package proxy;

/**
 * Virtual Proxy — delays creating the RealDatabaseConnection until
 * the first actual query is made. If no query is ever made (e.g.,
 * the service is initialized but never used in this request),
 * the expensive connection is never opened.
 *
 * This is exactly how Hibernate proxies work: entities are not
 * loaded from the database until you access a field on them.
 */
public class LazyConnectionProxy implements DatabaseConnection {

    private final String url;
    private RealDatabaseConnection real;  // null until first use

    public LazyConnectionProxy(String url) {
        this.url = url;
        System.out.println("[Proxy] Created for " + url + " (real connection NOT opened yet)");
    }

    // Lazy initialization — create and connect only on first real need
    private void initIfNeeded() {
        if (real == null) {
            System.out.println("[Proxy] First access — initializing real connection...");
            real = new RealDatabaseConnection(url);
            real.connect();
        }
    }

    @Override
    public void connect() {
        // Proxy absorbs the connect() call — real connection opened lazily
        System.out.println("[Proxy] connect() called — deferring to first query");
    }

    @Override
    public String executeQuery(String sql) {
        initIfNeeded();  // NOW we actually need the connection
        return real.executeQuery(sql);
    }

    @Override
    public void disconnect() {
        if (real != null) {
            real.disconnect();
            real = null;
        } else {
            System.out.println("[Proxy] disconnect() called but connection was never opened");
        }
    }
}