#!/usr/bin/python2
# -*- coding: utf-8 -*-

import sys
import re
import hashlib
import hmac

from base64 import b64encode


class PassHash(object):

    def __init__(self, args):

        super(PassHash, self).__init__()

        self.site_tag = args.site_tag
        self.master_key = args.master_key
        self.hashword_size = args.length if args.length > 0 and args.length <= 27 else 27
        self.require_digit = args.require_digit
        self.require_punctuation = args.require_punctuation
        self.require_mixedcase = args.require_mixedcase
        self.restrict_special = args.restrict_special
        self.restrict_digits = args.restrict_digits
        self.password = self.generate_hashword()

    def generate_hashword(self):
        s = b64encode(hmac.new(self.master_key, self.site_tag, hashlib.sha1).digest())
        if s[-1] == '=':
            s = s[:-1]

        sum = 0
        for i in s:
            sum += ord(i)

        if self.restrict_digits:
            s = self._convert_to_digits(s, sum)
        else:
            if self.require_digit:
                s = self._inject_special_character(s, 0, 4, sum, 48, 10)

            if self.require_punctuation and not self.restrict_special:
                s = self._inject_special_character(s, 1, 4, sum, 33, 15)

            if self.require_mixedcase:
                s = self._inject_special_character(s, 2, 4, sum, 65, 26)
                s = self._inject_special_character(s, 3, 4, sum, 97, 26)

            if self.restrict_special:
                s = self._remove_special_characters(s, sum)

        return s[:self.hashword_size]

    def _inject_special_character(self, sInput, offset, reserved, seed, cStart, cNum):
        pos0 = seed % self.hashword_size
        pos = (pos0 + offset) % self.hashword_size

        for i in xrange(self.hashword_size - reserved):
            i2 = (pos0 + reserved + i) % self.hashword_size
            c = ord(sInput[i2])
            if c >= cStart and c < cStart + cNum:
                return sInput

        sHead = sInput[:pos]
        sInject = chr(((seed + ord(sInput[pos])) % cNum) + cStart)
        sTail = sInput[pos+1:]

        return sHead + sInject + sTail

    def _convert_to_digits(self, sInput, seed):
        s = ''
        for c in sInput:
            if not c.isdigit():
                s += chr((seed + ord(c)) % 10 + 48)
            else:
                s += c
        return s

    def _remove_special_characters(self, sInput, seed):
        s = ''
        for c in sInput:
            if not c.isalnum():
                s += chr((seed + len(s)) % 26 + 65)
            else:
                s += c
        return s


if __name__ == '__main__':
    import argparse

    parser = argparse.ArgumentParser(description='Python2 implementation of PassHash')

    parser.add_argument(
        'site_tag',
        type=str,
        help='site name')

    parser.add_argument(
        'master_key',
        type=str,
        help='master password')

    parser.add_argument(
        '-l', '--length',
        type=int,
        default=10,
        help='length of the generated password [max 27]')

    parser.add_argument(
        '--no-digits',
        action='store_false',
        dest='require_digit',
        help='do not include at least one digit')

    parser.add_argument(
        '--no-punctuation',
        action='store_false',
        dest='require_punctuation',
        help='do not include at least one punctuation symbol')

    parser.add_argument(
        '--no-mixedcase',
        action='store_false',
        dest='require_mixedcase',
        help='do not make sure there\'s at least one upper and one lower case char')

    parser.add_argument(
        '--no-special',
        action='store_true',
        dest='restrict_special',
        help='exclude non-alphanumeric characters')

    parser.add_argument(
        '--digits-only',
        action='store_true',
        dest='restrict_digits',
        help='generate a digits-only password')

    args = parser.parse_args()

    print PassHash(args).password