import logging
import os
from shutil import copy
from typing import Any, final

import tomllib


@final
class Config:
    """Provides a wrapper for toml config files."""

    def __init__(self, file_name: str, sample_file_name: str):
        """Read in a config file and provide it as a :obj:`Config` object.

        Args:
            file_name (str): Path to a TOML config file.
            sample_file_name (str): Path to a sample TOML config file.
                Used if :param:`file_name` does not exist.
        """

        self.file_name = file_name
        """str: Path to a TOML config file."""

        self.sample_file_name = sample_file_name
        """str: Path to a sample TOML config file. Used if :attr:`file_name` does not exist."""

        self._toml_data = {}
        """dict: TOML data, parsed to a nested dict."""

        try:
            with open(str(self.file_name), "rb") as f:
                self._toml_data = tomllib.load(f)
        except OSError as error:
            file_name = copy(str(self.sample_file_name), str(self.file_name))
            logging.getLogger().warning(
                "Could not read config file %r, reason: %r",
                os.path.realpath(file_name),
                error,
            )

    def get(self, key: str, default: Any = None):
        """Recursively calls `get(key, default)` to search nested dictionary.

        Examples:
            Fetch a nested configuration value.

            >>> config = Config("config.toml", "config-sample.toml")
            >>> config.get("web.run", False)
            True

        Returns:
            Any: Value at key if found, provided default or None otherwise.
        """
        nested_key: list[str] = key.split(".")
        current_item: Any = self._toml_data

        # Traverse the dict for every depth of the key the user provided.
        # If any part of the key does not exist, bail and return default.
        for part in nested_key:
            if part not in current_item:
                return default
            current_item = current_item[part]

        # No parts left; `current_item` now holds the requested value.
        return current_item