function your_theme_enqueue_scripts() {
    wp_enqueue_script('jquery');
    // Add here any other scripts you need to enqueue
}

add_action('wp_enqueue_scripts', 'your_theme_enqueue_scripts');

function load_filtered_cats() {
    // Security check
    if (!check_ajax_referer('load_cats_nonce', 'nonce', false)) {
        wp_send_json_error('Invalid nonce', 400);
    }

    $categoryId = isset($_POST['categoryId']) ? intval($_POST['categoryId']) : 0;

    $args = [
        'taxonomy'   => 'product_cat',
        'hide_empty' => false,
        // Include or exclude parent categories as needed
    ];

    // Apply parent filtering only if a specific category ID is provided
    if ($categoryId > 0) {
        $args['parent'] = $categoryId;
    } else {
        // Exclude top-level categories if looking for all child categories initially
        // Remove the 'exclude' line if you also want top-level categories included initially
        $args['exclude'] = get_terms(['taxonomy' => 'product_cat', 'parent' => 0, 'fields' => 'ids']);
    }

    $categories = get_terms($args);
    $sorted_categories = [];

    // Sorting and grouping categories
    foreach ($categories as $category) {
        $products_in_category = new WP_Query([
            'post_type' => 'product',
            'posts_per_page' => -1,
            'tax_query' => [[
                'taxonomy' => 'product_cat',
                'field' => 'id',
                'terms' => $category->term_id,
            ]],
            'meta_query' => [[
                'key' => '_stock_status',
                'value' => 'instock',
            ]],
        ]);

        if ($products_in_category->have_posts()) {
            $first_letter = strtoupper(substr($category->name, 0, 1));
            $sorted_categories[$first_letter][] = $category;
        }
    }

    // Sort categories within each group alphabetically
    foreach ($sorted_categories as &$categories_group) {
        usort($categories_group, function($a, $b) {
            return strcmp($a->name, $b->name);
        });
    }

    // Sort groups by their starting letter
    ksort($sorted_categories);

// Output the sorted and grouped categories
foreach ($sorted_categories as $letter => $categories_group) {
    echo "<div class='category-group'><h2>" . $letter . "</h2><p class='category-count'>" . count($categories_group) . " marcas</p><hr>";
    foreach ($categories_group as $category) {
        echo '<a href="' . get_term_link($category) . '" class="category-button">' . esc_html($category->name) . '</a>';
    }
    echo "</div>"; // Close the category-group div
}

    wp_die(); // Terminate AJAX request correctly
}

add_action('wp_ajax_load_filtered_cats', 'load_filtered_cats');
add_action('wp_ajax_nopriv_load_filtered_cats', 'load_filtered_cats');