/**
*  @module Worker
*  @namespace cloudkid
*/
(function()
{
	// Include classes
	var FallbackWorker = include('cloudkid.FallbackWorker');

	// Combine prefixed URL for createObjectURL from blobs.
	var URL = window.URL || window.webkitURL;

	// Combine prefixed blob builder
	var BlobBuilder = window.BlobBuilder || window.WebKitBlobBuilder || window.MozBlobBuilder;

	/**
	 * The Web Workers specification defines an API for spawning background scripts in your web 
	 * application. Web Workers allow you to do things like fire up long-running scripts to 
	 * handle computationally intensive tasks, but without blocking the UI or other scripts 
	 * to handle user interactions. Because Workers aren't available on all browsers, we provide
	 * a helpful polyfill for backward compatibility. This worker is designed to run 
	 * asyncronously instead of calling an external file.
	 * 
	 *	var workerCode = "this.initialVariable = 10;" +
	 *	"this.onmessage = function(event)" +
	 *	"{" +
	 *		"var data = event.data;" +
	 *		"var returnVal = this.initialVariable + data.addValue;" +
	 *		"this.postMessage(returnVal);" +
	 *	"};";
	 *	
	 *	// Create the worker
	 *	var worker = cloudkid.Worker.init(workerCode);
	 *	worker.onmessage = function(e) {
	 *		// e.data is the returnVal (30)
	 *	};
	 *	
	 *	// Start the worker.
	 *	worker.postMessage({addValue:20}); 
	 *	
	 * @class Worker
	 */
	var Worker = {};

	/**
	 * Initialize the worker, this is how you create a Worker or FallbackWorker object.
	 * @method init
	 * @static
	 * @param {String} codeString The code in string form to make the worker from. As a string, fallback support is easier.
	 * @return {cloudkid.FallbackWorker|window.Worker} Either a Web Worker or a fallback with the same API to use.
	 */
	Worker.init = function(codeString)
	{
		if(!URL || !window.Worker) return new FallbackWorker(codeString);

		var blob;
		try
		{
			blob = new Blob([codeString], {type: 'application/javascript'});
		}
		catch (e)
		{
			// try Backwards-compatibility with blob builders
			if (!BlobBuilder) return new FallbackWorker(codeString);

			try
			{
				blob = new BlobBuilder();
				blob.append(codeString);
				blob = blob.getBlob();
			}
			catch(error)
			{
				// no way of generating a blob to create the worker from
				return new FallbackWorker(codeString);
			}
		}

		// if somehow no blob was created, return a fallback worker
		if (!blob) return new FallbackWorker(codeString);

		try
		{
			// IE 10 and 11, while supporting Blob and Workers, should 
			// throw an error here, so we should catch it and fall back
			var worker = new Worker(URL.createObjectURL(blob));
			return worker;
		}
		catch(e)
		{
			// can't create a worker
			return new FallbackWorker(codeString);
		}
	};

	// Assign to namespace
	namespace("cloudkid").Worker = Worker;
	
}());