from pathlib import Path
import os
import hashlib
import hmac
from typing import Tuple

class SovereignVault:
    def __init__(self, account_id: int, device_id: str):
        self._root_key = self._derive_root_key(account_id, device_id)

    def _derive_root_key(self, account_id: int, device_id: str) -> bytes:
        salt = b"lane-sovereign-root"
        data = f"{account_id}:{device_id}".encode("utf-8")
        return hashlib.pbkdf2_hmac("sha256", data, salt, 200_000, dklen=32)

    def derive_object_key(self, object_hash: str) -> bytes:
        return hmac.new(self._root_key, object_hash.encode("utf-8"), hashlib.sha256).digest()

    def encrypt(self, key: bytes, plaintext: bytes) -> Tuple[bytes, bytes]:
        nonce = os.urandom(16)
        stream = hashlib.sha256(key + nonce).digest()
        ciphertext = bytes(p ^ stream[i % len(stream)] for i, p in enumerate(plaintext))
        tag = hmac.new(key, nonce + ciphertext, hashlib.sha256).digest()
        return nonce + ciphertext, tag

    def decrypt(self, key: bytes, blob: bytes, tag: bytes) -> bytes:
        nonce = blob[:16]
        ciphertext = blob[16:]
        expected = hmac.new(key, nonce + ciphertext, hashlib.sha256).digest()
        if not hmac.compare_digest(expected, tag):
            raise ValueError("integrity_failure")
        stream = hashlib.sha256(key + nonce).digest()
        return bytes(c ^ stream[i % len(stream)] for i, c in enumerate(ciphertext))