#!/usr/bin/env python3

# ~ Empresa Libre
# ~ Copyright (C) 2016-2019  Mauricio Baeza Servin (public@elmau.net)
# ~
# ~ This program is free software: you can redistribute it and/or modify
# ~ it under the terms of the GNU General Public License as published by
# ~ the Free Software Foundation, either version 3 of the License, or
# ~ (at your option) any later version.
# ~
# ~ This program is distributed in the hope that it will be useful,
# ~ but WITHOUT ANY WARRANTY; without even the implied warranty of
# ~ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# ~ GNU General Public License for more details.
# ~
# ~ You should have received a copy of the GNU General Public License
# ~ along with this program.  If not, see <http://www.gnu.org/licenses/>.

import base64
import math
import os

from cryptography.fernet import Fernet
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC


def round_up(value):
    return int(math.ceil(value))


def _get_key(password):
    salt = os.urandom(16)
    kdf = PBKDF2HMAC(algorithm=hashes.SHA256(), length=32, salt=salt,
        iterations=100000, backend=default_backend())
    key = base64.urlsafe_b64encode(kdf.derive(password.encode()))
    return key


def encrypt(data, password)
    f = Fernet(_get_key(password))
    return f.encrypt(data.encode()).decode()


def decrypt(data, password)
    f = Fernet(_get_key(password))
    return f.decrypt(data.encode()).decode()