module.exports = function rubi( hook ) {
  // hook.io has a range of node modules available - see
  // https://hook.io/modules.
  // We use request (https://www.npmjs.com/package/request) for an easy way to
  // make the HTTP request.
  var request = require( 'request' );

  // The parameters passed in via the slash command POST request.
  var params = hook.params;

  // Check that the hook has been triggered from our slash command by
  // matching the token against the one in our environment variables.
  if( params.token === hook.env.rubi_token ) {

    // @cnewton for writing this code
    var regex = /(@\w+)(.*)/g
    var user = params.text.replace( regex, '<$1>' );
    var message = params.text.replace( regex, '$2');

    // Set up the options for the HTTP request.
    var options = {

      // Use the Webhook URL from the Slack Incoming Webhooks integration.
      uri: hook.env.rubi_url,

      method: 'POST',

      // Slack expects a JSON payload with a "text" property. Links should be
      // enclosed in '<', '>' for correct formatting in Slack.
      json: {
        'text': '<@' + params.user_name + '> sent a Rubi to ' + user + message
      }
    };

    // Make the POST request to the Slack incoming webhook.
    request( options, function( error, response, body ) {
      
      // Pass error back to client if request endpoint can't be reached.
      if ( error ) {
        hook.res.end( error.message );
      }

      // Finally, send the response. This will be displayed to the user after
      // they submit the slash command.
      hook.res.end('Success! Go to <#rubi> to see it :smile:');
    });
  } else {
    // If the token didn't match, send a response anyway for debugging.
    hook.res.end( 'Incorrect token.' );
  }
};