from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
from sqlalchemy.orm import sessionmaker
from sqlalchemy import text
import asyncio
from api.config import settings

DATABASE_URL = settings.DATABASE_URL
engine = create_async_engine(DATABASE_URL, echo=False, future=True)
SessionLocal = sessionmaker(engine, expire_on_commit=False, class_=AsyncSession)


async def wait_for_db(retries: int = 30, delay: float = 1.0) -> None:
	"""Wait until the database is available. Retries with exponential backoff.

	Raises RuntimeError if DB is still unavailable after retries.
	"""
	last_exc = None
	for attempt in range(1, retries + 1):
		try:
			async with engine.connect() as conn:
				await conn.execute(text("SELECT 1"))
				return
		except Exception as e:
			last_exc = e
			wait = min(delay * (2 ** (attempt - 1)), 5)
			await asyncio.sleep(wait)
	raise RuntimeError(f"Could not connect to DB after {retries} attempts") from last_exc