from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
from sqlalchemy.orm import declarative_base
from app.core.config import settings

# Configure async engine
engine = create_async_engine(
    settings.DATABASE_URL,
    echo=False,
    future=True,
    # SQLite-specific optimization if running SQLite
    connect_args={"check_same_thread": False} if "sqlite" in settings.DATABASE_URL else {}
)

AsyncSessionLocal = async_sessionmaker(
    bind=engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autoflush=False
)

Base = declarative_base()

async def get_db():
    """FastAPI dependency for obtaining async database sessions."""
    async with AsyncSessionLocal() as session:
        try:
            yield session
        finally:
            await session.close()

async def init_db():
    """Initializes database tables if they do not already exist."""
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)