<?php

/**
 * Menu Walker
 *
 * @see Walker::start_lvl()
 * @since 3.0.0
 *
 * @param string $output Passed by reference. Used to append additional content.
 * @param int    $depth Depth of page. Used for padding.
 * @param object $args Arguments.
 */
public function start_lvl(&$output, $depth = 0, $args = array())
{
    $indent = str_repeat("t", $depth);
    $output .= "n$indent<ul role="menu" class=" dvt-nav-dropdown closed">n";
}

/**
 * Bootstrap Menu Walker start
 *
 * @see Walker::start_el()
 * @since 3.0.0
 *
 * @param string $output Passed by reference. Used to append additional content.
 * @param object $item Menu item data object.
 * @param int    $depth Depth of menu item. Used for padding.
 * @param object $args Arguments.
 * @param int    $id Menu item ID.
 */
public function start_el(&$output, $item, $depth = 0, $args = array(), $id = 0)
{
    // Set level of indent.
    $indent = ($depth) ? str_repeat("t", $depth) : '';

    // Create nav menu item.
    $nav_menu_atts = array();
    $nav_menu_atts['id'] = apply_filters('nav_menu_item_id', 'menu-item-' . $item->ID, $item, $args);
    $nav_menu_atts['class'] = empty($item->classes) ? array() : (array) $item->classes;
    $nav_menu_atts['class'] = apply_filters('nav_menu_css_class', $nav_menu_atts['class'], $item, $args);

    // Create link attributes.
    $nav_menu_link_atts = array();
    $nav_menu_link_atts['title']  = ! empty($item->title)  ? $item->title  : '';
    $nav_menu_link_atts['target'] = ! empty($item->target) ? $item->target : '';
    $nav_menu_link_atts['rel']    = ! empty($item->xfn)    ? $item->xfn    : '';

    // If item has_children add atts to a.
    $nav_menu_link_atts['href'] = $args->has_children && 0 === $depth ? '#' : (!empty($item->url) ? $item->url : '');

    $nav_menu_link_atts = apply_filters('nav_menu_link_attributes', $nav_menu_link_atts, $item, $args);

    // Output LI menu item.
    $output .= $indent;
    $output .= '<li';
    // Output menu attributes.
    foreach ($nav_menu_atts as $attr => $value) {
        // Output attribute name.
        $output .= ' ' . esc_attr($attr);
        if (!empty($value)) {
            $output .= '="';
            // Add switch to handle escaping.
            switch ($attr) {
                case 'class':
                    $output .= esc_attr(join(' ', array_filter($value)));
                    break;
                default:
                    $output .= esc_attr($value);
                    break;
            }
            $output .= '"';
        }
    }
    $output .= '>';

    // Output A link.
    $item_output = $args->before;
    $item_output .= '<a';
    // Output link attributes.
    foreach ($nav_menu_link_atts as $attr => $value) {
        if (!empty($value)) {
            // Output attribute name.
            $item_output .= ' ' . esc_attr($attr) . '="';
            // Add switch to handle escaping.
            switch ($attr) {
                case 'href':
                    $item_output .= esc_url($value);
                    break;

                case 'class':
                    $item_output .= esc_attr(join(' ', array_filter($value)));
                    break;

                default:
                    $item_output .= esc_attr($value);
                    break;
            }
            $item_output .= '"';
        }
    }
    $item_output .= '>';
    $item_output .= $args->link_before . apply_filters('the_title', $item->title, $item->ID) . $args->link_after;
    $item_output .= '</a>';
    $item_output .= $args->after;

    $output .= apply_filters('walker_nav_menu_start_el', $item_output, $item, $depth, $args);
}

/**
 * Traverse elements to create list from elements.
 *
 * Display one element if the element doesn't have any children otherwise,
 * display the element and its children. Will only traverse up to the max
 * depth and no ignore elements under that depth.
 *
 * This method shouldn't be called directly, use the walk() method instead.
 *
 * @see Walker::start_el()
 * @since 2.5.0
 *
 * @param object $element Data object.
 * @param array  $children_elements List of elements to continue traversing.
 * @param int    $max_depth Max depth to traverse.
 * @param int    $depth Depth of current element.
 * @param array  $args Arguments.
 * @param string $output Passed by reference. Used to append additional content.
 * @return null Null on failure with no changes to parameters.
 */
public function display_element($element, &$children_elements, $max_depth, $depth, $args, &$output)
{
    if (! $element) {
        return;
    }

    $id_field = $this->db_fields['id'];

    // Display this element.
    if (is_object($args[0])) {
        $args[0]->has_children = ! empty($children_elements[ $element->$id_field ]);
    }

    parent::display_element($element, $children_elements, $max_depth, $depth, $args, $output);
}

/**
 * Menu Fallback
 * =============
 * If this function is assigned to the wp_nav_menu's fallback_cb variable
 * and a manu has not been assigned to the theme location in the WordPress
 * menu manager the function with display nothing to a non-logged in user,
 * and will add a link to the WordPress menu manager if logged in as an admin.
 *
 * @param array $args passed from the wp_nav_menu function.
 */
public static function fallback($args)
{
    if (current_user_can('manage_options')) {
        $fb_output = null;

        if ($args['container']) {
            echo '<' . esc_html($args['container']);

            if ($args['container_id']) {
                echo ' id="' . esc_attr($args['container_id']) . '"';
            }

            if ($args['container_class']) {
                echo ' class="' . esc_attr($args['container_class']) . '"';
            }

            echo '>';
        }

        echo '<ul';

        if ($args['menu_id']) {
            echo ' id="' . esc_attr($args['menu_id']) . '"';
        }

        if ($args['menu_class']) {
            echo ' class="' . esc_attr($args['menu_class']) . '"';
        }

        echo '>';
        echo '</ul>';

        if ($args['container']) {
            echo '</' . esc_html($args['container']) . '>';
        }
    }
}