from sqlalchemy import Column, Integer, DateTime, Boolean, String, JSON, func
from sqlalchemy.orm import declarative_mixin, declarative_base

Base = declarative_base()

@declarative_mixin
class CRUDMixin:
    id = Column(Integer, primary_key=True)
    created_at = Column(DateTime, default=func.now(), nullable=False)
    updated_at = Column(DateTime, default=func.now(), nullable=False, onupdate=func.now())

    def as_dict(self, fields: list[str] | None = None):
        """
        Serialize mapped columns. Honors projection if either:
            - 'fields' is passed explicitly, or
            -
        """
        allowed = None
        if fields:
            allowed = set(fields)
        else:
            allowed = getattr(self, "__crudkit_root_fields__", None)
        result = {}
        for cls in self.__class__.__mro__:
            if not hasattr(cls, "__table__"):
                continue
            for column in cls.__table__.columns:
                name = column.name
                if allowed is not None and name not in allowed and name != "id":
                    continue
                result[name] = getattr(self, name)
        return result

class Version(Base):
    __tablename__ = "versions"

    id = Column(Integer, primary_key=True)
    model_name = Column(String, nullable=False)
    object_id = Column(Integer, nullable=False)
    change_type = Column(String, nullable=False)
    data = Column(JSON, nullable=True)
    timestamp = Column(DateTime, default=func.now())

    actor = Column(String, nullable=True)
    meta = Column('metadata', JSON, nullable=True)