from collections.abc import Generator
from pathlib import Path

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

from app.core.config import settings


if settings.is_production and settings.database_url.startswith("sqlite"):
    raise RuntimeError("Production deployment requires DATABASE_URL configured for MySQL")


def _engine_kwargs() -> dict:
    """数据库连接：根据数据库类型设置 SQLAlchemy engine 参数。"""
    if settings.database_url.startswith("sqlite"):
        Path("storage").mkdir(exist_ok=True)
        return {"connect_args": {"check_same_thread": False}}
    return {"pool_pre_ping": True, "pool_recycle": 3600, "connect_args": {"connect_timeout": 5}}


engine = create_engine(settings.database_url, **_engine_kwargs())
SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, expire_on_commit=False)


def get_db() -> Generator[Session, None, None]:
    """请求依赖：为每个请求创建数据库会话并在结束后关闭。"""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()