# Copyright (c) 2018 - 2020  Peter Pentchev <roam@ringlet.net>
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"""An abstract metaclass for confget backends."""

import abc
import configparser

import six

from .. import defs

try:
    from typing import Dict, Text  # noqa: H301

    _TYPING_USED = (defs, Dict, Text)
except ImportError:
    pass


@six.add_metaclass(abc.ABCMeta)
class Backend(object):
    # pylint: disable=too-few-public-methods
    """An abstract confget parser backend."""

    def __init__(self, cfg):
        # type: (Backend, defs.Config) -> None
        self._cfg = cfg

    @abc.abstractmethod
    def read_file(self):
        # type: (Backend) -> defs.ConfigData
        """Read and parse the configuration file, invoke the callbacks."""
        raise NotImplementedError("Backend.read_file")

    @abc.abstractmethod
    def get_dict(self):
        # type: (Backend) -> defs.ConfigData
        """Return the sections and values from the configuration file."""
        raise NotImplementedError("Backend.get_dict")

    def get_configparser(self):
        # type: (Backend) -> configparser.ConfigParser
        """Return a ConfigParser object with the parsed values."""
        par = configparser.ConfigParser(interpolation=None)
        par.read_dict(self.get_dict())
        return par
