"""会话与消息入库；仅存 public 可见内容，隔离内部信息。"""
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models import ChatSession, Message


async def get_or_create_session(
    db: AsyncSession,
    external_user_id: str,
    external_name: str | None = None,
) -> ChatSession:
    r = await db.execute(select(ChatSession).where(ChatSession.external_user_id == external_user_id))
    row = r.scalar_one_or_none()
    if row:
        if external_name is not None and row.external_name != external_name:
            row.external_name = external_name
            await db.flush()
        return row
    session = ChatSession(external_user_id=external_user_id, external_name=external_name or None)
    db.add(session)
    await db.flush()
    return session


async def add_message(db: AsyncSession, session_id: int, role: str, content: str) -> Message:
    msg = Message(session_id=session_id, role=role, content=content)
    db.add(msg)
    await db.flush()
    return msg