// javascript document
(function($) {

    //custom scroll replacement to allow for interval-based 'polling'
    //rathar than checking on every pixel
    var uniquecntr = 0;
    $.fn.scrolled = function(waittime, fn) {
        if (typeof waittime === 'function') {
            fn = waittime;
            waittime = 200;
        }
        var tag = 'scrolltimer' + uniquecntr++;
        this.scroll(function() {
            var self = $(this);
            var timer = self.data(tag);
            if (timer) {
                cleartimeout(timer);
            }
            timer = settimeout(function() {
                self.removedata(tag);
                fn.call(self[0]);
            }, waittime);
            self.data(tag, timer);
        });
    };

    $.fn.aniview = function(options) {

        //some default settings. animatethreshold controls the trigger point
        //for animation and is subtracted from the bottom of the viewport.
        var settings = $.extend({
            animatethreshold: 0,
            scrollpollinterval: 20
        }, options);

        //keep the matched elements in a variable for easy reference
        var collection = this;

        //cycle through each matched element and wrap it in a block/div
        //and then proceed to fade out the inner contents of each matched element
        $(collection).each(function(index, element) {
            $(element).wrap('<div class="av-container"></div>');
            $(element).css('opacity', 0);
        });

        /**
         * returns boolean representing whether element's top is coming into bottom of viewport
         *
         * @param htmldomelement element the current element to check
         */
        function enteringviewport(element) {
            var elementoffset = $(element).offset();
            var elementtop = elementoffset.top + $(element).scrolltop();
            var elementbottom = elementoffset.top + $(element).scrolltop() + $(element).height();
            var viewportbottom = $(window).scrolltop() + $(window).height();
            return (elementtop < (viewportbottom - settings.animatethreshold)) ? true : false;
        }

        //cycle through each matched element to make sure any which should be animated into view,
        //are animated on page load rather than needing to wait for initial 'scrolled' event
        $(collection).each(function(index, element) {
            var elementparentcontainer = $(element).parent('.av-container');
            if ($(element).is('[av-animation]') && !$(elementparentcontainer).hasclass('av-visible') && enteringviewport(elementparentcontainer)) {
                $(element).css('opacity', 1);
                $(elementparentcontainer).addclass('av-visible');
                $(element).addclass('animated ' + $(element).attr('av-animation'));
            }
        });

        //enable the scrolled event timer to watch for elements coming into the viewport
        //from the bottom. default polling time is 20 ms. this can be changed using
        //'scrollpollinterval' from the user visible options
        $(window).scrolled(settings.scrollpollinterval, function() {
            $(collection).each(function(index, element) {
                var elementparentcontainer = $(element).parent('.av-container');
                if ($(element).is('[av-animation]') && !$(elementparentcontainer).hasclass('av-visible') && enteringviewport(elementparentcontainer)) {
                    $(element).css('opacity', 1);
                    $(elementparentcontainer).addclass('av-visible');
                    $(element).addclass('animated ' + $(element).attr('av-animation'));
                }
            });
        });
    };
})(jquery);