"""Database utilities for use inside Celery tasks (sync context).

Celery tasks bypass FastAPI middleware, so tenant RLS context must be set
manually.  Use _set_tenant() immediately after creating a sync DB session.

Usage::

    from app.core.db_utils import set_tenant_sync, get_sync_session

    with get_sync_session() as db:
        set_tenant_sync(db, tenant_id, role)
        # queries here will be RLS-filtered
"""
import contextlib
from typing import Generator

from sqlalchemy import create_engine, text
from sqlalchemy.orm import Session, sessionmaker

from app.config import settings


def set_tenant_sync(session: Session, tenant_id: str | None, role: str | None = None) -> None:
    """Set RLS tenant context on a *synchronous* SQLAlchemy session.

    Call this at the very start of any sync DB block inside a Celery task
    when you need tenant isolation.  Admins bypass RLS; all other roles get
    a scoped context.  If tenant_id is None the call is a no-op (global
    access, i.e. no RLS enforcement).
    """
    if not tenant_id:
        return
    if role == "admin":
        session.execute(text("SET LOCAL app.current_tenant_id = 'bypass'"))
    else:
        session.execute(
            text("SET LOCAL app.current_tenant_id = :tid"),
            {"tid": tenant_id},
        )


# Lazily created sync engine (reused across tasks in the same worker process)
_sync_engine = None


def _get_sync_engine():
    global _sync_engine
    if _sync_engine is None:
        sync_url = settings.database_url.replace("+asyncpg", "").replace("+aiosqlite", "")
        _sync_engine = create_engine(sync_url, pool_pre_ping=True, pool_size=5, max_overflow=10)
    return _sync_engine


@contextlib.contextmanager
def get_sync_session(tenant_id: str | None = None, role: str | None = None) -> Generator[Session, None, None]:
    """Context manager that yields a synchronous DB session with optional RLS.

    Prefer using the existing async session patterns in FastAPI routes.
    This helper is intended for Celery tasks only.
    """
    factory = sessionmaker(bind=_get_sync_engine(), expire_on_commit=False)
    with factory() as session:
        if tenant_id:
            set_tenant_sync(session, tenant_id, role)
        try:
            yield session
        except Exception:
            session.rollback()
            raise
        else:
            session.commit()