<?php

/**
 * Adds a taxonomy to the native 'post' object type.
 *
 * Also adds a rewrite endpoint to test the issue. Visiting any posts URL with
 * the taxonomy slug segment prepended will trigger output of the custom
 * taxonomy's terms assigned to the post; best to view page source.
 *
 * @link https://wordpress.org/support/topic/turning-off-frontend-actions-and-filter
 */
class OrgSupportTopic862744
{
    const TAXONOMY_SLUG = 'mytax';
    const OBJECT_TYPE = 'post';
    const PERMASTRUCT_TYPE = EP_ALL;
    const TEMPLATE_FILE = 'org-862744.php';

    const TAXONOMY_HOOK_PRIORITY = 11;
    const TEMPLAGE_HOOK_PRIORITY = 99;

    public function __construct()
    {
        $this->_construct();
    }

    protected function _construct()
    {

    }

    public function init()
    {
        $this->_hook();
    }

    protected function _hook()
    {
        $me = $this;
        add_action('init', function() use ($me) {
            $me->_registerTaxonomy();
        }, static::TAXONOMY_HOOK_PRIORITY);

    }

    public function _registerTaxonomy()
    {
        register_taxonomy(static::TAXONOMY_SLUG, static::OBJECT_TYPE, array(
            'label'             => 'My Tax',
            'hierarchical'      => true
        ));

        var_dump(static::PERMASTRUCT_TYPE);
        add_rewrite_endpoint(static::TAXONOMY_SLUG, static::PERMASTRUCT_TYPE);
        flush_rewrite_rules();

        add_filter('template_include', array($this, '_overrideTemplate'), static::TEMPLAGE_HOOK_PRIORITY);
    }

    public function generateTermList($objectId)
    {
        return get_the_term_list($objectId, static::TAXONOMY_SLUG);
    }

    public function _overrideTemplate($template)
    {
        global $wp_query;
        if ($this->_getQueryVar(static::TAXONOMY_SLUG) !== null && ($objectId = get_post()->ID)) {
            echo $this->generateTermList($objectId);
        }

        return $template;
//        return $this->_locateTemplateFile(static::TEMPLATE_FILE);
    }

    protected function _locateTemplateFile($files)
    {
        if (!is_array($files)) {
            $files = array($files);
        }

        return strlen($path = locate_template($files, false))
                ? $path
                : null;
    }

    protected function _getQueryVar($key)
    {
        return get_query_var($key, null);
    }
}

/**
 * @staticvar type $instance
 * @return \OrgSupportTopic862744
 * @link https://wordpress.org/support/topic/turning-off-frontend-actions-and-filter
 */
function orgSupportTopic862744()
{
    static $instance = null;

    if (is_null($instance)) {
        $instance = new OrgSupportTopic862744();
        $instance->init();
    }

    return $instance;
}