# coding=utf-8
from django.utils import timezone
import datetime
from datetime import timedelta

from web.algorithm import VerhoeffAlgorithm, LuhnAlgorithm


def is_valid_social_security_number(number):
    if number is not None and number != '':
        if len(number) != 13:
            return False
        if not number.isdigit():
            return False
        if not LuhnAlgorithm.is_luhn_valid(number[:12]):
            return False
        if not VerhoeffAlgorithm.is_valid_verhoeff(number[:11] + number[12]):
            return False

    return True


def get_today_midnight_date():
    today = timezone.now()
    today_midnight = datetime.datetime(
        today.year, today.month, today.day, tzinfo=today.tzinfo)
    return today_midnight


def get_weekdays_in_period(fromdate, todate):
    '''
    fromdate and todate must be generated using datetime.date or datetime.datetime like:

    from datetime import date
    fromdate = date(2010,1,1)
    todate = date(2010,3,31)

    fromdate = datetime.datetime(2018, 10, 3, 15, 00, 00)
    todate = datetime.datetime.today()

    but both dates must have the same format ! 
    todate is not included in the range

    Weekdays are returned as isoweekdays like the form described in week_choices from constants.py (starting at 1)
    '''
    if todate < fromdate:
        return set([])
    day_generator = (fromdate + timedelta(day)
                     for day in xrange((todate - fromdate).days))
    weekdays = set([date.isoweekday() for date in day_generator])
    return weekdays