"""An implementation of a slightly advanced key=value configuration file.
Commentary lines are started with # symbol.
Keys and values are separated by ' = ' (spaces are necessary).
Keys with . symbol are splited and right part is a nested dictionary.
Example:
    # A commentary line
    default_something = 10
    currency.RUB = ...
Above example is translated as a following dictionary:
    { "default_something": 10, "currency": { "RUB": "..." } }
"""

from os import getenv
from os.path import exists, join
from platform import system
from typing import Union

__all__ = ["Configuration", "get_configuration_path"]


def get_configuration_path() -> str:
    """Returns a path to where configuration is stored."""
    if system() == "Linux":
        return getenv("XDG_CONFIG_HOME") or f"{getenv('HOME')}/.config"
    elif system() == "Windows":
        return getenv("APPDATA")


DEFAULT_CONFIGURATION = {
    "default-currency": "SRUB" }

DEFAULT_CONFIGURATION_FILE = join(get_configuration_path(), "piggybank.conf")


class Configuration:
    def __init__(self, configuration_file: str = DEFAULT_CONFIGURATION_FILE,
                 default_configuration: dict = DEFAULT_CONFIGURATION) -> None:
        self._configuration_file = configuration_file
        self._configuration = dict()
        if exists(self._configuration_file):
            self.load()
        elif not default_configuration is None:
            self._configuration = default_configuration
            self.save()

    def load(self) -> None:
        for line in open(self._configuration_file, 'r'):
            if line[0] == "#":
                continue
            key, value = line[:-1].split(" = ")
            if key.find(".") != -1:
                k0, k1 = key.split(".")
                self._configuration[k0] = {k1 : value}
            else:
                self._configuration[key] = value

    def save(self) -> None:
        with open(self._configuration_file, 'w') as cf:
            for key, value in self._configuration.items():
                cf.write(f"{key} = {value}\n")

    def __getitem__(self, key: str) -> Union[int, str, bool]:
        return self._configuration[key]

    def __setitem__(self, key: str, value: Union[int, str, bool]) -> None:
        self._configuration[key] = value