/*
* Customize menu items, add custom post type posts under specific parent item
* https://blog.brain1981.com
*/
function brain1981_add_posts_to_menu($items, $args) {
	//只对特定的菜单进行处理，根据菜单名或位置调整，‘menu-top’是我对主菜单的命名
	if ($args->theme_location != 'primary' && $args->menu != 'menu-top' && $args->menu_slug != 'menu-top') {
	    return $items;
	}
 
	//查找目标父菜单项，我的父菜单是Brands，菜单ID是21，根据需要修改
	$parent_item = null;
	$parent_item_index = null;
	foreach ($items as $index => $item) {
		if ($item->title == 'Brands' || $item->post_name == 'Brands' || $item->object_id == '21') {
			$parent_item = $item;
			$parent_item_index = $index;
			break;
		}
	}
	//没有找到目标菜单就直接返回
	if (!$parent_item) {
	    return $items;
	}
 
	//获取所有brand文章，如果没有文章，直接返回
	$brand_posts = get_posts(array(
		'post_type' => 'brand',
		'numberposts' => -1,
		'orderby' => 'menu_order title',
		'order' => 'ASC',
		'post_status' => 'publish',
		'suppress_filters' => 0
	));
 
	//没有brand文章直接返回
	if (empty($brand_posts)) {
		return $items;
	}
 
	//为父菜单项添加‘has-children’类，有时候我们需要给父菜单以以样式区别
	if (!in_array('menu-item-has-children', $parent_item->classes)) {
		$parent_item->classes[] = 'menu-item-has-children';
		$items[$parent_item_index] = $parent_item;
	}
 
	//获取当前最大菜单项ID，并且加上一个大数字，这样新生成的菜单项的id不会和已有的重复
	$max_db_id = 0;
	foreach ($items as $item) {
		if ($item->db_id > $max_db_id) {
			$max_db_id = $item->db_id;
		}
	}
	$max_db_id+=100000;
 
	//开始为输出的对象添加内容，我们可以通过参数列表的classes参数定义特殊样式，也可以自定义target、description等输出内容作为特殊使用，以下列表应该已经列出了所有可能用得到的菜单输出项
	$new_items = array();
	$current_order = count($items) + 1;
	foreach ($brand_posts as $post) {
		$max_db_id++;//确保ID唯一
 
		//创建新的菜单项对象
		$new_item = new stdClass();
		$new_item->ID = $max_db_id;
		$new_item->db_id = $max_db_id;
		$new_item->title = $post->post_title;
		$new_item->url = get_permalink($post->ID);
		$new_item->menu_order = $current_order++;
		$new_item->menu_item_parent = $parent_item->ID;
		$new_item->type = 'post_type';
		$new_item->object = 'brand';
		$new_item->object_id = $post->ID;
		$new_item->classes = array('menu-brand-'.$post->ID, 'menu-brand-item');
		$new_item->target = '';
		$new_item->attr_title = '';
		$new_item->description = '';
		$new_item->xfn = '';
		$new_item->status = 'publish';
		$new_item->post_type = 'nav_menu_item';
		$new_item->post_status = 'publish';
		$new_item->post_name = 'brand-' . $post->post_name;
		$new_item->current = false;
		$new_item->current_item_ancestor = false;
		$new_item->current_item_parent = false;
		$new_items[] = $new_item;
	}
 
	//将新增加的菜单项插入到已指定的父菜单项之后
	$final_items = array();
	foreach ($items as $item) {
		$final_items[] = $item;
		if ($item->ID == $parent_item->ID) {
			//在父菜单项后插入所有子菜单项
			foreach ($new_items as $new_item) {
				$final_items[] = $new_item;
			}
		}
	}
 
	return $final_items;
}
add_filter('wp_nav_menu_objects', 'brain1981_add_posts_to_menu', 10, 2);