class Module
  attr_reader :mass
  def initialize(mass)
    @mass = mass
  end

  def fuel_required
    (mass / 3) - 2
  end

  def self.for(string)
    new(string.to_i)
  end
end

class Modules
  attr_reader :modules
  def initialize(modules)
    @modules = modules
  end

  def self.from_file(filename, module_type)
    new(File.read(filename).split.map{ |mass| module_type.for mass })
  end

  def total_fuel_required
    @modules.map(&:fuel_required).sum
  end
end

class HeavyFuelModule < Module
  def fuel_required
    super + Fuel.new(super).fuel_required
  end
end

class Fuel < Module
  def fuel_required
    return 0 if super < 0

    super + Fuel.new(super).fuel_required
  end
end

puts "Part 1: #{Modules.from_file("../data/2019/1/input.txt", Module).total_fuel_required}"
puts "Part 2: #{Modules.from_file("../data/2019/1/input.txt", HeavyFuelModule).total_fuel_required}"