from datetime import datetime, timezone
from typing import TYPE_CHECKING

from sqlalchemy import DateTime, Integer, String
from sqlalchemy.orm import Mapped, mapped_column, relationship

from db.base import Base

if TYPE_CHECKING:
    from db.models.message import Message


def _utcnow() -> datetime:
    return datetime.now(timezone.utc)


class Thread(Base):
    __tablename__ = "threads"

    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
    name: Mapped[str] = mapped_column(String(200), nullable=False)

    # Зарезервировано под Спринты 3+: мульти-пользователи и мульти-промпты.
    user_id: Mapped[int | None] = mapped_column(Integer, nullable=True, index=True)
    agent_config_id: Mapped[int | None] = mapped_column(Integer, nullable=True, index=True)

    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_utcnow, nullable=False)
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), default=_utcnow, onupdate=_utcnow, nullable=False
    )

    messages: Mapped[list["Message"]] = relationship(
        back_populates="thread",
        cascade="all, delete-orphan",
        order_by="Message.created_at",
    )