Slack Webhook Cloud Function handler

index.js

// Modified from the Google Cloud Build example with the addtion of custom slack webhook URLs.
// Some of the styling and additional slack message features were taken from
// https://github.com/Philmod/google-cloud-build-slack. You can find the LICENSE for that project
// in this gist as well.
const IncomingWebhook = require('@slack/client').IncomingWebhook;
const humanizeDuration = require('humanize-duration');

const DEFAULT_COLOR = '#4285F4'; // blue
const STATUS_COLOR = {
  QUEUED: DEFAULT_COLOR,
  WORKING: DEFAULT_COLOR,
  SUCCESS: '#34A853', // green
  FAILURE: '#EA4335', // red
  TIMEOUT: '#FBBC05', // yellow
  INTERNAL_ERROR: '#EA4335', // red
};

// filteredOnStatus returns true if the build should be filtered out because its
// status does not match, otherwise false. It does this by checking the
// substitution's '_STATUSES' value against the build's status.
const filteredOnStatus = (build) => {
  const statuses = build.substitutions['_STATUSES'].split(',').map(x => x.trim());
  
  // The config has * so we should build no matter the status.
  if (statuses.length === 1 && statuses[0] === '*') {
    return false;
  }
  return (statuses.indexOf(build.status) === -1);
}

// subscribe is the main function called by Cloud Functions.
module.exports.subscribe = (event) => {
  const build = eventToBuild(event.data);

  if (!build.substitutions.hasOwnProperty('_STATUSES')) {
    console.log(`No Statuses('_STATUSES') defined in build substitutions for Build(id=${build.id}). Skipping.`)
  }

  if (filteredOnStatus(build)) {
    console.log(`Build(id=${build.id}, status=${build.status}) is not in the list of status substitutions('_STATUSES').`);
    return;
  }

  if (!build.substitutions.hasOwnProperty('REPO_NAME')) {
    console.log(`Build(id=${build.id}) was not triggered by a git push.`);
    return;
  }

  if (!build.substitutions.hasOwnProperty('_SLACK_WEBHOOK_URL')) {
    console.log(`Build(id=${build.id}) does not contain a slack webhook URL, skipping...`);
  }
  webhookURL = build.substitutions['_SLACK_WEBHOOK_URL'];

  const webhook = new IncomingWebhook(webhookURL);

  // Send message to Slack.
  const message = createSlackMessage(build);
  webhook.send(message);
};

// eventToBuild transforms pubsub event message to a build object.
const eventToBuild = (data) => {
  return JSON.parse(Buffer.from(data, 'base64').toString());
}

const createSlackMessage = (build) => {
  const buildFinishTime = new Date(build.finishTime);
  const buildStartTime = new Date(build.startTime);

  const isWorking = build.status === 'WORKING';
  const timestamp = Math.round(((isWorking) ? buildStartTime : buildFinishTime).getTime() / 1000);

  const text = `${build.substitutions.REPO_NAME} build \`${build.id}\` ${build.status.toLowerCase()}`;

  const fields = [{
    title: 'Status',
    value: build.status,
  }];

  if (!isWorking) {
    const buildTime = humanizeDuration(buildFinishTime - buildStartTime);

    fields.push({
      title: 'Duration',
      value: buildTime,
    });
  }

  const message = {
    text,
    mrkdwn: true,
    attachments: [
      {
        color: STATUS_COLOR[build.status] || DEFAULT_COLOR,
        title: 'Build logs',
        title_link: build.logUrl,
        fields,
        footer: 'Google Cloud Build',
        footer_icon: 'https://ssl.gstatic.com/pantheon/images/containerregistry/container_registry_color.png',
        ts: timestamp,
      },
    ],
  };

  // Add source information to the message.
  const { repoSource } = build.source || null;
  if (repoSource) {
    message.attachments[0].fields.push({
      title: 'Repository',
      value: repoSource.repoName,
    });

    message.attachments[0].fields.push({
      title: 'Branch',
      value: repoSource.branchName,
    });
  }

  // Add image(s) to the message.
  const images = build.images || [];
  if (images.length) {
    message.attachments[0].fields.push({
      title: `Image${(images.length > 1) ? 's' : ''}`,
      value: images.join('\n'),
    });
  }
  return message;
};

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package.json

{
  "name": "google-container-slack",
  "version": "0.0.1",
  "description": "Slack integration for Google Cloud Build, using Google Cloud Functions",
  "main": "index.js",
  "dependencies": {
    "@slack/client": "3.9.0",
    "humanize-duration": "3.18.0"
  }
}