parsing mobiledoc in ruby

mobiledoc.rb

require 'keyword_struct'

Mobiledoc = KeywordStruct.new(:version, :markups, :atoms, :cards, :sections) do
  Markup = Struct.new(:tag, :attrs)
  Atom = Struct.new(:name, :text, :payload)
  Card = Struct.new(:name, :payload)

  # Parses a serialized Mobiledoc into a collection of Ruby objects
  def self.parse(str)
    json = JSON.parse(str)
    new(
      version: json['version'],
      markups: Array(json['markups']).map do |(tag, attrs)|
        Markup.new(tag, attrs.in_groups_of(2).to_h)
      end,
      atoms: Array(json['atoms']).map do |a|
        Atom.new(*a)
      end,
      cards: Array(json['cards']).map do |c|
        Card.new(*c)
      end,
      sections: json['sections'] # TODO
    )
  end
end