text: #!/usr/bin/env node
  
  /* eslint-disable */
  
  const jwt = require('jsonwebtoken');
  const github = require('@octokit/rest')();
  const prettyBytes = require('pretty-bytes');
  const fs = require('fs');
  const {execSync} = require('child_process');
  const zlib = require('zlib');
  
  const SIZE_CHECK_APP_ID = 14028;
  const SIZE_CHECK_APP_INSTALLATION_ID = 229425;
  
  const file = process.argv[2];
  const label = process.argv[3];
  const name = `Size - ${label}`;
  
  if (!file || !label) {
      console.log(`Usage: ${process.argv[0]} ${process.argv[1]} FILE LABEL`);
      process.exit(1);
  }
  
  const {size} = fs.statSync(file);
  const gzipSize = zlib.gzipSync(fs.readFileSync(file)).length;
  
  process.on('unhandledRejection', error => {
      // don't log `error` directly, because errors from child_process.execSync
      // contain an (undocumented) `envPairs` with environment variable values
      console.log(error.message || 'Error');
      process.exit(1)
  });
  
  const pk = process.env['SIZE_CHECK_APP_PRIVATE_KEY'];
  if (!pk) {
      console.log('Fork PR; not computing size.');
      process.exit(0);
  }
  
  const key = Buffer.from(pk, 'base64').toString('binary');
  const payload = {
      exp: Math.floor(Date.now() / 1000) + 60,
      iat: Math.floor(Date.now() / 1000),
      iss: SIZE_CHECK_APP_ID
  };
  
  const token = jwt.sign(payload, key, {algorithm: 'RS256'});
  github.authenticate({type: 'app', token});
  
  function getMergeBase() {
      const pr = process.env['CIRCLE_PULL_REQUEST'];
      if (pr) {
          const number = +pr.match(/\/(\d+)\/?$/)[1];
          return github.pullRequests.get({
              owner: 'mapbox',
              repo: 'mapbox-gl-js',
              pull_number: number
          }).then(({data}) => {
              const base = data.base.ref;
              const head = process.env['CIRCLE_SHA1'];
              return execSync(`git merge-base origin/${base} ${head}`).toString().trim();
          });
      } else {
          // Walk backward through the history (maximum of 10 commits) until
          // finding a commit on either master or release-*; assume that's the
          // base branch.
          const head = process.env['CIRCLE_SHA1'];
          for (const sha of execSync(`git rev-list --max-count=10 ${head}`).toString().trim().split('\n')) {
              const base = execSync(`git branch -r --contains ${sha} origin/master origin/release-* origin/publisher-production`).toString().split('\n')[0].trim().replace(/^origin\//, '');
              if (base) {
                  return Promise.resolve(execSync(`git merge-base origin/${base} ${head}`).toString().trim());
              }
          }
      }
  
      return Promise.resolve(null);
  }
  
  function getPriorSize(mergeBase) {
      if (!mergeBase) {
          console.log('No merge base available.');
          return Promise.resolve(null);
      }
  
      return github.checks.listForRef({
          owner: 'mapbox',
          repo: 'mapbox-gl-js',
          ref: mergeBase
      }).then(({data}) => {
          const run = data.check_runs.find(run => run.name === name);
          if (!run) {
              console.log('No matching check found.');
              return Promise.resolve(null);
          }
          const prior = +run.output.summary.match(/`.*` is (\d+) bytes/)[1];
          console.log(`Prior size was ${prettyBytes(prior)}.`);
          return prior;
      });
  }
  
  github.apps.createInstallationToken({installation_id: SIZE_CHECK_APP_INSTALLATION_ID})
      .then(({data}) => {
          github.authenticate({type: 'token', token: data.token});
          getMergeBase().then(getPriorSize).then(prior => {
              const title = (() => {
                  if (prior) {
                      const change = size - prior;
                      const percent = (change / prior) * 100;
                      return `${change >= 0 ? '+' : ''}${prettyBytes(change)} ${percent.toFixed(3)}% (${prettyBytes(size)})`;
                  } else {
                      return prettyBytes(size);
                  }
              })();
  
              const megabit = Math.pow(2, 12);
              const downloadTime3G = (gzipSize / (3 * megabit)).toFixed(0);
              const downloadTime4G = (gzipSize / (10 * megabit)).toFixed(0);
              const summary = `\`${file}\` is ${size} bytes (${prettyBytes(size)}) uncompressed, ${gzipSize} (${prettyBytes(gzipSize)}) gzipped.
  That's **${downloadTime3G} seconds** over slow 3G (3 Mbps), **${downloadTime4G} seconds** over fast 4G (10 Mbps).`;
  
              console.log(`Posting check result:\n${title}\n${summary}`);
  
              return github.checks.create({
                  owner: 'mapbox',
                  repo: 'mapbox-gl-js',
                  name: `Size - ${label}`,
                  head_branch: process.env['CIRCLE_BRANCH'],
                  head_sha: process.env['CIRCLE_SHA1'],
                  status: 'completed',
                  conclusion: 'success',
                  completed_at: new Date().toISOString(),
                  output: { title, summary }
              });
          })
      });
  