import crypto from 'crypto';
import { CLIENT_SECRET } from '../constants';

const IV_LENGTH = 16;
const ALGORITHM = 'aes-256-cbc';

export const generateString = (length: number): string =>
  crypto.randomBytes(length).toString('hex').slice(0, length);

// https://stackoverflow.com/q/52212430
/**
 * Symmetric encryption function
 * @param value String to encrypt
 * @returns Encrypted text
 */
export const encrypt = (value: string) => {
  const iv = crypto.randomBytes(IV_LENGTH);
  const cipher = crypto.createCipheriv(
    ALGORITHM,
    Buffer.from(CLIENT_SECRET, 'hex'),
    iv
  );
  let encrypted = cipher.update(value);
  encrypted = Buffer.concat([encrypted, cipher.final()]);
  return `${iv.toString('hex')}:${encrypted.toString('hex')}`;
};

/**
 * Symmetric decryption function
 * @param text Encrypted string
 * @returns Decrypted text
 */
export const decrypt = (text: string) => {
  const [iv, encryptedText] = text
    .split(':')
    .map((part) => Buffer.from(part, 'hex'));

  const decipher = crypto.createDecipheriv(
    ALGORITHM,
    Buffer.from(CLIENT_SECRET, 'hex'),
    iv
  );

  let decrypted = decipher.update(encryptedText);
  decrypted = Buffer.concat([decrypted, decipher.final()]);
  return decrypted.toString();
};