"""PiggyBank implementation."""

from __future__ import annotations
from os.path import exists
from typing import List

from piggybank import PIGGYBANK_FILE_EXTENSION
from piggybank.currencies import CURRENCIES, \
    CurrencyIsNotSupportedError, CurrenciesCoinCountMismatchError, \
    CurrencyMismatchError
from piggybank.transaction import Transaction, sum_transactions, TYPE_INCOME

__all__ = ["PiggyBank"]


class PiggyBank:
    """This class stores array of transactions and perform some actions on it."""
    def __init__(self, currency: str = None) -> None:
        if not currency is None:
            self.currency = currency
        self._transactions = []
        self._last_transaction = None

    def transact(self, coins: List[int], direction: str = TYPE_INCOME) -> None:
        """Make a transaction."""
        if len(coins) != CURRENCIES[self._currency]["count"]:
            raise ValueError("Length of passed coins list doesn't match the " \
                             f"currency's coins count. ({len(coins)} " \
                             f"!= {CURRENCIES[self._currency]['count']})")
        self._last_transaction = Transaction(coins, direction)
        self._transactions.append(self._last_transaction)
        for coin_count in sum_transactions(self._transactions):
            if coin_count < 0:
                del self._transactions[-1]
                self._last_transaction = None
                raise ValueError(
                    "You can't take out more than you have.")

    @property
    def currency(self) -> str:
        """Returns a currency of a PiggyBank."""
        return self._currency

    @currency.setter
    def currency(self, currency: str = None) -> None:
        """Sets a currency of a PiggyBank with check for support. And if count
        of coins doesn't match the old currency it won't set a new one."""
        currency = currency.upper()
        if not currency in CURRENCIES:
            raise CurrencyIsNotSupportedError
        if not self._currency is None and \
            CURRENCIES[currency]["count"] \
            != CURRENCIES[self._currency]["count"]:
            raise CurrenciesCoinCountMismatchError
        self._currency = currency

    @property
    def transactions(self) -> List[Transaction]:
        """Returns a list of transactions."""
        return self._transactions

    @staticmethod
    def from_file(filename: str) -> PiggyBank:
        """Returns a PiggyBank object loaded from a file."""
        piggybank = PiggyBank()
        piggybank.load(filename)
        return piggybank

    def save(self, filename: str) -> None:
        """Appends last successful transaction to a file. File will be created
        if not exist yet."""
        if self._last_transaction is None:
            raise ValueError("No successful transaction found.")
        if not filename.endswith(PIGGYBANK_FILE_EXTENSION):
            filename += PIGGYBANK_FILE_EXTENSION
        if not exists(filename):
            with open(filename, 'w') as pbf:
                pbf.write(f"{self.currency}\n{self._last_transaction}\n")
        else:
            with open(filename, 'a') as pbf:
                pbf.write(f"{self._last_transaction}\n")

    def load(self, filename: str) -> None:
        """Loads a PiggyBank from a file."""
        if not filename.endswith(PIGGYBANK_FILE_EXTENSION):
            filename += PIGGYBANK_FILE_EXTENSION
        if not exists(filename):
            raise FileNotFoundError(filename)
        with open(filename, 'r') as pbf:
            currency = pbf.readline()[:-1]
            if currency not in CURRENCIES:
                raise CurrencyIsNotSupportedError
            else:
                self._currency = currency
            for line in pbf:
                self._transactions.append(Transaction.from_string(line))

    def __eq__(self, piggybank: PiggyBank) -> str:
        """Compares only currency."""
        return self._currency == piggybank.currency

    def __add__(self, piggybank: PiggyBank) -> PiggyBank:
        if self != piggybank:
            raise CurrencyMismatchError
        new = PiggyBank(self._currency)
        new._transactions = self._transactions + piggybank._transactions
        return new