add_action('template_redirect', function () {
    if (!is_user_logged_in()) return;

    $current_user_id = get_current_user_id();
    $current_user    = get_userdata($current_user_id);
    $current_email   = $current_user->user_email ?? '';
    if (!$current_email) return;

    $all_keys = [];

    // Step 1: Collect all mh_network_keys from every site’s wishlist
    foreach (get_sites(['number' => 0]) as $site) {
        switch_to_blog($site->blog_id);

        $sub_user = get_user_by('email', $current_email);
        if (!$sub_user) {
            restore_current_blog();
            continue;
        }

        $wishlist = get_user_meta($sub_user->ID, 'blc_products_wish_list', true);
        if (!is_array($wishlist) || empty($wishlist['items'])) {
            restore_current_blog();
            continue;
        }

        foreach ($wishlist['items'] as $item) {
            $pid = (int) ($item['id'] ?? 0);
            if (!$pid) continue;

            $key = get_post_meta($pid, '_mh_network_key', true);
            if ($key) {
                $all_keys[$key] = true; // collect only keys in wishlists
            }
        }

        restore_current_blog();
    }

    // Step 2: Apply union to each site
    foreach (get_sites(['number' => 0]) as $site) {
        switch_to_blog($site->blog_id);

        $sub_user = get_user_by('email', $current_email);
        if (!$sub_user) {
            restore_current_blog();
            continue;
        }

        // Build map only for products in all_keys
        $key_to_local_id = [];
        if ($all_keys) {
            $products = get_posts([
                'post_type'      => 'product',
                'posts_per_page' => -1,
                'post_status'    => 'publish',
                'meta_query'     => [[
                    'key'   => '_mh_network_key',
                    'value' => array_keys($all_keys), // only keys we care about
                    'compare' => 'IN',
                ]],
                'fields' => 'ids',
            ]);

            foreach ($products as $pid) {
                $key = get_post_meta($pid, '_mh_network_key', true);
                if ($key) {
                    $key_to_local_id[$key] = $pid;
                }
            }
        }

        $final_ids = [];
        foreach ($all_keys as $key => $_) {
            if (isset($key_to_local_id[$key])) {
                $final_ids[$key_to_local_id[$key]] = true;
            }
        }

        $new_wishlist = [
            'v'     => 2,
            'items' => array_map(fn($id) => ['id' => $id], array_keys($final_ids)),
        ];

        update_user_meta($sub_user->ID, 'blc_products_wish_list', $new_wishlist);

        restore_current_blog();
    }
});