"""SQLAlchemy 引擎工厂（B7 · 开发计划挂账⑥）。

按库名缓存单例 Engine：deps / risk / simulate 路由每请求实例化 Repository 时
复用同一连接池，不再每次 create_engine（B6 复审 P3：实例化点泄漏）；应用
shutdown 经 dispose_engines 统一释放。测试直传 engine= 参数的用法不受影响；
monkeypatch settings 后须先 dispose_engines() 清缓存。
"""

from __future__ import annotations

from functools import lru_cache

from sqlalchemy import create_engine
from sqlalchemy.engine import Engine

from app.config.settings import settings


@lru_cache(maxsize=None)
def get_engine(database: str) -> Engine:
    """取指定库的单例 Engine（进程内共享连接池）。"""
    pwd = settings.mysql_password
    auth = f"{settings.mysql_user}:{pwd}" if pwd else settings.mysql_user
    url = (
        f"mysql+pymysql://{auth}@{settings.mysql_host}:{settings.mysql_port}"
        f"/{database}?charset=utf8mb4"
    )
    return create_engine(url, pool_pre_ping=True)


def dispose_engines() -> None:
    """释放全部缓存 Engine（lifespan shutdown / 测试隔离）。"""
    get_engine.cache_clear()