#include "shmqueue.h"

ShmQueue::ShmQueue(Shm *shm, ShmSlot slot, bool owner)
{
    _shm = shm;
    _owner = owner;

    if (owner) {
        ShmPlace queue_place = shm->alloc(sizeof(ShmQueueStart));
        shm->setSlot(slot, queue_place);
        ref(shm, queue_place, &_queue);
        _queue->first = SHM_NULL;
        _queue->last = SHM_NULL;
        _queue->count = 0;
    } else {
        ShmPlace queue_start = shm->slot(slot);
        ref(shm, queue_start, &_queue);
    }

    char buf[1024];
    sprintf(buf, "sem_%s_%d", shm->name(), slot);
    _queue_sem = shm->sem(buf, owner);
}

ShmQueue::~ShmQueue()
{
    if (_owner) {
        cleanup();
    }
}

void ShmQueue::cleanup()
{
    // does currently nothing
    delete _queue_sem;
}

int ShmQueue::depth()
{
    _shm->lock();
    int d = _queue->count;
    _shm->unlock();
    return d;
}

void ShmQueue::enqueue(int cmd, const QString &json_data)
{
    QByteArray b(json_data.toUtf8());

    int str_place = _shm->alloc(b.size() + 1);
    char *s;
    ref(_shm, str_place, &s);
    memcpy(s, b.constData(), b.size());
    s[b.size()] = '\0';

    int item_place = _shm->alloc(sizeof(ShmQueueItem));
    ShmQueueItem *item;
    ref(_shm, item_place, &item);
    item->cmd = cmd;
    item->data_place = str_place;
    item->prev = _queue->last;
    item->next = SHM_NULL;

    _shm->lock();
    _queue->last = item_place;
    if (_queue->first == SHM_NULL) {
        _queue->first = _queue->last;
    }
    _queue->count += 1;
    _shm->unlock();
    _queue_sem->post();
}

bool ShmQueue::dequeue(int &cmd, QString &json_data, bool wait)
{
    if (wait) {
        _queue_sem->wait();
    } else {
        if (!_queue_sem->trywait()) {
            return false;
        }
    }
    _shm->lock();

    ShmPlace item_place = _queue->first;
    ShmQueueItem *item;
    ref(_shm, item_place, &item);
    _queue->first = item->next;
    if (_queue->first == SHM_NULL) {
        _queue->last = SHM_NULL;
    }
    _queue->count -= 1;

    _shm->unlock();

    ShmPlace data_place = item->data_place;
    char *data;
    ref(_shm, data_place, &data);
    json_data = QString::fromUtf8(data, strlen(data));

    _shm->free(data_place);
    cmd = item->cmd;

    _shm->free(item_place);
    return true;
}