OOP: Elevator Design

Design an elevator control system

Interfaces:

-----------------
IElevator:
+ moveUp();
+ moveDown();
+ addDestination();

+ ElevatorStatus status();
+ ElevatorDirection direction();
---------------------

IElevatorControl:
+ pickUp(Integer pickUpFloor);
+ destination(Integer elevatorId, Integer destinationFloor);
+ step();

Enums:

ElevatorStatus:
+ ELEVATOR_BUSY,
+ ELEVATOR_FREE;
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ElevatorDirection:
+ ELEVATOR_UP,
+ ELEVATOR_DOWN,
+ ELEVATOR_HOLD;