import json
from typing import Optional

class Config():

    def __init__(self, filename: str) -> None:
        self.__filename = filename
        self.__config = {}
        self.__read()

    def get_on_message_for_chat_id(self, chat_id: int) -> Optional[dict]:
        chat_id_str = str(chat_id)
        if 'onMessage' in self.__config:
            on_message = self.__config['onMessage']
            if chat_id_str in on_message:
                return on_message[chat_id_str]
        return None

    def __read(self) -> None:
        with open(self.__filename, 'r') as f:
            self.__config = json.load(f)