package lab.util;

import java.util.ArrayList;
import java.util.List;

/**
 * A class for simulating a checkout line. A checkout line is a queue of customers.
 * 
 */
public class CheckoutLine {
  private Queue<Customer> queue;

  /**
   * Create a checkout line having an empty queue of customers.
   */
  public CheckoutLine() {
    
  	
  }

  /**
   * Returns true if there are customers in the checkout line , and false
   * otherwise.
   * 
   * @return true if there are customers in the checkout line, and false
   *         otherwise
   */
  public boolean hasCustomers() {
    
  	
  }

  /**
   * Returns the number of customers in the checkout line.
   * 
   * @return the number of customers in the checkout line
   */
  public int getNumberOfCustomers() {
    
  	
  }

  /**
   * Returns a reference to the customer currently at the front of the line
   * without removing the customer from the line.
   * Returns null if there are no customers in the line.
   * 
   * @return a reference to the customer currently at the front of the line, or
   *         null if there are no customers in the line
   */
  public Customer getCurrentCustomer() {
    
  	
  }

  /**
   * Add a customer to the back of the line.
   * 
   * @param c
   *          the customer to add to the back of the line
   * @pre. c != null
   */
  public void addCustomer(Customer c) {
    
  	
  }
  
  /**
   * Returns a list of this checkout line's queue of customers.
   * Modifying the returned list does not modify the queue of customers.
   * The state of this checkout line's queue of customers after
   * the method finishes is the same as when the method was invoked.
   * 
   * @return a list containing this checkout line's queue of customers
   */
  public List<Customer> getCustomersAsList() {
    
  	
  }

  /**
   * Process as many customers as possible starting from the front of the queue
   * given the current simulation time <code>currentTime</code>.
   * 
   * <p>
   * The default behaviour is to dequeue the first customer from the front
   * of the line ignoring the time. Subclasses should override this method
   * to process customers in the line given the current time.  
   * 
   * @param currentTime
   *          the current time in seconds of the simulation
   * @return the queue of customers that have been dequeued from this line
   *         during this update; the queue is empty if there are no customers
   *         in this line
   */
  public Queue<Customer> update(double currentTime) {
    Queue<Customer> processed = new Queue<Customer>();
    if (this.hasCustomers()) {
      processed.enqueue(this.queue.dequeue());
    }
    return processed;
  }

  /**
   * Provides access to the queue of customers for subclasses.
   * 
   * @return the queue of customers
   */
  protected Queue<Customer> getQueue() {
    return this.queue;
  }
}