main.js

const Config = require('config');
const DNS = require('@google-cloud/dns');
const rp = require('request-promise');

const config = Config.config;

const projectId = config.projectId;
const managedZones = config.managedZones;

const dns = new DNS({
  projectId: projectId,
  keyFilename: '/tmp/sa.json',
});

const zone = dns.zone('xss-moe');

rp({
  uri: 'https://ipinfo.io/',
  method: 'GET',
  json: true,
}).then(function(data) {
  const currentIp = data.ip;

  for(let managedZone of managedZones) {
    for(let domainName of managedZone.domainNames) {
      zone.getRecords({
        name: domainName,
        type: 'A',
      }).then(function(data) {
        const activeIp = data[0][0].data[0];
        if(activeIp == currentIp) {
          return;
        } else {
          const newRecord = zone.record('a', {
            name: domainName,
            ttl: managedZone.ttl,
            data: currentIp,
          });

          const oldRecord = zone.record('a', {
            name: domainName,
            ttl: managedZone.ttl,
            data: activeIp,
          });

          const diff = {
            add: newRecord,
            delete: oldRecord,
          }

          zone.createChange(diff).then(function(data) {
            const token = config.slack.token;
            const channel = config.slack.channel;
            const username = config.slack.username;
            const iconEmoji = config.slack.iconEmoji;

            rp({
              uri: 'https://slack.com/api/chat.postMessage',
              method: 'POST',
              form: {
                token: token,
                channel: channel,
                username: username,
                icon_emoji: iconEmoji,
                text: `Updated A record for ${domainName} from ${activeIp} to ${currentIp}`,
              },
              json: true,
            });
          });
        }
      });
    }
  }
});