from datetime import datetime

from sqlalchemy import DateTime
from sqlalchemy.orm import Mapped, mapped_column


class TimestampMixin:
    """时间字段：统一提供创建时间和更新时间。"""

    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
    updated_at: Mapped[datetime] = mapped_column(
        DateTime,
        default=datetime.utcnow,
        onupdate=datetime.utcnow,
    )