import argparse
import sys


def greet(args):
    output = '{0}, {1}!'.format(args.greeting, args.name)
    if args.caps:
        output = output.upper()
    print(output)


def main_parser():
    parser = argparse.ArgumentParser()
    subparsers = parser.add_subparsers()

    hello_parser(subparsers)
    goodbye_parser(subparsers)

    if len(sys.argv) == 1:
        parser.print_help()
        sys.exit(1)
    else:
        args = parser.parse_args()
        args.func(args)


def hello_parser(subparsers):
    p = subparsers.add_parser('hello')

    p.add_argument(
        'name',
        help='name of the person to greet')

    p.add_argument(
        '--greeting',
        default='Hello',
        help='word to use for the greeting')

    p.add_argument(
        '--caps',
        action='store_true',
        help='uppercase the output')

    p.set_defaults(func=greet)
    return p


def goodbye_parser(subparsers):
    p = subparsers.add_parser('goodbye')

    p.add_argument(
        dest='name',
        help='name of the person to greet')

    p.add_argument(
        dest='--greeting',
        default='Hello',
        help='word to use for the greeting')

    p.add_argument(
        dest='--caps',
        action='store_true',
        help='uppercase the output')

    p.set_defaults(func=greet)
    return p


if __name__ == '__main__':
    main_parser()