/*
cript: Assets.js

name: Assets

description: Provides methods to dynamically load JavaScript, CSS, and Image files into the document.

license: MIT-style license

authors:
  - Valerio Proietti

requires:
  - Core/Element.Event
  - /MooTools.More

provides: [Assets]

...
*/

var Asset = {

    javascript: function(source, properties){
        properties = $extend({
            onload: $empty,
            document: document,
            check: $lambda(true)
        }, properties);
        
        if (properties.onLoad) {
            properties.onload = properties.onLoad;
            delete properties.onLoad;
        }
        var script = new Element('script', {src: source, type: 'text/javascript'});

        var load = properties.onload.bind(script), 
            check = properties.check, 
            doc = properties.document;
        delete properties.onload;
        delete properties.check;
        delete properties.document;

        script.addEvents({
            load: load,
            readystatechange: function(){
                if (['loaded', 'complete'].contains(this.readyState)) load();
            }
        }).set(properties);

        if (Browser.Engine.webkit419) var checker = (function(){
            if (!$try(check)) return;
            $clear(checker);
            load();
        }).periodical(50);

        return script.inject(doc.head);
    },

    css: function(source, properties){
        properties = properties || {};
        var onload = properties.onload || properties.onLoad;
        if (onload) {
            properties.events = properties.events || {};
            properties.events.load = onload;
            delete properties.onload;
            delete properties.onLoad;
        }
        return new Element('link', $merge({
            rel: 'stylesheet',
            media: 'screen',
            type: 'text/css',
            href: source
        }, properties)).inject(document.head);
    },

    image: function(source, properties){
        properties = $merge({
            onload: $empty,
            onabort: $empty,
            onerror: $empty
        }, properties);
        var image = new Image();
        var element = document.id(image) || new Element('img');
        ['load', 'abort', 'error'].each(function(name){
            var type = 'on' + name;
            var cap = name.capitalize();
            if (properties['on' + cap]) {
                properties[type] = properties['on' + cap];
                delete properties['on' + cap];
            }
            var event = properties[type];
            delete properties[type];
            image[type] = function(){
                if (!image) return;
                if (!element.parentNode){
                    element.width = image.width;
                    element.height = image.height;
                }
                image = image.onload = image.onabort = image.onerror = null;
                event.delay(1, element, element);
                element.fireEvent(name, element, 1);
            };
        });
        image.src = element.src = source;
        if (image && image.complete) image.onload.delay(1);
        return element.set(properties);
    },

    images: function(sources, options){
        options = $merge({
            onComplete: $empty,
            onProgress: $empty,
            onError: $empty,
            properties: {}
        }, options);
        sources = $splat(sources);
        var images = [];
        var counter = 0;
        return new Elements(sources.map(function(source, index){
            return Asset.image(source, $extend(options.properties, {
                onload: function(){
                    options.onProgress.call(this, counter, index);
                    counter++;
                    if (counter == sources.length) options.onComplete();
                },
                onerror: function(){
                    options.onError.call(this, counter, index);
                    counter++;
                    if (counter == sources.length) options.onComplete();
                }
            }));
        }));
    }

};