function create_viber_chat_table() {
    global $wpdb;
    $table_name = $wpdb->prefix . 'viber_chat_messages';
    
    $charset_collate = $wpdb->get_charset_collate();
    
    $sql = "CREATE TABLE $table_name (
        id mediumint(9) NOT NULL AUTO_INCREMENT,
        sender varchar(255) NOT NULL,
        message text NOT NULL,
        sent_at datetime DEFAULT CURRENT_TIMESTAMP NOT NULL,
        PRIMARY KEY  (id)
    ) $charset_collate;";
    
    require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
    dbDelta($sql);
}
register_activation_hook(__FILE__, 'create_viber_chat_table');