random-magic-cube.rb

require 'nokogiri'
require 'open-uri'

class CardGenerator
  def initialize(format)
    @format = format
  end

  def random_card
    html = ""

    loop do
      html = fetch_random_card_html
      
      break unless is_card_illegal_for_format?(html)
    end

    Card.new(html)
  end

  class Card
    def initialize(html)
      @html = html
    end

    def title
      title = @html.xpath('//title').first.content.split("(").first
    end
  end

  private

  def fetch_random_card_html
    Nokogiri::HTML(open('http://magiccards.info/random.html'))
  end

  def is_card_illegal_for_format?(html)
    html.css('li.legal')
        .collect(&:content)
        .select{|v| v =~ /#{@format}/}
        .empty?
  end

end

card_count = (ENV['COUNT'] || "360").to_i
format = ENV['FORMAT'] || "Vintage"

generator = CardGenerator.new(format)

File.open('random-cube.txt', 'w') do |file|
  card_count.times do |card_number|
    card = generator.random_card
     
    file.puts "1 " + card.title
    puts "##{card_number + 1}: #{card.title}"
  end
end

I really like pulling logic out into helper methods, so that the logic reads more cleanly.

If I was doing this again, I'd change lines 26-30 to

    title =  html.xpath('//title').first.content.split("(").first

    file.puts "1 " + content
    puts "##{card_number + 1}: #{content}"

which is waaaay more clear. Don't do each loops over something that only has one element, unless sometimes you want more. :)

This version is super overkill, but if you wanted to start moving this logic into another application, this is how you'd do it.