cli.js

#!/usr/bin/env node

const { get } = require('https')
const { readFile, writeFile } = require('fs')

const getColour = coverage => {
  if (coverage < 80) {
    return 'red';
  }

  if (coverage < 90) {
    return 'yellow';
  }

  return 'brightgreen';
}

const reportKeys = ['lines', 'statements', 'functions', 'branches'];

const getBadge = (report, key) => {
  if (!(report && report.total && report.total[key])) {
    throw new Error('malformed coverage report');
  }

  const coverage = report.total[key].pct;
  const colour = getColour(coverage);

  return `https://img.shields.io/badge/Coverage-${coverage}${encodeURI('%')}-${colour}.svg`;
}

const download = (url, cb) => {
  get(url, res => {
    let file = '';
    res.on('data', chunk => (file += chunk));
    res.on('end', () => cb(null, file));
  }).on('error', err => cb(err));
};


const getBadgeByKey = (report) => (key) => {
  const url = getBadge(report, key);

  download(url, (err, res) => {
    if (err) throw err
    writeFile(`./coverage/badge-${key}.svg`, res, 'utf8', err => {
      if (err) throw err
    });
  });
};

readFile('./coverage/coverage-summary.json', 'utf8', (err, res) => {
  if (err) throw err
  const report = JSON.parse(res);
  reportKeys.forEach(getBadgeByKey(report));
});