from __future__ import annotations
from typing import TYPE_CHECKING
from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker, AsyncSession

if TYPE_CHECKING:
    from quart import Quart


def init_db(app: "Quart") -> None:
    """Create async engine and attach db_sessionmaker to app.

    Called during create_app() after config is loaded.
    Does not create tables — Alembic handles migrations.
    """
    db_url: str = app.config["DATABASE_URL"]
    engine = create_async_engine(db_url, echo=False)
    app.db_sessionmaker: async_sessionmaker[AsyncSession] = async_sessionmaker(
        engine, expire_on_commit=False
    )
    app._db_engine = engine