import os
from datetime import datetime
import random
import math
import base64
import hashlib
from Crypto import Random
from Crypto.Cipher import AES
import rsa
import string

encoding0 = int(os.environ['encoding'])
padding0 = int(os.environ['padding'])
encryption_difficulty0 = int(os.environ['encryption_difficulty'])
N_days0=int(os.environ['N_days'])
User_passcode0=int(os.environ['User_passcode'])
power0 = float(os.environ['power'])
#path0 = float(os.environ['path'])
#publicKey0 = int(os.environ['publicKey'])


def seedx(path , User_passcode=User_passcode0, N_days=N_days0, encryption_difficulty = encryption_difficulty0):
  try:
    with open(path +'indx.txt') as f:
      old_day_index = int(f.read())
  except:
    old_day_index = 0
    print('no old index was found')
  #os.environ['old_day_index'] = str(old_day_index)
  timestamp = datetime.timestamp(datetime.now())
  #total number of days since unix time
  days_span = timestamp/math.factorial(6)/120 + 0.1#*random.random() #first time calculate the days since unix, thae latter randomize the time zone by up to ~7 hours
  day_index = math.floor(days_span/N_days)
  seed = int(day_index**power0 + User_passcode)
  if day_index == old_day_index:
#      with open('prvt.pem', 'rb') as file:
#        key_data = file.read()
#        privateKey = rsa.PrivateKey.load_pkcs1(key_data)
      with open('pblc.pem', 'rb') as file:
          key_data = file.read()
          publicKey = rsa.PublicKey.load_pkcs1(key_data)
  else:
      publicKey, privateKey = rsa.newkeys(encryption_difficulty)
      old_day_index = day_index
      #save in a folder
      with open(path +'indx.txt', 'w') as f:
        f.write(str(old_day_index))
      #with open(path +'prvt.pem', 'w') as f:
      #  f.write(privateKey.save_pkcs1().decode('utf-8'))
      with open(path +'pblc.pem', 'w') as f:
        f.write(publicKey.save_pkcs1().decode('utf-8'))
        
  return {'seed':seed,'publicKey': publicKey} #, 'privateKey': privateKey}


def AES_encrypt(User_message,seed, publicKey,encoding = encoding0, padding = padding0):
  #number conversion to encrypt non-english content
  User_message_numbered = (int.from_bytes(bytes(User_message, 'utf-16'), "big"))
  #padding
  front_padding = ''.join(random.choices(string.digits, k=padding)) #string.ascii_lowercase +
  back_padding = ''.join(random.choices(string.digits, k=padding)) #string.ascii_lowercase +
  msg = front_padding + str(User_message_numbered) + back_padding
  msg_len =len(msg) #total number of charachters in the msg
  permutation_list = list(range(0,msg_len))
  random.seed(seed)
  random.shuffle(permutation_list)
  shffled_msg_list = [msg[i] for i in permutation_list]
  shffled_msg = ''.join(shffled_msg_list)
  #print(shffled_msg)
  encMessage = AESCipher(str(publicKey.n)).encrypt(shffled_msg)
  if encoding == 0:
    encMessage_int = encMessage
  elif encoding == 1:
    encMessage_int = encMessage.decode('utf-16')
  else:
    encMessage_int = int.from_bytes(encMessage, "big")
  return encMessage_int


class AESCipher(object):
    def __init__(self, key):
        self.bs = AES.block_size
        self.key = hashlib.sha256(key.encode()).digest()
    def encrypt(self, raw):
        raw = self._pad(raw)
        iv = Random.new().read(AES.block_size)
        cipher = AES.new(self.key, AES.MODE_CBC, iv)
        return base64.b64encode(iv + cipher.encrypt(raw.encode()))
    def decrypt(self, enc):
        enc = base64.b64decode(enc)
        iv = enc[:AES.block_size]
        cipher = AES.new(self.key, AES.MODE_CBC, iv)
        return AESCipher._unpad(cipher.decrypt(enc[AES.block_size:])).decode('utf-8')
    def _pad(self, s):
        return s + (self.bs - len(s) % self.bs) * chr(self.bs - len(s) % self.bs)
    @staticmethod
    def _unpad(s):
        return s[:-ord(s[len(s)-1:])]

def invert_perm_list(p):
    return [p.index(l) for l in range(len(p))]

def AES_decrypt(encMessage,seed,publicKey, encoding = encoding0, encryption_difficulty = encryption_difficulty0, padding = padding0):
  if encoding == 0:
    encMessage_byte = encMessage
  elif encoding == 1:
    encMessage_byte = encMessage.encode('utf-16')
  else:
    encMessage_byte = encMessage.to_bytes((encMessage.bit_length() + 7) // 8, "big")
  decMessage = AESCipher(str(publicKey.n)).decrypt(encMessage_byte)
  decMessage_len =len(decMessage) #total number of charachters in the msg
  permutation_list = list(range(0,decMessage_len))
  random.seed(seed)
  random.shuffle(permutation_list)
  inverted_permutation_list = invert_perm_list(permutation_list)
  recovered_list = [decMessage[i] for i in inverted_permutation_list]
  recovered_msg_i_pad = ''.join(recovered_list)
  recovered_msg_i = int(recovered_msg_i_pad[padding:-padding])
  recovered_msg = recovered_msg_i.to_bytes((recovered_msg_i.bit_length() + 7) // 8, "big").decode("utf-16")
  return recovered_msg



def Encrypt_msg(User_message,user_password,path=''):
    User_passcode = (int.from_bytes(bytes(str(user_password), 'utf-8'), "little"))
    Num_dict_enc = seedx(path, User_passcode)
    encMessage_i = AES_encrypt(User_message,Num_dict_enc['seed'], Num_dict_enc['publicKey'],encoding = encoding0, padding = padding0)
    #print(encMessage_i)
    return encMessage_i


def Decrypt_msg(encMessage,user_password,path=''):
    User_passcode = (int.from_bytes(bytes(str(user_password), 'utf-8'), "little"))
    Num_dict_enc = seedx(path, User_passcode)
    recovered_msg = AES_decrypt(encMessage,Num_dict_enc['seed'], Num_dict_enc['publicKey'], encoding = encoding0, encryption_difficulty = encryption_difficulty0, padding = padding0)
    #print(recovered_msg)
    return recovered_msg