import configparser
import os
from typing import Optional, overload

from django.core.exceptions import ImproperlyConfigured


class ZulipSettingsError(ImproperlyConfigured):
    pass


DEPLOY_ROOT = os.path.realpath(os.path.dirname(os.path.dirname(__file__)))

config_file = configparser.RawConfigParser()
config_file.read("/etc/zulip/zulip.conf")

# Whether this instance of Zulip is running in a production environment.
PRODUCTION = config_file.has_option("machine", "deploy_type")
DEVELOPMENT = not PRODUCTION
secrets_file = configparser.RawConfigParser()
if PRODUCTION:
    secrets_file.read("/etc/zulip/zulip-secrets.conf")
else:
    secrets_file.read(os.path.join(DEPLOY_ROOT, "zproject/dev-secrets.conf"))


@overload
def get_secret(key: str, default_value: str, development_only: bool = False) -> str:
    ...


@overload
def get_secret(
    key: str, default_value: Optional[str] = None, development_only: bool = False
) -> Optional[str]:
    ...


def get_secret(
    key: str, default_value: Optional[str] = None, development_only: bool = False
) -> Optional[str]:
    if development_only and PRODUCTION:
        return default_value
    return secrets_file.get("secrets", key, fallback=default_value)


def get_mandatory_secret(key: str) -> str:
    secret = get_secret(key)
    if secret is None:
        if os.environ.get("DISABLE_MANDATORY_SECRET_CHECK") == "True":
            return ""
        raise ZulipSettingsError(f'Mandatory secret "{key}" is not set')
    return secret


@overload
def get_config(section: str, key: str, default_value: str) -> str:
    ...


@overload
def get_config(section: str, key: str, default_value: Optional[str] = None) -> Optional[str]:
    ...


def get_config(section: str, key: str, default_value: Optional[str] = None) -> Optional[str]:
    return config_file.get(section, key, fallback=default_value)


def get_from_file_if_exists(path: str) -> str:
    if os.path.exists(path):
        with open(path) as f:
            return f.read()
    else:
        return ""

import configparser
import os
from typing import Optional, overload


class ZulipSettingsError(Exception):
    pass


DEPLOY_ROOT = os.path.realpath(os.path.dirname(os.path.dirname(__file__)))

config_file = configparser.RawConfigParser()
config_file.read("/etc/zulip/zulip.conf")

# Whether this instance of Zulip is running in a production environment.
PRODUCTION = config_file.has_option("machine", "deploy_type")
DEVELOPMENT = not PRODUCTION
secrets_file = configparser.RawConfigParser()
if PRODUCTION:
    secrets_file.read("/etc/zulip/zulip-secrets.conf")
else:
    secrets_file.read(os.path.join(DEPLOY_ROOT, "zproject/dev-secrets.conf"))


@overload
def get_secret(key: str, default_value: str, development_only: bool = False) -> str:
    ...


@overload
def get_secret(
    key: str, default_value: Optional[str] = None, development_only: bool = False
) -> Optional[str]:
    ...


def get_secret(
    key: str, default_value: Optional[str] = None, development_only: bool = False
) -> Optional[str]:
    if development_only and PRODUCTION:
        return default_value
    return secrets_file.get("secrets", key, fallback=default_value)


def get_mandatory_secret(key: str) -> str:
    secret = get_secret(key)
    if secret is None:
        if os.environ.get("DISABLE_MANDATORY_SECRET_CHECK") == "True":
            return ""
        raise ZulipSettingsError(f'Mandatory secret "{key}" is not set')
    return secret


@overload
def get_config(section: str, key: str, default_value: str) -> str:
    ...


@overload
def get_config(section: str, key: str, default_value: Optional[str] = None) -> Optional[str]:
    ...


def get_config(section: str, key: str, default_value: Optional[str] = None) -> Optional[str]:
    return config_file.get(section, key, fallback=default_value)


def get_from_file_if_exists(path: str) -> str:
    if os.path.exists(path):
        with open(path) as f:
            return f.read()
    else:
        return ""

Remove Django base class from ZulipSettingsError.