from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

# 暂时使用 sqlite，后续可轻松修改 SQLALCHEMY_DATABASE_URL 迁移到 MySQL 或 PostgreSQL
SQLALCHEMY_DATABASE_URL = "sqlite:///./qa_system.db"
# SQLALCHEMY_DATABASE_URL = "postgresql://user:password@postgresserver/db"

engine = create_engine(
    SQLALCHEMY_DATABASE_URL, connect_args={"check_same_thread": False}
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

Base = declarative_base()

# 依赖项：获取数据库会话
def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()
