# -*- coding: utf-8 -*-
 
# Copyright (c) 2018  Michael Rasmussen <mir@datanom.net>
 
# This file is part of SecureMail.

# SecureMail 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.
#
# SecureMail 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 SecureMail.  If not, see <https://www.gnu.org/licenses/>.

from nacl import __version__ as NACL_VERSION
from nacl.secret import SecretBox
from nacl.public import PrivateKey, Box
from nacl.utils import random, EncryptedMessage
from nacl.encoding import HexEncoder
import nacl.hash

class Cryptonize:
    """
    Encrypt and decrypt objects
    """
    
    def symmetric_encrypt(self, key, plain):
        skey = self.sanitize_key(key)
        box = SecretBox(skey)
        if NACL_VERSION < "1.1.0":
            nonce = random(SecretBox.NONCE_SIZE)
            cipher = box.encrypt(plain, nonce)
        else:
            cipher = box.encrypt(plain)
        box = skey = None
        
        return cipher
        
    def symmetric_decrypt(self, key, cipher):
        skey = self.sanitize_key(key)
        box = SecretBox(skey)
        plain = box.decrypt(cipher)
        box = skey = None
        
        return plain
        
    def asymmetric_encrypt(self, privkey, pubkey, plain):
        box = Box(privkey, pubkey)
        if NACL_VERSION < "1.1.0":
            nonce = random(Box.NONCE_SIZE)
            cipher = box.encrypt(plain, nonce)
        else:
            cipher = box.encrypt(plain)
        box = None
        
        return cipher
        
    def asymmetric_decrypt(self, privkey, pubkey, cipher):
        box = Box(privkey, pubkey)
        plain = box.decrypt(cipher)
        box = None
        
        return plain
        
    def get_random_key(self):
        return random(SecretBox.KEY_SIZE)
        
    def sanitize_key(self, key):
        if not isinstance(key, bytes):
            key = key.encode('utf-8')
        size = len(key)
        if size < SecretBox.KEY_SIZE:
            """ We must pad """
            newkey = key + bytes(SecretBox.KEY_SIZE - size)
        elif size > SecretBox.KEY_SIZE:
            newkey = key[:SecretBox.KEY_SIZE]
        else:
            newkey = key
        
                
        return newkey
        
    def get_key_pair(self):
        privkey = PrivateKey.generate()
        pubkey = privkey.public_key
        
        return (privkey, pubkey)

    def generate_hash(self, key):
        if not isinstance(key, bytes):
            key = key.encode('utf-8')
        HASHER = nacl.hash.sha512
        digest = HASHER(key, encoder=HexEncoder)

        return digest.decode()

    def create_EncryptedMessage(self, payload):
        nonce = payload[:SecretBox.NONCE_SIZE]
        ciphertext = payload[SecretBox.NONCE_SIZE:]
        
        return EncryptedMessage._from_parts(
            nonce, ciphertext,  nonce + ciphertext)