# -*- coding: utf-8 -*-

from __future__ import (
    print_function,
    unicode_literals,
    absolute_import,
    division)

import hashlib
import hmac
import six


try:
    compare_digest = hmac.compare_digest

except AttributeError:
    # Not secure when the length is supposed to be kept secret
    def compare_digest(a, b):
        if len(a) != len(b):
            return False

        return reduce(
            lambda x, y: x | y, [ord(x) ^ ord(y) for x, y in zip(a, b)]) == 0


def sign(secret, string_to_sign):
    return six.text_type(
        hmac.new(
            secret.encode('utf8'),
            string_to_sign.encode('utf8'),
            hashlib.sha256).hexdigest())


def verify(secret, string_to_sign, signature):
    return compare_digest(signature, sign(secret, string_to_sign))