import { curve } from '../variables'
import { CRYPTOGRAPHY_KEY_ALGORITHM } from '../constants/asymmetric-cryptography'

import { SignMessage } from '../../../@utility/data-structures/asymmetric-cryptography'
import { verifyKeyFormat } from './verify-key-format'
import { newError } from '../../../../@utility/algorithms/new-error'


const signMessage: SignMessage = method

async function method (message: Buffer, privateKey: string): Promise<any[]> {

  if (!(await verifyKeyFormat(privateKey))) {
    throw newError(ERROR_INVALID_KEY_FORMAT, arguments)
  }

  if (privateKey.indexOf(CRYPTOGRAPHY_KEY_ALGORITHM) >= 0) {
    privateKey = privateKey.split(`${CRYPTOGRAPHY_KEY_ALGORITHM}:`)[1]
  }

  const keyPair = curve.keyFromPrivate(privateKey)
  const signature = curve.sign(message, keyPair)
  return Promise.resolve([signature.toDER()])
}

const ERROR_INVALID_KEY_FORMAT = `Error: Invalid key format. Expected value '${CRYPTOGRAPHY_KEY_ALGORITHM}'`

export {
  signMessage
}