from collections.abc import Generator

from sqlalchemy import create_engine
from sqlalchemy.orm import Session, sessionmaker

from app.core.config import get_settings

settings = get_settings()

# pool_pre_ping避免调度器长时间空闲后拿到失效的MySQL连接。
engine = create_engine(settings.database_url, pool_pre_ping=True, future=True)
SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, future=True)


def get_db() -> Generator[Session, None, None]:
    # FastAPI依赖负责在请求结束后关闭数据库会话。
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()