import java.time.LocalDateTime;
import java.util.concurrent.ArrayBlockingQueue;

class BarberShop {
    private ArrayBlockingQueue<Customer> waitingSeats;
    private int haircutTime;

    BarberShop(int waitingRoomCapacity, int haircutTimeSeconds) {
        waitingSeats = new ArrayBlockingQueue<Customer>(waitingRoomCapacity);
        haircutTime = haircutTimeSeconds;
    }

    // as customers enter the shop, they seat themselves in the queue until
    // they are next in line, if the barber is sleeping they have to wake him up
    // they can only enter one by one in this implementation
    void enterShop() throws InterruptedException {
        Customer customer = (Customer) Thread.currentThread();
        LocalDateTime dt = LocalDateTime.now();
        System.out.println(customer.getName() + " arrived at " + dt.getHour() + ":" + dt.getMinute() + ":" + dt.getSecond() + ".");
        if (waitingSeats.remainingCapacity() > 0) {
            waitingSeats.offer(customer);
        } else {
            System.out.println("No more free seats in the waiting room, " + customer.getName() + " left.");
        }
        // when the customer arrives he wakes up the barber
        // if the barber is cutting hair he waits in line - nothing happens here
        synchronized (this) {
            notifyAll();
        }
    }

    // this method is called by the barber thread, where he serves customers
    // waiting in the queue, if there are none, he falls asleep
    synchronized void work() throws InterruptedException {
        System.out.println("Barber starts his shift.");

        // this loop is here to ensure, that after all customers are served,
        // the barber can fall asleep and then be woken up again.
        while (true) {
            while (waitingSeats.size() == 0) {
                System.out.println("Baber is sleeping in his chair...");
                wait();
            }

            serveCustomers();
        }
    }

    // this method ensures that barber doesn't fall asleep while there are
    // customers waiting in the queue
    private void serveCustomers() throws InterruptedException {
        System.out.println(waitingSeats.peek().getName() + " wakes up the barber.");

        while (!waitingSeats.isEmpty()) {
            // barber 'calls' a customer to get a haircut
            // - removes him from the queue
            waitingSeats.poll().sitInBarbersChair();
        }
    }

    // this method is called by a customer that was 'called' by the barber
    synchronized void getHaircut(Customer customer) throws InterruptedException {
        String name = customer.getName();

        System.out.println("The barber is cutting " + name + "'s hair...");
        cutHair();
        System.out.println(name + "'s hair is done.");
    }

    // timeout to get a better understanding how the program runs
    private void cutHair() throws InterruptedException {
        Thread.sleep(haircutTime * 1000);
    }
}