config.py

"""
Code related to .env config
"""
import os
from typing import get_type_hints, Union

from dotenv import load_dotenv

load_dotenv()


class AppConfigError(Exception):
    """
    Exception for config errors.
    """


def _parse_bool(val: Union[str, bool]) -> bool:  # pylint: disable=E1136
    return val if isinstance(val, bool) else val.lower()


class AppConfig:
    """
    Application configuration.
    """

    SNCFCONNECT_COOKIE: str

    """
    Map environment variables to class fields according to these rules:
      - Field won't be parsed unless it has a type annotation
      - Field will be skipped if not in all caps
      - Class field and environment variable name are the same
    """

    def __init__(self, env):
        for field in AppConfig.__annotations__:
            if not field.isupper():
                continue

            # Raise AppConfigError if required field not supplied
            default_value = getattr(self, field, None)
            if default_value is None and env.get(field) is None:
                raise AppConfigError(f'The {field} field is required in the .env file')

            # Cast env var value to expected type and raise AppConfigError on failure

            var_type = get_type_hints(AppConfig)[field]
            try:
                if var_type == bool:
                    value = _parse_bool(env.get(field, default_value))
                else:
                    value = var_type(env.get(field, default_value))

                self.__setattr__(field, value)
            except ValueError:
                raise AppConfigError(f'Unable to cast value of "{env[field]}" '
                                     f'to type "{var_type}" for "{field}" field') from None

    def __repr__(self):
        return str(self.__dict__)


# Expose Config object for app to import
Config = AppConfig(os.environ)