PiggyBank/piggybank/currencies.py

"""Here is a dictionary of supported currencies defined. Which could be easily
extended with new ones.

Each dictionary entry has an ISO code of a currency as its key. Or it can
slightly differ from an ISO to represent a modified version of a currency. An
example is SRUB entry for shortened version of RUB where coins of 1 and 5 kopek
value were removed. And value is an another dictionary consists of following
fields:
    name        -- a full name of a currency;
    description -- usually a country where this currency is used is being
        mentioned. Plus additional information;
    count       -- a number of coins in a currency;
    names       -- an array of names for each coins' face values;
    multipliers -- an array of multipliers for each face value in a decimal
        format. Decimal is used to avoid problems of rounding float numbers.
        So first two digits are used to store a fraction part. You can simply
        divide this number by 100 to get a regular floating-point number.
"""

from typing import Dict, List, TypedDict

__all__ = ["CURRENCIES", "DEFAULT_CURRENCY", "BaseCurrencyError",
           "CurrencyIsNotSupportedError", "CurrenciesCoinCountMismatchError",
           "CurrencyMismatchError", "print_supported_currencies"]


class BaseCurrencyError(Exception):
    """Base class for all currency exeptions."""
    def __init__(self, message=None, *args, **kwargs) -> None:
        if message is None:
            message = self.__doc__
        super().__init__(message, *args, **kwargs)


class CurrencyIsNotSupportedError(BaseCurrencyError):
    """Currency is not supported."""
    pass


class CurrencyMismatchError(BaseCurrencyError):
    """Currencies doesn't match, but they must do so."""
    def __init__(self, extra=None):
        if not extra is None:
            super().__init__(f"{self.__doc__} {extra}")
        else:
            super().__init__(self.__doc__)


class CurrenciesCoinCountMismatchError(BaseCurrencyError):
    """Count of coins of a new currency and an old one should be equal."""
    pass


DEFAULT_CURRENCY: str = "SRUB"


class Currency(TypedDict):
    name: str
    description: str
    count: int
    names: List[str]
    multipliers: List[int]


CURRENCIES: Dict[str, Currency] = {
    "RUB": {
        "name": "Ruble",
        "description": "Russian Federation",
        "count": 8,
        "names": ["1к.", "5к.", "10к.", "50к.", "1₽", "2₽", "5₽", "10₽"],
        "multipliers": [1, 5, 10, 50, 1_00, 2_00, 5_00, 10_00]
    },
    "SRUB": {
        "name": "Ruble (shortened)",
        "description": "Russian Federation. Excluding coins of 1 and 5 kopek",
        "count": 6,
        "names": ["10к.", "50к.", "1₽", "2₽", "5₽", "10₽"],
        "multipliers": [10, 50, 1_00, 2_00, 5_00, 10_00]
    },
    "BYN": {
        "name": "Belarusian ruble",
        "description": "Belarus",
        "count": 8,
        "names": ["1к.", "2к.", "5к.", "10к.", "20к.", "50к.", "1р.", "2р."],
        "multipliers": [1, 2, 5, 10, 20, 50, 1_00, 2_00]
    },
    "UAH": {
        "name": "Ukrainian hryvnia",
        "description": "Ukraine",
        "count": 10,
        "names": ["1к.", "2к.", "5к.", "10к.", "25к.", "50к.", "₴1", "₴2",
                  "₴5", "₴10"],
        "multipliers": [1, 2, 5, 10, 25, 50, 1_00, 2_00, 5_00, 10_00]
    },
    "USD": {
        "name": "Dollar",
        "description": "United States of America",
        "count": 6,
        "names": ["1¢", "5¢", "10¢", "25¢", "50¢", "$1"],
        "multipliers": [1, 5, 10, 25, 50, 1_00]
    },
    "EUR": {
        "name": "Euro",
        "description": "European Union",
        "count": 8,
        "names": ["1c", "2c", "5c", "10c", "20c", "50c", "€1", "€2"],
        "multipliers": [1, 2, 5, 10, 20, 50, 1_00, 2_00]
    },
    "GBP": {
        "name": "Pound sterling",
        "description": "United Kingdom",
        "count": 9,
        "names": ["1p", "2p", "5p", "10p", "20p", "25p", "50p", "£1", "£2"],
        "multipliers": [1, 2, 5, 10, 20, 25, 50, 1_00, 2_00]
    }
}


def print_supported_currencies() -> None:
    """Print a list of supported currencies."""
    print("Supported currencies are:")
    for cur in CURRENCIES:
        print(f"  {cur:^4} ┃ {CURRENCIES[cur]['name']:^31}"
              f"┃ {CURRENCIES[cur]['description']}")
    print("Default currency is", DEFAULT_CURRENCY)