#!/usr/bin/env python3

import argparse
import os
import sys

from bs4 import BeautifulSoup

parser = argparse.ArgumentParser(description='Prettify an HTML file')
aa = parser.add_argument
aa(dest='file', metavar='FILE', nargs='?', default=None)
args = parser.parse_args()

if args.file is None:
    args.file = sys.stdin
else:
    if not os.access(args.file, os.R_OK):
        print('Cannot read %s' % args.file, file=sys.stderr)
        sys.exit(1)
    args.file = open(args.file)

soup = BeautifulSoup(args.file, 'lxml')
print(soup.prettify())