/**
* jQuery.Preload
* Copyright (c) 2008 Ariel Flesler - aflesler(at)gmail(dot)com
* Dual licensed under MIT and GPL.
* Date: 3/12/2008
*
* @projectDescription Multifunctional preloader
* @author Ariel Flesler
* @version 1.0.7
*
* @id jQuery.preload
* @param {String, jQuery, Array< String, <a>, <link>, <img> >} original Collection of sources to preload
* @param {Object} settings Hash of settings.
*
* @id jQuery.fn.preload
* @param {Object} settings Hash of settings.
* @return {jQuery} Returns the same jQuery object, for chaining.
*
* @example Link Mode:
*	$.preload( '#images a' );
*
* @example Rollover Mode:
*	$.preload( '#images img', {
*		find:/\.(gif|jpg)/,
*		replace:'_over.$1'
*	});
*
* @example Src Mode:
*	$.preload( [ 'red', 'blue', 'yellow' ], {
*		base:'images/colors/',
*		ext:'.jpg'
*	});
*
* @example Placeholder Mode:
*	$.preload( '#images img', {
*		placeholder:'placeholder.jpg',
*		notFound:'notfound.jpg'
*	});
*
* @example Placeholder+Rollover Mode(High res):
*	$.preload( '#images img', {
*		placeholder:true,
*		find:/\.(gif|jpg)/,
*		replace:'_high.$1'
*	});
*/
; (function($) {

    var $preload = $.preload = function(original, settings) {
        if (original.split)//selector
            original = $(original);

        settings = $.extend({}, $preload.defaults, settings);
        var sources = $.map(original, function(source) {
            if (!source)
                return; //skip
            if (source.split)//URL Mode
                return settings.base + source + settings.ext;
            var url = source.src || source.href; //save the original source
            if (typeof settings.placeholder == 'string' && source.src)//Placeholder Mode, if it's an image, set it.
                source.src = settings.placeholder;
            if (url && settings.find)//Rollover mode
                url = url.replace(settings.find, settings.replace);
            return url || null; //skip if empty string
        });

        var data = {
            loaded: 0, //how many were loaded successfully
            failed: 0, //how many urls failed
            next: 0, //which one's the next image to load (index)
            done: 0, //how many urls were tried
            //found:false,//whether the last one was successful
            total: sources.length//how many images are being preloaded overall
        };

        if (!data.total)//nothing to preload
            return finish();

        var imgs = '<img/>', //ensure one
			thres = settings.threshold; //save a copy

        while (--thres > 0)//it could be oddly negative
            imgs += '<img/>';
        imgs = $(imgs).load(handler).error(handler).bind('abort', handler).each(fetch);

        function handler(e) {
            data.found = e.type == 'load';
            data.image = this.src;
            var orig = data.original = original[this.index];
            data[data.found ? 'loaded' : 'failed']++;
            data.done++;
            if (settings.placeholder && orig.src)//special case when on placeholder mode
                orig.src = data.found ? data.image : settings.notFound || orig.src;
            if (settings.onComplete)
                settings.onComplete(data);
            if (data.done < data.total)//let's continue
                fetch(0, this);
            else {//we are finished
                if (imgs.unbind)//sometimes IE gets here before finishing line 84
                    imgs.unbind('load').unbind('error').unbind('abort'); //cleanup
                imgs = null;
                finish();
            }
        };
        function fetch(i, img, retry) {
            if ($.browser.msie && data.next && data.next % $preload.gap == 0 && !retry) {//IE problem, can't preload more than 15
                setTimeout(function() { fetch(i, img, true); }, 0);
                return false;
            }
            if (data.next == data.total) return false; //no more to fetch
            img.index = data.next; //save it, we'll need it.
            img.src = sources[data.next++];
            if (settings.onRequest) {
                data.image = img.src;
                data.original = original[data.next - 1];
                settings.onRequest(data);
            }
        };
        function finish() {
            if (settings.onFinish)
                settings.onFinish(data);
        };
    };

    // each time we load this amount and it's IE, we must rest for a while, make it lower if you get stack overflow.
    $preload.gap = 14;

    $preload.defaults = {
        threshold: 2, //how many images to load simultaneously
        base: '', //URL mode: a base url can be specified, it is prepended to all string urls
        ext: '', //URL mode:same as base, but it's appended after the original url.
        replace: ''//Rollover mode: replacement (can be left empty)
        /*
        find:null,//Rollover mode: a string or regex for the replacement
        notFound:''//Placeholder Mode: Optional url of an image to use when the original wasn't found
        placeholder:'',//Placeholder Mode: url of an image to set while loading
        onRequest:function( data ){ ... },//callback called every time a new url is requested
        onComplete:function( data ){ ... },//callback called every time a response is received(successful or not)
        onFinish:function( data ){ ... }//callback called after all the images were loaded(or failed)
        */
    };

    $.fn.preload = function(settings) {
        $preload(this, settings);
        return this;
    };

})(jQuery);