from os import getenv
from dataclasses import dataclass
from argparse import ArgumentParser, Namespace

from utils import Singleton


@dataclass
class Config(metaclass=Singleton):
    """
    Notifier config dataclass.

    * `base_url`: url of domain
    * `port`: server port (default **3001**)
    * `teletoken`: telegram api token.
    * `bot_owner`: telegram id of bot owner.
    """
    base_url: str = ''
    port: int = 3001
    teletoken: str = ''
    bot_owner: int = 0


class ConfigError(Exception):
    """Config error exception."""
    pass


def _get_teletoken(cmd_arguments: Namespace) -> str:
    """
        Get Telegram bot token from command line arguments or
        **LTLNOTIFYER_TELETOKEN** environment variable.
        Can raise **ConfigError** if Telegram token not set or incorrect.

        :param cmd_arguments: command line arguments.
        :return: Telegram bot token.
    """
    teletoken = cmd_arguments.teletoken or getenv('LTLNOTIFYER_TELETOKEN')
    if not teletoken:
        raise ConfigError('Telegram token not set.')
    if len(teletoken) != 45 or \
            teletoken[9] != ':' \
            or not teletoken[:9].isdigit():
        raise ConfigError('Telegram token incorrect.')
    return teletoken


def _get_bot_owner_id(cmd_arguments: Namespace) -> int:
    """
        Get bot owner telegram id from command line arguments or
        **LTLNOTIFYER_BOT_OWNER** environment variable.
        Can raise **ConfigError** if bot owner id not set or incorrect.

        :param cmd_arguments: command line arguments object.
        :return: bot owner Telegram id.
    """
    bot_owner = cmd_arguments.owner or getenv('LTLNOTIFYER_BOT_OWNER')
    if not bot_owner:
        raise ConfigError('Bot owner telegram id not set.')
    try:
        if len(bot_owner) != 9:
            raise ValueError
        bot_owner = int(bot_owner)
    except ValueError:
        raise ConfigError('Bot owner telegram id incorrect.')
    return bot_owner


def _get_base_url(cmd_arguments: Namespace) -> str:
    """
        Get server base url from command line arguments or
        **LTLNOTIFYER_BASE_URL** environment variable.
        Can raise **Config error** if base url not set.

        :param cmd_arguments: command line arguments object.
        :return: server base url.
        """
    base_url = cmd_arguments.base_url or getenv('LTLNOTIFYER_BASE_URL')
    if not base_url:
        raise ConfigError('Server base url not set.')
    return base_url


def _get_port(cmd_arguments: Namespace) -> int:
    """
    Get server port from command line arguments or
    **LTLNOTIFYER_PORT** environment variable.

    :param cmd_arguments: command line arguments object.
    :return: port number or 3001 if port not set or incorrect.
    """
    port = cmd_arguments.port or getenv('LTLNOTIFIER_PORT', default='')
    port = int(port) if port.isdigit() else 3001
    return port


def _init_config(arguments: Namespace) -> None:
    """
    Initialisation Config singleton.

    :param arguments: command line arguments object.
    """
    teletoken = _get_teletoken(arguments)
    bot_owner = _get_bot_owner_id(arguments)
    base_url = _get_base_url(arguments)
    port = _get_port(arguments)
    Config(teletoken=teletoken,
           port=port,
           bot_owner=bot_owner,
           base_url=base_url)


_parser = ArgumentParser(description="ltlNotifyer server.")
_parser.add_argument('--teletoken', default='',
                     help='Telegram bot token.\n'
                          'Must be set if LTLNOTIFYER_TELETOKEN environment'
                          'variable not set.')
_parser.add_argument('--owner', default='',
                     help='Bot owner Telegram id.\n'
                          'Must be set if LTLNOTIFYER_BOT_OWNER environment'
                          'variable not set.')
_parser.add_argument('--base_url', default='',
                     help='Server base url.\n'
                          'Must be set if LTLNOTIFIER_BASE_URL environment'
                          'variable not set.')
_parser.add_argument('--port', default='',
                     help='Server port (default = 3001. \n'
                          'Can be set in LTLNOTIFYER_PORT environment '
                          'variable.)')

_init_config(_parser.parse_args())

__all__ = ('Config',)