gulpfile.js

var gulp = require('gulp');
var csso = require('gulp-csso');
var uglify = require('gulp-uglify');
var concat = require('gulp-concat');
var sass = require('gulp-sass');
var plumber = require('gulp-plumber');
var cp = require('child_process');
var imagemin = require('gulp-imagemin');
var browserSync = require('browser-sync');

var jekyllCommand = (/^win/.test(process.platform)) ? 'jekyll.bat' : 'jekyll';

var gutil = require('gulp-util');
var livereload = require('gulp-livereload');

var postcss = require('gulp-postcss');
var sourcemaps = require('gulp-sourcemaps');

// postcss plugins
var autoprefixer = require('autoprefixer');
var colorFunction = require('postcss-color-function');
var cssnano = require('cssnano');
var customProperties = require('postcss-custom-properties');
var easyimport = require('postcss-easy-import');

var swallowError = function swallowError(error) {
    gutil.log(error.toString());
    gutil.beep();
    this.emit('end');
};

/*
 * Build the Jekyll Site
 * runs a child process in node that runs the jekyll commands
 */
gulp.task('jekyll-build', function (done) {
    return cp.spawn(jekyllCommand, ['build'], {stdio: 'inherit'})
        .on('close', done);
});

/*
 * Rebuild Jekyll & reload browserSync
 */
gulp.task('jekyll-rebuild', ['jekyll-build'], function () {
    browserSync.reload();
});

/*
 * Build the jekyll site and launch browser-sync
 */
gulp.task('browser-sync', ['jekyll-build'], function () {
    browserSync({
        server: {
            baseDir: '_site'
        }
    });
});

/*
* Compile and minify sass
*/
gulp.task('sass', function () {
    gulp.src('node_modules/devicon-2.2/devicon.css')
        .pipe(gulp.dest('src/styles/vendor/devicon/'));
    gulp.src('node_modules/devicon-2.2/devicon-colors.css')
        .pipe(gulp.dest('src/styles/vendor/devicon/'));
    gulp.src('src/styles/**/*.scss')
        .pipe(plumber())
        .pipe(sass())
        .pipe(csso())
        .pipe(gulp.dest('assets/css/'));
});

gulp.task('css', function () {
    var processors = [
        easyimport,
        customProperties,
        colorFunction(),
        autoprefixer({browsers: ['last 2 versions']}),
        cssnano()
    ];

    return gulp.src('assets/css/*.css')
        .on('error', swallowError)
        .pipe(sourcemaps.init())
        .pipe(postcss(processors))
        .pipe(sourcemaps.write('.'))
        .pipe(gulp.dest('assets/built/'))
        .pipe(livereload());
});

/*
* Compile fonts
*/
gulp.task('fonts', function () {
    gulp.src('node_modules/devicon-2.2/fonts/*')
        .pipe(gulp.dest('src/styles/vendor/devicon/fonts/'));
    gulp.src('src/fonts/**/*.{ttf,woff,woff2}')
        .pipe(plumber())
        .pipe(gulp.dest('assets/css/fonts/'));
    gulp.src('node_modules/font-awesome/fonts/*')
        .pipe(gulp.dest('src/styles/vendor/font-awesome/fonts/'));
    gulp.src('src/styles/vendor/font-awesome/fonts/**/*.{ttf,woff,woff2}')
        .pipe(plumber())
        .pipe(gulp.dest('assets/fonts/'));
});

/*
 * Minify images
 */
gulp.task('imagemin', function () {
    return gulp.src('src/img/**/*.{jpg,png,gif}')
        .pipe(plumber())
        .pipe(imagemin({optimizationLevel: 3, progressive: true, interlaced: true}))
        .pipe(gulp.dest('assets/img/'));
});

/**
 * Compile and minify js
 */
gulp.task('js', function () {
    return gulp.src('src/js/**/*.js')
        .pipe(plumber())
        .pipe(concat('main.js'))
        .pipe(uglify())
        .pipe(gulp.dest('assets/js/'))
});

gulp.task('watch', function () {
    gulp.watch('src/styles/**/*.scss', ['sass', 'jekyll-rebuild']);
    gulp.watch('src/js/**/*.js', ['js']);
    gulp.watch('src/fonts/**/*.{tff,woff,woff2}', ['fonts']);
    gulp.watch('src/img/**/*.{jpg,png,gif}', ['imagemin']);
    gulp.watch(['*html', '_includes/*html', '_layouts/*.html'], ['jekyll-rebuild']);
});

gulp.task('default', ['js', 'sass', 'css', 'fonts', 'browser-sync', 'watch']);