import logging
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
from sqlalchemy.pool import NullPool

class DbConnector:
    """
    Must create instance of singleton and then must be initialized using method init.
    Right place for init db is for example in main before uvicorn.run

    :raises: SQLAlchemyError, IntegrityError, OperationalError, ...
    """
    _instances = {}

    def __new__(cls, db_id="default"):
        # print("==================")
        # [print(f"{i} -> {id(cls._instances[i])}") for i in cls._instances]
        # print("==================")
        if db_id not in cls._instances:
            cls._instances[db_id] = super().__new__(cls)
        return cls._instances[db_id]

    def __init__(self, db_id:str="default"):
        self.logger = logging.getLogger("spirent_service_db_connector")

    def init(self, db_type:str, host:str, port:int, db_name:str, user:str, password:str):
        """

        :param db_type: Example: mysql, postgresql, ...
        :param host:
        :param port:
        :param db_name:
        :param user:
        :param password:
        """

        self.db_type = db_type
        self.host = host
        self.port = port
        self.name = db_name
        self.user = user
        self.password = password

        protocol = {
            'mysql': 'mysql+aiomysql',
            'postgresql': 'postgresql+asyncpg',
        }

        sqlalchemy_database_url = f"{protocol[self.db_type]}://{user}:{password}@{host}:{port}/{db_name}"
        # for security reason, password not print in logs.
        sqlalchemy_database_url_log = f"mysql://{user}:******@{host}:{port}/{db_name}"
        self.logger.debug(f"Connecting to db {sqlalchemy_database_url_log}")

        self.engine = create_async_engine(sqlalchemy_database_url, poolclass=NullPool)
        self.async_session_local = async_sessionmaker(bind=self.engine,
                                                      expire_on_commit=False,
                                                      class_=AsyncSession,
                                                      autoflush=False,
                                                    )

    def get_db(self):
        return self.async_session_local