Umbra-Bookshelf/umbra-bookshelf/includes/library/class-umbra-bookshelf-helper.php

<?php
// Copyright 2026 Umbra Tools (umbratools.com)
// SPDX-License-Identifier: GPL-2.0-or-later

/**
 * Main Plugin Class
 *
 * @package Umbra_Bookshelf_Helper
 */

if (!defined('ABSPATH')) {
    exit;
}

class Umbra_Bookshelf_Helper {
    private static $instance = null;

    /**
     * Get instance
     *
     * @return Umbra_Bookshelf_Helper
     */
    public static function instance() {
        if (null === self::$instance) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    /**
     * Constructor
     */
    private function __construct() {
        $this->init_hooks();
    }

    /**
     * Initialize hooks
     */
    private function init_hooks() {
        add_action('init', array($this, 'register_post_types'));
        add_action('init', array($this, 'register_taxonomies'));
        add_action('init', array($this, 'register_shortlinks'));
        add_action('init', array($this, 'register_shortcodes'));
        add_action('template_redirect', array($this, 'handle_shortlink_requests'));

        // Hook for future plugin integration
        add_filter('bdm_nav_menu_items', array($this, 'filter_series_menu_item'), 10, 2);

        if (is_admin()) {
            Umbra_Bookshelf_Helper_Admin::instance();
        }

        // Schedule cron jobs on init
        add_action('init', array($this, 'schedule_cron_events'));

        // Rating refresh is owned by Umbra_Rating_Sync (bd_bookshelf_sync_ratings),
        // which drives Umbra_Goodreads_Scraper. The former
        // bd_bookshelf_goodreads_refresh and bd_bookshelf_amazon_scrape hooks
        // pointed at empty stubs and have been removed.
    }

    /**
     * Register custom post type
     */
    public function register_post_types() {
        register_post_type('book', array(
            'labels' => array(
                'name'               => esc_html__('Books', 'umbra-bookshelf'),
                'singular_name'      => esc_html__('Book', 'umbra-bookshelf'),
                'add_new'            => esc_html__('Add New', 'umbra-bookshelf'),
                'add_new_item'       => esc_html__('Add New Book', 'umbra-bookshelf'),
                'edit_item'          => esc_html__('Edit Book', 'umbra-bookshelf'),
                'new_item'           => esc_html__('New Book', 'umbra-bookshelf'),
                'view_item'          => esc_html__('View Book', 'umbra-bookshelf'),
                'search_items'       => esc_html__('Search Books', 'umbra-bookshelf'),
                'not_found'          => esc_html__('No books found', 'umbra-bookshelf'),
                'not_found_in_trash' => esc_html__('No books found in trash', 'umbra-bookshelf'),
            ),
            'public'             => true,
            'has_archive'        => true,
            'show_in_menu'       => 'umbra-bookshelf',
            'supports'           => array('title', 'editor', 'thumbnail', 'excerpt', 'custom-fields'),
            'rewrite'            => array('slug' => 'book'),
            'menu_icon'          => 'dashicons-book-alt',
            'show_in_rest'       => true,
            'capability_type'    => 'post',
            'map_meta_cap'       => true,
        ));
    }

    /**
     * Register taxonomies
     */
    public function register_taxonomies() {
        register_taxonomy('series', 'book', array(
            'labels' => array(
                'name'              => esc_html__('Series', 'umbra-bookshelf'),
                'singular_name'     => esc_html__('Series', 'umbra-bookshelf'),
                'search_items'      => esc_html__('Search Series', 'umbra-bookshelf'),
                'all_items'         => esc_html__('All Series', 'umbra-bookshelf'),
                'edit_item'         => esc_html__('Edit Series', 'umbra-bookshelf'),
                'update_item'       => esc_html__('Update Series', 'umbra-bookshelf'),
                'add_new_item'      => esc_html__('Add New Series', 'umbra-bookshelf'),
                'new_item_name'     => esc_html__('New Series Name', 'umbra-bookshelf'),
                'not_found'         => esc_html__('No series found', 'umbra-bookshelf'),
            ),
            'hierarchical'      => true,
            'public'             => true,
            'show_admin_column'  => true,
            'rewrite'            => array('slug' => 'series'),
            'show_in_rest'       => true,
            'show_ui'            => true,
        ));
    }

    /**
     * Register rewrite rules for short links
     */
    public function register_shortlinks() {
        add_rewrite_rule('^([a-z0-9]{2,6})/?$', 'index.php?book_short_slug=$matches[1]', 'top');
        add_rewrite_rule('^([a-z0-9]{2,6})r([agbckpl])/?$', 'index.php?book_short_slug=$matches[1]&review_site=$matches[2]', 'top');
    }

    /**
     * Handle short link requests
     */
    public function handle_shortlink_requests() {
        $short_slug = get_query_var('book_short_slug');

        if (empty($short_slug)) {
            return;
        }

        global $wpdb;
        $book_id = $wpdb->get_var($wpdb->prepare(
            "SELECT post_id FROM {$wpdb->postmeta} WHERE meta_key = 'short_link_slug' AND meta_value = %s",
            $short_slug
        ));

        if ($book_id) {
            wp_redirect(get_permalink($book_id), 301);
            exit;
        }
    }

    /**
     * Filter series menu item visibility
     *
     * @param string $items Menu items HTML.
     * @param stdClass $args Menu args.
     * @return string
     */
    public function filter_series_menu_item($items, $args) {
        if ($args->theme_location !== 'primary') {
            return $items;
        }

        $series_count = self::series_count();
        if ($series_count > 0) {
            $series_item = '<li class="menu-item menu-item-type-taxonomy series-menu-item"><a href="' . home_url('/series/') . '">' . esc_html__('Series', 'umbra-bookshelf') . '</a></li>';

            if (preg_match('/(<li[^>]*>.*?Books.*?<\/li>)/s', $items, $matches)) {
                $books_item = $matches[1];
                $items = str_replace($books_item, $books_item . $series_item, $items);
            }
        }

        return $items;
    }

    /**
     * Schedule cron events
     *
     * Rating refresh is owned solely by Umbra_Rating_Sync, which schedules the
     * single 'bd_bookshelf_sync_ratings' event (every 12 hours) and drives the
     * one surviving scraper, Umbra_Goodreads_Scraper.
     *
     * The former 'bd_bookshelf_goodreads_refresh' (daily) and
     * 'bd_bookshelf_amazon_scrape' (six-hourly) events are no longer scheduled.
     * Both pointed at empty stub methods, so each tick only fired HTTP-free
     * no-ops -- and the Amazon one duplicated work the rating sync already did.
     * Existing installations still get them cleared on deactivation and on
     * uninstall, so no stale schedules are left behind.
     */
    public function schedule_cron_events() {
        // Intentionally empty: see the note above.
    }

    /**
     * Register shortcodes
     */
    public function register_shortcodes() {
        add_shortcode('bd-book', array($this, 'shortcode_book'));
        add_shortcode('bd-books', array($this, 'shortcode_books_list'));
    }

    /**
     * Shortcode: [bd-book]
     * Display single book by ID or title
     */
    public function shortcode_book($atts) {
        $atts = shortcode_atts(array(
            'book' => '',
        ), $atts);

        if (empty($atts['book'])) {
            return '<p class="bd-book-error">Please specify a book ID or title in the shortcode.</p>';
        }

        $book_id = intval($atts['book']);
        if ($book_id > 0) {
            $book = get_post($book_id);
        } else {
            $books = get_posts(array(
                'post_type' => 'book',
                'title'     => $atts['book'],
                'posts_per_page' => 1,
            ));
            $book = !empty($books) ? $books[0] : null;
        }

        if (!$book || 'book' !== $book->post_type) {
            return '<p class="bd-book-error">Book not found.</p>';
        }

        return $this->render_book_display($book);
    }

    /**
     * Shortcode: [bd-books]
     * Display all books in a list
     */
    public function shortcode_books_list($atts) {
        $atts = shortcode_atts(array(
            'limit' => -1,
            'order' => 'title',
        ), $atts);

        $books = get_posts(array(
            'post_type'      => 'book',
            'posts_per_page' => intval($atts['limit']),
            'post_status'    => 'publish',
            'orderby'        => 'title',
            'order'          => 'ASC',
        ));

        if (empty($books)) {
            return '<p class="bd-book-error">No books available.</p>';
        }

        $output = '<div class="bd-books-list">';
        foreach ($books as $book) {
            $output .= $this->render_book_display($book);
        }
        $output .= '</div>';

        return $output;
    }

    /**
     * Render book display HTML
     *
     * @param WP_Post $book Book post object.
     * @return string
     */
    private function render_book_display($book) {
        $cover_url = Umbra_Bookshelf_Helper::get_cover_url($book->ID, 'medium');
        $pen_name = Umbra_Bookshelf_Helper::get_pen_name($book->ID);
        $blurb = Umbra_Bookshelf_Helper::get_localized_blurb($book->ID);
        $links = Umbra_Bookshelf_Helper::get_retailer_links($book->ID);

        ob_start();
        ?>
        <div class="bd-book-listing">
            <div class="book-entry" style="display: flex; gap: 2rem; margin-bottom: 2rem; padding-bottom: 2rem; border-bottom: 1px solid #ccc;">
                <?php if ($cover_url): ?>
                <div class="book-cover" style="flex: 0 0 150px;">
                    <img src="<?php echo esc_url($cover_url); ?>" alt="<?php echo esc_attr($book->post_title); ?> Cover" style="width: 100%; max-width: 150px; height: auto; box-shadow: 0 4px 8px rgba(0,0,0,0.2);">
                </div>
                <?php endif; ?>
                <div class="book-details" style="flex: 1;">
                    <h2 style="margin-top: 0; margin-bottom: 0.5rem;"><?php echo esc_html($book->post_title); ?></h2>
                    <p style="margin: 0 0 1rem 0; color: #666;">by <?php echo esc_html($pen_name); ?></p>
                    <?php if ($blurb): ?>
                    <div class="book-description" style="margin-bottom: 1rem; padding: 1rem; border: 1px solid #e0e0e0; background: #f9f9f9; border-radius: 4px;">
                        <?php echo wp_kses_post(wp_trim_words($blurb, 50)); ?>
                    </div>
                    <?php endif; ?>
                    <?php if (!empty($links)): ?>
                    <div class="book-buttons" style="display: flex; gap: 1rem; flex-wrap: wrap;">
                        <?php foreach ($links as $link): ?>
                            <a href="<?php echo esc_url($link['url']); ?>" target="_blank" rel="noopener" class="bd-book-btn" style="background-color: #FF9900; color: #000; padding: 0.5rem 1rem; text-decoration: none; border-radius: 4px; font-weight: bold;"><?php echo esc_html($link['name']); ?></a>
                        <?php endforeach; ?>
                    </div>
                    <?php endif; ?>
                </div>
            </div>
        </div>
        <?php
        return ob_get_clean();
    }

    /**
     * Migrate books from BD Books plugin
     *
     * @return array Migration result
     */
    public static function migrate_from_bd_books() {
        global $wpdb;
        $old_table = $wpdb->prefix . 'bd_books';

        // Check if old table exists
        $table_exists = $wpdb->get_var("SHOW TABLES LIKE '$old_table'") === $old_table;
        if (!$table_exists) {
            return array('success' => false, 'message' => 'Old BD Books table not found.');
        }

        $old_books = $wpdb->get_results("SELECT * FROM {$old_table}");
        if (empty($old_books)) {
            return array('success' => true, 'message' => 'No books to migrate.', 'count' => 0);
        }

        $migrated = 0;

        foreach ($old_books as $old_book) {
            // Check if already migrated (by title)
            $existing = get_posts(array(
                'post_type' => 'book',
                'title'     => $old_book->title,
                'posts_per_page' => 1,
            ));

            if (!empty($existing)) {
                continue;
            }

            // Create new book post
            $post_id = wp_insert_post(array(
                'post_type'    => 'book',
                'post_title'   => sanitize_text_field($old_book->title),
                'post_content' => '',
                'post_status'  => 'publish',
                'post_author'  => get_current_user_id(),
                'post_date'    => $old_book->created_at,
            ));

            if (is_wp_error($post_id)) {
                continue;
            }

            // Set author/pen name
            if (!empty($old_book->author)) {
                // Try to find or create pen name
                global $wpdb;
                $pen_names_table = $wpdb->prefix . 'bd_pen_names';
                $pen_name_id = $wpdb->get_var($wpdb->prepare(
                    "SELECT id FROM {$pen_names_table} WHERE pen_name = %s",
                    $old_book->author
                ));

                if ($pen_name_id) {
                    update_post_meta($post_id, 'pen_name_id', $pen_name_id);
                } else {
                    // Insert new pen name
                    $wpdb->insert($pen_names_table, array(
                        'pen_name'   => sanitize_text_field($old_book->author),
                        'active'     => 1,
                        'created_at' => current_time('mysql'),
                    ));
                    $new_pen_id = $wpdb->insert_id;
                    if ($new_pen_id) {
                        update_post_meta($post_id, 'pen_name_id', $new_pen_id);
                    }
                }
            }

            // Set description/blurb
            if (!empty($old_book->description)) {
                update_post_meta($post_id, 'blurb_en', wp_kses_post($old_book->description));
            }

            // Set cover image
            if (!empty($old_book->cover_image_id)) {
                set_post_thumbnail($post_id, intval($old_book->cover_image_id));
            } elseif (!empty($old_book->cover_image_url)) {
                // Download and attach external image
                $attachment_id = self::import_external_image($old_book->cover_image_url, $old_book->title);
                if ($attachment_id) {
                    set_post_thumbnail($post_id, $attachment_id);
                }
            }

            // Parse and set purchase links
            $links = json_decode($old_book->purchase_links, true);
            if (!empty($links) && is_array($links)) {
                foreach ($links as $link) {
                    $label = isset($link['label']) ? strtolower($link['label']) : '';
                    $url = isset($link['url']) ? $link['url'] : '';

                    if (strpos($label, 'amazon') !== false) {
                        update_post_meta($post_id, 'ebook_url_amazon', esc_url_raw($url));
                    } elseif (strpos($label, 'apple') !== false) {
                        update_post_meta($post_id, 'ebook_url_apple', esc_url_raw($url));
                    } elseif (strpos($label, 'barnes') !== false || strpos($label, 'b&n') !== false) {
                        update_post_meta($post_id, 'ebook_url_barnes', esc_url_raw($url));
                    } elseif (strpos($label, 'kobo') !== false) {
                        update_post_meta($post_id, 'ebook_url_kobo', esc_url_raw($url));
                    } elseif (strpos($label, 'google') !== false) {
                        update_post_meta($post_id, 'ebook_url_google', esc_url_raw($url));
                    }
                }
            }

            $migrated++;
        }

        return array(
            'success' => true,
            'message' => sprintf('Migrated %d books.', $migrated),
            'count'   => $migrated,
        );
    }

    /**
     * Import external image as attachment
     *
     * @param string $url Image URL.
     * @param string $title Image title.
     * @return int|false Attachment ID
     */
    private static function import_external_image($url, $title) {
        require_once(ABSPATH . 'wp-admin/includes/file.php');
        require_once(ABSPATH . 'wp-admin/includes/media.php');
        require_once(ABSPATH . 'wp-admin/includes/image.php');

        $tmp = download_url($url);
        if (is_wp_error($tmp)) {
            return false;
        }

        $file_array = array(
            'name'     => sanitize_file_name($title) . '.jpg',
            'tmp_name' => $tmp,
        );

        $id = media_handle_sideload($file_array, 0, $title);
        @unlink($tmp);

        if (is_wp_error($id)) {
            return false;
        }

        return $id;
    }

    // =====================
    // Static Helper Methods
    // =====================

    /**
     * Get featured books
     *
     * @param int $limit Number of books to return.
     * @return array
     */
    public static function get_featured_books($limit = 5) {
        $query = new WP_Query(array(
            'post_type'      => 'book',
            'posts_per_page' => $limit,
            'post_status'    => 'publish',
            'orderby'        => 'meta_value',
            'meta_key'       => 'publish_date',
            'order'          => 'DESC',
        ));

        return $query->posts;
    }

    /**
     * Get cover URL for a book
     *
     * @param int    $book_id Book post ID.
     * @param string $size    Image size.
     * @param string $lang    Language code.
     * @return string
     */
    public static function get_cover_url($book_id, $size = 'thumbnail', $lang = 'en') {
        $meta_key = 'cover_' . $lang;
        $cover_id = get_post_meta($book_id, $meta_key, true);

        if (!$cover_id) {
            $cover_id = get_post_thumbnail_id($book_id);
        }

        if ($cover_id) {
            $image = wp_get_attachment_image_url($cover_id, $size);
            if ($image) {
                return $image;
            }
        }

        return UMBRA_BOOKSHELF_URL . 'assets/images/default-cover.png';
    }

    /**
     * Get book URL (short link)
     *
     * @param int $book_id Book post ID.
     * @return string
     */
    public static function get_book_url($book_id) {
        $slug = get_post_meta($book_id, 'short_link_slug', true);

        if ($slug) {
            return home_url('/' . $slug);
        }

        return get_permalink($book_id);
    }

    /**
     * Get ratings for a book
     *
     * @param int $book_id Book post ID.
     * @return array
     */
    public static function get_ratings($book_id) {
        $ratings = array();

        $amazon = get_post_meta($book_id, 'amazon_rating', true);
        if ($amazon) {
            $ratings['amazon'] = $amazon;
        }

        $goodreads = get_post_meta($book_id, 'goodreads_rating', true);
        if ($goodreads) {
            $ratings['goodreads'] = $goodreads;
        }

        return $ratings;
    }

    /**
     * Get retailer links for a book
     *
     * @param int    $book_id Book post ID.
     * @param string $format  Format (ebook, paperback, hardback).
     * @return array
     */
    public static function get_retailer_links($book_id, $format = 'ebook') {
        $links = array();

        $retailers = array(
            'amazon'  => array('name' => 'Amazon', 'base_url' => 'https://www.amazon.com/dp/'),
            'apple'   => array('name' => 'Apple Books', 'base_url' => 'https://books.apple.com/'),
            'barnes'  => array('name' => 'Barnes & Noble', 'base_url' => 'https://www.barnesandnoble.com/'),
            'kobo'    => array('name' => 'Kobo', 'base_url' => 'https://www.kobo.com/'),
            'google'  => array('name' => 'Google Play', 'base_url' => 'https://play.google.com/store/apps/details?id='),
        );

        $affiliates = get_option('bdm_affiliate_codes', array());

        foreach ($retailers as $key => $retailer) {
            $url_meta = $format . '_url_' . $key;
            $url = get_post_meta($book_id, $url_meta, true);

            if (!$url && $key === 'amazon') {
                $asin = get_post_meta($book_id, 'asin', true);
                if ($asin) {
                    $affiliate = isset($affiliates[$key]) ? $affiliates[$key] : '';
                    $url = $retailer['base_url'] . $asin . '?tag=' . $affiliate;
                }
            }

            if ($url) {
                $links[] = array(
                    'name'     => $retailer['name'],
                    'url'      => $url,
                    'retailer' => $key,
                );
            }
        }

        return $links;
    }

    /**
     * Display retailer links
     *
     * @param int    $book_id Book post ID.
     * @param string $format  Format.
     */
    public static function display_retailer_links($book_id, $format = 'ebook') {
        $links = self::get_retailer_links($book_id, $format);

        foreach ($links as $link) {
            printf(
                '<a href="%s" class="retailer-link retailer-%s" target="_blank" rel="noopener noreferrer">%s</a>',
                esc_url($link['url']),
                esc_attr($link['retailer']),
                esc_html($link['name'])
            );
        }
    }

    /**
     * Get localized title
     *
     * @param int    $book_id Book post ID.
     * @param string $lang   Language code.
     * @return string
     */
    public static function get_localized_title($book_id, $lang = 'en') {
        $title = get_post_meta($book_id, 'title_' . $lang, true);
        return $title ?: get_the_title($book_id);
    }

    /**
     * Get localized blurb
     *
     * @param int    $book_id Book post ID.
     * @param string $lang   Language code.
     * @return string
     */
    public static function get_localized_blurb($book_id, $lang = 'en') {
        return get_post_meta($book_id, 'blurb_' . $lang, true) ?: '';
    }

    /**
     * Get preview excerpt
     *
     * @param int    $book_id Book post ID.
     * @param string $lang   Language code.
     * @return string
     */
    public static function get_preview_excerpt($book_id, $lang = 'en') {
        return get_post_meta($book_id, 'preview_excerpt_' . $lang, true) ?: '';
    }

    /**
     * Get pull quotes
     *
     * @param int    $book_id Book post ID.
     * @param string $lang   Language code.
     * @return array
     */
    public static function get_pull_quotes($book_id, $lang = 'en') {
        $quotes = array();

        for ($i = 1; $i <= 5; $i++) {
            $quote = get_post_meta($book_id, 'pull_quote_' . $lang . '_' . $i, true);
            if ($quote) {
                $quotes[] = $quote;
            }
        }

        return $quotes;
    }

    /**
     * Get reviews for a book
     *
     * @param int $book_id Book post ID.
     * @return array
     */
    public static function get_reviews($book_id) {
        global $wpdb;
        $table_name = $wpdb->prefix . 'bd_reviews';

        $reviews = $wpdb->get_results($wpdb->prepare(
            "SELECT * FROM {$table_name} WHERE book_id = %d ORDER BY display_order ASC",
            $book_id
        ));

        return $reviews ?: array();
    }

    /**
     * Get pen name for a book
     *
     * @param int $book_id Book post ID.
     * @return string
     */
    public static function get_pen_name($book_id) {
        $pen_name_id = get_post_meta($book_id, 'pen_name_id', true);

        if ($pen_name_id) {
            global $wpdb;
            $table_name = $wpdb->prefix . 'bd_pen_names';

            $pen_name = $wpdb->get_var($wpdb->prepare(
                "SELECT pen_name FROM {$table_name} WHERE id = %d AND active = 1",
                $pen_name_id
            ));

            return $pen_name ?: 'B.D. Murphy';
        }

        return 'B.D. Murphy';
    }

    /**
     * Get series info for a book
     *
     * @param int $book_id Book post ID.
     * @return array|null
     */
    public static function get_series_info($book_id) {
        $terms = get_the_terms($book_id, 'series');

        if ($terms && !is_wp_error($terms)) {
            $series = $terms[0];
            $volume = get_post_meta($book_id, 'volume_number', true);

            return array(
                'id'     => $series->term_id,
                'name'   => $series->name,
                'slug'   => $series->slug,
                'volume' => $volume ?: 1,
            );
        }

        return null;
    }

    /**
     * Count series
     *
     * @return int
     */
    public static function series_count() {
        $terms = get_terms(array(
            'taxonomy'   => 'series',
            'hide_empty' => true,
            'fields'     => 'count',
        ));

        return $terms ?: 0;
    }

    /**
     * Get supported languages
     *
     * @return array
     */
    public static function get_supported_languages() {
        return array(
            'en' => 'English',
            'fr' => 'Français',
            'de' => 'Deutsch',
            'es' => 'Español',
            'it' => 'Italiano',
            'pt' => 'Português',
            'ru' => 'Русский',
            'ja' => '日本語',
            'zh' => '中文',
        );
    }

    /**
     * Get awards list
     *
     * @return array
     */
    public static function get_awards() {
        return get_option('bdm_awards', array());
    }

    /**
     * Generate SEO tags for a book
     *
     * @param int $book_id Book post ID.
     */
    public static function output_seo_tags($book_id) {
        $title = get_post_meta($book_id, 'seo_title', true) ?: get_the_title($book_id) . ' | ' . get_bloginfo('name');
        $description = get_post_meta($book_id, 'seo_description', true) ?: get_post_meta($book_id, 'blurb', true);

        if ($description) {
            $description = substr($description, 0, 160);
        }

        printf('<meta name="description" content="%s">' . "\n", esc_attr($description));
        printf('<meta property="og:title" content="%s">' . "\n", esc_attr($title));
        printf('<meta property="og:description" content="%s">' . "\n", esc_attr($description));
        printf('<meta property="og:type" content="book">' . "\n");
        printf('<meta name="twitter:card" content="summary_large_image">' . "\n");
    }

    /**
     * Generate schema.org data
     *
     * @param int $book_id Book post ID.
     * @return array
     */
    public static function generate_schema($book_id) {
        $book = get_post($book_id);

        $schema = array(
            '@context' => 'https://schema.org',
            '@type'    => 'Book',
            'name'     => $book->post_title,
            'author'   => array(
                '@type' => 'Person',
                'name'  => get_bloginfo('name'),
            ),
        );

        $asin = get_post_meta($book_id, 'asin', true);
        if ($asin) {
            $schema['isbn'] = $asin;
        }

        $cover_id = get_post_thumbnail_id($book_id);
        if ($cover_id) {
            $cover_url = wp_get_attachment_url($cover_id);
            $schema['image'] = $cover_url;
        }

        $blurb = get_post_meta($book_id, 'blurb', true);
        if ($blurb) {
            $schema['description'] = $blurb;
        }

        $series_term = get_the_terms($book_id, 'series');
        if ($series_term && !is_wp_error($series_term)) {
            $schema['isPartOf'] = array(
                '@type' => 'BookSeries',
                'name'  => $series_term[0]->name,
            );
        }

        return $schema;
    }
}