import typing
from pathlib import Path
import tomli
import os


@typing.no_type_check
class SingletonMeta(type):
    """
    Singleton metaclass to ensure only one instance of a class exists.
    """

    _instances = {}

    @typing.no_type_check
    def __call__(cls, *args, **kwargs):
        if cls not in cls._instances:
            cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
        return cls._instances[cls]


class Config(metaclass=SingletonMeta):
    def __init__(
        self,
        config_path: Path | None = Path(__file__).parent.parent / "config.toml",
    ):
        """
        Initialize the configuration object.

        Args:
            config_path (Path): Path to the configuration file.
        """

        if config_path is None and "ADL_CONFIG_PATH" in os.environ:
            self.config_path = Path(os.environ["ADL_CONFIG_PATH"])
        elif config_path is not None:
            self.config_path = config_path
        else:
            raise ValueError("Either config_path or ADL_CONFIG_PATH must be provided")

        self.loaded_config_path = None
        self._load_config()

    def _load_config(self):
        """
        Load the configuration from the specified file.
        """
        with open(self.config_path, "rb") as f:
            config = tomli.load(f)
            self.loaded_config_path = str(self.config_path)
            print(f"Loaded config from {self.config_path}")

        self._config_dict = config

    def __getitem__(self, key: str):
        """
        Get a configuration value by key.

        Args:
            key (str): The key of the configuration value.

        Returns:
            The configuration value.
        """
        return self._config_dict.get(key, None)