev;
	int next;
} list;

list* clib_llist_elt(list* parent, int index)
{
	return parent + index;
}

list* clib_llist_prev(list* parent, list* elt)
{
	return clib_llist_elt(parent, elt->prev);
}

list* clib_llist_next(list* parent, list* elt)
{
	return clib_llist_elt(parent, elt->next);
}

int clib_llist_prev_index(list* elt)
{
	return elt->prev;
}

int clib_llist_next_index(list* elt)
{
	return elt->next;
}

void clib_llist_remove(list* parent, list* elt)
{
	assert ( elt != clib_llist_next(parent, elt));
	assert ( elt->next != -1);
	assert ( elt->prev != -1);
	list* prev = clib_llist_prev(parent, elt);
	list* next = clib_llist_next(parent, elt);
	
	prev->next = elt->next;
	next->prev = elt->prev;
	elt->next = elt->prev = -1;
}

void clib_llist_insert(list* parent, list* elt, list* prev, list* next)
{
	elt->prev = next->prev;
	elt->next = prev->next;
	next->prev = elt - parent;
	prev->next = elt - parent;
}

int clib_llist_is_empty(list* parent, list* elt)
{
	return (elt - parent) == elt->next;
}

int clib_llist_elt_is_cycle(list* elt)
{
	return elt->next == elt->prev;
}

void clib_llist_add_tail(list* parent, list* elt, list* he)
{
	list* prev = clib_llist_prev (parent, he);
	clib_llist_insert(parent, elt, prev, he);
}

int clib_llist_elt_is_linked(list* elt)
{
	return (elt->next != -1) && (elt->prev != -1);
}

int main(int argc, const char** argv, const char** env)
{
	list elts[17] = { -1 };
	for (int i = 0; i < sizeof(elts) / sizeof(list); i++)
	{
		elts[i].index = i;
	}

	elts[4].prev = 16;
	elts[4].next = 12;

	elts[12].prev = 4;
	elts[12].next = 16;
	
	elts[16].prev = 12;
	elts[16].next = 4;

	list* event_elts = elts, *elt, *he;
	int ei = 0, next_ei = 0, pending_main_ei = 4;

	he = clib_llist_elt (event_elts, pending_main_ei);
	ei = clib_llist_next_index (he);
	while (ei != pending_main_ei)
	{
		elt = clib_llist_elt(event_elts, ei);
		next_ei = clib_llist_next_index(elt);
		clib_llist_remove(event_elts, elt);
		
		he = clib_llist_elt(event_elts, pending_main_ei);
#ifdef LOOP
		if ((!clib_llist_is_empty(event_elts, he))) //infinite loop
#else
		if ((!clib_llist_elt_is_cycle(he)))
#endif
		{
			clib_llist_add_tail(event_elts, elt, he);
		}
		else
		{
			printf("Processing: %d\r\n", ei);
		}

		elt = clib_llist_elt (event_elts, ei);
		if (clib_llist_elt_is_linked (elt))
		{
			printf("free elt: %d\r\n", elt->index);
		}

		ei = next_ei;
	}

	return 0;
}