#!/usr/bin/env python3

""" Reverse complement """

import argparse

import os

from typing import NamedTuple

class Args(NamedTuple):

""" Command-line arguments """

dna: str

# --------------------------------------------------

def get_args() -> Args:

""" Get command-line arguments """

parser = argparse.ArgumentParser(

description='Print the reverse complement of DNA',

formatter_class=argparse.ArgumentDefaultsHelpFormatter)

parser.add_argument('dna', metavar='DNA', help='Input sequence or file')

args = parser.parse_args()

if os.path.isfile(args.dna):

args.dna = open(args.dna).read().rstrip()

return Args(args.dna)

# --------------------------------------------------

def main() -> None:

""" Make a jazz noise here """

args = get_args()

revc = ''

for base in reversed(args.dna):

if base == 'A':

revc += 'T'

elif base == 'T':

revc += 'A'

elif base == 'G':

revc += 'C'

elif base == 'C':

revc += 'G'

elif base == 'a':

revc += 't'

elif base == 't':

revc += 'a'

elif base == 'g':

revc += 'c'

elif base == 'c':

revc += 'g'

else:

revc += base

print(revc)

# --------------------------------------------------

if __name__ == '__main__':

main()