#!/usr/bin/env python3
import random
import string
import json
from base64 import b64encode, b64decode
import pyDH
from Crypto.Hash import SHA512
from Crypto.Cipher import ChaCha20_Poly1305, PKCS1_OAEP
from Crypto.PublicKey.RSA import RsaKey
from Crypto.Random import get_random_bytes

from netsim import network_interface


class NetWrapper:
    def __init__(self, privateKey: RsaKey, clientAddress: str, username: str, serverPubKey: RsaKey,
                 serverAddr: str = 'A'):
        # Create network_interface:  network_interface(path, addr) path root is shared with network / addr is own address
        self.network = network_interface('./../../netsim/network/', clientAddress)
        self.serverAddr = serverAddr
        self.username = username
        self.privateKey = privateKey
        self.serverPubKey = serverPubKey
        self.cipherkey = "".encode('UTF-8')

    def randomStringGenerator(self, str_size: int = 128,
                              allowed_chars: str = string.ascii_letters + string.punctuation) -> str:
        return ''.join(random.choice(allowed_chars) for x in range(str_size))

    def identifyServer(self) -> bool:
        randommsg = self.randomStringGenerator()
        cipher_rsa = PKCS1_OAEP.new(self.serverPubKey)
        identMsg = json.dumps(
            {'type': 'IDY', 'source': self.network.own_addr, 'username': self.username,
             'message': b64encode(cipher_rsa.encrypt(randommsg.encode('UTF-8'))).decode('ASCII')}).encode(
            'UTF-8')
        self.network.send_msg(self.serverAddr, identMsg)
        returnJson = {'source': '', 'type': ''}
        while not (returnJson['source'] == self.serverAddr and returnJson['type'] == 'IDY'):
            status, msg = self.network.receive_msg(blocking=True)
            if not status:
                raise Exception('Network error during connection.')
            returnJson = json.loads(msg.decode('UTF-8'))
        cipher_rsa = PKCS1_OAEP.new(self.privateKey)
        retmsg = cipher_rsa.decrypt(b64decode(returnJson['message'])).decode('UTF-8')
        return retmsg == randommsg

    def createEncryptedChannel(self):
        dh = pyDH.DiffieHellman()
        cipher_rsa = PKCS1_OAEP.new(self.serverPubKey)
        mypubkey = b64encode(cipher_rsa.encrypt(str(dh.gen_public_key()).encode('UTF-8'))).decode('ASCII')
        jsonmsg = json.dumps({'type': 'DH', 'source': self.network.own_addr, 'message': mypubkey}).encode('UTF-8')
        self.network.send_msg(self.serverAddr, jsonmsg)
        decodedmsg = {'source': '', 'type': ''}
        while not (decodedmsg['source'] == self.serverAddr and decodedmsg['type'] == 'DH'):
            status, msg = self.network.receive_msg(blocking=True)
            if not status:
                raise Exception('Network error during connection.')
            decodedmsg = json.loads(msg.decode('UTF-8'))
        cipher_rsa = PKCS1_OAEP.new(self.privateKey)
        serverpubkey = int(cipher_rsa.decrypt(b64decode(decodedmsg['message'])).decode('UTF-8'))
        cipherkey = dh.gen_shared_key(serverpubkey).encode('UTF-8')
        hasher = SHA512.new()
        hasher.update(cipherkey)
        self.cipherkey = (hasher.hexdigest()[:32]).encode('UTF-8')

    def authenticate(self, password: str):
        message = f"LIN {self.username} {password}".encode('UTF-8')
        cipher = ChaCha20_Poly1305.new(key=self.cipherkey)
        header = json.dumps({'type': 'AUT', 'source': self.network.own_addr}).encode('UTF-8')
        cipher.update(header)
        ciphertext, tag = cipher.encrypt_and_digest(message)
        nonce = b64encode(cipher.nonce).decode('UTF-8')
        ct = b64encode(ciphertext).decode('UTF-8')
        b64tag = b64encode(tag).decode('UTF-8')
        sendjson = json.dumps(
            {'header': b64encode(header).decode('UTF-8'), 'nonce': nonce, 'message': ct, 'tag': b64tag}).encode(
            'UTF-8')
        self.network.send_msg(self.serverAddr, sendjson)
        try:
            status, msg = self.network.receive_msg(blocking=True)
            if not status:
                raise Exception('Network error during connection.')
            b64 = json.loads(msg.decode('UTF-8'))
            retnonce = b64decode(b64['nonce'])
            retciphertext = b64decode(b64['message'])
            retcipher = ChaCha20_Poly1305.new(key=self.cipherkey, nonce=retnonce)
            retcipher.update(b64decode(b64['header']))
            retheader = json.loads(b64decode(b64['header']).decode('UTF-8'))
            plaintext = retcipher.decrypt_and_verify(retciphertext, b64decode(b64['tag'])).decode('UTF-8')
            if plaintext != "OK" or not (retheader['source'] == self.serverAddr and retheader['type'] == 'AUT'):
                raise Exception('Authentication error')
        except Exception as e:
            print(e)

    def connectToServer(self):
        identStatus = self.identifyServer()
        if not identStatus:
            raise Exception('Server identification faliure')
        self.createEncryptedChannel()
        print('Please enter your password:')
        pw = input()
        self.authenticate(pw)

    def sendMessage(self, message: bytes):
        cipher = ChaCha20_Poly1305.new(key=self.cipherkey)
        header = json.dumps({'type': 'CMD', 'source': self.network.own_addr}).encode('UTF-8')
        cipher.update(header)
        ciphertext, tag = cipher.encrypt_and_digest(message)
        nonce = b64encode(cipher.nonce).decode('UTF-8')
        ct = b64encode(ciphertext).decode('UTF-8')
        sendjson = json.dumps({'header': b64encode(header).decode('UTF-8'), 'nonce': nonce, 'message': ct,
                               'tag': b64encode(tag).decode('UTF-8')}).encode(
            'UTF-8')
        self.network.send_msg(self.serverAddr, sendjson)

    def recieveMessage(self) -> bytes:
        try:
            status, msg = self.network.receive_msg(blocking=True)
            if not status:
                raise Exception('Network error during connection.')
            b64 = json.loads(msg.decode('UTF-8'))
            retnonce = b64decode(b64['nonce'])
            retciphertext = b64decode(b64['message'])
            retcipher = ChaCha20_Poly1305.new(key=self.cipherkey, nonce=retnonce)
            retcipher.update(b64decode(b64['header']))
            plaintext = retcipher.decrypt_and_verify(retciphertext, b64decode(b64['tag']))
            retheader = json.loads(b64decode(b64['header']).decode('UTF-8'))
            if not (retheader['source'] == self.serverAddr and retheader['type'] == 'CMD'):
                return "ERROR".encode('UTF-8')
            return plaintext
        except Exception:
            print("Incorrect decryption")
            return "ERROR".encode('UTF-8')