import pytest_asyncio
from httpx import ASGITransport, AsyncClient
from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
from sqlalchemy.pool import NullPool

from app.config import settings
from app.db import Base, get_db
from app.main import app

# pytest-asyncio gives each test function its own event loop by default;
# asyncpg connections are bound to the loop they were opened on, so a pooled
# connection from one test's loop breaks the next test. NullPool sidesteps
# this by opening a fresh connection per checkout — scoped to this dedicated
# test engine so app.db.engine (used by production) is unaffected.
test_engine = create_async_engine(settings.database_url, poolclass=NullPool)
TestSessionLocal = async_sessionmaker(test_engine, expire_on_commit=False)


@pytest_asyncio.fixture(autouse=True)
async def _reset_db():
    async with test_engine.begin() as conn:
        await conn.run_sync(Base.metadata.drop_all)
        await conn.run_sync(Base.metadata.create_all)
    yield


async def _override_get_db():
    async with TestSessionLocal() as session:
        yield session


app.dependency_overrides[get_db] = _override_get_db


@pytest_asyncio.fixture
async def client():
    transport = ASGITransport(app=app)
    async with AsyncClient(transport=transport, base_url="http://test") as ac:
        yield ac