CPT with tax slug

cpt-with-tax-slug.php

<?php # -*- coding: utf-8 -*-
namespace CPTPermalinkDemo;
/**
 * Plugin Name: Custom post type with taxonomy permalink
 * Description:
 * Plugin URI:
 * Version:     2013.07.19
 * Author:      Thomas Scholz
 * Author URI:  http://toscho.de
 * Licence:     MIT
 * License URI: http://opensource.org/licenses/MIT
 * Textdomain:
 * Domain Path: /languages
 * Network:
 */

\add_action( 'init', array ( __NAMESPACE__ . '\Controller', 'init' ) );

class Controller {

	protected $post_type = 'product';
	protected $taxonomy  = 'color';

	public static function init()
	{
		static $instance = NULL;

		if ( NULL === $instance )
			$instance = new self;

		return $instance;
	}

	protected function __construct()
	{
		$permalink = new Permalink( $this->post_type, $this->taxonomy );
		\add_filter( 'post_type_link', array ( $permalink, 'filter_permalink' ), 10, 2 );

		$post_type = new Post_Type( $this->post_type, $this->taxonomy );
		$taxonomy  = new Taxonomy( $this->taxonomy, $this->post_type );
	}
}

class Post_Type
{
	protected $taxonomy;

	public function __construct( $post_type, $taxonomy )
	{
		$this->taxonomy = $taxonomy;

		\register_post_type( $post_type, $this->get_args( $post_type ) );
	}

	protected function get_args( $post_type )
	{
		$u = \ucfirst( $post_type );
		$l = \mb_strtolower( $post_type );

		return array (
			'can_export'           => TRUE,
			'description'          => '',
			'exclude_from_search'  => FALSE,
			'has_archive'          => TRUE,
			'hierarchical'         => FALSE,
			'labels'               => array (
				'add_new'            => 'Add new',
				'add_new_item'       => "Add new $l",
				'all_items'          => "All {$l}s",
				'edit_item'          => "Edit $l",
				'name'               => $u . 's',
				'name_admin_bar'     => $u,
				'new_item'           => "New $l",
				'not_found'          => "No {$l}s found.",
				'not_found_in_trash' => "No {$l}s in trash.",
				'parent_item_colon'  => "Parent $l:",
				'search_items'       => "Search {$l}s",
				'singular_name' => $u,
				'view_item'          => "View $l"
			),
			//'map_meta_cap'         => TRUE,
			'menu_icon'            => null,
			'menu_position'        => null,
			'permalink_epmask'     => EP_PERMALINK,
			'public'               => TRUE,
			'publicly_queryable'   => TRUE,
			'query_var'            => $l,
			// Use a translated slug in pretty permalinks
			'rewrite'              => array (
				//'slug'       => $l,
				'slug'       => "%$this->taxonomy%",
				'with_front' => FALSE
			),
			'show_in_nav_menus'    => TRUE,
			'show_in_menu'         => TRUE,
			'show_in_admin_bar'    => TRUE,
			'show_ui'              => TRUE,
			'supports'             => array(
				'author',
				'comments',
				'editor',
				'excerpt',
				'revisions',
				'thumbnail',
				'title',
			),
		);
	}
}

Unfortunately, GitHub cannot save the rest of the file as a Gist, so I had to put it into a comment.

class Taxonomy
{
    public function __construct( $taxonomy, $post_type )
    {
        \register_taxonomy( $taxonomy, array( $post_type ), $this->get_args( $taxonomy ) );
    }

    protected function get_args( $taxonomy )
    {
        $u = \ucfirst( $taxonomy );
        $l = \mb_strtolower( $taxonomy );
        return array(
            'hierarchical'          => TRUE,
            'public'                => TRUE,
            'query_var'             => $taxonomy,
            'rewrite'               => TRUE,
            'labels'                => array(
                'name'                       => $u . 's',
                'singular_name'              => $u,
                'search_items'               => "Search {$l}s",
                'popular_items'              => "Popular {$l}s",
                'all_items'                  => "All {$l}s",
                'parent_item'                => "Parent {$l}",
                'parent_item_colon'          => "Parent {$l}:",
                'edit_item'                  => "Edit $l",
                'view_item'                  => "View $l",
                'update_item'                => "Update $l",
                'add_new_item'               => "Add new $l",
                'new_item_name'              => "New $l name",
                'separate_items_with_commas' => "Separate {$l}s with commas",
                'add_or_remove_items'        => "Add or remove {$l}s",
                'choose_from_most_used'      => "Choose from the most used {$l}s",
            ),
            // make sure the oldest taxonomy will be used for the slug
            'sort'                  => TRUE,
            'show_admin_column'     => TRUE,
            'show_in_nav_menus'     => TRUE,
            'show_tagcloud'         => FALSE,
            'show_ui'               => TRUE,
            'update_count_callback' => '',
        );
    }
}

class Permalink
{
    protected $post_type;
    protected $taxonomy;

    public function __construct( $post_type, $taxonomy )
    {
        $this->post_type = $post_type;
        $this->taxonomy  = $taxonomy;
    }

    /**
     * Parse post link and replace the placeholder.
     *
     * @param   string $link
     * @param   object $post
     * @return  string
     */
    public function filter_permalink( $link, $post )
    {
        static $cache = array (); // Don't repeat yourself.

        if ( isset ( $cache[ $post->ID ] ) )
            return $cache[ $post->ID ];

        if ( $this->post_type !== $post->post_type )
        {
            echo "$this->post_type !== $post->post_type";
            $cache[ $post->ID ] = $link;
            return $link;
        }

        $cache[ $post->ID ] = $this->get_link_replacement( $link, $post );

        return $cache[ $post->ID ];
    }

    protected function get_link_replacement( $link, $post )
    {
        $term         = $this->get_post_term( $post->ID );
        $place_holder = "%$this->taxonomy%";

        if ( ! $term ) // insert a fallback value
            return \str_replace( $place_holder, $this->post_type, $link );

        return \str_replace( $place_holder, $term, $link );
    }

    /**
     * Get the slug of first assigned tag.
     *
     * Solution by Christopher Davis.
     * @link http://wordpress.stackexchange.com/a/72712
     *
     * @see   init()
     * @param int $id          Post ID
     * @return boolean|string  FALSE if no tags are found, the slug otherwise.
     */
    protected function get_post_term( $id )
    {
        $args = array ( 'orderby' => 'term_order' );
        $tags = \wp_get_object_terms( $id, $this->taxonomy, $args );

        if ( ! $tags )
            return FALSE;

        return \current( (array) $tags )->slug;
    }
}