class Walker_Nav_Menu_Edit_Custom_Fields extends Walker_Nav_Menu_Edit {

	/**
	 * Start the element output.
	 *
	 * @see Walker_Nav_Menu_Edit::start_el()
	 *
	 * @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.
	 * @param array $args
	 */
	public function start_el( &$output, $item, $depth = 0, $args = array() ) {
		$item_output = '';
		parent::start_el( $item_output, $item, $depth, $args );
		$output .= preg_replace( '/(<p[^>]+class="[^"]*field-description(?:.|\n)*?<\/p>)/', "$1 \r\n " . $this->get_custom_fields( $item, $depth, $args ), $item_output, 1 );
	}

	/**
	 * Get custom fields
	 *
	 * @uses do_action() Calls 'menu_item_custom_fields' hook
	 *
	 * @param object $item Menu item data object.
	 * @param int $depth Depth of menu item. Used for padding.
	 * @param array $args Menu item args.
	 *
	 * @return string Additional fields or html for the nav menu editor.
	 */
	protected function get_custom_fields( $item, $depth, $args = array() ) {
		ob_start();
		$item_id = intval( $item->ID );
		/**
		 * Get menu item custom fields from plugins/themes
		 *
		 * @param int $item_id post ID of menu
		 * @param object $item Menu item data object.
		 * @param int $depth Depth of menu item. Used for padding.
		 * @param array $args Menu item args.
		 *
		 * @return string Custom fields
		 */
		do_action( 'wp_nav_menu_item_custom_fields', $item_id, $item, $depth, $args );

		return ob_get_clean();
	}
}