import os
import json

class Storage:
    def __init__(self):
        self._file_path = os.path.join(os.path.dirname(__file__), "device_data.json")
        self._cache = None

    def get_device_data(self):
        if self._cache is not None:
            return self._cache
        if not os.path.exists(self._file_path):
            return {}
        try:
            with open(self._file_path, "r", encoding="utf-8") as f:
                self._cache = json.load(f)
                return self._cache
        except Exception:
            return {}

    def set_device_data(self, data):
        if not isinstance(data, dict):
            raise ValueError("data must be a dict")
        self._cache = data
        try:
            with open(self._file_path, "w", encoding="utf-8") as f:
                json.dump(data, f, ensure_ascii=False)
        except Exception:
            pass