index.js

/**
 * A simple GroupMe bot building and hosting module.
 * @module my-groupme-bot
 * @see module:my-groupme-bot
 */

/**
 * A GroupMe message object.<br/>
 * Go to the <a href="https://dev.groupme.com/tutorials/bots">GroupMe website</a> for more information.
 * @typedef {Object} Message
 * @property {Array} attachments - Array of URLs attached to the message.
 * @property {string} avatar_url - Avatar URL of the user which sent the message.
 * @property {number} created_at - Number indicating when the message was sent.
 * @property {string} group_id - ID of the group where the message was sent.
 * @property {string} id - ID of the message.
 * @property {string} name - Name of the user which sent the message.
 * @property {string} sender_id
 * @property {string} sender_type - Will always be user (bot does not respond to other bots).
 * @property {string} source_guid
 * @property {boolean} system
 * @property {string} text - Actual text of the message.
 * @property {string} user_id - ID of the user which sent the message.
 */

const http = require('http')
const request = require('request')

let botId
const features = []

const server = http.createServer((req, res) => {
  const chunks = []

  req.on('data', chunk => chunks.push(chunk)).on('end', () => {
    if (req.method === 'POST') {
      res.writeHead(200)
      res.end('OK')

      const message = JSON.parse(chunks.join(''))

      if (message['sender_type'] === 'user') {
        features
          .filter(feature => feature.check && feature.check(message))
          .forEach(feature => feature.respond(message))
      }
    } else {
      res.writeHead(400)
      res.end('Invalid request method!')
    }
  })
})

function quote (str) {
  return str.replace(/[.?*+^$[\]\\(){}|-]/g, '\\$&')
}

/**
 * Configures the module with the ID of the bot.<br/>
 * Returns the module itself to allow for builder pattern.
 * @param {string} id - The GroupMe ID of the bot.
 * @returns {*}
 */
module.exports.config = id => {
  botId = id
  return module.exports
}

/**
 * A callback which receives the potential error result of sending a GroupMe bot message.
 * @callback send
 * @param {Error} [err] - Error object indicating why the message could not be sent or undefined if it sent successfully.
 */

/**
 * Sends a message as the bot to its GroupMe chat.
 * @param {string} message - A message to send as the bot to its GroupMe chat.
 * @param {string} [imageUrl] - An image URL to send as an attachment with the bot's message.
 * @param {send} [cb] - A callback which receives the potential error result of sending a GroupMe bot message.
 */
module.exports.send = (message, imageUrl, cb) => {
  const params = {
    bot_id: botId,
    text: message.trim()
  }

  if (typeof imageUrl === 'string') {
    params.picture_url = imageUrl
  } else if (cb == null) {
    cb = imageUrl
  }

  request({
    url: 'https://api.groupme.com/v3/bots/post',
    method: 'POST',
    qs: params
  }, (err, res, body) => {
    if (cb) {
      if (err) {
        cb(err)
      } else if (res.statusCode === 202) {
        cb()
      } else {
        cb(new Error(body))
      }
    }
  })
}

/**
 * A callback which checks if a message should be responded to by the bot.
 * @callback check
 * @param {Message} message - The message which was sent by a user.
 * @returns {boolean}
 */

/**
 * A callback which uses the bot to respond to a message.
 * @callback respond
 * @param {Message} message - The message which was sent by a user.
 */

/**
 * Adds a feature to the bot.<br/>
 * Returns the module itself to allow for builder pattern.
 * @param {string} [desc] - A description of the feature to be added.
 * @param {check} check - A callback which checks if a message should be responded to by the bot.
 * @param {respond} respond - A callback which uses the bot to respond to a message and which is only called if 'check' returned true.
 * @returns {*}
 */
module.exports.feature = (desc, check, respond) => {
  if (respond == null) {
    respond = check
    check = desc
    desc = ''
  }

  features.push({
    desc: desc,
    check: check,
    respond: respond
  })

  return module.exports
}

/**
 * A callback which uses the bot to respond to a message and pattern matches in it.
 * @callback patternRespond
 * @param {Message} message - The message which was sent by a user.
 * @param {RegExpMatchArray} - An array of the pattern matches in the message sent by the user.
 */

/**
 * Adds a regular expression pattern or literal string for the bot to look for in messages and respond to.<br/>
 * Returns the module itself to allow for builder pattern.
 * @param {string} [desc] - A description of the feature to be added.
 * @param {RegExp|string} pattern - A regular expression pattern or literal string for the bot to look for in messages.
 * @param {patternRespond} respond - A callback which uses the bot to respond to a message if the pattern matches in it.
 * @returns {*}
 */
module.exports.pattern = (desc, pattern, respond) => {
  if (respond == null) {
    respond = pattern
    pattern = desc
    desc = ''
  }

  if (typeof pattern === 'string') {
    pattern = new RegExp(quote(pattern), 'g')
  }

  return module.exports.feature(
    desc,
    message => pattern.test(message['text']),
    message => respond(message, message['text'].match(pattern))
  )
}

/**
 * A callback which uses the bot to respond to a user command message.
 * @callback commandRespond
 * @param {Message} message - The message which was sent by a user.
 * @param {string[]} - An array of the whitespace separated arguments provided by user after the command.
 */

/**
 * Adds a command in the form of '/<commandname> [arguments]' for the bot to look for in messages and respond to.<br/>
 * Returns the module itself to allow for builder pattern.
 * @param {string} name - A name for the command which will be called as follows: '/name'.
 * @param {string} [desc] - A description of the command to be added.
 * @param {string} [sep] - A RegExp or string to separate the command arguments.
 * @param {commandRespond} respond - A callback which uses the bot to respond to a user command message.
 * @returns {*}
 */
module.exports.command = (name, desc, sep, respond) => {
  if (respond == null) {
    if (sep == null) {
      respond = desc
      desc = ''
    } else {
      respond = sep
      sep = /\s+/
      desc = ` - ${desc.trim()}`
    }
  } else {
    desc = ` - ${desc.trim()}`
  }

  sep = new RegExp(typeof sep === 'string' ? quote(sep) : sep, 'g')
  const regex = new RegExp(`^/${quote(name)}(\\s|$)`, 'g')

  return module.exports.pattern(
    `/${name}${desc}`,
    regex,
    message => respond(message, message['text'].replace(regex, '').trim().split(sep))
  )
}

/**
 * A callback which supplies a message for the bot to send.
 * @callback stringSupplier
 * @returns {string}
 */

/**
 * Adds a command in the form of '/<commandname> [arguments]' for the bot to look for in messages and respond to.<br/>
 * Great for querying random quotes or frequently changing input.<br/>
 * Returns the module itself to allow for builder pattern.
 * @param {string} name - A name for the command which will be called as follows: '/name'.
 * @param {string} [desc] - A description of the command to be added.
 * @param {string[]|stringSupplier} supply - A string array to randomly pick a string from or a string supplier to get a string from for the bot to send.
 * @returns {*}
 */
module.exports.random = (name, desc, supply) => {
  if (supply == null) {
    supply = desc
    desc = undefined
  }

  return module.exports.command(
    name, desc,
    () => module.exports.send(Array.isArray(supply) ? supply[Math.floor(Math.random() * supply.length)] : supply())
  )
}

/**
 * Adds a '/help' command which displays all of the bot's commands and its other described features.<br/>
 * Returns the module itself to allow for builder pattern.
 * @returns {*}
 */
module.exports.help = () => module.exports.command(
  'help',
  'Displays help information about the bot.',
  () => module.exports.send(features.map(feature => feature.desc).filter(desc => desc !== '').join('\n'))
)

/**
 * @param args - Arguments, such as a simple port number, passed to the 'listen' function of the 'Server' provided by 'http.createServer'.
 */
module.exports.listen = args => {
  features.sort((a, b) => a.desc < b.desc ? -1 : a.desc > b.desc ? 1 : 0)
  server.listen(args)
}

/**
 * A plugin.
 * @typedef {Object} Plugin
 * @property {string} name - A name for the plugin.
 * @property {function} fn - A function to add to the module's members the module as `this`.
 */

/**
 * Uses an arbitrary number of plugins.
 * @param {Plugin[]} plugins - An array of plugins.
 * @returns {*}
 */
module.exports.use = (...plugins) => {
  plugins.forEach(plugin => {
    if (module.exports.hasOwnProperty(plugin.name)) {
      throw new Error(`Duplicate plugin name '${plugin.name}'!`)
    } else {
      module.exports[plugin.name] = (...args) => {
        plugin.fn.apply(module.exports, args)
        return module.exports
      }
    }
  })

  return module.exports
}