comment.js

require('dotenv').config();

const fs = require('fs');
const lighthouse = require('lighthouse');
const puppeteer = require('puppeteer');
const cluster = require('cluster');
const numCPUs = require('os').cpus().length;
const DOMAIN = process.env.DOMAIN;

const fetch = require('isomorphic-fetch');
const FormData = require('form-data');
const branchName = require('current-git-branch');

// Branch from which we are making merge request
// In the pipeline we have environment variable `CI_COMMIT_REF_NAME`, 
// which contains name of this banch. Function `branchName` 
// will return something like «HEAD detached» message in the pipeline. 
// And name of the branch outside of pipeline
const CURRENT_BRANCH = process.env.CI_COMMIT_REF_NAME || branchName();

// Merge request target branch, usually it's master
const DEFAULT_BRANCH = process.env.CI_DEFAULT_BRANCH || 'master';

// ID of the project
const GITLAB_PROJECT_ID = process.env.CI_PROJECT_ID || '18090019';
// Token 
const TOKEN = process.env.GITLAB_TOKEN;

// GitLab domain
const GITLAB_DOMAIN = process.env.CI_SERVER_HOST || process.env.GITLAB_DOMAIN || 'gitlab.com';
// User or organization name
const NAME_SPACE = process.env.CI_PROJECT_NAMESPACE || process.env.PROJECT_NAMESPACE || 'silentimp';
// Repo name
const PROJECT = process.env.CI_PROJECT_NAME || process.env.PROJECT_NAME || 'lighthouse-comments';
// Name of the job, which create an artifact
const JOB_NAME = process.env.CI_JOB_NAME || process.env.JOB_NAME || 'lighthouse';

/**
 * Return part of report for specific page
 * 
 * @param report {Object} — report
 * @param subject {String} — subject, that allow find specific page
 * @return {Object} — page report
 */
const getPage = (report, subject) => report.find(item => (item.subject === subject));

/**
 * Return specific metric for the page
 * 
 * @param page {Object} — page
 * @param name {String} — metrics name
 * @return {Object} — metric
 */
const getMetric = (page, name) => page.metrics.find(item => item.name === name);

/**
 * Return table cell for desired metric
 * 
 * @param branch {Object} - report from feature branch
 * @param master {Object} - report from master branch
 * @param name {String} - metrics name
 */
const buildCell = (branch, master, name) => {
  const branchMetric = getMetric(branch, name);
  const masterMetric = getMetric(master, name);
  const branchValue = branchMetric.value;
  const masterValue = masterMetric.value;
  const desiredLarger = branchMetric.desiredSize === 'larger';
  const isChanged = branchValue !== masterValue;
  const larger = branchValue > masterValue;
  if (!isChanged) return `${branchValue}`;
  if (larger) return `${branchValue} ${desiredLarger ? '💚' : '💔' } **+${Math.abs(branchValue - masterValue).toFixed(2)}**`;
  return `${branchValue} ${!desiredLarger ? '💚' : '💔' } **-${Math.abs(branchValue - masterValue).toFixed(2)}**`;
};

/**
 * Returns text of the comment with table inside
 * This table contain changes in all metrics
 *
 * @param branch {Object} report from feature branch
 * @param master {Object} report from master branch
 * @return {String} comment markdown
 */
const buildCommentText = (branch, master) =>{
  const md = branch.map( page => {
    const pageAtMaster = getPage(master, page.subject);
    if (!pageAtMaster) return '';
    const md = `|${page.subject}|${buildCell(page, pageAtMaster, 'Performance')}|${buildCell(page, pageAtMaster, 'Accessibility')}|${buildCell(page, pageAtMaster, 'Best Practices')}|${buildCell(page, pageAtMaster, 'SEO')}|
`;
    return md;
  }).join('');
  return `
|Path|Performance|Accessibility|Best Practices|SEO|
|--- |--- |--- |--- |--- |
${md}
`;
};

/**
 * Returns an artifact
 *
 * @param name {String} artifact file name
 * @return {Object} object with performance artifact
 * @throw {Error} thhrow an error, if artifact contain string, that can't be parsed as a JSON. Or in case of fetch errors.
 */
const getArtifact = async name => {
  const response = await fetch(`https://${GITLAB_DOMAIN}/${NAME_SPACE}/${PROJECT}/-/jobs/artifacts/master/raw/${name}?job=${JOB_NAME}`);
  if (!response.ok) throw new Error('Artifact not found');
  const data = await response.json();
  return data;
};

/**
 * Returns iid of the merge request from feature branch to master
 * @param from {String} — name of the feature branch
 * @param to {String} — name of the master branch
 * @return {Number} — iid of the merge request
 */
const getMRID = async (from, to) => {
  const response = await fetch(`https://${GITLAB_DOMAIN}/api/v4/projects/${GITLAB_PROJECT_ID}/merge_requests?target_branch=${to}&source_branch=${from}`, {
    method: 'GET',
    headers: {
      'PRIVATE-TOKEN': TOKEN,
    }
  });
  if (!response.ok) throw new Error('Merge request not found');
  const [{iid}] = await response.json();
  return iid;
};

/**
 * Adding comment to merege request
 * @param md {String} — markdown text of the comment
 */
const addComment = async md => {
  const iid = await getMRID(CURRENT_BRANCH, DEFAULT_BRANCH);
  const commentPath = `https://${GITLAB_DOMAIN}/api/v4/projects/${GITLAB_PROJECT_ID}/merge_requests/${iid}/notes`;
  const body = new FormData();
  body.append('body', md);

  await fetch(commentPath, {
    method: 'POST',
    headers: {
      'PRIVATE-TOKEN': TOKEN,
    },
    body,
  });
};

// Count of measurements we want to make
const MEASURES_COUNT = 3;

// build report for single url
const buildReport = browser => async url => {
  const data = await lighthouse(
    `${DOMAIN}${url}`,
    {
      port: new URL(browser.wsEndpoint()).port,
      output: 'json',
    },
    {
      extends: 'lighthouse:full',
    }
  );
  const { report: reportJSON } = data;
  const report = JSON.parse(reportJSON);
  const metrics = [
    {
      name: report.categories.performance.title,
      value: report.categories.performance.score,
      desiredSize: 'larger',
    },
    {
      name: report.categories.accessibility.title,
      value: report.categories.accessibility.score,
      desiredSize: 'larger',
    },
    {
      name: report.categories['best-practices'].title,
      value: report.categories['best-practices'].score,
      desiredSize: 'larger',
    },
    {
      name: report.categories.seo.title,
      value: report.categories.seo.score,
      desiredSize: 'larger',
    },
    {
      name: report.categories.pwa.title,
      value: report.categories.pwa.score,
      desiredSize: 'larger',
    },
  ];
  return {
    subject: url,
    metrics: metrics,
  };
};

/**
 * Reducer which will calculate an avarage value of all page measurements
 * @param pages {Object} — accumulator
 * @param page {Object} — page
 * @param page {Object} — page with avarage metrics values
 */
const mergeMetrics = (pages, page) => {
  if (!pages) return page;
  return {
    subject: pages.subject,
    metrics: pages.metrics.map((measure, index) => {
      let value = (measure.value + page.metrics[index].value)/2;
      value = +value.toFixed(2);
      return {
        ...measure,
        value,
      }
    }),
  }
}


/**
 * Returns urls array splited to chunks accordin to cors number
 *
 * @param urls {String[]} — URLs array
 * @param cors {Number} — count of available cors
 * @return {Array<String[]>} — URLs array splited to chunks
 */
function chunkArray(urls, cors) {
  const chunks = [...Array(cors)].map(() => []);
  let index = 0;
  urls.forEach((url) => {
    if (index > (chunks.length - 1)) {
      index = 0;
    }
    chunks[index].push(url);
    index += 1;
  });
  return chunks;
}

const urls = [
  '/inloggen',
  '/wachtwoord-herstellen-otp',
  '/lp/service',
  '/send-request-to/ww-tammer',
  '/post-service-request/binnenschilderwerk',
];

(async () => {
  if (cluster.isMaster) {
    // Parent proccess
    const chunks = chunkArray(urls, numCPUs);
    chunks.map(chunk => {
      const worker = cluster.fork();
      worker.send(chunk);
    });
    let report = [];
    let reportsCount = 0;
    cluster.on('message', async (worker, msg) => {
      report = [...report, ...msg];
      worker.disconnect();
      reportsCount++;
      if (reportsCount === chunks.length) {
        fs.writeFileSync(`./performance.json`, JSON.stringify(report));
        if (CURRENT_BRANCH === DEFAULT_BRANCH) process.exit(0);
        try {
          const masterReport = await getArtifact('performance.json');
          const md = buildCommentText(report, masterReport)
          await addComment(md);
        } catch (error) {
          console.log(error);
        }
        process.exit(0);
      }
    });
  } else {
    // Child process
    process.on('message', async (urls) => {
      const browser = await puppeteer.launch({
        args: ['--no-sandbox', '--disable-setuid-sandbox', '--headless'],
      });
      const builder = buildReport(browser);
      const report = [];
      for (let url of urls) {
        // Let's measure MEASURES_COUNT times and calculate the avarage
        let measures = [];
        let index = MEASURES_COUNT;
        while(index--){
          const metric = await builder(url);
          measures.push(metric);
        }
        const measure = measures.reduce(mergeMetrics);
        report.push(measure);
      }
      cluster.worker.send(report);
      await browser.close();
    });
  }
})();