from sqlalchemy import MetaData as _MetaData

__all__ = [
    'MetaData',
]


class MetaData(_MetaData):
    """
    App specific subclass of the SQLAlchemy MetaData class.
    """

    # Define naming convention for constraints
    _naming_convention = {
        "ix": 'ix_%(column_0_label)s',
        "uq": "uq_%(table_name)s_%(column_0_name)s",
        "ck": "ck_%(table_name)s_%(constraint_name)s",
        "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
        "pk": "pk_%(table_name)s"
    }

    def __init__(self, *args, naming_convention=None, **kwargs):
        if not naming_convention:
            naming_convention = self._naming_convention
        super().__init__(*args, naming_convention=naming_convention, **kwargs)