$(document).ready(function() {
    var widgetWidth = 180;
    var animationSpeed = 700;
    var easing = "swing";
    var itemCount = $("#twitter_widget_list li").length;
    var currentItemIndex = 0;

    if (itemCount == 1)
        $("#btnTwitter_next").addClass("disabled");

    $("#btnTwitter_previous").click(function() {
        if (currentItemIndex > 0) {
            $("#twitter_widget_list").animate({
                left: "+=" + widgetWidth
            }, animationSpeed, easing,
                function() {
                    if (currentItemIndex == 0) {
                        $("#btnTwitter_previous").addClass("disabled");
                    }
                });

            currentItemIndex--;
            $("#btnTwitter_next").removeClass("disabled");
        }
    });

    $("#btnTwitter_next").click(function() {
        if (currentItemIndex < itemCount - 1) {
            $("#twitter_widget_list").animate({
                left: "-=" + widgetWidth
            }, animationSpeed, easing,
                function() {
                    if (currentItemIndex == itemCount - 1)
                        $("#btnTwitter_next").addClass("disabled");
                });

            currentItemIndex++;
            $("#btnTwitter_previous").removeClass("disabled");
        }
    });
});