package com.interview.design.pattern.j2ee;

/**
 * Created_By: stefanie
 * Date: 14-12-3
 * Time: 下午6:22
 *
 * The front controller design pattern is used to provide a centralized request handling mechanism
 * so that all requests will be handled by a single handler.
 * This handler can do the authentication/ authorization/ logging or tracking of request and then pass the requests
 * to corresponding handlers.
 *
 * Following are the entities of this type of design pattern.
 * Front Controller - Single handler for all kind of request coming to the application (either web based/ desktop based).
 * Dispatcher - Front Controller may use a dispatcher object which can dispatch the request to corresponding specific handler.
 * View - Views are the object for which the requests are made.
 */
public class FrontControlPattern {
    static class HomeView {
        public void show(){
            System.out.println("Displaying Home Page");
        }
    }

    static class StudentView {
        public void show(){
            System.out.println("Displaying Student Page");
        }
    }

    static class Dispatcher {
        private StudentView studentView;
        private HomeView homeView;
        public Dispatcher(){
            studentView = new StudentView();
            homeView = new HomeView();
        }

        public void dispatch(String request){
            if(request.equalsIgnoreCase("STUDENT")){
                studentView.show();
            }else{
                homeView.show();
            }
        }
    }

    static class FrontController {

        private Dispatcher dispatcher;

        public FrontController(){
            dispatcher = new Dispatcher();
        }

        private boolean isAuthenticUser(){
            System.out.println("User is authenticated successfully.");
            return true;
        }

        private void trackRequest(String request){
            System.out.println("Page requested: " + request);
        }

        public void dispatchRequest(String request){
            //log each request
            trackRequest(request);
            //authenticate the user
            if(isAuthenticUser()){
                dispatcher.dispatch(request);
            }
        }
    }

    public static void main(String[] args) {
        FrontController frontController = new FrontController();
        frontController.dispatchRequest("HOME");
        frontController.dispatchRequest("STUDENT");
    }
}