# <>---< Encryptor/Decrypter >---<>
#
# WARNING! USE +PYTHON 3 TO RUN THIS SCRIPT!
# NOTE: To use in python 2.7, remove all types.
#
# Dependencies: pycryptodome, python +3
# install:
#   <> Option I: pip3 install pycryptodome
#   <> Option II: pip3 install pycryptodomex (not tested)

import base64
from io import TextIOWrapper
from typing import BinaryIO
from Crypto.Cipher import AES
from Crypto.Util.Padding import pad,unpad

# Asks an input from the user. Validates that len is the wanted_len.
# Returns it as string.
#
# param txt (str): text displayed in console to the user
# param wanted_len (int): the len that should have the input
def get_string_with_specific_len(text: str, wanted_len: int) -> str :
    value: str = ''

    while len(value) != wanted_len:
        value = str(input(text))
        if len(value) != wanted_len:
            print('      <> Format Error: date should be typed as yyyy-MM-dd format! (2023-01-01)')
            print('')
            
    return value

# Asks about the customer to the user. It applies a validation. len(customer) 
# must be > 0 and <=16. Returns a string with the user input.
def get_customer() -> str :
    customer: str = ''

    while len(customer) == 0 or len(customer) > 16:
        customer = str(input('   Customer code: '))
        if len(customer) == 0 or len(customer) > 16:
            print('      <> Format Error: customer code should have between 1 and 16 characters!')
            print('')
    return customer.upper()

# Asks the user about the expiration date and builds a formatted string
# for Angular Date() type instance. Returns it as string.
def get_expiration_date() -> str:
    print('   Expiration Date (yyyy-MM-dd):')
    year: str = get_string_with_specific_len('      > year: ', 4)
    month: str = get_string_with_specific_len('      < month: ', 2)
    day: str = get_string_with_specific_len('      > day: ', 2)

    return year + '-' + month + '-' + day

# Reads plain text from the provided file and return the content as a string.
#
# param filename (str): the name and path of the file
def read_file(filename: str) -> str:
    file: TextIOWrapper = open(filename, 'r')
    result: str = file.read()
    file.close()
    return result

# Writes a file as binary. If there is no file with
# provided name then creates a new one.
def write_file(filename: str, content: bytes):
    file: BinaryIO = open(filename, 'wb')
    file.write(content)
    file.close()

def generate_key(customer: str) -> str:
    key: str = customer
    counter: int = 0
    while len(key) < 16:
        key += key[counter]
        counter += 1

    return key

# Encrypt the provided raw using the provided key. Returns the encrypted 
# information as bytes.
#
# param raw (str): raw string to encrypt
# param key (str): key used for encryptation
def encrypt(raw: str, key: str) -> bytes:
    raw = pad(raw.encode(), 16)
    cipher = AES.new(key.encode(), AES.MODE_ECB)
    return base64.b64encode(cipher.encrypt(raw))

# Decrypt the provided bytes using the provided key. Then returns it.
#
# param enc (str): raw string to decrypt
# param key (str): key used for decryptation
def decrypt(enc: bytes, key: str):
    enc: bytes = base64.b64decode(enc)
    cipher = AES.new(key.encode(), AES.MODE_ECB)
    return unpad(cipher.decrypt(enc), 16)

if __name__ == '__main__':
    print("-----------------------------------------")
    print(">---<>---< Encryptor/Decrypter >---<>---<")
    print("-----------------------------------------")
    print("")

    # Get the info from the user
    customer: str = get_customer()
    expiration: str = get_expiration_date()

    # Format the string as json
    new_license: str = '{"expiration": "' + expiration + '","customer": "' + customer + '"}'

    # Generates the key using the customer code
    key: bytes = generate_key(customer)

    # Encrypt / decrypt the license and write it into a file
    encrypted: bytes = encrypt(new_license, key)
    decrypted = decrypt(encrypted, key)

    write_file('license.lic', encrypted)

    # Prints the results and ends the script
    print("")
    print("<==>----<=>----< Results >----<=>----<==>")
    print('')
    
    print(' -> Generated key: ', key)
    print(' -> Data: ', decrypted.decode("utf-8", "ignore"))
    print(' -> Encrypted ECB:', encrypted.decode("utf-8", "ignore"))

    print("")
    print("-----------------------------------------")
    print(">---<>---< Process Completed!! >---<>---<")
    print("-----------------------------------------")