import datetime
from calendar import monthrange
from django.utils import timezone


def start_of_month(a_day):
    """ Returns first of the month of a given datetime object"""
    return a_day.replace(day=1,hour=0,minute=0,second=0, microsecond=0)

def end_of_month(a_day):
    """ Returns first of the month of a given datetime object"""

    _, last_day = monthrange(a_day.year, a_day.month)
    return a_day.replace(day=last_day,hour=23,minute=59,second=59, microsecond=0)

def start_of_this_month():
    """ Returns first of this month"""
    a_day = timezone.now()
    return a_day.replace(day=1,hour=0,minute=0,second=0, microsecond=0)

def end_of_this_month():
    """ Returns first of this month"""
    a_day = timezone.now()

    _, last_day = monthrange(a_day.year, a_day.month)
    return a_day.replace(day=last_day,hour=23,minute=59,second=59, microsecond=0)

def end_before(a_date):
    """ Return suitable datetimefield for ending just before a_date """
    return a_date - datetime.timedelta(seconds=1)

def start_after(a_date):
    """ Return suitable datetimefield for starting just after a_date """
    return a_date + datetime.timedelta(seconds=1)