(function($) {
    $.fn.scrollContent = function(instanceSettings) {

        var shortcut = $.fn.scrollContent;

        shortcut.defaultsSettings = {
            scrollType: 'button', // button or slider
            btnPrev: null,
            btnNext: null,
            btnSpecific: null,
            auto: null,
            speed: 200,
            easing: null,
            vertical: 0,
            circular: 1,
            visible: 1,
            start: 0,
            scrollAtATime: 1,
            beforeStart: null,
            afterEnd: null
        };

        var settings = $.extend({}, $.fn.scrollContent.defaultsSettings, instanceSettings || {});

        return this.each(function() {                           // Returns the element collection. Chainable.

            var running = false;
            var animCss = settings.vertical ? "top" : "left";
            var sizeCss = settings.vertical ? "height" : "width";
            var div = $(this);
            var ul = $("ul", div);
            var tLi = $("li", ul);
            var tl = tLi.size();
            var v = settings.visible;

            if (settings.circular) {
                ul.prepend(tLi.slice(tl - v - 1 + 1).clone())
              .append(tLi.slice(0, v).clone());
                settings.start += v;
            }

            var li = $("li", ul);
            var itemLength = li.size();
            var curr = settings.start;
            div.css("visibility", "visible");

            li.css({ overflow: "hidden", float: settings.vertical ? "none" : "left" });
            ul.css({ margin: "0", padding: "0", position: "relative", "list-style-type": "none", "z-index": "1" });
            div.css({ overflow: "hidden", position: "relative", "z-index": "2", left: "0px" });

            var liSize = settings.vertical ? height(li) : width(li);   // Full li size(incl margin)-Used for animation
            var ulSize = liSize * itemLength;                   // size of full ul(total length, not just for the visible items)
            var divSize = liSize * v;                           // size of entire div(total length for just the visible items)

            li.css({ width: li.width(), height: li.height() });
            ul.css(sizeCss, ulSize + "px").css(animCss, -(curr * liSize));

            div.css(sizeCss, divSize + "px");                     // Width of the DIV. length of visible images

            if (settings.btnPrev) {
                $(settings.btnPrev).click(function() {
                    return go(curr - settings.scrollAtATime);
                });
            }

            if (settings.btnNext) {
                $(settings.btnNext).click(function() {
                    return go(curr + settings.scrollAtATime);
                });
            }

            if (settings.btnSpecific) {
                $.each(settings.btnSpecific, function(i, val) {
                    $(val).click(function() {
                        return go(settings.circular ? settings.visible + i : i);
                    });
                });
            }

            if (settings.auto) {
                setInterval(function() {
                    go(curr + settings.scrollAtATime);
                }, settings.auto + settings.speed);
            }

            function vis() {
                return li.slice(curr).slice(0, v);
            }

            function go(to) {
                if (!running) {

                    if (settings.beforeStart) {
                        settings.beforeStart.call(this, vis());
                    }

                    if (settings.circular) {            // If circular we are in first or last, then goto the other end
                        if (to <= settings.start - v - 1) {           // If first, then goto last
                            ul.css(animCss, -((itemLength - (v * 2)) * liSize) + "px");
                            // If "scroll" > 1, then the "to" might not be equal to the condition; it can be lesser depending on the number of elements.
                            curr = to == settings.start - v - 1 ? itemLength - (v * 2) - 1 : itemLength - (v * 2) - settings.scrollAtATime;
                        } else if (to >= itemLength - v + 1) { // If last, then goto first
                            ul.css(animCss, -((v) * liSize) + "px");
                            // If "scroll" > 1, then the "to" might not be equal to the condition; it can be greater depending on the number of elements.
                            curr = to == itemLength - v + 1 ? v + 1 : v + settings.scrollAtATime;
                        } else { curr = to; }
                    } else {                    // If non-circular and to points to first or last, we just return.
                        if (to < 0 || to > itemLength - v) {
                            return;
                        } else {
                            curr = to;
                        }
                    }                           // If neither overrides it, the curr will still be "to" and we can proceed.

                    running = true;

                    ul.animate(
                    animCss == "left" ? { left: -(curr * liSize)} : { top: -(curr * liSize) }, settings.speed, settings.easing,
                    function() {
                        if (settings.afterEnd) {
                            settings.afterEnd.call(this, vis());
                        }
                        running = false;

                    }
                );
                    // Disable buttons when the carousel reaches the last/first, and enable when not
                    if (!settings.circular) {
                        $(settings.btnPrev + "," + settings.btnNext).removeClass("disabled");
                        $((curr - settings.scrollAtATime < 0 && settings.btnPrev) || (curr + settings.scrollAtATime > itemLength - v && settings.btnNext) || []).addClass("disabled");
                    }

                }
                return false;
            }
        });
    };

    function css(el, prop) {
        return parseInt($.css(el[0], prop)) || 0;
    };

    function width(el) {
        return el.outerWidth() + css(el, 'marginLeft') + css(el, 'marginRight');
    }
    function height(el) {
        return el.outerHeight() + css(el, 'marginTop') + css(el, 'marginBottom');
    }

})(jQuery);