"""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",
    "currency": {
        "RUB": "RUB;Russian ruble;Russian Federation;8;" \
            "1к,5к,10к,50к,1₽,2₽,5₽,10₽;1,5,10,50,100,200,500,1000",
        "SRUB": "SRUB;Russian ruble (short);No 1 and 5 kopek;6;" \
            "10к,50к,1₽,2₽,5₽,10₽;10,50,100,200,500,1000",
        "BYN": "BYN;Belarusian ruble;Belarus;8;" \
            "1к,2к,5к,10к,20к,50к,1р,2р;1,2,5,10,20,50,100,200",
        "UAH": "UAH;Ukrainian hryvnia;Ukraine;10;" \
            "1к,2к,5к,10к,25к,50к,₴1,₴2,₴5,₴10;1,2,5,10,25,50,100,200,500,1000",
        "USD": "USD;US Dollar;United States of America;6;" \
            "1¢,5¢,10¢,25¢,50¢,$1;1,5,10,25,50,100",
        "EUR": "EUR;Euro;European Union;8;" \
            "1c,2c,5c,10c,20c,50c,€1,€2;1,2,5,10,20,50,100,200",
        "GBP": "GBP;Pound sterling;United Kingdom;9;" \
            "1p,2p,5p,10p,20p,25p,50p,£1,£2;1,2,5,10,20,25,50,100,200" } }

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] == "#" or line[0] == "\n":
                continue
            key, value = line[:-1].split(" = ")
            if key.find(".") != -1:
                k0, k1 = key.split(".")
                if not k0 in self._configuration:
                    self._configuration[k0] = dict()
                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():
                if type(value) is dict:
                    for subkey, subvalue in value.items():
                        cf.write(f"{key}.{subkey} = {subvalue}\n")
                else:
                    cf.write(f"{key} = {value}\n")

    @property
    def items(self) -> dict:
        return self._configuration

    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