"""SQLAlchemy async database engine and session management."""

from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
from sqlalchemy.orm import DeclarativeBase

from backend.config.settings import get_settings


class Base(DeclarativeBase):
    """SQLAlchemy declarative base for all models."""
    pass


_settings = get_settings()

engine = create_async_engine(
    _settings.database_url,
    echo=_settings.debug,
    connect_args={"check_same_thread": False},
)

async_session_factory = async_sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False,
)


async def init_db() -> None:
    """Create all database tables."""
    # Import models so they register with Base.metadata
    import backend.db.models  # noqa: F401

    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)


async def get_async_session() -> AsyncSession:
    """Yield an async database session."""
    async with async_session_factory() as session:
        yield session