# ird.py - functions for handling New Zealand IRD numbers
# coding: utf-8
#
# Copyright (C) 2019 Leandro Regueiro
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301 USA

"""IRD number (New Zealand Inland Revenue Department (Te Tari Tāke) number).

The IRD number is used by the New Zealand Inland Revenue Department (Te Tari
Tāke in Māori) to identify businesses and individuals for tax purposes. The
number consists of 8 or 9 digits where the last digit is a check digit.

More information:

* https://www.ird.govt.nz/
* https://www.ird.govt.nz/-/media/Project/IR/PDF/2020RWTNRWTSpecificationDocumentv10.pdf
* https://www.oecd.org/tax/automatic-exchange/crs-implementation-and-assistance/tax-identification-numbers/New%20Zealand-TIN.pdf

>>> validate('4909185-0')
'49091850'
>>> validate('NZ 49-098-576')
'49098576'
>>> validate('136410133')
Traceback (most recent call last):
    ...
InvalidChecksum: ...
>>> validate('9125568')
Traceback (most recent call last):
    ...
InvalidLength: ...
>>> format('49098576')
'49-098-576'
"""

from stdnum.exceptions import *
from stdnum.util import clean, isdigits


def compact(number):
    """Convert the number to the minimal representation."""
    number = clean(number, ' -').upper().strip()
    if number.startswith('NZ'):
        return number[2:]
    return number


def calc_check_digit(number):
    """Calculate the check digit.

    The number passed should not have the check digit included.
    """
    primary_weights = (3, 2, 7, 6, 5, 4, 3, 2)
    secondary_weights = (7, 4, 3, 2, 5, 2, 7, 6)
    # pad with leading zeros
    number = (8 - len(number)) * '0' + number
    s = -sum(w * int(n) for w, n in zip(primary_weights, number)) % 11
    if s != 10:
        return str(s)
    s = -sum(w * int(n) for w, n in zip(secondary_weights, number)) % 11
    return str(s)


def validate(number):
    """Check if the number is a valid IRD number."""
    number = compact(number)
    if len(number) not in (8, 9):
        raise InvalidLength()
    if not isdigits(number):
        raise InvalidFormat()
    if not 10000000 < int(number) < 150000000:
        raise InvalidComponent()
    if number[-1] != calc_check_digit(number[:-1]):
        raise InvalidChecksum()
    return number


def is_valid(number):
    """Check if the number is a valid IRD number."""
    try:
        return bool(validate(number))
    except ValidationError:
        return False


def format(number):
    """Reformat the number to the standard presentation format."""
    number = compact(number)
    return '-'.join([number[:-6], number[-6:-3], number[-3:]])