YUI module loading extension for System.js

yui-module-extension

(function yui() {
	var 	systemInstantiate = System.instantiate,
		//Store just one Y sandbox
		YSandbox;

	//Extracts the dependency list from the YUI module source code (if any exist)
	function getYUIDeps(src, Y, load) {
		var 	stripRequire = /(\"requires\"|\'requires\'|\s*requires\s*)\s*:\s*/g,
			findRequire = /(\"requires\"|\'requires\'|\s*requires\s*)\s*:\s*\[[\s\S]*?\](\s*,\s*(\"skinnable\"|skinnable|\'skinnable\')\s*:\s*(true|false))*/g,
			skinnable = /(\"skinnable\"|skinnable|\'skinnable\')\s*:\s*(true|false)/
			splitDeps = /(('|\")(.*?)('|\")(,|\s*))/g;

		//I freely admit I am bad at regex. This gets the job done

		//find the requires array(s)
		var 	req = src.match(findRequire),
			deps = [];

		if(req){
			req.forEach(function(dep, index, req) {
				var 	depsModified,
					skinnableProp = dep.match(skinnable);

				// Skinnable modules always have a css file corresponding to the module name
				if(skinnableProp && skinnableProp[2].trim() === 'true') {
					deps.push(load.name + '.css!');
				}

				// Strip the require and skinnable statements
				depsModified = dep.replace(stripRequire, '');
				depsModified = depsModified.replace(skinnable, '');
				depsModified = depsModified.match(splitDeps);

				if(depsModified) {
					depsModified.forEach(function(dep, index, depsModified) {
						depsModified[index] = dep.replace(/[\"\',\s]+/gi,'');
					});
					deps = deps.concat(depsModified);
				}
			});

			if(deps) {
				deps.forEach(function(dep, index){
					//remove all the commas and junk
					deps[index] = dep.replace(/[\"\',\s]+/gi,'');
				});

				//Don't add dependencies that are already attached. this is mainly to circumvent the fact that yui-base
				//is already attached to the YUI seed and when invoked messes with the global YUI object. Basically it just
				//doesn't behave quite like a proper module.
				deps = deps.filter(function(dep) {
					return ! Y.Env._attached[dep];
				});
			}
		}

		return deps ? deps : [];
	}

	System.instantiate = function(load) {
		//The YUI file is loaded at this point. This is why we load YUI seed file without Loader. It makes no
		//sense for YUI to handle module loading anymore.
		if (load.metadata.format == 'yui' ||
			//yet another bad regex, this one doesn't support having a comment with the word YUI.add in it in your code :P
			//will fix at some point
			!load.metadata.format && load.source.match(/YUI\.add\(/)) {

			load.metadata.format = 'yui';

			if(! YSandbox) {
				//Need to think of a sane way to provide the YUI config to the extension.
				//Suspect a global is the simplest
				if(window.YUI) {
					YSandbox = window.YUI({ lang: 'en' });
				}
				else {
					throw new Error('YUI Seed must be loaded to load YUI modules via System.js');
				}
			}

			// don't forget that just like YUI, System.js will need to know what paths to find these modules in
			load.metadata.deps = getYUIDeps(load.source, YSandbox, load);

			// main execution function
			load.metadata.execute = function(require, exports, moduleName) {
				System.__exec(load);

				//the Y instance becomes the exports
				return YSandbox.use(moduleName.id);
			}
		}

		// pass the metadata on to the register extension for instantiate handling now
		return systemInstantiate.call(this, load);
	}
})();