app/lib/database.py

from collections.abc import AsyncGenerator

from sqlalchemy.ext.asyncio import (
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)
from sqlalchemy.orm import DeclarativeBase

from app.lib.config import settings


class Base(DeclarativeBase):
    pass


engine = create_async_engine(
    settings.database_url,
    echo=settings.debug,
    pool_pre_ping=True,   # critical for Neon cold-start / stale connections
    pool_recycle=300,     # recycle before Neon's idle timeout
)

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


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    async with AsyncSessionLocal() as session:
        yield session