#!/usr/bin/python3
from itertools import permutations, zip_longest


def get_result():
    checked = []
    for permutation in permutations_of_items_in_bins(items='aabbb', number_of_bins=3, items_per_bin=2):
        if permutation in checked:
            continue
        checked.append(permutation)
        if is_valid_result(permutation):
            return permutation
    # this is for debug only
    for x in sorted(checked):
        print(_format(x))
    return None


def is_valid_result(result):
    return False  # in reality, this may return True


# from: http://stackoverflow.com/questions/312443/how-do-you-split-a-list-into-evenly-sized-chunks
def _get_chunks(n, iterable, padvalue=None):
    "grouper(3, 'abcdefg', 'x') --> ('a','b','c'), ('d','e','f'), ('g','x','x')"
    return zip_longest(*[iter(iterable)]*n, fillvalue=padvalue)


def _format(iterable):
    return ','.join([''.join(c) for c in iterable])


def permutations_of_items_in_bins(items: str, items_per_bin: int, number_of_bins: int, pad='z'):
    # if not enough items to fit in all the bins, pad them with a value representing "empty"
    items = items.rjust(number_of_bins * items_per_bin, pad)
    # get all possible sort orders of the items
    _permutations = permutations(items)
    # that are unique
    unique_permutations = set(_permutations)

    # for each sort order, split them into bins in that order
    for permutation in unique_permutations:
        # split items into bins
        chunks = list(_get_chunks(items_per_bin, permutation))
        # item sort order in bins doesn't matter, so let's always sort the items in each bin
        normalized = [tuple(sorted(x)) for x in chunks]
        yield normalized


get_result()

"""
aa,bb,bz
aa,bz,bb
ab,ab,bz
ab,az,bb
ab,bb,az
ab,bz,ab
az,ab,bb
az,bb,ab
bb,aa,bz
bb,ab,az
bb,az,ab
bb,bz,aa
bz,aa,bb
bz,ab,ab
bz,bb,aa
"""