#include <kernel/queue.h>

size_t queue_length(struct queue *q)
{
	size_t i = 0;
	struct queue_entry *x = q->q_first;
	while (x) {
		i++;
		x = x->qe_next;
	}

	return i;
}

void queue_insert_before(struct queue *q, struct queue_entry *entry, struct queue_entry *before)
{
	struct queue_entry *x = before->qe_prev;
	if (x) {
		x->qe_next = entry;
	} else {
		q->q_first = entry;
	}

	entry->qe_prev = x;

	before->qe_prev = entry;
	entry->qe_next = before;
}
	 
void queue_insert_after(struct queue *q, struct queue_entry *entry, struct queue_entry *after)
{
	struct queue_entry *x = after->qe_next;
	if (x) {
		x->qe_prev = entry;
	} else {
		q->q_last = entry;
	}

	entry->qe_prev = x;

	after->qe_next = entry;
	entry->qe_prev = after;
}

void queue_push_front(struct queue *q, struct queue_entry *entry)
{
	if (q->q_first) {
		q->q_first->qe_prev = entry;
	}
	    
	entry->qe_next = q->q_first;
	entry->qe_prev = NULL;

	q->q_first = entry;

	if (!q->q_last) {
		q->q_last = entry;
	}
}

void queue_push_back(struct queue *q, struct queue_entry *entry)
{
	if (q->q_last) {
		q->q_last->qe_next = entry;
	}

	entry->qe_prev = q->q_last;
	entry->qe_next = NULL;

	q->q_last = entry;

	if (!q->q_first) {
		q->q_first = entry;
	}
}

struct queue_entry *queue_pop_front(struct queue *q)
{
	struct queue_entry *x = q->q_first;
	if (x) {
		queue_delete(q, x);
	}

	return x;
}

struct queue_entry *queue_pop_back(struct queue *q)
{
	struct queue_entry *x = q->q_last;
	if (x) {
	    queue_delete(q, x);
	}
	
	return x;
}

void queue_delete(struct queue *q, struct queue_entry *entry)
{
	if (!entry) {
		return;
	}
		
	if (entry == q->q_first) {
		q->q_first = q->q_first->qe_next;
	}

	if (entry == q->q_last) {
		q->q_last = q->q_last->qe_prev;
	}

	if (entry->qe_next) {
		entry->qe_next->qe_prev = entry->qe_prev;
	}

	if (entry->qe_prev) {
		entry->qe_prev->qe_next = entry->qe_next;
	}

	entry->qe_next = entry->qe_prev = NULL;
}

void queue_delete_all(struct queue *q)
{
	struct queue_entry *x = q->q_first;
	while (x) {
		struct queue_entry *next = x->qe_next;
		x->qe_next = x->qe_prev = NULL;
		x = next;
	}

	q->q_first = q->q_last = NULL;
}