"""Logic for Hello.

Verify that the application and its dependencies are available.
"""

from oto import response
from sqlalchemy.exc import SQLAlchemyError

from product.connectors.mysql import db_session
from product.connectors.sentry import sentry_client
from product.constants import error
from product.models.sql.heartbeat import QUERY_DB_HEARTBEAT


def health_check():
    """Health check handler.

    Checks database connection. 200 if OK, otherwise 503 service unavailable.

    Returns:
        Response: the system status.
    """
    with db_session() as session:
        try:
            session.execute(QUERY_DB_HEARTBEAT)
        except SQLAlchemyError:
            if sentry_client:
                sentry_client.captureException()
            return response.create_error_response(
                code=error.INTERNAL_ERROR,
                message='could not connect to mysql',
                status=503)

    return response.Response(message={'status': 'ok'}, status=200)