"""Public demonstration key only. Never use this key to protect real data.
Requires Python 3.10+ and cryptography. No network operations.
"""
import base64
import json
import os
import sys
from cryptography.hazmat.primitives.ciphers.aead import AESGCM

PUBLIC_TEST_KEY_HEX = '000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f'
KEY = bytes.fromhex(PUBLIC_TEST_KEY_HEX)
DEMO_MESSAGE = 'Hello from Node.js — Hola, niño 🔐'


def encrypt(message=DEMO_MESSAGE):
    iv, aad = os.urandom(12), b'hashytools:raw-demo'
    combined = AESGCM(KEY).encrypt(iv, message.encode('utf-8'), aad)
    return dict(algorithm='AES-256-GCM', encoding='hex', iv=iv.hex(),
                ciphertext=combined[:-16].hex(), tag=combined[-16:].hex(), aad=aad.hex())


def decode(value, encoding):
    if not isinstance(value, str):
        raise ValueError('Expected an encoded string')
    if encoding == 'hex':
        result = bytes.fromhex(value)
        if result.hex() != value.lower():
            raise ValueError('Invalid hex')
        return result
    if encoding not in ('base64', 'base64url'):
        raise ValueError('Invalid encoding')
    bare = value.rstrip('=')
    padded = bare + '=' * (-len(bare) % 4)
    if '=' in value and padded != value:
        raise ValueError('Invalid padding')
    result = base64.b64decode(padded, altchars=b'-_' if encoding == 'base64url' else None, validate=True)
    canonical = (base64.urlsafe_b64encode(result) if encoding == 'base64url' else base64.b64encode(result)).decode().rstrip('=')
    if canonical != bare:
        raise ValueError('Invalid encoding')
    return result


def decrypt(payload):
    if payload['algorithm'] != 'AES-256-GCM':
        raise ValueError('Expected AES-256-GCM')
    def field(name):
        return decode(payload.get(name, ''), payload['encoding'])
    iv, ciphertext, aad = field('iv'), field('ciphertext'), field('aad')
    if payload.get('tagLayout') == 'appended':
        ciphertext, tag = ciphertext[:-16], ciphertext[-16:]
    else:
        tag = field('tag')
    if len(iv) != 12 or len(tag) != 16:
        raise ValueError('Expected 12-byte IV and 16-byte tag')
    return AESGCM(KEY).decrypt(iv, ciphertext + tag, aad)


if __name__ == '__main__':
    if len(sys.argv) != 3 or sys.argv[1] not in ('encrypt', 'decrypt'):
        raise SystemExit('Usage: python raw-python.py encrypt|decrypt parameters.json')
    if sys.argv[1] == 'encrypt':
        with open(sys.argv[2], 'w', encoding='utf-8') as output:
            json.dump(encrypt(), output, indent=2)
    else:
        with open(sys.argv[2], encoding='utf-8') as source:
            plaintext = decrypt(json.load(source))
        sys.stdout.buffer.write(plaintext)