import crypto from 'crypto';

let ENCRYPTION_ALGORITHM = 'aes-256-gcm' as const;

export async function sha256String(str) {
  return crypto.createHash('sha256').update(str).digest('base64');
}

export function randomBytes(n) {
  return crypto.randomBytes(n);
}

export function encrypt(masterKey, value) {
  let masterKeyBuffer = masterKey.getValue().raw;
  // let iv = createKeyBuffer({ numBytes: 12, secret: masterKeyBuffer });
  let iv = crypto.randomBytes(12);
  let cipher = crypto.createCipheriv(ENCRYPTION_ALGORITHM, masterKeyBuffer, iv);
  let encrypted = cipher.update(value);
  encrypted = Buffer.concat([encrypted, cipher.final()]);

  let authTag = cipher.getAuthTag();

  return {
    value: encrypted,
    meta: {
      keyId: masterKey.getId(),
      algorithm: ENCRYPTION_ALGORITHM,
      iv: iv.toString('base64'),
      authTag: authTag.toString('base64'),
    },
  };
}

export function decrypt(masterKey, encrypted, meta) {
  let masterKeyBuffer = masterKey.getValue().raw;
  let { algorithm, iv, authTag } = meta;
  iv = Buffer.from(iv, 'base64');

  authTag = Buffer.from(authTag, 'base64');

  let decipher = crypto.createDecipheriv(algorithm, masterKeyBuffer, iv);
  decipher.setAuthTag(authTag);

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

export function createKey({ secret, salt }) {
  let buffer = createKeyBuffer({ secret, salt });
  return {
    raw: buffer,
    base64: buffer.toString('base64'),
  };
}

export function importKey(str) {
  return {
    raw: Buffer.from(str, 'base64'),
    base64: str,
  };
}

/**
 * Generates a Buffer of a desired byte length to be used as either an encryption key or an initialization vector.
 *
 * @private
 */
function createKeyBuffer({
  numBytes,
  secret,
  salt,
}: {
  numBytes?: number;
  secret?: string;
  salt?: string;
}) {
  return crypto.pbkdf2Sync(
    secret || crypto.randomBytes(128).toString('base64'),
    salt || crypto.randomBytes(32).toString('base64'),
    10000,
    numBytes || 32,
    'sha512',
  );
}