import logging

from app import app
from data.database import UseThenDisconnect, QueueItem
from workers.worker import Worker
from datetime import timedelta, datetime

logger = logging.getLogger(__name__)

DELETION_DATE_THRESHOLD = timedelta(days=7)
DELETION_COUNT_THRESHOLD = 50
BATCH_SIZE = 500
QUEUE_CLEANUP_FREQUENCY = app.config.get('QUEUE_CLEANUP_FREQUENCY', 60*60*24)

class QueueCleanupWorker(Worker):
  def __init__(self):
    super(QueueCleanupWorker, self).__init__()
    self.add_operation(self._cleanup_queue, QUEUE_CLEANUP_FREQUENCY)

  def _cleanup_queue(self):
    """ Performs garbage collection on the queueitem table. """
    with UseThenDisconnect(app.config):
      while True:
        # Find all queue items older than the threshold (typically a week) and delete them.
        threshold_ago = datetime.now() - DELETION_DATE_THRESHOLD
        to_delete = list(QueueItem.select()
                                  .where(QueueItem.processing_expires <= threshold_ago)
                                  .limit(BATCH_SIZE))

        if len(to_delete) < DELETION_COUNT_THRESHOLD:
          return

        QueueItem.delete().where(QueueItem.id << to_delete).execute()


if __name__ == "__main__":
  worker = QueueCleanupWorker()
  worker.start()