from pathlib import Path

from PySide6.QtCore import QObject, QFileSystemWatcher


class QssReloader(QObject):
    instance = None

    def __new__(cls, *args, **kwargs):
        if cls.instance is None:
            cls.instance = super().__new__(cls)
        return cls.instance

    def __init__(self):
        super().__init__()
        self.path2objs = {}
        self.watcher = QFileSystemWatcher(self)
        self.watcher.fileChanged.connect(self.on_file_changed)

    def register(self, qss_path: str, ui_obj):
        path = str(Path(qss_path).resolve())
        obj_list = self.path2objs.setdefault(path, [])
        if ui_obj not in obj_list:
            obj_list.append(ui_obj)
        if path not in self.watcher.files():
            self.watcher.addPath(path)
        self.apply_one(path, ui_obj)

    def on_file_changed(self, path: str):
        for obj in self.path2objs.get(path, []):
            self.apply_one(path, obj)
        if path not in self.watcher.files():
            self.watcher.addPath(path)

    @staticmethod
    def apply_one(path: str, obj):
        qss = Path(path).read_text(encoding="utf-8")
        obj.setStyleSheet(qss)


qss_reloader = QssReloader()