class Battery

  attr_accessor :battery_kwh, :battery_max_kwh

  def initialize(battery_capacity=10.0)
    @battery_kwh = 0.0
    @battery_max_kwh = battery_capacity
  end
  
  def charge(kwh)
    return 0.0 if kwh.nil?
    if battery_kwh + kwh <= battery_max_kwh
      @battery_kwh += kwh.to_f
      #p "Battery is now at %s kwh" % battery_kwh
      return kwh
    else
      old_kwh = battery_kwh
      battery_kwh = battery_max_kwh
      #p "Battery is now at %s kwh" % battery_kwh
      return (battery_max_kwh-old_kwh)
    end
  end
    
  def discharge(kwh)
    return 0.0 if kwh.nil?
    if battery_kwh > kwh.to_f
      @battery_kwh -= kwh.to_f
      #p "Battery is now at %s kwh" % battery_kwh
      return kwh
    else
      old_kwh = battery_kwh
      battery_kwh = 0.0
      #p "Battery is now at %s kwh" % battery_kwh
      return old_kwh
    end        
  end  
end