import java.util.HashMap;
import java.util.Map;

/**
 * {@link <a href=
 * "https://[Log in to view URL]"
 * target= "_blank"></a>}
 * 
 * @author itammb ( Italia Massimiliano Buscati )
 * @version JDK 1.15
 *
 */
class Main {

	public interface ServiceInterface {
		String getUserData(String userId);
	}

	public static class UserServiceProxy implements ServiceInterface {

		private final ServiceInterface realUserService;
		private final Map<String, String> cache = new HashMap<>();

		public UserServiceProxy(ServiceInterface realUserService) {
			this.realUserService = realUserService;
		}

		@Override
		public String getUserData(String userId) {
			// query logica
			if (cache.containsKey(userId)) {
				System.out.println("Retrieved from cache: " + userId);

				return cache.get(userId);
			}

			// query fisica
			String data = realUserService.getUserData(userId);
			cache.put(userId, data);
			System.out.println("Fetched from database and cached: " + userId);
			return data;
		}
	}

	public static class RealUserService implements ServiceInterface {

		@Override
		public String getUserData(String userId) {
			// Simulate a slow database query
			try {
				Thread.sleep(2000);
				// 2-second delay } catch
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			return "Data for user: " + userId;
		}
	}

	public static void main(String args[]) {
		// Unit test - uso del design pattern: proxy
		ServiceInterface realUserService = new RealUserService();
		ServiceInterface proxy = new UserServiceProxy(realUserService);

		System.out.println(proxy.getUserData("user1")); // dalla cache
		System.out.println(proxy.getUserData("user2")); // dal database
		System.out.println(proxy.getUserData("user2")); // dalla cache
	}
}