"""
Database engine and session management.

Provides async SQLAlchemy engine and session factory for dependency injection.
"""
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
from sqlalchemy.orm import DeclarativeBase
from app.core.settings import get_settings

settings = get_settings()

engine = create_async_engine(
    settings.DATABASE_URL,
    echo=settings.DEBUG,
    pool_pre_ping=True,
    pool_size=20,
    max_overflow=10,
)

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


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


async def get_db() -> AsyncSession:
    """FastAPI dependency that provides a database session."""
    async with async_session() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()
