package proxy;

/**
 * Proxy Design Pattern — Runnable Demo
 *
 * Shows two proxy types:
 *  1. Virtual Proxy (lazy connection)
 *  2. Logging Proxy (cross-cutting concern)
 *  3. Proxy chaining (both together)
 *
 * Run: javac proxy/*.java && java proxy.Main
 * Article: https://ankurm.com/proxy-design-pattern-java/
 */
public class Main {

    public static void main(String[] args) throws InterruptedException {
        System.out.println("=== Proxy Design Pattern Demo ===\n");

        // --- Virtual Proxy: lazy connection ---
        System.out.println("-- Virtual Proxy (lazy loading) --");
        DatabaseConnection lazy = new LazyConnectionProxy("jdbc:postgresql://localhost/mydb");
        lazy.connect();  // absorbed by proxy, no real connection yet
        System.out.println("(no real connection yet — saved startup time)");
        System.out.println("Result: " + lazy.executeQuery("SELECT * FROM users WHERE id=1"));
        System.out.println("Result: " + lazy.executeQuery("SELECT COUNT(*) FROM orders"));
        lazy.disconnect();

        System.out.println();

        // --- Logging Proxy: wraps the real connection ---
        System.out.println("-- Logging Proxy --");
        DatabaseConnection real = new RealDatabaseConnection("jdbc:mysql://localhost/shopdb");
        real.connect();
        DatabaseConnection logged = new LoggingProxy(real);
        logged.executeQuery("SELECT * FROM products LIMIT 10");
        logged.disconnect();

        System.out.println();

        // --- Proxy chaining: lazy + logging ---
        System.out.println("-- Chained Proxies: Lazy + Logging --");
        DatabaseConnection chain =
            new LoggingProxy(
                new LazyConnectionProxy("jdbc:oracle://localhost/warehouse"));
        chain.connect();
        chain.executeQuery("SELECT SUM(quantity) FROM inventory");
        chain.disconnect();

        System.out.println("\n=== Demo complete ===");
    }
}