"""SQLAlchemy 引擎与 Session 工厂。"""
from contextlib import contextmanager
from typing import Iterator

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

from app.config import get_settings

settings = get_settings()

# SQLite 需要 check_same_thread=False（虽然我们用 FastAPI async/threadpool，但仍建议）
connect_args = {}
if settings.DATABASE_URL.startswith("sqlite"):
    connect_args["check_same_thread"] = False

engine = create_engine(
    settings.DATABASE_URL,
    connect_args=connect_args,
    pool_pre_ping=True,
    future=True,
)

SessionLocal = sessionmaker(
    bind=engine,
    autoflush=False,
    autocommit=False,
    expire_on_commit=False,
    class_=Session,
)


class Base(DeclarativeBase):
    """所有 ORM 模型的基类。"""

    pass


def get_db() -> Iterator[Session]:
    """FastAPI 依赖：每次请求一个 Session。"""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


@contextmanager
def session_scope() -> Iterator[Session]:
    """普通上下文管理器版本，供非请求路径使用（如初始化、调度器）。"""
    db = SessionLocal()
    try:
        yield db
        db.commit()
    except Exception:
        db.rollback()
        raise
    finally:
        db.close()