databases.py

from flask_sqlalchemy import SQLAlchemy

from logger import setup_logger

services_log = setup_logger('services.log')
APP_NAMES = ['app_RTP', 'app_TTP']


class DB_singleton:
    _instances = {}

    def __new__(cls, app_name):
        if app_name not in cls._instances:
            instance = super(DB_singleton, cls).__new__(cls)
            instance.db = cls._create_db_instance(app_name)
            cls._instances[app_name] = instance
        return cls._instances[app_name]

    @staticmethod
    def _create_db_instance(app_name):

        DB_INSTANCE_CREATORS = [create_DB_instance_BA(), create_DB_instance_TTP(), create_DB_instance_RTP()]
        try:
            index = APP_NAMES.index(app_name)
            return DB_INSTANCE_CREATORS[index]
        except Exception as e:
            services_log.error(
                f"Ошибка при создании экземпляра SQLAlchemy для {app_name}: {str(e)}"
            )
            return None


def create_DB_instance_BA():
    return SQLAlchemy()


def create_DB_instance_TTP():
    return SQLAlchemy()


def create_DB_instance_RTP():
    return SQLAlchemy()