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"""
This is the logic to help you save money

>>> cofrinho(2016)
[2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104]

>>> cofrinho(2016, group_by='month')
[20, 52, 84, 150, 156, 188, 280, 260, 370, 332, 364, 500]

>>>
"""

def cofrinho(year, factor=2, group_by='week'):
    """
    Return the amount of money to be saved per week.
    """

    import arrow
    initial_date = arrow.get(year, 1, 1)
    weeks_from = year
    week_number = 1
    amount_saved = []
    amount_saved_month = []
    amount_per_month = 0
    initial_month = 1

    initial_date = initial_date.replace(weeks=+1)

    while weeks_from == year:
        amount_saved.append( week_number * factor )
        # print "---> ", week_number, "-->", initial_date
        initial_date = initial_date.replace(weeks=+1)

        amount_per_month += week_number * factor
        if initial_month != initial_date.month:
            # print "    -->", amount_per_month
            amount_saved_month.append(amount_per_month)
            initial_month = initial_date.month
            amount_per_month = 0

        weeks_from = initial_date.year
        week_number += 1

    # print "amount_saved:", amount_saved
    if group_by != 'week':
        return amount_saved_month
    return amount_saved


if __name__ == "__main__":
    import doctest
    doctest.testmod()