"""
Project Euler Problem 8
=======================

Find the greatest product of thirteen consecutive digits in the 1000-digit
number.

            73167176531330624919225119674426574742355349194934
            96983520312774506326239578318016984801869478851843
            85861560789112949495459501737958331952853208805511
            12540698747158523863050715693290963295227443043557
            66896648950445244523161731856403098711121722383113
            62229893423380308135336276614282806444486645238749
            30358907296290491560440772390713810515859307960866
            70172427121883998797908792274921901699720888093776
            65727333001053367881220235421809751254540594752243
            52584907711670556013604839586446706324415722155397
            53697817977846174064955149290862569321978468622482
            83972241375657056057490261407972968652414535100474
            82166370484403199890008895243450658541227588666881
            16427171479924442928230863465674813919123162824586
            17866458359124566529476545682848912883142607690042
            24219022671055626321111109370544217506941658960408
            07198403850962455444362981230987879927244284909188
            84580156166097919133875499200524063689912560717606
            05886116467109405077541002256983155200055935729725
            71636269561882670428252483600823257530420752963450
"""
from functools import reduce


BIG_CUBE = ''.join("""
    73167176531330624919225119674426574742355349194934
    96983520312774506326239578318016984801869478851843
    85861560789112949495459501737958331952853208805511
    12540698747158523863050715693290963295227443043557
    66896648950445244523161731856403098711121722383113
    62229893423380308135336276614282806444486645238749
    30358907296290491560440772390713810515859307960866
    70172427121883998797908792274921901699720888093776
    65727333001053367881220235421809751254540594752243
    52584907711670556013604839586446706324415722155397
    53697817977846174064955149290862569321978468622482
    83972241375657056057490261407972968652414535100474
    82166370484403199890008895243450658541227588666881
    16427171479924442928230863465674813919123162824586
    17866458359124566529476545682848912883142607690042
    24219022671055626321111109370544217506941658960408
    07198403850962455444362981230987879927244284909188
    84580156166097919133875499200524063689912560717606
    05886116467109405077541002256983155200055935729725
    71636269561882670428252483600823257530420752963450
""".split())


def scoper(s, width, pos=0):
    """
    Takes a string and a width, and yields consecutive chunks of `s`
    to the size of `width` until we hit the end of `s`.
    """
    while True:
        yield s[pos:pos + width]

        if pos + width == len(s):
            break

        pos += 1


def product_of_string(s):
    """
    Takes a string containing integers and returns the product.
    """
    return reduce(lambda x, y: x * y, [int(i) for i in s])


def main(length=13):
    return max([product_of_string(s) for s in scoper(BIG_CUBE, length)])


def test_scoper():
    assert list(scoper('Beata', 2)) == ['Be', 'ea', 'at', 'ta']
    assert list(scoper('Beata', 3)) == ['Bea', 'eat', 'ata']


def test_product_of_string():
    assert product_of_string('245') == 40


def test_main():
    assert main(4) == 5832

print(main())
