Work CPT

<?php
/*
Plugin Name: Work post type
Description: Plugin for Work custom post type
Author: Luis Abarca
Author Uri: http://luisabarca.com
*/

$product = Work::instance();


class Work {
    const CUSTOM_TYPE_NAME = 'work';
    const TAXONOMY_NAME = 'work_category';
    private static $instance;

    /***************************************************************************
     * Static functions
     **************************************************************************/
    public static function instance () {

        if ( ! isset( self::$instance ) ) {
            $class_name = __CLASS__;
            self::$instance = new $class_name;
        }

        return self::$instance;

    }

    private function __construct()
    {
        add_action('init', array($this, 'register_custom_types') );
        add_filter('post_type_link', array($this, 'custom_permalinks'), 1, 3);

        register_activation_hook(__FILE__, array($this, 'activate') );
        register_deactivation_hook(__FILE__, array($this, 'deactivate') );

    }

    /*
     *
     */
    public function custom_permalinks($url, $post = null, $leavename = false)
    {
        // products only
        if ($post->post_type != self::CUSTOM_TYPE_NAME) {
            return $url;
        }

        $post_id = $post->ID;

        $taxonomy = self::TAXONOMY_NAME;
        $taxonomy_tag = '%' . $taxonomy . '%';

        // Check if exists the product type tag
        if (strpos($taxonomy_tag, $url) < 0) {
            // replace taxonomy tag
            $url = str_replace($taxonomy_tag, '', $url);
        } else {
            // Get the terms
            $terms = wp_get_post_terms($post_id, $taxonomy);

            if (is_array($terms) && sizeof($terms) > 0) {
                $category = $terms[0];
                // replace taxonomy tag with the term slug
                $url = str_replace($taxonomy_tag, $category->slug, $url);
            }
        }

        return $url;
    }


    /*
     *
     *
     */
    public function register_custom_types()
    {
        global $wp_rewrite;
        global $wp_query;

        register_post_type(self::CUSTOM_TYPE_NAME, array(
            'label'           => 'Works',
            'description'     => '',
            'public'          => true,
            'show_ui'         => true,
            'show_in_menu'    => true,
            'capability_type' => 'post',
            'hierarchical'    => true,
            'rewrite'         => array('slug' => self::CUSTOM_TYPE_NAME),
            'query_var'       => true,
            'has_archive'     => true,
            'menu_position'   => 6,
            'supports'        => array( 'title', 'editor', 'excerpt', 'trackbacks', 'revisions', 'thumbnail', 'author' ),
            'labels'          => array(
                'name'               => 'Works',
                'singular_name'      => 'Work',
                'menu_name'          => 'Works',
                'add_new'            => 'Add Work',
                'add_new_item'       => 'Add New Work',
                'edit'               => 'Edit',
                'edit_item'          => 'Edit Work',
                'new_item'           => 'New Work',
                'view'               => 'View Work',
                'view_item'          => 'View Work',
                'search_items'       => 'Search Works',
                'parent'             => 'Parent Work')
            )
        );

        register_taxonomy(self::TAXONOMY_NAME, self::CUSTOM_TYPE_NAME, array(
            'hierarchical'   => true,
            'label'          => 'Work categories',
            'show_ui'        => true,
            'query_var'      => true,
            'rewrite'        => array('slug' => self::CUSTOM_TYPE_NAME . '/' . self::TAXONOMY_NAME),
            'singular_label' => 'Work Category')
        );

        $wp_rewrite->extra_permastructs[self::CUSTOM_TYPE_NAME][0] = '/' . self::CUSTOM_TYPE_NAME . '/%' . self::TAXONOMY_NAME . '%/%' . self::CUSTOM_TYPE_NAME . '%';


    }


    /**
     *
     */
    public function activate()
    {
        self::register_custom_types();
        flush_rewrite_rules();
    }

    // }}}
    // {{{

    /**
     *
     */
    public function deactivate()
    {
        flush_rewrite_rules();
    }

}