from celery import Celery
from celery.schedules import crontab

# Create Celery instance without Flask app initially
celery = Celery(
    'scipaperloader',
    broker='redis://localhost:6379/0',
    backend='redis://localhost:6379/0',
)

def configure_celery(app=None):
    """Configure Celery with the Flask app settings and ensure tasks run in the app context."""
    if app is None:
        # Import here to avoid circular import
        from scipaperloader import create_app
        app = create_app()

    # Update Celery configuration using the app settings
    celery.conf.update(
        broker_url=app.config.get('CELERY_BROKER_URL', 'redis://localhost:6379/0'),
        result_backend=app.config.get('CELERY_RESULT_BACKEND', 'redis://localhost:6379/0'),
        task_serializer='json',
        accept_content=['json'],
        result_serializer='json',
        timezone='UTC',
        enable_utc=True,
        task_time_limit=3600,         # 1 hour max runtime
        task_soft_time_limit=3000,      # 50 minutes soft limit
        worker_max_tasks_per_child=10,  # Restart workers after 10 tasks
        worker_max_memory_per_child=1000000,  # 1GB memory limit
        task_acks_late=True,            # Acknowledge tasks after completion
        task_reject_on_worker_lost=True,  # Requeue tasks if worker dies
        # Configure Beat schedule for periodic tasks
        beat_schedule={
            'scheduled-scraper-hourly': {
                'task': 'scipaperloader.blueprints.scraper.dummy_scheduled_scraper',
                'schedule': crontab(minute=0),  # Run at the start of every hour
                'options': {'expires': 3600}
            },
        }
    )

    # Create a custom task class that pushes the Flask application context
    class ContextTask(celery.Task):
        abstract = True

        def __call__(self, *args, **kwargs):
            with app.app_context():
                return self.run(*args, **kwargs)

    celery.Task = ContextTask
    return celery