#!/usr/bin/env python3

import concurrent.futures
import hashlib
import os
import string
import sys

# Constants

ALPHABET = string.ascii_lowercase + string.digits

# Functions

def usage(exit_code=0):
    progname = os.path.basename(sys.argv[0])
    print(f'''Usage: {progname} [-a ALPHABET -c CORES -l LENGTH -p PATH -s HASHES]
    -a ALPHABET Alphabet to use in permutations
    -c CORES    CPU Cores to use
    -l LENGTH   Length of permutations
    -p PREFIX   Prefix for all permutations
    -s HASHES   Path of hashes file''')
    sys.exit(exit_code)

def md5sum(s):
    ''' Compute md5 digest for given string. '''
    # TODO: Use the hashlib library to produce the md5 hex digest of the given
    # string.
    return ''

def permutations(length, alphabet=ALPHABET):
    ''' Recursively yield all permutations of alphabet up to given length. '''
    # TODO: Use yield to create a generator function that recursively produces
    # all the permutations of the given alphabet up to the provided length.
    yield None

def flatten(sequence):
    ''' Flatten sequence of iterators. '''
    # TODO: Iterate through sequence and yield from each iterator in sequence.
    yield None

def crack(hashes, length, alphabet=ALPHABET, prefix=''):
    ''' Return all password permutations of specified length that are in hashes
    by sequentially trying all permutations. '''
    # TODO: Return list comprehension that iterates over a sequence of
    # candidate permutations and checks if the md5sum of each candidate is in
    # hashes.
    return []

def whack(arguments):
    ''' Call the crack function with the specified list of arguments '''
    return []

def smash(hashes, length, alphabet=ALPHABET, prefix='', cores=1):
    ''' Return all password permutations of specified length that are in hashes
    by concurrently subsets of permutations concurrently.
    '''
    # TODO: Create generator expression with arguments to pass to whack and
    # then use ProcessPoolExecutor to apply whack to all items in expression.
    return []

# Main Execution

def main():
    arguments   = sys.argv[1:]
    alphabet    = ALPHABET
    cores       = 1
    hashes_path = 'hashes.txt'
    length      = 1
    prefix      = ''

    # TODO: Parse command line arguments

    # TODO: Load hashes set

    # TODO: Execute crack or smash function

    # TODO: Print all found passwords

if __name__ == '__main__':
    main()

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