const fs = require('fs');
const { exec } = require('child_process');

function diff(arr1, arr2) {
  return arr1.filter(item => !arr2.includes(item));
}

function readAllFiles() {
  return new Promise((resolve, reject) => {
    // Get files list of src folder with relative path
    exec('find src -type f', (err, stdout) => {
      if (err) {
        reject(err);
      } else {
        resolve(stdout.split('\n'));
      }
    });
  });
}

readAllFiles().then((allFiles) => {
  // Get webpack stats file and read list of used files in build
  const webpackStats = JSON.parse(fs.readFileSync('stats.json', 'utf8'));
  const webpackFiles = webpackStats.chunks[0].modules
    .map(item => item.name)
    .filter(item => !item.includes('node_modules'))
    .map((item) => {
      if (item.startsWith('./')) return item.replace('./', 'src/');
      if (item.startsWith('../')) return item.replace('../', 'src/');
      return item;
    });

  const unusedFiles = diff(allFiles, webpackFiles);
  fs.writeFile('unusedFiles.txt', unusedFiles.sort().join('\n'), (err) => {
    if (err) {
      console.log(err);
    } else {
      console.log('done!');
    }
  });
});