ElevatorSystem.h

/**
 * Author: Colin Scott-Fleming
 * Created: 2012-11-09
 * DEVELOPER CODING EXERCISE: Model an Elevator System
 *
 * Features:
 *
 *  1.  Each elevator should be able to report what floor it is on, whether it
 *      is moving, and what floor it is going to next.
 *
 *      It should also report what floors passengers have requested.
 *
 *      NOTE: This information is accesible directly from properties:
 *        elevator.currentFloor;
 *        elevator.isMoving;
 *        elevator.destinationFloor;
 *        elevator.floorRequests;
 *
 *  2.  The Elevator System should be able to accept a service request from
 *      any floor, and select only one elevator to respond to it.
 *
 *      The selection algorithm should be reasonable.
 *
 *  3.  Each elevator should be able to respond to a service request from a
 *      floor (via #2) and move towards that floor.
 *
 *      NOTE: Because physical implementation of this system would take time 
 *      for elevators to move from one floor to the other, I invision the coded
 *      implementation using a step system where elevators spend 1 step per 
 *      floor and 0 steps to load and unload passengers.
 *
 *  4.  Each elevator should be able to respond to floor requests from
 *      passengers inside the elevator.
 *
 *      NOTE: This is called by the elevator since these buttons exist inside 
 *      the elevator car.
 *
 *  5.  Each elevator should be able to deal with both a service request and a
 *      floor request at the same time and decide what floor to go to next.
 *
 *      NOTE: Because destination is set programatically at the end of a 
 *      service request or floor request, whichever function finishes first 
 *      will inevitably update the destination first.
 *
 *      Both of these functions will update destination accordingly based on 
 *      direction - that is to say that if we are going up, and a floor 
 *      or service request is placed above our current destination, then the 
 *      destination will be updated to the higher floor.
 *
 *  6.  Each elevator should keep track of how many floors it has travelled
 *      over time.
 *
 *      Again accessible via properties:
 *        elevator.totalFloorsTravelled;
 *
 *  7.  The Elevator System should keep track of how many service requests it
 *      has processed from people wanting an elevator.
 *
 *      Same:
 *        elevatorSystem.totalServiceRequests;
 *
 *      NOTE: This is the count of the number of service requests from people 
 *      not in the elevator car when a floor request is made. If we want to 
 *      update this count to reflect floor requests, we should implement a 
 *      count on elevators that gets incremented when a floor request is made 
 *      from inside the elevator, and return the sum of these values as well 
 *      as the totalServiceRequests value.
 *
 *  8.  An elevator should be able to be put into 'Maintenance Mode' where it
 *      no longer responds to service requests and waits at floor 1. The
 *      Elevator System should handle this gracefully and send all requests to
 *      the functioning elevator, or do nothing in both elevators are in
 *      Maintenance Mode.
 *
 *      NOTE: For the sake of time, my implementation drops all floor requests 
 *      and current destinations from an elevator upon toggling Maintenance 
 *      Mode. This can be remedied, but would take extra time to implement.
 *
 *  9.  The Elevator System should function for 3 elevators and have all of
 *      the above functionality.
 *
 * 10.  The Elevator System should function for any number of elevators and
 *      have all of the above functionality.
 *
 *      Added function - (void)addElevator;
 */

#import <Foundation/Foundation.h>
#import "Elevator.h"

@interface ElevatorSystem : NSObject

@property NSMutableArray *elevators;
@property int totalServiceRequests;

- (void) serviceRequestFromFloor:(int)floor;
- (void) addElevator;

@end