class ArticlesQuery
  TEXT_LENGTH = 3

  def initialize(comments = Comment.all)
    @comments = comments
  end

  def all
    comments
      .where("user_id IS NOT NULL")
      .where("LENGTH(content) #{condition}")
  end

  def condition
    "> #{TEXT_LENGTH}"
  end
end

class LongArticlesQuery < ArticlesQuery
  TEXT_LENGTH = 5

  def condition
    ">= #{TEXT_LENGTH}"
  end
end