var MouseoverNav = {
    _back_class: "MouseoverNav_back",
    _back_mouseover_class: "MouseoverNav_back_mouseover",
    _next_class: "MouseoverNav_next",
    _next_mouseover_class: "MouseoverNav_next_mouseover",
    _create_node: function ( link, classname, mouseover_classname ) {
        var node = document.createElement( "div" );
        node.className = classname;
        node.onmouseover = function () {
            node.className += " " + mouseover_classname;
        };
        node.onmouseout = function () {
            node.className = classname;
        };
        node.onclick = function () {
            window.location = link;
        };

        return node;
    },
    _create_back_node: function ( link ) {
        return MouseoverNav._create_node(
            link,
            MouseoverNav._back_class,
            MouseoverNav._back_mouseover_class
        );
    },
    _create_next_node: function ( link ) {
        return MouseoverNav._create_node(
            link,
            MouseoverNav._next_class,
            MouseoverNav._next_mouseover_class
        );
    },
    add: function ( id, back_link, next_link ) {
        var node = document.getElementById( id );
        if ( !node ) {
            throw new Error( "MouseoverNav was unable to find element.\n\tid=" + id );
        }

        node.style.position = "relative";

        if ( null != back_link && "" != back_link ) {
            var back_node = MouseoverNav._create_back_node( back_link );
            node.appendChild( back_node );
        }

        if ( null != next_link && "" != next_link ) {
            var next_node = MouseoverNav._create_next_node( next_link );
            node.appendChild( next_node );
        }
    }
};