Sass->CSS build task that can be run as an npm script (not done)

build-css.js

#!/usr/bin/env node

const path = require('path');
const fs = require('fs');
const glob = require('glob');
const sass = require('node-sass');
const importOnce = require('node-sass-import-once');
const postcss = require('postcss');
const autoprefixer = require('autoprefixer');
const cssmin = require('clean-css');

function getFileNames(matching) {
  return new Promise((resolve, reject) => {
    glob(matching, {}, (err, files) => {
      if (err) reject(err);
      resolve(files);
    });
  });
};

function fileNamesToPaths(fileNames) {
  return Promise.resolve(
    fileNames.map(fileName => path.join(process.cwd(), fileName))
  );
};

function forAllFiles(files, fn) {
  return Promise.all(
    files.map(fn)
  );
};

function read(filePath) {
  return new Promise((resolve, reject) => {
    fs.readFile(filePath, 'utf8', (err, text) => {
      if (err) reject(err);
      resolve({
        filePath: filePath,
        text: text
      });
    });
  });
};

const sassOptions = text => ({
  data: text,
  importer: importOnce,
  importOnce: {
    index: true,
    bower: true
  }
});

function compile(file) {
  return new Promise((resolve, reject) => {
    sass.render(sassOptions(file.text), (err, compiled) => {
      if (err) reject(err);
      resolve({
        filePath: file.filePath,
        text: compiled.css.toString()
      });
    });
  });
};

function clean(file) {
  return postcss([autoprefixer, cssmin]).then((result))
};

getFileNames('./sass/**.scss')
  .then(fileNamesToPaths)
  .then(files => forAllFiles(files, read))
  .then(files => forAllFiles(files, compile))
  .then(files => forAllFiles(files, clean))
  .then(files => console.log(files[0]))
  // .then(compileAllFiles)
  // .then(files => console.log(files[0]))
  // .catch((e) => console.log(e));