# standard imports
import os
import logging
import hashlib

from Crypto.Cipher import AES
from Crypto.Util import Counter

from .base import Encrypter

logg = logging.getLogger(__name__)


class AESCTREncrypt(Encrypter):

    aes_block_size = 1 << 7
    counter_bytes = int(128 / 8)

    def __init__(self, db_dir, secret):
        self.secret = secret


    def key_to_iv(self, k):
        h = hashlib.sha256()
        h.update(k.encode('utf-8'))
        h.update(self.secret)
        z = h.digest()
        return int.from_bytes(z[:self.counter_bytes], 'big') 


    def encrypt(self, k, v):
        iv = self.key_to_iv(k)
        ctr = Counter.new(self.aes_block_size, initial_value=iv)
        cipher = AES.new(self.secret, AES.MODE_CTR, counter=ctr)
        return cipher.encrypt(v)
       

    def decrypt(self, k, v):
        iv = self.key_to_iv(k)
        ctr = Counter.new(self.aes_block_size, initial_value=iv)
        cipher = AES.new(self.secret, AES.MODE_CTR, counter=ctr)
        return cipher.decrypt(v)