import base64
import os

from cryptography.hazmat.primitives.ciphers.aead import AESGCM

NONCE_LEN = 12


class SecretBox:
    def __init__(self, key: bytes):
        self._aes = AESGCM(key)

    def encrypt(self, plaintext: str, context: str) -> str:
        nonce = os.urandom(NONCE_LEN)
        ciphertext = self._aes.encrypt(nonce, plaintext.encode(), context.encode())
        return base64.b64encode(nonce + ciphertext).decode()

    def decrypt(self, token: str, context: str) -> str:
        raw = base64.b64decode(token)
        return self._aes.decrypt(raw[:NONCE_LEN], raw[NONCE_LEN:], context.encode()).decode()


def generate_master_key() -> str:
    return base64.b64encode(os.urandom(32)).decode()