gulpfile.js

var gulp        = require('gulp');
var rename      = require('gulp-rename');
var cssmin      = require('gulp-minify-css');
var prefix      = require('gulp-autoprefixer');
var size        = require('gulp-size');
var uncss       = require('gulp-uncss');
var header      = require('gulp-header');
var gutil       = require('gulp-util');
var a11y        = require('a11y');
var rework      = require('gulp-rework');
var reworkNpm   = require('rework-npm');
var reworkVars  = require('rework-vars');
var reworkMedia = require('rework-custom-media')

var pkg = require('./package.json');
var banner = ['/**',
              ' * <%= pkg.name %> - <%= pkg.description %>',
              ' * @author <%= pkg.author %>',
              ' * @version v<%= pkg.version %>',
              ' * @link <%= pkg.homepage %>',
              ' * @license <%= pkg.license %>',
              ' */\n\n'].join('\n');

gulp.task('css', function() {
  return gulp.src('css/src/styles.css')
    .pipe(rework(reworkNpm(), reworkVars(), reworkMedia()))
    .pipe(size({ gzip: true, showFiles: true }))
    .pipe(prefix("last 1 version", "> 1%", "ie 10"))
    .pipe(rename('c.css'))
    .pipe(header(banner, { pkg : pkg } ))
    .pipe(gulp.dest('css'))
    .pipe(cssmin())
    .pipe(size({ gzip: true, showFiles: true }))
    .pipe(rename({ suffix: '.min' }))
    .pipe(gulp.dest('css'));
});

gulp.task('uncss', ['css'], function() {
  return gulp.src('css/c.min.css')
    .pipe(size({ gzip: true, showFiles: true }))
    .pipe(uncss({ html: ['index.html'] }))
    .pipe(rename('css/c.un.min.css'))
    .pipe(cssmin())
    .pipe(size({ gzip: true, showFiles: true }))
    .pipe(gulp.dest('./'));
});

gulp.task('a11y', function() {
  a11y('https://markdowncss.github.io', function(err, reports) {
    if (err) {
      gutil.log(gutil.colors.red('gulp a11y error: ' + err));
      return;
    }

    reports.audit.forEach(function(report) {
      if (report.result === 'FAIL') {
        gutil.log(displaySeverity(report), gutil.colors.red(report.heading), report.elements);
      }
    });
  });
});

function displaySeverity(report) {
  if (report.severity == 'Severe') {
    return gutil.colors.red('[' + report.severity + '] ');
  } else if (report.severity == 'Warning') {
    return gutil.colors.yellow('[' + report.severity + '] ');
  } else {
    return '[' + report.severity + '] ';
  }
}

gulp.task('watch', function() {
  gulp.watch('css/src/*.css', ['css', 'uncss']);
  gulp.watch('index.html', ['uncss']);
});

gulp.task('default', ['css', 'uncss', 'watch']);