package Lab3;

import java.util.*;
import java.util.concurrent.Semaphore;

public class Exercise5 {

    static int waitingCustomers = 0;

    static Semaphore availableSeats = new Semaphore(5);
    static Semaphore lock = new Semaphore(1);
    static Semaphore work = new Semaphore(1);
    static Semaphore customerHere = new Semaphore(0);


    static class Customer extends Thread {
        String ID;

        public Customer(String ID) {
            this.ID = ID;
        }

        void customerComesIn() throws InterruptedException {
            // TODO: 3/29/20 Synchronize this method, invoked by a Customer thread
            if (waitingCustomers == 5) {
                System.out.println("No free seats for customer" + ID);
                return;
            }
            availableSeats.acquire();
            System.out.println("Customer " + ID + " coming in...");
            lock.acquire();
            waitingCustomers++;
            lock.release();
            customerHere.release();
        }

        @Override
        public void run() {
            try {
                customerComesIn();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    static class Barber extends Thread {
        public Barber() {
        }

        void barber() throws InterruptedException {
            // TODO: 3/29/20 Synchronize this method, invoked by Barber thread
            while (true) {
                customerHere.acquire();
                work.acquire();
                System.out.println("Haircut...");
                waitingCustomers--;
                work.release();
                availableSeats.release();
            }
        }

        @Override
        public void run() {
            try {
                barber();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        // TODO: 3/29/20 Synchronize the scenario
        Barber barber = new Barber();
        HashSet<Customer> customers = new HashSet<Customer>();

        for (int i = 0; i < 20; i++) {
            Customer c = new Customer(Integer.toString(i));
            customers.add(c);
        }

        for (Thread t : customers) {
            t.start();
        }

        barber.start();
    }
}