actions.js

/* eslint-disable no-console */
const qs = require('querystring');
const fetch = require('node-fetch');

const log = (event) => {
  console.log('Event', JSON.stringify(event, null, 2));
  return Promise.resolve(event);
};

const getCommand = text => /^<@[A-Z0-9]*>(.+)/.exec(text)[1].trim();

const parseConvertCommand = (command) => {
  const pattern = /[a-z\s]*(\d+).*([a-z]{3}).*([a-z]{3})/i;
  const matches = command.match(pattern);
  if (matches) {
    return {
      amount: +matches[1],
      source: matches[2],
      target: matches[3],
    };
  }
  return null;
};

// Make an API call to http://fixer.io/
const callFixer = (command) => {
  const url = `https://api.fixer.io/latest?base=${command.source}&symbols=${command.target}`;
  console.log(`Requesting ${url}`);
  return fetch(url)
    .then(response => response.json())
    .then((json) => {
      if (json.error === 'Invalid base') {
        return `No rates found for currency "${command.source}"`;
      }
      if (!json.rates[command.target]) {
        return `No rates found for currency "${command.target}"`;
      }
      const result = json.rates[command.target] * command.amount;
      const displayResult = parseFloat(Math.round(result * 100) / 100).toFixed(2);
      return `${command.amount}${command.source} is ${displayResult}${command.target}`;
    });
};

// Generate a response to the command.
const doCommand = (event) => {
  const rawCommand = event.slack.event.text;
  const command = getCommand(rawCommand);
  const convertCommand = parseConvertCommand(command);
  if (convertCommand) {
    return callFixer(convertCommand)
      .then(reply => Object.assign(event, { reply }));
  }
  const defaultReply = `I'm sorry, I don't understand the command "${command}"
Please use a format like "convert 1AUD to USD"`;
  return Object.assign(event, { reply: defaultReply });
};

// Send a response via Slack.
const sendResponse = (event) => {
  const params = {
    token: event.team.bot.bot_access_token,
    channel: event.slack.event.channel,
    text: event.reply,
  };
  const url = `https://slack.com/api/chat.postMessage?${qs.stringify(params)}`;
  console.log(`Requesting ${url}`);
  return fetch(url)
    .then(response => response.json())
    .then((response) => {
      if (!response.ok) throw new Error('SlackAPIError');
      return Object.assign(event, { response });
    });
};

module.exports.handler = (event, context, callback) => log(event)
  .then(doCommand) // Attempt the command
  .then(sendResponse) // Update the channel
  .then(() => callback(null)) // Sucess
  .catch(callback); // Error