package observer;

/**
 * Observer Design Pattern — Runnable Demo
 * Run: javac observer/*.java -d out/observer && java -cp out/observer observer.Main
 * Article: https://ankurm.com/observer-design-pattern-java/
 */
public class Main {
    public static void main(String[] args) {
        System.out.println("=== Observer Design Pattern Demo ===\n");

        StockMarket aapl = new StockMarket("AAPL", 175.00);

        StockObserver alert    = new AlertObserver("RiskEngine", 2.0);
        StockObserver alice    = new PortfolioObserver("Alice", 100);
        StockObserver bob      = new PortfolioObserver("Bob", 50);

        aapl.subscribe(alert);
        aapl.subscribe(alice);
        aapl.subscribe(bob);

        System.out.println();
        aapl.setPrice(178.50);  // +2% — should trigger alert

        System.out.println();
        aapl.setPrice(179.00);  // small move

        System.out.println("\n-- Bob unsubscribes --");
        aapl.unsubscribe(bob);

        System.out.println();
        aapl.setPrice(165.00);  // big drop — Bob doesn't hear it

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