"""核心计算模块的惰性装载器（原 advanced_router._get_cached_import，D1 拆分时上提共用）。

- 惰性导入：避免路由模块级加载核心包（含 OCC 重模块）的导入开销与循环依赖
- 装载失败返回 None 且不缓存失败（与原实现一致，端点统一 503「服务不可用」）
- 实例缓存：设计/加工模块为纯 Python 计算（构造后无 self 突变，方法仅读入参），
  可安全地被 asyncio.to_thread 并发调用；OCC 相关的 side_action_designer
  经 processing_service.run_occ 的常驻 OCC 进程池使用（方案 B，见
  docs/topics/performance/OCC_THROUGHPUT.md）
"""
import threading
from typing import Optional

from shared.utils.logger import get_logger

logger = get_logger(__name__)

_lock = threading.Lock()
_instances: dict = {}

_LOADERS = {
    "side_action_designer": ("moldinsight.core.side_action_designer", "SideActionDesigner"),
    "cavity_layout_optimizer": ("moldinsight.core.cavity_layout_optimizer", "CavityLayoutOptimizer"),
    "mold_system_designer": ("moldinsight.core.mold_system_designer", "MoldSystemDesigner"),
    "mold_cam_designer": ("moldinsight.core.mold_cam", "MoldCAMDesigner"),
    "collision_detector": ("moldinsight.core.mold_machining", "CollisionDetector"),
    "toolpath_optimizer": ("moldinsight.core.mold_machining", "ToolpathOptimizer"),
    "edm_designer": ("moldinsight.core.mold_machining", "EDMElectrodeDesigner"),
    "machining_simulator": ("moldinsight.core.mold_machining", "MachiningSimulator"),
}


def get_core_module(key: str):
    if key in _instances:
        return _instances[key]
    if key not in _LOADERS:
        return None
    with _lock:
        if key in _instances:
            return _instances[key]
        module_path, class_name = _LOADERS[key]
        try:
            module = __import__(module_path, fromlist=[class_name])
            instance = getattr(module, class_name)()
        except Exception as e:
            logger.warning(f"核心模块 {key} 加载失败: {e}")
            return None
        _instances[key] = instance
        return instance