import middy from 'middy'
import JWTAuthMiddleware, { EncryptionAlgorithms, IAuthorizedEvent } from 'middy-middleware-jwt-auth'
import { httpErrorHandler, httpHeaderNormalizer } from 'middy/middlewares'
import createHttpError from 'http-errors'

interface ITokenPayload {
  permissions: string[]
}

function isTokenPayload (token: any): token is ITokenPayload {
  return token != null &&
    Array.isArray(token.permissions) &&
    token.permissions.every((permission: any) => typeof permission === 'string')
}

// This is your AWS handler
const helloWorld = async (event: IAuthorizedEvent) => {
  // The middleware adds auth information if a valid token was added
  // If no auth was found, event.auth will remain undefined. You have to check
  // that it exists and that it has the expected form.
  if (!isTokenPayload(event.auth)) {
    throw createHttpError(401, 'No valid bearer token was set in the authorization header', {
      type: 'AuthenticationRequired'
    })
  }
  const auth: ITokenPayload = event.auth

  // Check for authorization
  if (auth.permissions.indexOf('helloWorld') === -1) {
    throw createHttpError(403, `User not authorized for helloWorld, only found permissions [${auth.permissions.join(', ')}]`, {
      type: 'NotAuthorized'
    })
  }

  return {
    body: JSON.stringify({ data: 'Hello world!' }),
    statusCode: 200
  }
}

// Let's "middyfy" our handler, then we will be able to attach middlewares to it
export const handler = middy(helloWorld)
  .use(httpHeaderNormalizer()) // Make sure authorization header is saved in lower case
  .use(httpErrorHandler()) // This middleware is needed do handle the errors thrown by the JWTAuthMiddleware
  .use(JWTAuthMiddleware({
    /** Algorithm to verify JSON web token signature */
    algorithm: EncryptionAlgorithms.HS256,
    /** A string or buffer containing either the secret for HMAC algorithms, or the PEM encoded public key for RSA and ECDSA */
    secretOrPublicKey: 'secret'
  }))