// @flow
import { randomBytes, createCipheriv } from 'crypto';
import { sha3 } from 'ethereumjs-util';
import scrypt from 'scryptsy';
import uuid from 'uuid';

export const scryptSettings = {
  n: 1024
};

export const kdf = 'scrypt';

export function pkeyToKeystore(
  pkey: Buffer,
  address: string,
  password: string
) {
  const salt = randomBytes(32);
  const iv = randomBytes(16);
  let derivedKey;
  const kdfparams: Object = {
    dklen: 32,
    salt: salt.toString('hex')
  };
  if (kdf === 'scrypt') {
    // FIXME: support progress reporting callback
    kdfparams.n = 1024;
    kdfparams.r = 8;
    kdfparams.p = 1;
    derivedKey = scrypt(
      new Buffer(password),
      salt,
      kdfparams.n,
      kdfparams.r,
      kdfparams.p,
      kdfparams.dklen
    );
  } else {
    throw new Error('Unsupported kdf');
  }
  const cipher = createCipheriv('aes-128-ctr', derivedKey.slice(0, 16), iv);
  if (!cipher) {
    throw new Error('Unsupported cipher');
  }
  const ciphertext = Buffer.concat([cipher.update(pkey), cipher.final()]);
  const mac = sha3(
    Buffer.concat([derivedKey.slice(16, 32), new Buffer(ciphertext, 'hex')])
  );
  return {
    version: 3,
    id: uuid.v4({
      random: randomBytes(16)
    }),
    address,
    Crypto: {
      ciphertext: ciphertext.toString('hex'),
      cipherparams: {
        iv: iv.toString('hex')
      },
      cipher: 'aes-128-ctr',
      kdf,
      kdfparams,
      mac: mac.toString('hex')
    }
  };
}

export function getV3Filename(address) {
  const ts = new Date();
  return ['UTC--', ts.toJSON().replace(/:/g, '-'), '--', address].join('');
}