Bundler

asset-bundler.js

var gulp = require('gulp');
var fs = require('fs');
var path = require('path');
var glob = require('glob');
var useref = require('node-useref');
var concat = require('gulp-concat');
var through = require('through2');

// Yes there are gulp plugins out there that do exactly this
// but ran into issues with a number of them so gave up and
// wrote this. gulp-usemin used to work perfectly but recent
// changes broke where it saves results and the repo owner
// doesen't seem very active.

module.exports = function(source, target, pipeline) {
    return Promise.all(glob.sync(source).map(function(htmlFile) {
        var promises = [];
        var basePath = path.dirname(htmlFile);
        var targetHtmlFile = target == '.' ? htmlFile :
            path.join(basePath, target);
        var result = useref(fs.readFileSync(htmlFile).toString());
        var html = result[0];
        for (resourceType in result[1]) {
            var resource = result[1][resourceType];
            for (block in resource) {
                var assets = resource[block].assets.map(function(x) {
                    return path.join(basePath, x);
                });
                var pipe = gulp.src(assets);
                if (pipeline[resourceType]) {
                    pipeline[resourceType].forEach(function(plugin) {
                        pipe = pipe.pipe(plugin == 'concat' ?
                            concat(path.basename(block)) : plugin);
                    });
                }
                var writeHtmlFile = function(oldAssetName) {
                    return through.obj(function (file, enc, cb) {
                        var newAssetName = path.basename(file.path);
                        html = html.replace(new RegExp('(["/])' + oldAssetName +
                            '(["?])', 'gi'), '$1' + newAssetName + '$2');
                        fs.writeFileSync(targetHtmlFile, html);
                        cb(null, file);
                    });
                };
                promises.push(pipe.pipe(writeHtmlFile(path.basename(block)))
                    .pipe(gulp.dest(path.join(basePath, path.dirname(block)))));
            }
        }
        return promises;
    }));
}

gulpfile.js

var gulp = require('gulp');
var assetBundler = require('./asset-bundler');
var uglify = require('gulp-uglify');
var minifyCss = require('gulp-minify-css');
var rev = require('gulp-rev');
var removeBom = require('fd-gulp-removebom');

gulp.task('default', function() {
    return assetBundler('src/*/index.html', '.', {
        css: [ minifyCss(), 'concat', rev() ],
        js: [ removeBom(), 'concat', uglify(), rev() ]
    });
});