"""RLS-enforced database access for plugins (SPEC §11.1 + privacy hardening).

``plugin_session(user_id)`` yields a normal SQLAlchemy session whose transaction
has been dropped to the least-privilege :data:`~app.plugins.rls.PLUGIN_ROLE` and
bound to the per-user RLS context. Both are set with transaction-local scope
(``SET LOCAL`` / ``set_config(..., is_local=true)``), so they auto-revert on
commit/rollback and cannot leak across pooled connections.

Because the role is non-superuser / non-owner / NOBYPASSRLS, the row-level policy
from :mod:`app.plugins.rls` is actually enforced: a plugin query that forgets to
filter ``user_id`` still returns only the current user's rows, and it cannot write
rows for anyone else (policy ``WITH CHECK``).
"""

from __future__ import annotations

import uuid
from collections.abc import AsyncIterator
from contextlib import asynccontextmanager

from sqlalchemy import text
from sqlalchemy.ext.asyncio import AsyncSession

from app.db import get_sessionmaker
from app.plugins.rls import PLUGIN_ROLE


@asynccontextmanager
async def plugin_session(user_id: uuid.UUID) -> AsyncIterator[AsyncSession]:
    """A transactional session scoped to ``user_id`` under RLS (SPEC §11.1)."""
    async with get_sessionmaker()() as session:
        try:
            # Bind the RLS user context first (while still the privileged role), then
            # drop into the restricted role for the rest of the transaction.
            await session.execute(
                text("SELECT set_config('app.current_user_id', :uid, true)"),
                {"uid": str(user_id)},
            )
            await session.execute(text(f"SET LOCAL ROLE {PLUGIN_ROLE}"))
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise