fjord/main.rb

class Gate
  STATIONS = [:umeda, :juso, :mikuni]
  FARES = [160, 190]
  def initialize(name)
    @name = name
  end
  def enter(ticket)
    ticket.stamp(@name)
  end
  def exit(ticket)
    fare = calc_fare(ticket)
    fare <= ticket.fare
  end
  def calc_fare(ticket)
   from = STATIONS.index(ticket.stamped_at)
   to = STATIONS.index(@name)
   distance = to - from
   FARES[distance - 1]
  end
end

class Ticket
  attr_reader :fare, :stamped_at
  def initialize(fare)
    @fare = fare
  end
  def stamp(name)
    @stamped_at = name
  end
end