Elevator Algorithm in Ruby

elevator_algorithm.rb

# Continue traveling in the same direction while there are remaining requests in that same direction.
# If there are no further requests in that direction, then stop and become idle, 
# or change direction if there are requests in the opposite direction.

require 'set'

class Elevator
  attr_reader :floors_up, :floors_down
  attr_accessor :direction, :current_floor

  def initialize(elevator_rules = [ElevatorRule.new])
    @elevator_rules = elevator_rules
    @current_floor = 3
    @direction = :up
    @floors_up = SortedSet.new
    @floors_down = SortedSet.new
  end

  def press_floor(floor)
    return if current_floor == floor

    current_floor > floor ? @floors_down << floor : @floors_up << floor
    puts "floors: #{floors_down + floors_up}"
  end

  def next_floor
    @elevator_rules.each { |rule| rule.apply(self) }
  end
end

class ElevatorRule
  def apply(elevator)
    @elevator = elevator
    return 'No floors to go' if @elevator.floors_down.empty? && @elevator.floors_up.empty?

    set_elevator_direction!
    set_current_floor!
  end

  private

  def set_elevator_direction!
    @elevator.direction = :up if @elevator.floors_up.any? && @elevator.floors_down.empty?
    @elevator.direction = :down if @elevator.floors_up.empty? && @elevator.floors_down.any?
  end

  def set_current_floor!
    if @elevator.direction == :up
      next_floor = @elevator.floors_up.min
      @elevator.current_floor = next_floor
      @elevator.floors_up.delete(next_floor)
    elsif @elevator.direction == :down
      next_floor = @elevator.floors_down.max
      @elevator.current_floor = next_floor
      @elevator.floors_down.delete(next_floor)
    end

    puts "current_floor: #{@elevator.current_floor}"
  end
end

e = Elevator.new
e.press_floor(1)
e.press_floor(3)
e.press_floor(5)
e.press_floor(8)
e.next_floor