mbank-to-mt940/mt940.py

from data import Transaction

BANK_NAME = "mBank"
BANK_BIC = "BREXPLPWMBK"

DEFAULT_SEQUENCE_NO = 1


class Mt940Writer:
    def __init__(self, filename, account_iban, range, starting_balance, date_start):
        self.file = open(filename, "w")
        self.account_iban = account_iban
        self.range = range
        self.starting_balance = starting_balance
        self.date_start = date_start

        self._write_header()
        self._written_starting_balance = False
        self._written_ending_balance = False

        self._balance = None
        self._date = None

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.release()

    def write_transaction(self, transaction: Transaction):
        if not self._written_starting_balance:
            self._write_starting_balance(self.starting_balance)

        self.file.writelines(
            [
                Mt940.make_61(transaction.datetime, transaction.amount),
                Mt940.make_86(
                    transaction.iban, transaction.name, transaction.description
                ),
            ]
        )

        self._balance = transaction.after_balance
        self._date = transaction.datetime

    def release(self):
        if (
            not self.file.closed
            and self._written_starting_balance
            and not self._written_ending_balance
        ):
            self._write_ending_balance()

        if not self.file.closed:
            self.file.close()

    def _write_header(self):
        self.file.write(Mt940.make_header(BANK_BIC))
        self.file.writelines(
            [
                Mt940.make_20(BANK_NAME, self.range),
                Mt940.make_25(self.account_iban, CURRENCY),
                Mt940.make_28(self.range),
            ]
        )

    def _write_starting_balance(self, balance):
        self.file.write(Mt940.make_60f(self.date_start, balance, CURRENCY))
        self._written_starting_balance = True

    def _write_ending_balance(self):
        self.file.write(Mt940.make_62f(self._date, self._balance, CURRENCY))
        self._written_ending_balance = True


CURRENCY = "PLN"

# format identifier
TAG_940 = "940"

# header
FORMAT_HEADER = "{bic}\n" + TAG_940 + "\n" + "{bic}\n"

# transaction ref
FORMAT_20 = ":20:{bank}{range}\n"

# account id
FORMAT_25 = ":25:{iban} {currency}\n"

# sequence no
FORMAT_28 = ":28:{seqno}\n"

# opening balance
FORMAT_60F = ":60F:{sign}{date}{currency}{amount}\n"

# closing balance
FORMAT_62F = ":62F:{sign}{date}{currency}{amount}\n"

# transaction
FORMAT_61 = ":61:{date}{date2}{amount}{magic}\n"

# transaction 2
FORMAT_86 = ":86:/IBAN/{iban}/NAME/{name}/REMI/{description}\n"

MAGIC = "NTRFNONREF"


class Mt940:
    @staticmethod
    def make_header(bic):
        return FORMAT_HEADER.format(bic=bic)

    @staticmethod
    def make_20(bank, range):
        return FORMAT_20.format(bank=bank, range=range)

    @staticmethod
    def make_25(iban, currency):
        return FORMAT_25.format(iban=iban, currency=currency)

    @staticmethod
    def make_28(seqno):
        return FORMAT_28.format(seqno=Mt940.pad_5(seqno))

    @staticmethod
    def make_60f(datetime, balance, currency):
        return FORMAT_60F.format(
            sign=Mt940.amount_sign(balance),
            date=Mt940.date(datetime),
            currency=currency,
            amount=Mt940.amount_val(balance),
        )

    @staticmethod
    def make_62f(datetime, balance, currency):
        return FORMAT_62F.format(
            sign=Mt940.amount_sign(balance),
            date=Mt940.date(datetime),
            currency=currency,
            amount=Mt940.amount_val(balance),
        )

    @staticmethod
    def make_61(datetime, amount):
        return FORMAT_61.format(
            date=Mt940.date(datetime),
            date2=Mt940.date(datetime, with_year=False),
            amount=Mt940.amount(amount),
            magic=MAGIC,
        )

    @staticmethod
    def make_86(iban, name, description):
        return FORMAT_86.format(iban=iban, name=name, description=description)

    @staticmethod
    def pad_5(val):
        return str(val).zfill(5)

    @staticmethod
    def amount_sign(val):
        return "C" if val > 0 else "D"

    @staticmethod
    def amount_val(val):
        return "{0:.2f}".format(abs(val)).replace(".", ",")

    @staticmethod
    def amount(val):
        return Mt940.amount_sign(val) + Mt940.amount_val(val)

    @staticmethod
    def date(val, with_year=True):
        if with_year:
            return val.strftime("%y%m%d")
        else:
            return val.strftime("%m%d")