Drupal 8 - PHP - Set and Truncate Title tag and meta tag head items in Drupal 8

Drupal 8 - Set and Truncate Title tag and meta tag head items in Drupal 8

/**
 * Gets a title from the field_headline first and falls back on the node
 * title, then truncates the site name (/admin/config/system/site-information).
 * - Stays under 58 characters, as that is best for SEO
 * - Used for <title> and <meta name="title" content="xxxxxx">.
 * - Will truncate the page title, and always add the full ' | site-name'.
 * - Example output: <meta name="title" content="Homepage | MyCompany, Inc.">
 * @param  string $raw_title
 * @param  string $site_name
 * @return string truncated and joined title string up to 58 characters
 */
function _get_perfect_meta_title() {
    $node = \Drupal::routeMatch()->getParameter('node');
    $meta_title = _get_meta_title($node);
    $site_name = ' | ' . \Drupal::config('system.site')->get('name');
    $truncated_title = _get_truncated_title($meta_title, $site_name);
    return $truncated_title . $site_name;
}

/**
 * Gets the field_headline from the hero on the node
 * or uses the node title as backup
 * @param  object $node
 * @return string raw title for the page
 */
function _get_meta_title($node) {
    if($node) {
        // we have a node, so use headline in hero, or fall back to node title
        if($node->field_hero_section && $node->field_hero_section->getValue() && $node->field_hero_section->getValue()[0]) {
            $paragraph = $node->field_hero_section->getValue()[0];
            $paragraph_entity = \Drupal\paragraphs\Entity\Paragraph::load( $paragraph['target_id'] );
            return $paragraph_entity->field_headline->value;
        } else {
            return $node->getTitle();
        }
    } elseif ($non_node_request = \Drupal::request()->get('contact_form')) {
        // we have a contact form, so use the contact form title
        return $non_node_request->label();
    } else {
        // not node or contact form, so use the site slogan
        // set here: /admin/config/system/site-information?q=/admin/config/system/site-information
        return \Drupal::config('system.site')->get('slogan');
    }
}

/**
 * Truncates the title to be up to 58 characters (including the site-name)
 * @param  string $raw_title
 * @param  string $site_name
 * @return string truncated title with room left for the site name
 */
function _get_truncated_title($raw_title, $site_name) {
    $title_limit = 58;
    $title_length = strlen($raw_title);
    $suffix_length = strlen($site_name);
    $allowable_length = $title_limit - $suffix_length;
    $allowable_length_w_ellipse = $allowable_length - 3;
    // truncate <title> to 58 characters minus the suffix length
    return $title_length > $allowable_length ? substr($raw_title, 0, $allowable_length_w_ellipse) . '...' : $raw_title;
}

preprocessing.php

function mytheme_preprocess_html(&$variables) {
    $full_fixed_title = _get_perfect_meta_title();

    // Get best <title> from field_headline and if not, from node title
    $variables['head_title']['title'] = $full_fixed_title;

    // Loop through the <meta /> and <link /> tags
    foreach($variables['page']['#attached']['html_head'] as &$head_item) {
        switch ($head_item[1]) {
            case 'title':
            // Get best <meta name="title" content="xxxxxx"> from field_headline and
            // if not, from node title.
            $head_item[0]['#attributes']['content'] = $full_fixed_title;
            break;
        }
    }
}