/**
 * After building the project it embeds the scripts/styles resources with the rel="preload"
 */
const fs = require('fs');
const pathToEntry = './build/index.html';
const bundlesRegExp = /\/static\/\w+\/\w+.[\da-z]+.\w{2,8}.\w{2,3}/g;
const splitBy = '</title>';

const builtHTMLContent = fs.readFileSync(pathToEntry).toString();
const links = builtHTMLContent.match(bundlesRegExp);
const parts = builtHTMLContent.split(splitBy);

let fileWithPreload = [parts[0], splitBy];
if (links) {
  for (const link of links) {
    let fileType = 'script';

    if (/\.css$/.test(link)) {
      fileType = 'style';
    }

    fileWithPreload = [
      ...fileWithPreload,
      `<link rel="preload" href="/pax${link}" as="${fileType}">`,
    ];
  }
}

fileWithPreload = [...fileWithPreload, parts[1]];

fs.writeFileSync(pathToEntry, fileWithPreload.join(''));