gulpfile.js

let gulp         = require('gulp'),
    concat       = require('gulp-concat'),
    imagemin     = require('gulp-imagemin'),
    include      = require('gulp-include'),
    plumber      = require('gulp-plumber'),
    rename       = require('gulp-rename'),
    sourcemaps   = require('gulp-sourcemaps'),
    uglify       = require('gulp-uglify'),
    yaml         = require('gulp-yaml'),
    browserSync  = require('browser-sync'),
    cp           = require('child_process'),
    del          = require('del'),
    fs           = require('fs'),
    jsonSass     = require('json-sass'),
    source       = require('vinyl-source-stream');

/**
 * Notify
 * 
 * Show a notification in the browser's corner.
 * 
 * @param {*} message 
 */
function notify(message) {
  browserSync.notify(message);
}

/**
 * Config Task
 * 
 * Build the main YAML config file.
 */
function config() {
  return gulp.src('src/yml/_config.yml')
    .pipe(include())
    .on('error', console.error)
    .pipe(gulp.dest('./'));
}

/**
 * Jekyll Task
 * 
 * Build the Jekyll Site.
 * 
 * @param {*} done 
 */
function jekyll(done) {
  notify('Building Jekyll...');
  let bundle = process.platform === "win32" ? "bundle.bat" : "bundle";
  return cp
    .spawn(bundle, ['exec', 'jekyll build'], { stdio: 'inherit' })
    .on('close', done);
}

/**
 * Server Task
 * 
 * Launch server using BrowserSync.
 * 
 * @param {*} done 
 */
function server(done) {
  browserSync({
    server: {
      baseDir: '_site'
    }
  });
  done();
}

/**
 * Reload Task
 * 
 * Reload page with BrowserSync.
 * 
 * @param {*} done 
 */
function reload(done) {
  notify('Reloading...');
  browserSync.reload();
  done();
}

/**
 * Theme Tasks
 * 
 * These three tasks are responsible for:
 * 1. Converting src/yml/theme.yml to src/tmp/theme.json
 * 2. Converting src/tmp/theme.json to _sass/_theme.scss
 * 3. Deleting src/tmp
 * 
 * With these tasks we can apply the theme colors to SVGs and CSS elements using
 * just the src/yml/theme.yml file.
 */

function yamlTheme() {
  return gulp.src('src/yml/theme.yml')
    .pipe(yaml({ schema: 'DEFAULT_SAFE_SCHEMA' }))
    .pipe(gulp.dest('src/tmp/'));
}

function jsonTheme() {
  return fs.createReadStream('src/tmp/theme.json')
    .pipe(jsonSass({
      prefix: '$theme: ',
    }))
    .pipe(source('src/tmp/theme.json'))
    .pipe(rename('_sass/_theme.scss'))
    .pipe(gulp.dest('./'));
}

function cleanTheme() {
  return del(['src/tmp']);
}

const theme = gulp.series(yamlTheme, jsonTheme, cleanTheme);

/**
 * Main JS Task
 * 
 * All regular .js files are collected, minified and concatonated into one
 * single scripts.min.js file (and sourcemap)
 */
function mainJs() {
  notify('Building JS files...');
  return gulp.src('src/js/main/**/*.js')
    .pipe(sourcemaps.init())
    .pipe(uglify())
    .pipe(concat('scripts.min.js'))
    .pipe(plumber())
    .pipe(sourcemaps.write('.'))
    .pipe(gulp.dest('_site/assets/js/'))
    .pipe(browserSync.reload({ stream: true }))
    .pipe(gulp.dest('assets/js'));
}

/**
 * Preview JS Task
 * 
 * Copy preview JS files to the assets folder.
 */
function previewJs() {
  notify('Copying preview files...');
  return gulp.src('src/js/preview/**/*.*')
    .pipe(gulp.dest('assets/js/'));
}

/**
 * JavaScript Task
 * 
 * Run all the JS related tasks.
 */
const js = gulp.parallel(mainJs, previewJs);

/**
 * Images Task
 * 
 * All images are optimized and copied to assets folder.
 */
function images() {
  notify('Copying image files...');
  return gulp.src('src/img/**/*.{jpg,png,gif,svg}')
    .pipe(plumber())
    .pipe(imagemin({ optimizationLevel: 5, progressive: true, interlaced: true }))
}

/**
 * Watch Task
 * 
 * Watch files to run proper tasks.
 */
function watch() {
  // Watch YAML files for changes & recompile
  gulp.watch(['src/yml/*.yml', '!src/yml/theme.yml'], gulp.series(config, jekyll, reload));

  // Watch theme file for changes, rebuild styles & recompile
  gulp.watch(['src/yml/theme.yml'], gulp.series(theme, config, jekyll, reload));

  // Watch SASS files for changes & rebuild styles
  gulp.watch(['_sass/**/*.scss'], gulp.series(jekyll, reload));

  // Watch JS files for changes & recompile
  gulp.watch('src/js/main/**/*.js', mainJs);

  // Watch preview JS files for changes, copy files & reload
  gulp.watch('src/js/preview/**/*.js', gulp.series(previewJs, reload));

  // Watch images for changes, optimize & recompile
  gulp.watch('src/img/**/*', gulp.series(images, config, jekyll, reload));

  // Watch html/md files, rebuild config, run Jekyll & reload BrowserSync
  gulp.watch(['*.html', '_includes/*.html', '_layouts/*.html', '_posts/*', '_authors/*', 'pages/*', 'category/*'], gulp.series(config, jekyll, reload));
}

/**
 * Default Task
 *
 * Running just `gulp` will:
 * - Compile the theme, SASS and JavaScript files
 * - Optimize and copy images to its folder
 * - Build the config file
 * - Compile the Jekyll site
 * - Launch BrowserSync & watch files
 */
exports.default = gulp.series(gulp.parallel(js, theme, images), config, jekyll, gulp.parallel(server, watch));

/**
 * Build Task
 * 
 * Running just `gulp build` will:
 * - Compile the theme, SASS and JavaScript files
 * - Optimize and copy images to its folder
 * - Build the config file
 * - Compile the Jekyll site
 */
exports.build = gulp.series(gulp.parallel(js, theme, images), config, jekyll);