#!/usr/bin/python

import sys, os, termios, hmac, hashlib, getopt, getpass

def usage(out):
    out.write("usage: mkhtpasswd [-h] FILE USERNAME\n")

opts, args = getopt.getopt(sys.argv[1:], "h")
for o, a in opts:
    if o == "-h":
        usage(sys.stdout)
        sys.exit(0)
if len(args) < 2:
    usage(sys.stderr)
    sys.exit(1)

def hashpw(usr, pw):
    dig = hmac.new(pw, digestmod=hashlib.sha1)
    dig.update(usr)
    return dig.hexdigest()

if ':' in args[1]:
    sys.stderr.write("mkhtpasswd: username cannot contain `:'\n")
    sys.exit(1)

passwds = {}
if os.path.exists(args[0]):
    with open(args[0]) as fp:
        for line in fp:
            usr, pw = line.strip().split(':')
            passwds[usr] = pw

passwds[args[1]] = hashpw(args[1], getpass.getpass())

with open(args[0], "w") as fp:
    for usr, pw in passwds.iteritems():
        fp.write("%s:%s\n" % (usr, pw))