from datetime import datetime
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
from sqlalchemy.sql import func

class Base(DeclarativeBase):
    """
    所有 SQLAlchemy ORM 模型的抽象基类。
    包含了审计字段：创建时间、更新时间、逻辑删除标识。
    """
    pass

class AuditMixin:
    """审计字段 Mixin"""
    created_time: Mapped[datetime] = mapped_column(server_default=func.now(), comment="创建时间")
    updated_time: Mapped[datetime] = mapped_column(server_default=func.now(), onupdate=func.now(), comment="更新时间")
    delete_flag: Mapped[int] = mapped_column(default=0, server_default="0", comment="逻辑删除(0未删, 1已删)")