PiggyBank/piggybank/transaction.py

"""Transaction class implementation."""

from __future__ import annotations
from operator import add, sub, mul
from time import strftime, strptime, gmtime
from typing import Optional, List, Union

from piggybank import CURRENCIES

__all__ = ["Transaction", "sum_transactions",
           "TYPE_INCOME", "TYPE_OUTCOME", "TIME_FORMAT"]


TYPE_INCOME = "i"
TYPE_OUTCOME = "o"
TIME_FORMAT = "%Y-%m-%dT%H:%M:%S"


def sum_transactions(transactions: List[Transaction]) -> List[int]:
    """Sums all the coins and returns resulting list. All transactions must have
    same length of coins' list."""
    coins = [0] * len(transactions[0].coins)
    for transaction in transactions:
        if transaction.direction == TYPE_INCOME:
            coins = list(map(add, coins, transaction.coins))
        else:
            coins = list(map(sub, coins, transaction.coins))
    return coins


class Transaction:
    """An object that holds a single transaction.

    Arguments:
        - coins     -- a list of numbers represent count for each face value;
        - direction -- is this income or outcome. Takes TYPE_INCOME
                       or TYPE_OUTCOME;
        - timestamp -- date and time formated accordingly to TIME_FORMAT."""
    def __init__(self, coins: List[int], direction: str = TYPE_INCOME,
                 timestamp: Optional[str] = None) -> None:
        self.coins = coins
        self.direction = direction
        self.timestamp = timestamp

    @property
    def coins(self) -> List[int]:
        return self._coins

    @coins.setter
    def coins(self, coins: List[int]) -> None:
        if type(coins) is list:
            self._coins = coins
        else:
            raise TypeError("Coins must be of type 'list'.")

    @property
    def direction(self) -> str:
        return self._direction

    @direction.setter
    def direction(self, direction: str = TYPE_INCOME) -> None:
        if direction in [TYPE_INCOME, TYPE_OUTCOME]:
            self._direction = direction
        else:
            raise ValueError("Direction may only be of TYPE_INCOME(\"i\") " \
                             "or TYPE_OUTCOME(\"o\").")

    @property
    def timestamp(self) -> str:
        return self._timestamp

    @timestamp.setter
    def timestamp(self, timestamp: str = None) -> None:
        if timestamp is None:
            self._timestamp = strftime(TIME_FORMAT, gmtime())
        else:
            try:
                strptime(timestamp, TIME_FORMAT)
            except ValueError:
                raise ValueError(f"Timestamp {timestamp} has wrong format. " \
                                 f"The right one is \"{TIME_FORMAT}\".")
            self._timestamp = timestamp

    @staticmethod
    def from_string(transaction: str) -> Transaction:
        """Makes a Transaction object from its string output."""
        timestamp, direction, coins = transaction.split()
        coins = list(map(int, coins.split(",")))
        return Transaction(coins, direction, timestamp)

    def __str__(self) -> str:
        return f"{self.timestamp} {self.direction} " \
            f"{','.join(map(str, self.coins))}"