/* Set attribute rel="external" element in order to make a _blank window link opening */
    function externalLinks()
    {
        if (!document.getElementsByTagName)
            return;
        var anchors = document.getElementsByTagName("a");
        for (var i=0; i<anchors.length; i++)
        {
            var anchor = anchors[i];
            if (anchor.getAttribute("href") && anchor.getAttribute("rel") == "external")
                anchor.target = "_blank";
        }
    }
    window.onload = externalLinks;

    /* AJAX Functions */

    /* Clear all child node in the element with the given id */
    function clear_node(id)
    {
        while ($(id).childNodes.length > 0)
            $(id).removeChild($(id).childNodes[0]);
    }

    var oldSubmenu = null;

    /* To be used to make a set of dynamic menu of products */
    function group_list(category_id)
    {
        new Ajax.Request
        (
            "group-ajax-service.php?category_id=" + encodeURI(category_id),
            {
                method: "get",
                onComplete: function(xhr)
                {
                    var xmlResult = xhr.responseXML;
                    var categoryNode = xmlResult.getElementsByTagName("category")[0];
                    var groupNode = categoryNode.getElementsByTagName("group");
                    var html = "";
                    for (var i = 0; i < groupNode.length; i++)
                        html += "<a href='./index.php?page=products&group_id=" + groupNode[i].getElementsByTagName("id")[0].firstChild.nodeValue + "' class='submenu'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;- " + groupNode[i].getElementsByTagName("name")[0].firstChild.nodeValue + "</a><br />";
                    if (oldSubmenu)
                        clear_node(oldSubmenu);
                    $("group_area_" + category_id).innerHTML = html;
                    oldSubmenu = "group_area_" + category_id;
                }
            }
        );
    }


    /* Make drop-down list with id 'group_select' shows list depending on category drop-down list change */
    function group_select()
    {
        var category_id = $("category_select_area").value;
        new Ajax.Request(
            "../group-ajax-service.php?category_id=" + encodeURI(category_id),
            {
                method: "get",
                onComplete: function(xhr)
                {
                    xmlResult = xhr.responseXML;
                    var categoryNode = xmlResult.getElementsByTagName("category")[0];
                    var groupNode = categoryNode.getElementsByTagName("group");
                    html = "";
                    for (var i = 0; i < groupNode.length; i++)
                        html += "<option value='" + groupNode[i].getElementsByTagName('id')[0].firstChild.nodeValue + "'>" + groupNode[i].getElementsByTagName('name')[0].firstChild.nodeValue + "</option>";
                    $("group_select_area").innerHTML = html;
                }
            }
        );
    }