asset embedding for node.js

asset-embed.js

var _ = require('underscore');
var fs = require('fs');
var path = require('path');
var debug = require('debug')('asset-embed');

module.exports = function() {
	var self = {
		loaders: {
			less: function(a, callback) {
				self.loaders.plain(a, function(err, res) {
					if (err) return callback(err);		

					var less = require('less');
					var parser = new less.Parser(self.loaders.less.options);
					parser.parse(res, function(err, tree) {
						if (err) return callback(err);
						callback(null, '<style>' + tree.toCSS(self.loaders.less.options) + '</style>');
					});
				});
			},

			css: function(a, callback) {
				self.loaders.plain(a, function(err, res) {
					if (err) return callback(err);
					callback(null, '<style>' + res + '</style>');
				});
			},

			js: function(a, callback) {
				self.loaders.plain(a, function(err, res) {
					if (err) return callback(err);
					var uglify = require('uglify-js');
			    	res = uglify.parser.parse(res);
	                res = uglify.uglify.ast_squeeze(res);
	                res = uglify.uglify.gen_code(res);
	                res = '<script>' + res + '</script>';
	                callback(null, res);
				});
			},

			plain: function(a, callback) {
				debug('loading asset file', a);
				fs.readFile(a, 'utf8', callback);
			}
		},

		assets: {},

		load: function(names, callback)  {
			if (!_.isArray(names)) names = [names];
			var left = names.length, panic = false;
			_.each(names, function(names) {
				var loader = path.extname(names);
				if (loader) loader = loader.substr(1);

				if (!loader || !_.has(self.loaders, loader)) {
					loader = 'plain';
				}

				self.loaders[loader](names, function(err, res) {
					if (panic) return;

					if (err) {
						panic = true;
						if (_.isFunction(callback)) {
							return callback(err);
						}
						throw err;
					}

					self.assets[names] = res;

					if (!--left && _.isFunction(callback)) {
						return callback();
					}
				});
			});
		},

		embed: function(name) {
			if (!_.has(self.assets, name)) {
				throw new Error(name + ' not loaded');
			}

			return self.assets[name];
		}
	};

	self.loaders.less.options = { compress: true };

	return _.extend(self.embed, self);
};