#include <linux/kernel.h>
#include <linux/tty.h>
#include <linux/slab.h>

#include "../include/utils.h"
#include "../include/queue.h"
#include "../include/message.h"

/**
 * init_queue()
 *
 * Initializes empty queue and returns a pointer to it.
 */
queue *init_queue(void)
{
	queue *Q;

	Q = kmalloc(sizeof(queue), GFP_KERNEL);
	if (!Q) {
		return NULL;
	}

	Q->len = 0;
	Q->total_size = 0;
	INIT_LIST_HEAD(&Q->list);

	return Q;
}

/**
 * enqueue()
 *
 * @q: pointer to queue.
 * @m: pointer to message.
 *
 * Inserts the message at the end of the given queue.
 */
void enqueue(queue *q, message *m)
{
	queue *new_q;

	new_q = kmalloc(sizeof(queue), GFP_KERNEL);
	if (!new_q) {
		printk("%s - [ERROR]: Failed to allocate memory for queue element\n",
		       MODNAME);
		return;
	}
	new_q->m = m;

	q->len++;
	q->total_size += m->length;

	// new entry is added at the end of the list
	list_add_tail(&(new_q->list), &(q->list));
}

/**
 * dequeue()
 *
 * @q: pointer to queue.
 *
 * Extract message on top of the queue and returns a pointer to it
 */
message *dequeue(queue *q)
{
	queue *tmp_q;
	message *m;

	if (q->len == 0)
		return NULL;

	// get message on top of queue
	tmp_q = list_entry(q->list.next, queue, list);
	list_del(q->list.next);
	m = tmp_q->m;

	// decrement size and free memory
	q->len--;
	q->total_size -= m->length;
	kfree(tmp_q);

	return m;
}

/**
 * flush_queue()
 *
 * @q: pointer to queue.
 *
 * Empties the content of a queue.
 */
void flush_queue(queue *q)
{
	int i;
	int length = q->len;
	message *m;

	for (i = 0; i < length; i++) {
		m = dequeue(q);
		destroy_message(m);
	}
}