PR Review Bot

plzreview.js

var express = require('express');
var Webtask = require('webtask-tools');
var bodyParser = require('body-parser');
var urlParse = require('url-parse');
var rp = require('request-promise');

var app = express();

app.use(bodyParser.urlencoded({extended: true}));
app.use(bodyParser.json());

app.post('/event', function(req, res) {
  if (req.body.challenge) { return res.json({challenge: req.body.challenge}); }
  var prUrl = req.body.event.links[0].url;
  return fetchGithubPrAndRespond(req.webtaskContext.secrets, prUrl, res);
  // TODO: To make this work, we have to return a response within 3 seconds. 
  // Let's return a button to convert to Github link instead of trying to fetch PR right away.
});

app.post('/create', function(req, res) {
  var body = req.body;
  if (!verifyToken(body.token, req)) { return res.status(401); }

  var prUrl = body.text;
  return fetchGithubPrAndRespond(req.webtaskContext.secrets, prUrl, res);
});

app.post('/update', function(req, res) {
  var parsedPayload = JSON.parse(req.body.payload);
  if (!verifyToken(parsedPayload.token, req)) { return res.status(401); }

  var action = parsedPayload.actions[0].name;
  var prUrl = parsedPayload.actions[0].value;
  switch (action) {
    case 'refresh':
      return fetchGithubPrAndRespond(req.webtaskContext.secrets, prUrl, res, false);
    case 'bump':
      return fetchGithubPrAndRespond(req.webtaskContext.secrets, prUrl, res, true);
    default:
      return res.status(500).json({error: "Invalid action type"});
  }
});

function verifyToken(token, req) {
  return token === req.webtaskContext.secrets.SLACK_TOKEN;
}

function parsePRUrl(url) {
  var parsedUrl = urlParse(url);
  if (parsedUrl.host === 'github.com') {
    return parsePathname(parsedUrl.pathname);
  }
  return null;
}

function parsePathname(pathname) {
  var sections = pathname.split('/');
  return {
    org: sections[1],
    repo: sections[2],
    pr: sections[4],
  };
  // TODO: input validation
}

function fetchGithubPrAndRespond(secrets, prUrl, res, isBump) {
  var gUrl = parsePRUrl(prUrl);
  fetchGithubPr(secrets, gUrl.org, gUrl.repo, gUrl.pr)
    .then(response => {
      var parsed = JSON.parse(response);
      res.json(buildPrResponse(parsed, isBump));
    }).catch(error => {
      console.log('ERROR: ' + error);
      res.status(500).json({error: error});
    });
}

function fetchGithubPr(secrets, org, repo, pr) {
  var username = secrets.GITHUB_USERNAME;
  var password = secrets.GITHUB_PASSWORD;

  var githubApiUrl = "https://" + username + ":" + password + "@api.github.com/repos/" + org + "/" + repo + "/pulls/" + pr;
  var options = {
    url: githubApiUrl,
    headers: {
      'User-Agent': 'GetReview'
    }
  };
  return rp(options);
}

function buildPrResponse(parsedResponse, isBump) {
  var title = parsedResponse.title + " [+" + parsedResponse.additions + "/-" + parsedResponse.deletions + "]";
  var text = truncateText(parsedResponse.body, 250);

  return {
    replace_original: isBump ? false : true,
    response_type: "in_channel",
    text: isBump ? "*Bump:*" : "",
    mrkdwn: true,
    attachments: [
      {
        author_name: parsedResponse.user.login,
        author_link: parsedResponse.user.url,
        author_icon: parsedResponse.user.avatar_url,
        title: title,
        title_link: parsedResponse.html_url,
        text: text,
        callback_id: "update",
        fallback: "Review this PR",
        attachment_type: "default",
        actions: [
          {
            name: "refresh",
            text: "Refresh",
            type: "button",
            value: parsedResponse.html_url
          },
          {
            name: "bump",
            text: "Bump",
            type: "button",
            style: "danger",
            value: parsedResponse.html_url
          }
        ]
      }
    ]
  };
}

function truncateText(text, limit) {
  return text.substring(0, limit) + "...";
}

module.exports = Webtask.fromExpress(app);