/*! copyright (c) 2013 brandon aaron (http://brandonaaron.net)
 * licensed under the mit license (license.txt).
 *
 * version 3.0.0
 */

(function (factory) {
    if (typeof define === 'function' && define.amd) {
        // amd. register as an anonymous module.
        define(['jquery'], factory);
    } else {
        // browser globals
        factory(jquery);
    }
}(function ($) {
    $.fn.bgiframe = function(s) {
        s = $.extend({
            top         : 'auto', // auto == bordertopwidth
            left        : 'auto', // auto == borderleftwidth
            width       : 'auto', // auto == offsetwidth
            height      : 'auto', // auto == offsetheight
            opacity     : true,
            src         : 'javascript:false;',
            conditional : true // expresion or function. return false to prevent iframe insertion
        }, s);

        // wrap conditional in a function if it isn't already
        if (!$.isfunction(s.conditional)) {
            var condition = s.conditional;
            s.conditional = function() { return condition; };
        }

        var $iframe = $('<iframe class="bgiframe"frameborder="0"tabindex="-1"src="'+s.src+'"'+
                           'style="display:block;position:absolute;z-index:-1;"/>');

        return this.each(function() {
            var $this = $(this);
            if ( s.conditional(this) === false ) { return; }
            var existing = $this.children('iframe.bgiframe');
            var $el = existing.length === 0 ? $iframe.clone() : existing;
            $el.css({
                'top': s.top == 'auto' ?
                    ((parseint($this.css('bordertopwidth'),10)||0)*-1)+'px' : prop(s.top),
                'left': s.left == 'auto' ?
                    ((parseint($this.css('borderleftwidth'),10)||0)*-1)+'px' : prop(s.left),
                'width': s.width == 'auto' ? (this.offsetwidth + 'px') : prop(s.width),
                'height': s.height == 'auto' ? (this.offsetheight + 'px') : prop(s.height),
                'opacity': s.opacity === true ? 0 : undefined
            });

            if ( existing.length === 0 ) {
                $this.prepend($el);
            }
        });
    };

    // old alias
    $.fn.bgiframe = $.fn.bgiframe;

    function prop(n) {
        return n && n.constructor === number ? n + 'px' : n;
    }

}));