import java.util.*;
public class Elevator {
	public static final int IDLE = 0;
	public static final int BUSY = 1;
	public static final double TIME_BETWEEN_FLOORS = 10.0; //Time to travel to adjacent floor is 10.0 seconds
	
	private int currentFloor;
	private ArrayList<Person> passengers;
	private int status;
	private int requestsServed;
	
	public Elevator() {
		setCurrentFloor(1); //All elevators are initially on ground floor
		passengers = new ArrayList<Person>();
		setIdle(); //All elevators are initially idle
		requestsServed = 0;
	}
	
	public void setCurrentFloor(int floor) {
		currentFloor = floor;
	}
	
	public int getCurrentFloor() {
		return currentFloor;
	}

	public void setIdle() {
		status = IDLE;
	}
	
	public void setBusy() {
		status = BUSY;
	}
	
	public boolean isIdle() {
		if (status == IDLE) {
			return true;
		} else {
			return false;
		}
	}
	
	public void incrementRequestsServed() {
		requestsServed++;
	}
	
	public int getRequestsServed() {
		return requestsServed;
	}

	/**
	 * Loads passengers into the elevator.
	 * The pasengers are stored in order of increasing destination floor.
	 *
	 * @param newPassengers the list of people getting on the elevator
	 */
	public void load(ArrayList<Person> newPassengers) {
		for (Person person : newPassengers) {
			int i = 0;
			while (i < passengers.size()) {
				if (person.getDestination() < passengers.get(i).getDestination()) {
					break;
				} else {
					i++;
				}
			}
			passengers.add(i, person);
		}
	}
	
	/**
	 * Unloads passengers from the elevator.
	 *
	 * @return the list of people getting off the elevator
	 */
	public ArrayList<Person> unload() {
		ArrayList<Person> exitingPassengers = new ArrayList<Person>();
		/*
		Since the passengers are already ordered by increasing destination floor,
		keep popping off the passenger at the head of the list until reaching a
		passenger whose destination floor is not the elevator's current floor.
		*/
		for (int i = 0; i < passengers.size(); i++) {
			if (passengers.get(i).getDestination() == currentFloor) {
				exitingPassengers.add(passengers.get(i));
			}
		}
		passengers.removeAll(exitingPassengers);
		return exitingPassengers;
	}
	
	/**
	 * This method checks if the elevator currently contains any passengers.
	 *
	 * @return true if the elevator is empty, false otherwise
	 */
	public boolean isEmpty() {
		if (passengers.size() == 0) {
			return true;
		} else {
			return false;
		}
	}
	
	/**
	 * This method determines which floor the elevator should go to next.
	 *
	 * @return the floor number that the elevator should go to next
	 */
	public int getNextFloor() {
		return passengers.get(0).getDestination();
	}
	
	/**
	 * This method determines the time it will take for the elevator
	 * to get to a given floor from its current floor.
	 * 
	 * @param destination the floor the elevator will go to
	 * @return the amount of time it will take the elevator to get to the new floor
	 */
	public double getTravelTime(int destination) {
		int difference = Math.abs(currentFloor - destination);
		return difference * TIME_BETWEEN_FLOORS;
	}	
}