index.js

'use strict';

const Botkit = require('botkit');
const {VM} = require('vm2');
const fs = require('fs');
const path = require('path');
const babel = require('babel-core');
const entities = new (require('html-entities').AllHtmlEntities)();

const BABEL_PRESETS = ['es2015-loose', 'react', 'stage-0'];
const BABEL_PRESETS_NODE6 = ['node6'].concat(BABEL_PRESETS.slice(1));
const BABEL_PLUGINS = ['transform-decorators-legacy'];

const token = fs.readFileSync(path.join(__dirname, '.token')).toString('utf8').trim();

var controller = Botkit.slackbot({
  debug: false,
});

controller.spawn({
  token: token,
  // retry: Infinity // broken, see https://github.com/howdyai/botkit/issues/261
}).startRTM(function(err) {
  if (err) throw new Error(err);
  console.log('Slack connection opened.');
});

controller.on('rtm_close', function() {
  console.error('Slack connection closed! Exiting.');
  process.exit(1);
});

const VM_OPTIONS = {
  timeout: 1000,
  sandbox: {}
};
const vm = new VM(VM_OPTIONS);

//--- Built-ins

vm.run(
  'help = function(object) {' +
  '  return Object.getOwnPropertyNames(object);' +
  '};'
);

//--- End Built-ins

const codeRegex = /(^`+|`+$)/g;
const crappySingleQuoteRegex = /([‘’])/g;
const crappyDoubleQuoteRegex = /([“”])/g;
const babelRegex = /^babel(-node6)?:?\s*([\s\S]*)/i;
controller.hears(['[\s\S]*'],['direct_message','direct_mention','mention'], function(bot, message) {
  let {text} = message;

  // Ping
  if (text === 'ping') return bot.reply('pong');

  // Shortcut for `help(this)`
  if (text === 'help') text += '(this);';

  try {
    // Babel transpile
    const match = text.match(babelRegex);
    if (match && match.length) {
      // Get raw code
      let code = match[match.length - 1];
      // Comes in escaped
      code = cleanupCode(code);

      // Get presets
      const isNode6 = match[1] === '-node6';
      const presets = isNode6 ? BABEL_PRESETS_NODE6 : BABEL_PRESETS;

      // Transform
      let transformed = babel.transform(code, {presets, plugins: BABEL_PLUGINS, highlightCode: false}).code;
      transformed = transformed.replace('"use strict";\n\n', '');
      return bot.reply(message, '```' + transformed + '```');
    } else {
      // Regular eval
      text = cleanupCode(text);
      const result = vm.run(text);
      bot.reply(message, `\`${result && result.toString()}\``);
    }

  } catch (e) {
    bot.reply(message, '```' + e.message + '```');
  }
});

function cleanupCode(text) {
  return entities.decode(
    text
    .replace(codeRegex, '')
    .replace(crappySingleQuoteRegex, "'")
    .replace(crappyDoubleQuoteRegex, '"')
  );
}