"""SQLAlchemy async database engine and session."""
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
from sqlalchemy.orm import DeclarativeBase
from app.config import get_settings


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


settings = get_settings()

engine = create_async_engine(
    settings.database_url,
    echo=False,
    pool_pre_ping=True,
)

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


async def get_db() -> AsyncSession:
    """Dependency: yield an async database session."""
    async with async_session() as session:
        try:
            yield session
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()


async def init_db() -> None:
    """Create all tables (for testing / first run)."""
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)