base_class.py

import datetime
import re
from typing import Optional

from sqlalchemy import func
from sqlalchemy.orm import Mapped, as_declarative, declared_attr, mapped_column

from core.config import EnvironmentEnum, settings


def camel_to_snake(name):
    """
    Convert camel case to snake case and lowercase the result
    """
    name = re.sub("(.)([A-Z][a-z]+)", r"\1_\2", name)
    return re.sub("([a-z0-9])([A-Z])", r"\1_\2", name).lower()


@as_declarative()
class TimestampedBase:
    id: Mapped[int] = mapped_column(primary_key=True)
    created_at: Mapped[datetime.datetime] = mapped_column(
        nullable=False, server_default=func.current_timestamp()
    )
    updated_at: Mapped[datetime.datetime] = mapped_column(
        nullable=False,
        server_default=func.current_timestamp(),
        onupdate=func.current_timestamp(),
    )
    deleted_at: Mapped[Optional[datetime.datetime]] = mapped_column(
        nullable=True, server_default=None
    )
    __name__: str

    # so that created_at and updated_at columns can be accessed without querying the database
    __mapper_args__ = {"eager_defaults": True}

    # Generate __tablename__ automatically
    @declared_attr.directive
    def __tablename__(cls) -> str:
        default_name = camel_to_snake(cls.__name__)
        if settings.ENVIRONMENT == EnvironmentEnum.TEST:
            return f"test_{default_name}"

        return default_name