# Standard library imports
import sys

# PyQt imports

# Third party imports
from alchemical import Alchemical  # type:ignore

# App imports


def is_alembic_command():
    # Define keywords that indicate Alembic is being invoked.
    alembic_keywords = {'alembic', 'revision', 'upgrade', 'downgrade', 'history', 'current'}
    return any(arg in alembic_keywords for arg in sys.argv)


class DatabaseManager:
    """
    Singleton class to ensure we only ever have one db object
    """

    __instance = None

    def __init__(self, database_url: str, **kwargs: dict) -> None:
        if DatabaseManager.__instance is None:
            self.db = Alchemical(database_url, **kwargs)
            if not is_alembic_command():
                self.db.create_all()
            DatabaseManager.__instance = self
        else:
            raise Exception("Attempted to create a second DatabaseManager instance")

    @staticmethod
    def get_instance(database_url: str, **kwargs: dict) -> Alchemical:
        if DatabaseManager.__instance is None:
            DatabaseManager(database_url, **kwargs)
        return DatabaseManager.__instance