const urljoin = require('url-join');
  const config = require('komodo-sdk/config');
  const composeApikey = require('./compose-apikey');
  
  module.exports = (xid, task, isPostpaid) => {
      const callbackUrl = config
          && config.partner
          && config.partner.callback
          && config.partner.callback.url;
  
      if (!callbackUrl) return null;
  
      return urljoin(
          [
              callbackUrl,
              'apikey',
              composeApikey(xid) || '-',
              isPostpaid ? 'postpaid' : 'prepaid',
              (task && task.trx_id) || null,
          ].filter((item) => item),
      );
  };