"""数据库连接与会话管理。"""

from __future__ import annotations

from typing import Generator

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

from app.config import get_settings


class Base(DeclarativeBase):
    pass


_settings = get_settings()

import os as _os
_pool_size = int(_os.environ.get("DB_POOL_SIZE", "20"))
_max_overflow = int(_os.environ.get("DB_MAX_OVERFLOW", "30"))

_engine_kwargs: dict = dict(
    echo=_settings.db_echo,
    future=True,
    pool_pre_ping=True,
    pool_size=_pool_size,
    max_overflow=_max_overflow,
)

engine = create_engine(_settings.db_url, **_engine_kwargs)

SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, future=True)


def get_db() -> Generator[Session, None, None]:
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()