import sys

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

from app.config import settings

# pytest-asyncio gives each test function its own event loop by default, but
# this engine (and its connection pool) is a module-level singleton created
# once and reused across every test. asyncpg connections are bound to the
# event loop they were opened on, so pooling them across per-test loops
# raises "got Future attached to a different loop". NullPool sidesteps this
# by opening a fresh connection per checkout instead of reusing one from a
# prior loop. Only applied under pytest; production keeps normal pooling.
_engine_kwargs = {"echo": False}
if "pytest" in sys.modules:
    _engine_kwargs["poolclass"] = NullPool

engine = create_async_engine(settings.database_url, **_engine_kwargs)
async_session_maker = async_sessionmaker(engine, expire_on_commit=False)


class Base(DeclarativeBase):
    pass


async def get_db() -> AsyncSession:
    async with async_session_maker() as session:
        yield session