def _recently_added(self, bl, user):
""" Filtering key point: recently added.
If more than self.NEXT_LIMIT books available, randomly pick some
Otherwise, pick enough ones by the updated time
@returns: a list of isbns
"""
now = datetime.datetime.now()
dt = datetime.timedelta(days=30)
one_month_ago = now - dt
month_list = bl.isbns_after(one_month_ago)
if len(month_list) >= self.NEXT_LIMIT:
# enough books for random
return random.sample(month_list, self.NEXT_LIMIT)
# otherwise, pick enough ones by the updated time
helper = SortHelper(user)
sorted_isbns = helper.by_updated_time(booklist.LIST_INTERESTED)
return sorted_isbns[:self.NEXT_LIMIT]
