from contextlib import contextmanager
from datetime import datetime

from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker
from apollo_main_db.push_notifications.models import PushMessageReduced

from apollo_clear_notifications.config import Config


_config = Config()
engine = create_engine(
    'mysql+pymysql://{user}:{password}@{host}:{port}/{database_name}'
    '?binary_prefix=true'.format(
        user=_config.DB_USER,
        password=_config.DB_PASS,
        host=_config.DB_HOST,
        port=_config.DB_PORT,
        database_name=_config.DB_NAME),
    pool_recycle=_config.DB_POOL_RECYCLE, pool_size=_config.DB_POOL_SIZE
)
_session_factory = scoped_session(sessionmaker(bind=engine))
_session = _session_factory()


@contextmanager
def session_scope():
    """Provide a transactional scope around a series of operations."""
    try:
        yield _session
        _session.commit()
    except:
        _session.rollback()
        raise
    finally:
        _session.close()


def delete_push_messages(date: datetime):
    """Clear push messages records before passed date."""
    with session_scope() as session:
        session.query(PushMessageReduced).filter(PushMessageReduced.date < date).delete(synchronize_session=False)
        session.commit()